Improving contrast on a Daystar... double stack?

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Improving contrast on a Daystar... double stack?

Post by GHarris » Sat Mar 07, 2015 10:27 am

I'm in a bit of a pickle.

I have a Daystar Quantum SE 0.3A that I bought some time ago in the hope of using it for outreach with a 6 inch f/8 refractor. The views I am currently able to obtain through it have good resolution but low contrast. The contrast is adequate if you're used to looking for subtle details in a telescope and are able to use a binoviewer to squeeze every drop of available contrast out. So it's fine for personal use.

But I bought it for outreach. People not used to chasing low contrast stuff in an eyepiece, people who haven't looked through a telescope before/often, i.e. the entire blasted target audience... they just aren't seeing much or any on-disk features and detail, even with coaching and a little patience.

I'm of the opinion that there is nothing inherently wrong with the Daystar, but that there might be something wrong with the equipment it's being used with (in terms of choice of parts used, or an important component not giving of its best) and that the Quantum itself can deliver better views. I've tried all sorts of minor adjustments and equipment swaps to no unambiguously positive effect.

I have reason to believe that a Daystar Quantum SE of 0.3A bandpass can provide a stunning view - for example a friend of mine has heaped enormous praise on the view Richard Winters' well optimised rig provided when he looked through it a few years back ("unforgettable", "once in a lifetime", "like something you'd see in a professional photo", you get the idea). (The rig is described / pictured here http://stargazerslounge.com/topic/59672 ... f-the-sun/ and here http://stargazerslounge.com/topic/64648 ... m-kelling/). So I'm not bringing this whole discussion up to criticise Daystar and I wouldn't want anyone to take that conclusion away from reading all this. The blame for this rig underperforming lies with me. I just don't know quite how yet!

The thing is that I've been bashing my head against this conundrum for almost a year now and I'm running out of ideas. The remaining options each seem (to me) quite expensive relative to the low probability that one of them will turn out to be a magic bullet. (In short, the options I can think of that I'm left to try are a high quality full sized Baader D-ERF, or sending my refractor back to APM for a focuser upgrade and thorough collimation check/tuneup). I'd be grateful for any advice anyone can offer as to what else I might try.

I asked about all this on the CN forum first because I was already registered there. I made a total mess of that thread, getting bogged down composing badly written posts full of technical detail and then in overreacting to a warning from the mods regarding safety. For further information if anyone is curious, or to avoid writing too many technical details twice, the original trainwreck of a thread which describes my current rig in more detail is available to read here: http://www.cloudynights.com/topic/49333 ... rming-rig/

I suspect the nature of my puzzle is better served by discussing it on the Solarchat forum, which I've often enjoyed reading in the past year. I get the impression we're freer to discuss modding and unconventional setups here. I was surprised to find that I didn't already have an account.

One option I am now seriously considering is to find a way to double stack the Quantum. I'm hoping that it will give "something different" even if I eventually do have the "Eureka!" moment with the Daystar on its own. In theory (haha) it should boost contrast enough to make the views of on-disc features much more accessible to an untrained eye.

While something involving adding a sub-aperture/internal etalon might be economical I have no modding/practical skills whatsoever and I suspect there would be a lot of issues to iron out to make it perform well that way. So I'm leaning towards a front-mounted full size etalon. Specifically the LS100FHa. The 100mm aperture means it stops down the 6 inch refractor considerably. But it's probably still "enough" resolution, and right now I have a glut of resolution and a lack of contrast.

One thing that makes me apprehensive about the LS100F is that there isn't a great deal of discussion about its use and what peoples' impressions are of the views through it. I infer from what eyewitness accounts I have been able to read that it probably works well, but it's a bit ambiguous**** (especially compared to the volumes of discussion available to read on the more widely-owned LS80 for example).

I think one or two people here own an LS100F (including Stephen himself) and I'd be grateful if any of you could comment on how well it works for you.

Tuning the filters to double stack well would be an interesting experience the first time round, I've no doubt of that. After a good setting for the Quantum has been picked, the LS100F, being at the front of a long scope, will have to be tuned by trial and error, walking back and forth between it and the eyepiece. The Quantum regulates its internal oven to provide the requested wavelength setting regardless of external temperatures, and remembers the last setting used before it was turned off, so at least once I've decided on what works I can keep the Quantum set the same way in future.

The views through my Daystar Quantum are pretty bright. So I suspect and hope that there is enough spare light available for a double stack to be attempted, even though this is an unconventional combination of filters. I believe I would not require a Lunt blocking filter because the Daystar Quantum fills that role, which helps with brightness (Reader, don't take my word for it and try this yourself unless you are sure of what you are doing... sorry, got the impression that mentioning this idea on the CN forum created some aggro so thought I had better say that).

Only one of the two filters to be used, the LS100F, is tilt tuned (at least I presume it is! This is a fine example of why I wish there were more hard discussion of the LS100F that I could read). So hopefully there will not be any undue source of sweetspotting/banding.

