Current options for a C6-R focuser upgrade?

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Current options for a C6-R focuser upgrade?

Post by BillyBoyBoy »

I am finally with approval from the boss that I can build my solar rig. It's only going to cost me in trade a kitchen renovation.

I am getting a Celestron C6-R as the scope. Visual and imaging, solar only. With the substandard stock focuser requiring an upgrade, what focuser is currently available as a good choice? It seems all the focusers both recommended and compatible are not available.

Any insight?

Thanks,

Bill


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Re: Current options for a C6-R focuser upgrade?

Post by solarchat »

Feathertouch makes a super nice one for it but it costs more than the scope.
Moonlite makes one, or made one, but they only ship motorized focusers now.
GSO 2 speed focuser is about the only option at around $300 plus the adaptor if you can find one.

if you are going to make a Hydrogen alpha scope, you are really going about it the expensive way by trying to build up this scope into one. if you are going for a white light set up, you should be fine.


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Re: Current options for a C6-R focuser upgrade?

Post by BillyBoyBoy »

Happy new year, Stephen.

My goal is high definition Ha imaging. My daytime seeing is often pretty good in my area, so the idea is to maximize the objective aperture to as big as my seeing will allow at best and I'm not overdoing it. I also want to maximize my clear aperture on the sensor end.

I did a ton or research a few years ago, then got into DSO imaging and put solar on hold. My approach to this was built on that research... not sure if it's already out-of-date.

The imaging design is as follows, plus the reasoning I am following:

Baader DERF / C6-R / ReplacementFocuser / Baader TZ-4 / Daystar Quantum / ZWO ASI174MM

The DERF is to lengthen the etalon's life and reduce heat in the OTA.
The C6-R gives me 150mm and is fine for Ha work as an achromatic. I don't need an APO for Ha.
I'm guessing a motorized focuser would be nice to be able to dial in focus without having to touch the focuser.
The TZ-4 gets me to F/32. A current unknown is that I don't know if the TZ-4 is a choke point for the image circle and renders the clear aperture of the etalon a waste.
The Quantum (or Solar Spectrum) is for sheer clear aperture and a higher quality across the surface.
The 174MM is for the size of the chip and the speed of the frames.

As far as I have understood thus far, by not going custom, I am having to settle for a significantly smaller objective aperture and clear aperture at the sensor end, which I would expect to impact my imaging definition. I don't like the small size of the 'sweet spot' with the pressure etalons I've seen through. That said, it's been about 3 years since I've had a look through a pressure etalon so they might have improved. I have not looked at the SolarMax, but 90mm seems small for my purposes.

As far as the focuser upgrade, the trick is finding one with all the supply chain issues. I am trying to avoid the expense of an FT of course. I was disappointed to see the GSO one nowhere to be found.

Thoughts? I'm happy to get any holes punched in the idea here. Remember the goal is high definition Ha imaging. Most of my research has been on SolarChat and offline with a member or two. If what I propose if overkill, or there is a cheaper route to the same end here, I'm all ears. This is a new realm for me, as the last few years have been all about nighttime imaging. I could use some helpful insight considering my goals.

Thanks,

Bill


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Re: Current options for a C6-R focuser upgrade?

Post by solarchat »

it sounds like you have about a million times more knowledge on this than I do so I will just sit back and watch you create the magic.


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Re: Current options for a C6-R focuser upgrade?

Post by BillyBoyBoy »

Honestly, I'm just trying to verify what I think I understand. Based on the fact that most of my research has been done on SolarChat, this seemed like the place to come to do that.

Any insight from anyone is appreciated.

Bill


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Re: Current options for a C6-R focuser upgrade?

Post by marktownley »

Hi Bill.

Sounds like you had a big chunk of $$$ to spend here. OTA with decent focuser is a must.

Regards the Quantum, unless you are able to test it thorougly first in the long term (with complete flexibility in return if it turns out to be a $10000 paperweight) i'd be very tempted to go the Quark route.

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Re: Current options for a C6-R focuser upgrade?

Post by MapleRidge »

Bill...

I have the same scope (with internal 110mm Baader ERF), with a Daystar Quantum 0.45A SE and AS174MM camera...works very nicely. My focuser choice was the Moonlite with remote focuser control. I used it a lot during the last solar max, but over time I tweaked my Lunt double stacked etalon based mod on the scope and have used the Daystar few times in the past few years.