I'd use the Daystar filter probably mostly with a 3x telecentric giving f/36, and even if a longer f/ratio might make for a better bandpass the double stack effect ought to be the overwhelming factor in image quality. From my own use so far with the Quantum I know that this setup will provide a full disc image (with a 55mm Plossl or other wide 2" eyepiece). The puzzle will be what image quality issues (banding, sweet spots, uniformity?) might arise across the FoV from this odd hybrid arrangement of filters.

If the combination of LS100F + Daystar turns out to be a total dud, I can console myself with having a 100mm front etalon that I can mount on the front of my old 4" Televue Genesis as a "grab and go" of sorts with minimal fiddle factor. It might work OK like this in outreach too (even though the image would still be a single stack, not having to force the magnification so high as with the Daystar might just help make on-disc features more noticeable (a big filament magnified to appear super-huge and fill a lot of the FoV may not stand out as well from its surroundings as when the magnification is backed off a bit).

What little I can work out for myself looks good, "on paper", right now. I am trying to find out what the 'gotcha's are, that I haven't heard of/thought of yet.

Yet another option is just to give up entirely on making my Daystar filter work for outreach (for the forseeable future), and just buy an LS80 DSII to use on its own. That feels very inefficient given the money and time I've spent on it. But I would know what I'm getting, it would be fairly simple to use, grab-and-go, and would "work".

Congrats to anyone who managed to read all that tripe to the end. Any and all comments, suggestions, insults and browbeatings will be gratefully received!

Cheers
Geoffrey Harris

P.S. I'm unsure whether this thread should be in the "Commercial Filters" section, since it refers to Daystar and Lunt, or the "Mods" section since it discusses combining two companies' filters in an odd way. Please feel free to move it if required.

****
- I see that the LS100F has been used to good result in outreach (here for example... http://solarchat.natca.net/viewtopic.php?f=4&t=69 and here http://solarchat.natca.net/viewtopic.php?f=4&t=10059)

- Last post on this thread ("I would pick up the single etalon LS100 and call it a day"... but "I think my LS100 single is a better scope all around then when I put on the external 100mm to double stack it"):
http://solarchat.natca.net/viewtopic.php?f=4&t=2627


- 6th post - "I think that the LS100F or the SM90 external give about the same image visually and through the camera". Makes one wonder why one would go for the 100 over the 90...?
and
- 3rd to last post - "the system works well visually"
http://solarchat.natca.net/viewtopic.php?f=4&t=1530

- Another small example of the LS100FHa in use:
http://solarchat.natca.net/viewtopic.php?f=4&t=6508


- And here's a rough example of the "dream" level of visual improvement I'm hoping to achieve from someone who got there from a broadly comparable starting point (6 inch solar scope stopped down to 4 by an LS100F):
http://solarchat.natca.net/viewtopic.ph ... 55&start=0

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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Sat Mar 07, 2015 11:16 am

Hi Geoffrey.

Slow down a bit here. Can you post a picture of your setup so I can see how you have it all connected together please.

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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Sat Mar 07, 2015 11:19 am

BTW, I deleted your double post in the mods section, depending on how this thread develops may move it over there...
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Re: Improving contrast on a Daystar... double stack?

Post by GHarris » Sat Mar 07, 2015 12:23 pm

Hi Mark

A photo is attached to this post if I haven't done it wrong. Not great quality I know. Taken last year in the Summer. The rig has changed slightly since but I'll describe how it is in the photo and then describe the changes.

From right to left, we have
1) APM ED152-1200K (6" f/8 airspaced doublet refractor)

2) APM 3" focuser. It's good, feels solid, but can't rule out the slim chance of a tiny hard-to-see sag which a Feathertouch MIGHT fix, or of perhaps a slight miscollimation of focuser to optical axis... no reason to suspect this though. The focuser is racked out practically its entire 114mm length to achieve focus (the need for this varies depending on which telecentric barlow is used, but with the 4x PM it needs to go a long way out).

3) Baader 2" UV/IR cut filter (not visible) on the end of an 80mm extension tube

4) Televue 4x Powermate (giving f/32 in this case) with T-ring adapter to mate it to the...

5) Daystar Quantum

6) SCT thread (on the outer side of the Daystar) to 2" adapter

7) Baader 2" Click-lock mirror diagonal

8) 55mm Televue Plossl

Changes since the photo (none of which noticeably helped contrast)
- The visual back (if that's the right word... the part on the end of the focuser that holds onto whatever gets inserted into the focuser) was replaced with a Baader Clicklock as this holds onto the 80mm extension tube better (the old visual back wasn't very long, and didn't grip well thanks to the extension tube's large undercut, causing visible sag)

- I've tried a screw-in-direct-to-the-focuser extension tube instead of the 80mm 2" wide one + visual back, again to minimise potential sources of sag (not that I can spot any with the Baader visual back used)

- Aperture stop at the front of the scope, down to 120mm (making focal ratio of f/40 with the 4x Powermate, and reducing the amount of light coming in to the filter if that matters)

- Using different telecentric barlows - Beloptic 3x (http://beloptik.de/en/left/telecentric-lens-systems/), giving f/30 with the 120mm aperture stop, and even a 2x Powermate giving f/20. The 2x PM was not tried in the hope of improvement, but because it rather interestingly reveals only a small, if any, image contrast difference to the other barlows, even though it "ought" to be very visibly worse according to the conventional wisdom of needing to achieve f/30+).

- A mild ND filter was placed ahead of the Quantum, in case the problem was merely that the view was somehow 'too bright' to see subtle features. The effect was that the view became dimmer but no better.

- The Quantum was originally a 0.5A model but was upgraded to a 0.3A in the hope of boosting the contrast. It didn't noticeably help. I'm not attempting to claim that there was *no* difference between the 0.5 and the 0.3 version of the Quantum SE. Just that it was small enough for the difference, whatever it may be, to be unnoticeable to me, perhaps owing to the passage of time between comparing the two (waiting multiple weeks for redelivery) despite my having become familiar with the kinds of views provided prior to sending the unit off for upgrade.

Sky conditions aren't the issue - I've tried on enough different days and times of day by now to be confident of that.

The scope itself once went out of collimation (long before I bought the Quantum). The problem was, I thought, fixed (and collimation was tightened down a lot harder this time to stop it shifting again) but of course there's the slim possibility that the re-collimation was done "good" but not "perfect" (perhaps the Daystar is fussier about perfect collimation than other night-time uses?). I am not a knowledgeable star tester (I have Suiter's book but never get around to finishing it!) but I can't see anything obviously disastrous in the airy disc when the scope is pointed at a bright star. The unlikely prospect of the objective being miscollimated, or the unlikely prospect of some remaining focuser sag, or of the focuser not being perfectly square to the optical axis, was what made me think of sending the scope back to APM for a focuser upgrade and careful recollimation. But I think it's a long shot and wouldn't be cheap.

I am using a UV/IR cut filter within the OTA rather than a 'proper' front-of-scope ERF. I tread carefully in mentioning this because, while I have reason to believe it is fine to do so in my very specific use case (I am not suggesting others do it without knowing what they're doing), I don't want to start arguments, or subject my sources on this decision to criticism. Still, if the hordes demand "put a ruddy ERF on it for pity's sake!" I'd consider trying out a 160mm Baader D-ERF (the Daystar ERF isn't as good from what I have heard). It's not cheap, I am skeptical that it would help and, because of the cost of it, if I tried it and it didn't help I could no longer afford the LS100F double-stack bodge I have been contemplating.

So... yeah. What would you do in my shoes? I would be grateful for extra ideas for improvement but in the absence of them, the quirky step to buy a LS100F and hope it helps appears, to me, to be the least worst option, in that I could at least use the LS100F on its own (with a suitable blocking filter) even if I end up giving up on the Daystar filter altogether (which I would very much not like to do).

Hope I haven't forgotten anything. Apologies if I have.

(BTW Sorry for the double post in the Mods section... thought I'd lost the original post at first and when I "reposted" I wondered if it might be better to put it in Mods than Commercial)
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Old photo of my Daystar rig

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Re: Improving contrast on a Daystar... double stack?

Post by swisswalter » Sat Mar 07, 2015 3:53 pm

Hi Geoffrey

welcome to that wonderful site. Have fun in the sun.

To make my point as short as possible. For outreach, take the LUNT80 way, for HIRES Ha work use the Daystar 0,3A
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Re: Improving contrast on a Daystar... double stack?

Post by GHarris » Sat Mar 07, 2015 4:40 pm

Hi Swisswalter,

I found your reply refreshingly brief!

Both the LS80 DSII and the LS100F front mounted filter are a similar price, right at the very top of my budget. I don't like to collect OTAs if I can avoid it - already got one reflector and two refractors - and the neatness of adapting an existing scope to H-Alpha appeals to me more than buying a whole extra scope for one role. All things being equal I'd rather adapt my Televue Genesis to a grab-and-go H Alpha rig instead of buying a new entire scope, and (to look at it the other way round than before) maybe the Daystar Quantum can add something more to the LS100F's performance if both the LS100F and Quantum were mounted onto the bigger refractor. Still, if it's purely a matter of what will work best for the outreach role then perhaps there isn't a lot more to talk about...?

The question in my mind is, why not the LS100F?

The nice thing about the LS80 DSII, I agree, is that it will just plain "work". It does what it does, and we all know it can work well.

This is a matter of personal preferences, of what motivates me and what I personally like... but for me... using the Quantum for just personal, high-res viewing is akin to saying "don't use the Quantum much/at all". I know that sounds a bit extreme. But it's outreach that motivates me the most. When I'm looking at something interesting through a scope by myself I often think "other people ought to have a chance to see this too!". In particular if I'm going to go to the trouble of grunt-and-heaving a big heavy tracking mount into position, then putting the big 6" OTA on it, plugging the battery in, aligning it, assembling the string of adapters and extension tubes (etc.), and warming up the Quantum... all to get the hi res views... well then I'd quite like to be sharing those nice views with someone for the sake of that effort. (Maybe if I had a permanent observatory, where I could leave most of the kit set up all the time, I'd use the Quantum+big refractor a lot more frequently for solo/personal use. But that's another can of worms!)