Some prefer other focusers, Feathertouch is maybe considered the best, but on a cost/performance basis I can't fault the 5 Moonlite units I have. Last discussion I had with Ron at Moonlite was that they were limited to motorized operation only due to supply chain issues, but this may have changed over the past 6-9 months.

Brian


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Re: Current options for a C6-R focuser upgrade?

Post by BillyBoyBoy »

Mark and Brian, thank you for your insights. Brian, I think you and I have actually met in person before, at NEAF 2019 I believe. I think it was Franco Fellah that introduced us.

Ugh. As I am diving back in to solar to get my first Ha rig together, I am quickly being reminded of the difficulty in finding consistency with etalons… at least the solid heated variety. I am suddenly reminded that the focuser upgrade is one of the least of my concerns.

Well look what I'm about to do. I’m highjacking my own thread.

Mark, your advice about needing to experience a Quantum long term and Brian, reading of your Lunt DS concoction to depart from a solid etalon reminds me of this. I recall George's (Gerorge9's) words to me about how every solid etalon is different and how long it took him to find an acceptable sample.

DSO imaging has been with relative ease for me from a build standpoint. I built custom as I utilize an ONAG and though it took a lot of research and figuring, I got my short and long focal length rigs built 100% right on the first try, give or take an image train tilt tweak or two. I think the difference is consistency of product. It just seems like sub-5-figure etalon acquisition is best as a hand-picked affair rather than what is usually a reliable result with other components. I can't justify the cost of a research grade solid etalon at the bandwidth I'd prefer. I know that little slice of mica will vary because it is not 100% synthetic material like a camera sensor or a filter wheel. I suppose the one thing that comes close is a lens, but even that is cheaper to get to a consistent spec than the mica. I know the mica slice thing is a difficult process with an inconsistent probability of success, so I recognize the reason for its expense. I recall the necessity to accept that.

Brian, how does your current Ha setup with the DS compare with the Quantum 0.45A you sound like you've phased out? How much trial and error is involved with getting a component or component combination right in the non-solid etalon realm? Is this an easy answer or is it all really still a crapshoot with inconsistency, even with pressure etalons?

Perhaps the best question to summarize all these is this… given the following:

1) A budget on under $10K for a full Ha rig (not including mount, tripod, and camera… I have all that),
2) A desire to image at high resolution (hence 150mm aperture),
3) A desire to use the Ha rig for visual as well,
4) A desire to have as big of a field of view as possible (not shooting for full disk of course) to minimize the need to mosaic (hence ZWO ASI174MM),
5) A location (I am not on a mountaintop) with some above average to excellent seeing on a regular occasion (hence 150mm aperture),
6) A notion to start at no wider than 0.6A bandwidth, and
7) A desire to minimize trial and error as much as possible,

… what seems to be the BEST PRACTICE for an etalon setup these days?

Not sure what to do at this point but ask the questions, and here I am, back in the rabbit hole of Ha research LOL. I now recall why Ha went on the shelf and I dove into DSO.

I recognize Ha solar is not as straightforward from a build standpoint as any other aspect of amateur astronomy and that it's an expensive endeavor for good reason. I'm pretty sure there's no simple answer. I know that there is always a compromise needing to be made. I guess I just want to narrow it down to the best options given the parameters above and rip the cord on something. What I don't want to do is stall from analysis paralysis as we move further into solar maximum.

Thanks,

Bill


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Re: Current options for a C6-R focuser upgrade?

Post by Rusted »

My viewpoint is that an FT focuser can be fitted and forgotten. They are solid, pretty and don't flex or mess you about.
As everything else in the observatory looks more and more dilapidated the FTs just go on looking like new.

https://youtu.be/zm9SCXzSIX4

A Lunt 60MT etalon and blocking filter can provide a lot of hi-res fun on the end of a 150mm.
Even if it means buying a whole MT telescope just to get the parts.
You can go DS with two 60 MT PS etalons stacked. Shock yourself and the whole solar community!! :shock:
Almost "plug and play" according to some fascinating build threads here.

Even larger Lunt etalons and blocking filters are available separately from stock according to some dealer's websites.

Wishing upon a/our star that you will get a perfect etalon is likely to lead to buyer fatigue.
If the Lunt 60 MT fails to delight then you have a return policy from any decent dealer.
Better, surely, to forge ahead now. With a proven set-up. To hone your solar imaging skills?


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Re: Current options for a C6-R focuser upgrade?

Post by Bob Yoesle »

Hi Bill,

Solar observing and equipment is a specialty, and your nighttime DSO observing and imaging will not prepare you in any way for it.