To get a working solar outreach rig I'd rather make the Quantum, which I've poured so much money and time and effort into, a part of the solution rather than sideline it. *IF* that is the remotest bit practical to accomplish. If not, I concede, the LS80 is a straightforward answer. Just feels like a shame to have to settle for that, somehow.

Talking about the LS80 has reminded me... I don't think I've seen anyone else mention it anywhere yet and I completely forgot to mention it myself before now... I recall that on here and Cloudy Nights there had been some interest a year or so ago in the fact that while designing the DS module for the LS152 Lunt had found a way, using some sort of polarising filter, to cut down on any "red glow" from scatter/reflections between the two internal etalons. This glow is particularly famous in the LS80 DSII, appearing around the edge of the sun (making the background sky reddish instead of black) as the only fly in the ointment of what is otherwise an excellent scope for full-disc viewing. At NEAF they'd stated that they were soon going to offer this same innovation for their already-released LS80 and LS100 DSII modules somehow.

Well at the Astrofest show in London a month ago, I spoke to a European Lunt rep who stated that the LS80's polarising filter, to stamp out or reduce this red glow, is a few months away from becoming available and will be an extra add-on for something like 140 Euros (don't quote me on that, but it was that kind of price, give or take a few tens of euros). He insisted that there won't be a new kind of LS80 or a new kind of DSII module released with it built-in... it will be an add-on module for present and future owners just the same, the existing LS80/DSII design won't change.

Thought someone might find that interesting to know! It's probably the best way to get people who would otherwise have waited before buying an LS80, in case a new "better" DSII module came out, to go ahead and buy the scope if it's what they want... no sting in the tail later on from thinking you could have gotten the "shinier, newer" version of the kit. I know it's given me something to think about!

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Re: Improving contrast on a Daystar... double stack?

Post by swisswalter » Sat Mar 07, 2015 6:53 pm

Hi Geoffry

to make it once more very short. I have over 24 scopes, and I tell you, there won't be an end to it, but that is to now interest here. We are only interested in simple working horses ;)
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Sun Mar 08, 2015 12:04 am

There are a few things here that will be letting the performance of that Daystar down: Firstly too may thumbscrews on those adapters from the end of the focuser to the neck of the daystar. They need to all be T-thread. Regardless of how you think you all have it centred I guarantee it isn't, and as a result there is sag which causes a broadening (and lack of contrast) with the filter. The televue is not a true telecentric either, if you are after top notch performance you really need to be using the Baader TZ4.

I genuinely think if you are after a scope purely for outreach a doublestack Lunt is the way to go, the Daystar is quite a specialist piece of kit that is never going to appeal to the masses in the way a full disk double stack view does. If you dont want to spend £5k on of the larger DS lunts get a DS50, the views will amaze.
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Re: Improving contrast on a Daystar... double stack?

Post by Derek Klepp » Sun Mar 08, 2015 7:28 am

Geoff the Daystar really is a research grade piece of equipment and probably best used for hi res work and posting pics on forums such as this.Unless you have very good live view setups.In all honesty a Lunt 80 or 100 would be far better for outreach and quick to setup as well as giving a whole disc view to those viewing.You could use the pics captured with the Hi res setup to accentuate what people are viewing through the smaller scopes.Just my two bobs worth
Cheers Derek

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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Sun Mar 08, 2015 10:53 am

Hi Geoffrey,

Just read the whole thread on CN.

Firstly where are you in the UK?

Regards the D-ERF issue, I use a full aperture one on my ED80 with the Quark, visually it makes no real difference, I don't think, but in terms of imaging the difference in quite pronounced, it really steadies the seeing. You have to remember the purpose of an ERF is to keep all but the light you want out of the OTA, and as a result stop tube currents. Personally I think at 6" aperture it is essential.

The improvements I suggested above would definitely give you a bit more contrast, especially when imaging, but again, visually I don't think Joe Public would even notice.

So, a solution. You need to double stack, but not in a conventional way and not in a way to break the bank. I would get a basic lunt 35 package http://www.telescopehouse.com/acatalog/ ... ckage.html and then mount the etalon alone directly behind your daystar and infront of the diagonal, where that spacer is currently. It would be fairly easy to connect using readily available step up / down rings from off ebay. You could sell the b400 blocker with it for a hundred quid or so, or keep hold of it and still have a grab and go scope for quick Ha views...

I've double stacked my quark and the views I get through that are incredibly contrasty, certainly more so than any of the double stacked Lunts i've looked through. I'm up in the west midlands, you're welcome to come by anytime its sunny and check out the visuals through this scope. Here's an image I took with it yesterday in less than ideal seeing, and yes, visually it does show this level of contrast.

Imagear12297 by Mark Townley, on Flickr

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Re: Improving contrast on a Daystar... double stack?

Post by GHarris » Sun Mar 08, 2015 3:41 pm

I can see that everyone's suggestions to start from scratch with an LS80 DSII make some sense but starting from where I am now it would feel pretty horrible to just write off the money, and more importantly time and stress, spent over the last year trying to get the Daystar up to scratch for my uses. I'd like to make it a part of the solution, if that can sensibly be done.

By the way I might have forgotten to mention throughout all this waffle - I am a 100% visual user. No photography. Don't know the first thing about it, respect those who do, but daren't lose months of my life to starting out in it (at least not this decade thanks!) as I know it can be very technical and fussy work. My outreach uses would be pure visual too.
marktownley wrote:Hi Geoffrey,

Just read the whole thread on CN.

Firstly where are you in the UK?

Regards the D-ERF issue, I use a full aperture one on my ED80 with the Quark, visually it makes no real difference, I don't think, but in terms of imaging the difference in quite pronounced, it really steadies the seeing. You have to remember the purpose of an ERF is to keep all but the light you want out of the OTA, and as a result stop tube currents. Personally I think at 6" aperture it is essential.

The improvements I suggested above would definitely give you a bit more contrast, especially when imaging, but again, visually I don't think Joe Public would even notice.

So, a solution. You need to double stack, but not in a conventional way and not in a way to break the bank. I would get a basic lunt 35 package http://www.telescopehouse.com/acatalog/ ... ckage.html and then mount the etalon alone directly behind your daystar and infront of the diagonal, where that spacer is currently. It would be fairly easy to connect using readily available step up / down rings from off ebay. You could sell the b400 blocker with it for a hundred quid or so, or keep hold of it and still have a grab and go scope for quick Ha views...

I've double stacked my quark and the views I get through that are incredibly contrasty, certainly more so than any of the double stacked Lunts i've looked through. I'm up in the west midlands, you're welcome to come by anytime its sunny and check out the visuals through this scope. Here's an image I took with it yesterday in less than ideal seeing, and yes, visually it does show this level of contrast.

Mark
Really patient of you to read through all of my waffling on both forums!

This is extremely helpful. Brilliant even. Thank you very much. It's an option I wouldn't otherwise have considered as I wouldn't have known where to begin!

Not to look a gift horse in the mouth but I can't help wondering what the catch would be (besides "it's unconventional and you didn't even know it could be done until just now"!). In terms of image quality I mean. Is the LS35 etalon what you used to do your own double stack (I'd seen reference to double stacking a Quark on your website in some photo captions)? I'm particularly pleased to hear you speak highly of the visual contrast on your own double-stack-Quark setup because of my own preference for visual.

The horribly expensive LS100F might (though I'd be happier knowing more) be expected to just "do what it does" - it's a front mounted filter so there can be no major complications arising from sub-aperture filtering (not that I'd really know what those would be). The only snags are the aperture "only" being 100mm (but 100mm is still very decent), the need for the operator to have 6-foot-long arms to tune the view at the other end of the OTA, and the crippling expense (making even what 'looks good on paper' feel scarily risky)! All of which are (potentially) solved by this alternative.

From near the end of this page,
http://www.astrosurf.com/viladrich/astr ... P-Coro.htm
Potentially the 35mm filter would have an unusually wide bandpass (1A or more) as a result of it being an airspaced filter receiving an f/30ish light cone. But the most important thing is that it's double stacking at all, since what really needs to be knocked on the head is the chunk of way-off-band light which a single stack can't help but let through. (One also never knows if a graph of theoretical performance holds for a particular etalon design the author didn't refer to directly). So that sounds OK on paper I think.

The LS35 filter has a 35mm aperture, which is more than the Quantum's 32mm clear aperture, so that side of it doesn't sound like a problem either. The limitations on getting a full disc view should be the same as they were with the Quantum on its own and no worse (shouldn't they... aside from the other thoughts below)? I can get a full disc visually with certain fairly viable combinations of barlows and aperture stops etc. (the Quantum's clear aperture, being larger than the Quark, is helpful) and I know full disc views are particularly easy to "understand" (in terms of recognising they're looking at) for a first-time view by Joe Public.

In Lunt scopes certain close-together double stack etalon arrangements have glow/reflections due to the two internal etalons' close proximity... is that made likely here too?

Is sweetspotting/banding more likely to rear its head?

Is image *sharpness* likely to be particularly affected in any way by this being a smallish rear-aperture filter (one that wasn't made for the role originally)? E.g. is the basic quality of the optics decent in this role it wasn't made for? I know double stacking can be blurrier, but would/could this be moreso than "normal" (or than the LS100F etc)?

All of these imagined downsides are probably acceptable tradeoffs, it would just be nice to hear more (even if it's only guesswork). I am much more comfortable just "giving it a go" at least, for the price.

This cheaper double stack plan leaves budget to get a full size front mounted D-ERF which is great news too.

Aside from simply not really knowing what's possible to attempt, I've always been apprehensive of mods merely because I know that I'm not the traditional modder type - I can't machine up an adapter or go into a garage with some power tools and bodge something together myself (I've no practical skills at all!). I have assumed before now that those who got a mod up and running probably had to do a lot of trial and error and at least a bit of custom machining to get there in the end.