Do you have previous experience with solar H alpha? If not IMHO you're putting the cart before the horse. My sincere recommendation is that you first get a reasonable scope like the aforementioned Lunt60 andl learn the ins & outs of solar observing and imaging with it before jumping into attempting high res solar H alpha. Just learning to tune an ultra narrow band filter can be pretty difficult if you haven't learned what an on-band image should look like, and the mica filter systems with their temperature tuning lag and variable CWL with f ratio are the most difficult to learn this with or to optimize their implementaion. Hence the plethora of mediocre off-band images I see from these systems.

Get a good reference book or two like Jenkins' Solar Observers Guide, and then graduate to Viladrich's Solar Astronomy. A 60-100 mm front or internal etalon scope will be ideal for visual use and good full-disc imageng to boot, and can be double stacked, giving you much better contrast performance. Then as Rusted states, you can use the PT etalon module for your high-res DIY implementation.

Some other considerations:

Do your live on an island with near perfect daytime seeing? If not, the 150 @ f32 has an EFL of 4.8 meters, and for visual use this might be near impossible to use. Try a white light view at this focal length to see what you can get out of such an EFL (beside a headache ;-). A 25 mm eyepice will yield a magnification of 192 x. Where I live I rarely go over 120 x with my 150 f8 for visual. You can use a focal reducer, but these might not give the result you'd be looking for.

Telecentric etalon systems are not any different than collimator etalon systems with regard to optimization, and for a dedicated solar telescope the telecentric needs ideally to be in a fixed position for the best implentation; NOT placed in a focuser. For the Baader TZ4, the original focus position needs to be fixed 93 mm behind the front of the telecentic lens assembly, then the etalon is plced onto the telecentric assembly, and then the focuser. And at f32, any well-built rack & pinon focuser would be just fine - with no need for 10:1 fine focusing, etc.

Bob


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Re: Current options for a C6-R focuser upgrade?

Post by MapleRidge »

Hi Bill...

My modded solar work has progressed over the last 10+ years and since I owned the DSII module for my Lunt LS80T already and no PST I decided to start with it.

The first mod was to fit the DSII to a 102mm, f10 Celestron refractor with a full aperture ERF. I had the tube cut so that when I placed the etalon/Moonlite focuser put the focus position at the same spot as the original location. It seemed to work fine this way and I did not make any more changes. When I picked up the 150mm, f8 version of the Celestron OTA I used the same theory to mount it and found that I could mount the etalon without cutting the tube, but it has very little in focus left. At the time I had a pair of these OTA's and used one to image in WL and CaK and would use the Daystar on it as well, but the slow cycle of the solid etalon to tune is what made me use the mod more. I still like to change the tuning to image in the wings and the pressure tuned scope does this almost instantly.

A few tears ago I decided to try adding a second DSII unit to the system and found that it worked very well. I did not do any fancy math on setting either the single or double stack up...and maybe it could be fine tuned a bit more but I'm happy with it. The biggest downfall is the limited FOV covered by the sweet spot compared to the Quantum, but my use of the mod is with a barlow to get high res images, so the sweet spot is not a major inconvenience.

When I put the system together I posted some sample pics and asked what the experienced folk here though I was getting as far as band-pass, and the overall guesstimate was less than 0.5A. Two years ago I started on a plan to consolidate tow observatories into one and chose to setup a 130mm, f7 APO as a modular scope with the DS home-brew for Ha and a relatively quick swap back to the standard config to do WL/CaK and deep sky work at night. Changing to the f7 scope did improve the size of the sweet spot as well since the Lunt scopes are f7 too. I still use the DS LS80T + Lunt 75mm front mount etalon for full disk work since the mods would require too much extra work doing full disk mosaics (more my time use).

As Bob pointed out there is no one perfect system...we each really need to fine tune a system around existing scopes if you plan to use them or carefully purchase components. Get a dealer you can trust to work with you when things need service, bi once you start modding you are on our own ;)

If you are looking to buy, my person choices might be the Lunt modular line...either the 130mm or 150mm depending upon your budget and very versatile scope.

Brian


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10'x15 Roll-off Roof Observatory
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Re: Current options for a C6-R focuser upgrade?