But really, thanks very much indeed. This sounds promising. I will try to find the ebay adapters you mentioned. The "eyepiece" side of the Daystar has a standard SCT thread so I will look for something that fits it all together if I can work it out for myself. If not, guess who I'll be plaguing again...

P.S. - I'm in Lincolnshire so not too close to you sadly. But it's nice of you to offer and I do wish I had more opportunity to see others' high-performance kit in person!

P.P.S. I made a hash of explaining how things have changed since that old photo so I will quickly clarify - I now use the rig with a 3x "proper" telecentric from Beloptik, with the scope stopped down to 120mm, giving f/30. The heap of set screws in the adapter train in front of the Daystar has been largely cleared up... a 100mm extension is screwed directly into the focuser (M68 thread iirc), then a Baader Clicklock goes into the end of that (M68 again) to hold onto a 2"-to-T2 adapter (which it seems to do v well, but I admit it might be worth swapping Clicklock+T2 adapter for a single, screwed-in M68 to T2 adapter), then the 3x telecentric is all T2 direct into the Daystar. So the Clicklock holding the 2" to T2 adapter is the only remaining saggable bit now and it's further down the tube/holding less weight than in the old days (since it's on the end, not front, of the extension tube). I may still upgrade it.

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Re: Improving contrast on a Daystar... double stack?

Post by GHarris » Sun Mar 08, 2015 5:30 pm

I am having trouble finding out what screw thread the LS35 etalon housing has on it.

EDIT: - Think I found it in another thread http://solarchat.natca.net/viewtopic.php?f=9&t=13382 - M60x0.75 if I haven't misunderstood the diagrams in a post partway down the page.

(PRE_EDIT GIBBERISH) It should be the same one front and back so that a 2nd double stack etalon can be fitted, as was once possible but hasn't been sold for a while. There isn't much hard data around that I've been able to find on the web yet. I see that the LS50F uses an M90 screw thread:
(Source- http://www.365astronomy.com/Lunt-LS50FH ... ilter.html)

Is this likely to be the same for the LS35? (END OF PRE_EDIT GIBBERISH)


Would a direct screw-thread adapter from the Daystar's SCT thread to the LS35's M60 thread on one side, then the LS35's M60 thread to a standard 2" thread for a diagonal (or an adapter to 2" tube perhaps) on the other side, be appropriate? With just diagonal + eyepiece or (at worst) binoviewer hanging off it, this wouldn't stress the LS35's housing, or would it...?

EDIT: If it's OK, - I think this does the job from Daystar to LS35 http://www.firstlightoptics.com/borg-m5 ... apter.html
(And unless I am suffering a total common sense meltdown, not uncommon for me works on the other side too. To go to the diagonal I can either use it with my existing SCT-to-2"-tube/compression tube adapter or (I just noticed) thread it straight onto the entrance socket of my Baader 2" Clicklock diagonal which, unexpectedly, has an SCT thread on its telescope-facing side (though that might not suit as the rotation of the diagonal may end up somewhere silly)


I saw some LS35 mods making some sort of big metal enclosure/housing for the LS35 etalon (e.g. here http://solarchat.natca.net/viewtopic.php?f=9&t=8336), not sure why this would be needed but guessing/hoping it's because they are trying to create a custom spacing to a particular telecentric lens for their own rig and so it isn't needed in my case.

(Am trying to answer these questions myself, but posting them here is a way of keeping notes as I go along, and someone might know a quick answer to one or two of them...)

BTW I notice that the LS35 is cheaper at 365astronomy right now http://www.365astronomy.com/Lunt-LS35TH ... ckage.html

So... just need to get a bit more confident about whether the whole idea "makes sense" (thinking about image quality ramifications) or perhaps just bite the bullet and try it out. Worst case, I have a few spare adapter widgets and a LS35 I might occasionally use solo.

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Re: Improving contrast on a Daystar... double stack?

Post by GreatAttractor » Sun Mar 08, 2015 9:45 pm

Hi Geoffrey,
GHarris wrote:EDIT: - Think I found it in another thread viewtopic.php?f=9&t=13382 - M60x0.75 if I haven't misunderstood the diagrams in a post partway down the page.
Yes, that's correct. Though I can imagine they could change it anytime, so I'd measure first before ordering any adapters.
GHarris wrote:I saw some LS35 mods making some sort of big metal enclosure/housing for the LS35 etalon (e.g. here viewtopic.php?f=9&t=8336), not sure why this would be needed but guessing/hoping it's because they are trying to create a custom spacing to a particular telecentric lens
Spacing is one thing (I myself don't have a telecentric setup, so I actually need as small a distance as possible), but the other is rigidity and strength. Unless you use this approach: http://solarchat.natca.net/viewtopic.php?f=9&t=11271, you probably shouldn't hang anything long and heavy (like the positive lens + its tube + BF diagonal + camera) on just the LS35 assembly. Remember it's tilt-tuned; the main part is connected to the rear mounting ring with just a small hinge (read: a thin metal strip) and 3 small tilting screws.
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Re: Improving contrast on a Daystar... double stack?

Post by mdwmark » Mon Mar 09, 2015 1:26 am

OK, Geoffrey the Quantum uses a heater to keep the bandpass on band. The most common problem is that it is not on band. Do not go by the wavelength number on the oven. These really mean nothing unless your telescope system was calibrated with that filter. I would start at a lower wavelength to make sure that you are in the blue wing. Let it stabilize there. Do this with the scope not on the sun. After it heats up then move it to the sun at see what the contrast looks like. When you are off band the solar image will look brighter. The closer you are in the center of the line, then darker orange it will look. Then start moving up from there. Change the temperature, take the scope off the sun and let it stabilize. Keep doing this till you get your best contrast. Once you are at this point leave the scope on the sun and see if the contrast stays the same. Since you are not using an ERF the bandpass should move towards the red. Lower your setting to a lower wavelength and see if the contrast holds. The difference between an Baader ERF and a red glass ERF can be as much as 10C differences to hold the set point.
The operating temperature of your etalon is important also. If it is on band between 30-40C. It can move off band in few minutes with your set up. Even etalons that run at 60C without an ERF will drift red. Give this a try and let us know what happens.
Mark W.

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Re: Improving contrast on a Daystar... double stack?

Post by Valery » Mon Mar 09, 2015 4:36 am

mdwmark wrote:OK, Geoffrey the Quantum uses a heater to keep the bandpass on band. The most common problem is that it is not on band. Do not go by the wavelength number on the oven. These really mean nothing unless your telescope system was calibrated with that filter. I would start at a lower wavelength to make sure that you are in the blue wing. Let it stabilize there. Do this with the scope not on the sun. After it heats up then move it to the sun at see what the contrast looks like. When you are off band the solar image will look brighter. The closer you are in the center of the line, then darker orange it will look. Then start moving up from there. Change the temperature, take the scope off the sun and let it stabilize. Keep doing this till you get your best contrast. Once you are at this point leave the scope on the sun and see if the contrast stays the same. Since you are not using an ERF the bandpass should move towards the red. Lower your setting to a lower wavelength and see if the contrast holds. The difference between an Baader ERF and a red glass ERF can be as much as 10C differences to hold the set point.
The operating temperature of your etalon is important also. If it is on band between 30-40C. It can move off band in few minutes with your set up. Even etalons that run at 60C without an ERF will drift red. Give this a try and let us know what happens.
Mark W.
Thanks a lot, Mark!

I believe this will helpful for many peoples who use heat tuning filters, not DayStar only.

We see how important to have a full aperture ERF filter on the scope, especially if a scope is big.


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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Mon Mar 09, 2015 7:16 am

Excellent diagnostic on tuning Mark.

I would most definitely try this method first Geoffrey.

Shows exactly the importance of a full aperture ERF.
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Re: Improving contrast on a Daystar... double stack?

Post by GHarris » Mon Mar 09, 2015 7:17 am

GreatAttractor wrote:Hi Geoffrey,
GHarris wrote:EDIT: - Think I found it in another thread viewtopic.php?f=9&t=13382 - M60x0.75 if I haven't misunderstood the diagrams in a post partway down the page.
Yes, that's correct. Though I can imagine they could change it anytime, so I'd measure first before ordering any adapters.
GHarris wrote:I saw some LS35 mods making some sort of big metal enclosure/housing for the LS35 etalon (e.g. here viewtopic.php?f=9&t=8336), not sure why this would be needed but guessing/hoping it's because they are trying to create a custom spacing to a particular telecentric lens
Spacing is one thing (I myself don't have a telecentric setup, so I actually need as small a distance as possible), but the other is rigidity and strength. Unless you use this approach: http://solarchat.natca.net/viewtopic.php?f=9&t=11271, you probably shouldn't hang anything long and heavy (like the positive lens + its tube + BF diagonal + camera) on just the LS35 assembly. Remember it's tilt-tuned; the main part is connected to the rear mounting ring with just a small hinge (read: a thin metal strip) and 3 small tilting screws.
The only thing that'll hang off the LS35 are the diagonal and the eyepiece - the rest is on the other side of the Quantum higher up the optical train. No idea if that's enough weight to be queasy enough or not. But thanks for pointing it out.
mdwmark wrote:OK, Geoffrey the Quantum uses a heater to keep the bandpass on band. The most common problem is that it is not on band. Do not go by the wavelength number on the oven. These really mean nothing unless your telescope system was calibrated with that filter. I would start at a lower wavelength to make sure that you are in the blue wing. Let it stabilize there. Do this with the scope not on the sun. After it heats up then move it to the sun at see what the contrast looks like. When you are off band the solar image will look brighter. The closer you are in the center of the line, then darker orange it will look. Then start moving up from there. Change the temperature, take the scope off the sun and let it stabilize. Keep doing this till you get your best contrast. Once you are at this point leave the scope on the sun and see if the contrast stays the same. Since you are not using an ERF the bandpass should move towards the red. Lower your setting to a lower wavelength and see if the contrast holds. The difference between an Baader ERF and a red glass ERF can be as much as 10C differences to hold the set point.
The operating temperature of your etalon is important also. If it is on band between 30-40C. It can move off band in few minutes with your set up. Even etalons that run at 60C without an ERF will drift red. Give this a try and let us know what happens.
Mark W.
Thanks very much indeed for taking the time to explain this, I'd never seen or heard it anywhere else. Another example of how this is a great site. I haven't clearly noticed this effect so far... the Quantum never felt clearly warmer to touch on-sun than when not (just the action of the internal oven makes it feel warm), and I've not noticed the view change with long study, though I've sometimes felt the contrast was better a small number of 10ths of an Angstrom on the blue side (so maybe that was because of this effect). Since I wasn't looking for this effect I might have easily missed it. Really helpful. Thanks.