Post by BillyBoyBoy »

"Solar observing and equipment is a specialty, and your nighttime DSO observing and imaging will not prepare you in any way for it." No kidding, Bob! Wow. I did a LOT of research on Ha before and I thought I had my Ha plan pretty well mapped out. I shall slow my roll with my re-entry into it. I have access to my local club's Lunt 60 so that gets me time on that system. I plan to go to NEAF this year and I'll spend some real quality time out in the field with the solar scopes. Thanks for the tough love, wisdom and advice.

Brian, you said "a few tears ago" and I'm pretty sure you truly meant to put a 't' instead of a 'y'. You and Rusted have given me a direction to look into with the modular Lunt stuff. After a few looks through Lunts before I wonder if I maybe didn't give it enough of a chance.

Thanks all! I'm happy to know I can always come here for insight and wisdom.

Bill


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Re: Current options for a C6-R focuser upgrade?

Post by thesmiths »

I would watch this video. I've marked it at the summary segment at the end, but it's worth watching the whole thing. Since your budget is quite generous, maybe just have Lunt put the whole thing together for you. You'll save yourself a year of your life (and maybe some money as well). In my experience, 100mm aperture is a real sweet spot for solar imaging (I've tried 40mm, 60mm, 80mm, 100mm, 130mm and 140mm).

https://youtu.be/rKpV4Vxyy1Q?t=1660


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Re: Current options for a C6-R focuser upgrade?

Post by MalVeauX »

Hi,

Depending on what filter system you get into, a strong good focuser is pretty important, however I didn't see any mention of mechanizing the focuser and I will stress that this is crucial for a high res setup. While manual focus can be done, heck I do it all the time, but I wouldn't suggest it to others. If you have budget for a quality focuser, make sure you also have budget for a mechanized focuser either specific to the focuser or modular. Quite frankly even an "ok" focuser like a linear bearing GSO is totally fine for this if you have an electronic motor controlling the focuser. The idea of "smooth" is pointless in imaging because you're not making delicate changes with your fingers, you're making changes with a step motor that has a defined range of motion per step. So if you want to do this on a budget, a linear bear GSO focuser with an electronic focuser (Rigel nStep, ZWO EAF, etc) will do the job. Or you can spend twice as much or more on a Feathertouch/Moonlite/etc.

On the subject, are you sure you want a Baader DERF? Why limit to that (HA only)? I would suggest you look at Altair Astro instead and get a dual band DERF or more (basically Cak & HA), in a nice resin filter holder to put on your scope so you can do more than just HA; then you could do CaK, Continuum and HA from one filter set and just change out the imaging filter.

Also on the subject, why a Quantum? I wouldn't bother with their prices. If you are sure you want mica-spaced and only go single stacked, then maybe look at Solar Spectrum instead. Frankly I would just reboot this whole filter idea and instead approach it with what will allow you to double stack because its a huge game changer, especially in high res, where you will see the differences quite well. Instead, I would urge you to consider two Lunt 80 DS II modules (the internal pressure tuned double stack module, not the scope, they're $1800ish each). Put those behind a Baader TZ4 and you have a killer double stack with real time pressure tuning that is modular. Way better than any single Quantum. No electronics to fail over time. Modular so you can use what you want.

Also, what's your seeing conditions? You mentioned it's pretty good, but how did you assess that during daytime? Have you imaged photosphere or something to assess this? There's a huge difference between 2 arc-seconds and 0.8~1 arc-seconds in terms of resolution potential. A 150mm in 656nm in daytime will need 0.8~1 arc-second to actually start pulling away from a smaller aperture's resolution potential. A 120~127mm will be around 1.2 arc-seconds. 102mm is around 1.6 arc-seconds. 80mm is around 2 arc-seconds. You should probably see where your max resolution is going to fall based on your seeing conditions before spending big on a large aperture that you may not even be able to benefit from (the big cost coming from the D-ERF at 150mm). You don't need a full aperture DERF under 150mm on a refractor frankly.

If your seeing generally greater than 1 arc-second, I would just suggest looking into a Lunt 100 system that can be double stacked. Turn key solution.

Here's a very similar system you've proposed. C6-R base refractor with a tri-band D-ERF in a 3D printed holding cell. Linear bearing GSO focuser (it takes a Rigel nStep electronic step motor focuser that I have). Two air spaced etalons with a Baader TZ4 telecentric for a high res double stack. Overall pretty inexpensive to build relative to the aperture and filter qualities. But the priceless thing is the sub-arc-second seeing I benefit from nearly every morning here in Florida that allows this thing to even work.
SolarSetup_01112023.jpg
SolarSetup_01112023.jpg (166.48 KiB) Viewed 2159 times
Very best,


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