As a result of going for the LS35 mod option instead of the full LS100F front filter (which I found scarily expensive despite it lookling like it 'ought' to work) I can now afford to buy a full size ERF. Depending on how long it takes to arrive and how often/soon there is sunshine in the meantime I don't know if I'll end up ever really testing for this heating effect now but it's something to be aware of.

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Re: Improving contrast on a Daystar... double stack?

Post by fjabet » Sat Mar 21, 2015 12:12 am

A simple 1,5A etalon in addition of my 0,6 PE daystar gives a more flattering result for a small price.
I tested the LS50+Daystar and it very dark.

I tend to prefer now to have more resolution rather than more contrast anyway. I used to have a marvellous SM60 DS combination, it was great, but I don't regret to have sell it and having now the resolution of the HaT.
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Re: Improving contrast on a Daystar... double stack?

Post by Valery » Sat Mar 21, 2015 2:45 am

fjabet wrote:A simple 1,5A etalon in addition of my 0,6 PE daystar gives a more flattering result for a small price.
Thanks for the info about this.

Is this Bob's Omega 1,5A H-a filter? Does it have a tilt mechanism?

Can you show us the pictures which illustrate the difference between the DayStar as is and with 1,5A filter added?


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Re: Improving contrast on a Daystar... double stack?

Post by fjabet » Sat Mar 21, 2015 7:43 am

Yes it is Valery, I use the full stack rather than the single etalon that does require more tilt.
I use it with the Daystar at the telecentric entry, there is a tiltable mount there and the sun's image being only 19mm, it doesn't reduce the FoV.
The result is more plaisant to the eye, I think it reduces the Daystar wings but doesn't reduce the FWHM.

I don't use the Daystar for imaging, just for visual.
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Re: Improving contrast on a Daystar... double stack?

Post by marktownley » Sat Mar 21, 2015 8:24 am

Try it with a naked PST etalon Frederic, this will give better results (I find) than the Bob filters which I also have. I use this wih my quark on the output side of the telecentric beam.
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Re: Improving contrast on a Daystar... double stack?

Post by Valery » Sat Mar 21, 2015 9:12 am

marktownley wrote:Try it with a naked PST etalon Frederic, this will give better results (I find) than the Bob filters which I also have. I use this wih my quark on the output side of the telecentric beam.

Mark,

1. If I remove both front and rear lenses from the PST etalon, will it function as before - no need any another mechanical actions?

2. Where did you place the PST naked etalon behind the Quark etalon module? Can you show us the picture?

3. How much dimmer the images became? Enough for visual at medium power? Enough for binoviewing?

4. Any sweet spot?

Thanks


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Last edited by Valery on Sat Mar 21, 2015 9:16 am, edited 2 times in total.
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Re: Improving contrast on a Daystar... double stack?

Post by Valery » Sat Mar 21, 2015 9:14 am

marktownley wrote:Try it with a naked PST etalon Frederic, this will give better results (I find) than the Bob filters which I also have. I use this wih my quark on the output side of the telecentric beam.
Have you tested the Quark coupled with the Bob's filter?

What is the bandpass of your Bob's filter?

Is the improvement with Bob's filter worth to make it?


Thanks,


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Re: Improving contrast on a Daystar... double stack?

Post by fjabet » Sat Mar 21, 2015 9:37 am

marktownley wrote:Try it with a naked PST etalon Frederic, this will give better results (I find) than the Bob filters which I also have. I use this wih my quark on the output side of the telecentric beam.
I tried Mark, but it's dim as well.
This solution (the 1,5A etalon) is the best I tested up to now and it is very nice visually.
But my goal is to get rid of the Daystar.
I managed to get a nice result visually from both the Lunt and the PST. I know that the best combination would be the 2xLSFHa. Even if Lunt etalon is not top notch, when DSed it does the trick.
But I am plaggued with 2 parasite reflections for one very nice DS image. Reflections are far from focus and present themself has large high background areas.
I need to try again with some linear polarazing filter as reflections should be polarized.

I tried also two PST, but it was dim again, and lacked homogeneity.
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Re: Improving contrast on a Daystar... double stack?

Post by Valery » Sat Mar 21, 2015 5:23 pm

fjabet wrote: I use the full stack rather than the single etalon that does require more tilt.
Thanks, Frederic!

Can you, please, clarify me what does it mean "full stack" and "single etalon" in this case (Bob's filters)?

Thanks in advance.

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