PST Etalon with a Quark, Log & Results

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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Tue Jan 01, 2019 6:50 pm

Haven't had good weather lately, just rain and clouds... "Sunny Florida."

Anyhow, got a small break this morning without clouds, so I tested things out.

I tried tuning the Quark & PST Etalon together to maximize contrast on the large filament on the disc today as I figure the darker it got, the more on band I was (maybe this is incorrect?). I couldn't use the limb by itself as a good judge with the poor seeing rippling in and out. So I went for contrast with the AR and filament. Then I slewed to an area to image and judge the limb and the tuning.

I'm still seeing a double limb. I'm guessing so far that while the PST etalon helps shave down the skirt, it's not doing enough, so this may be a bust in terms of keeping it going. While I do get a positive effect from the PST etalon with the Quark, it comes at the price of longer exposure and higher gain values which makes it harder of course. I'm still on the fence with whether I will keep this up, or ditch the PST etalon back into a PST telescope and call it a day there.

Here's the test on the limb from this morning. I filled the histogram to 70% per recommendation to allow a little more room with highlight and shadow recovery and stuff. This is 180 frames stacked, when seeing was quite good.
Test_DS_Limb_Tune.jpg
Test_DS_Limb_Tune.jpg (144.69 KiB) Viewed 1149 times
Another edit to see how things handle when I compress mid-tones, increase contrast and recovery some shadow at the limb:
Test_DS_Limb_Tune_02.jpg
Test_DS_Limb_Tune_02.jpg (53.38 KiB) Viewed 1147 times
Here's another test. Single stack and Double stack to compare the limb at small scale, this was through the ST80 (masked to 60mm):

Single stack (Quark only):
Test_Limb_SS.jpg
Test_Limb_SS.jpg (13.35 KiB) Viewed 1141 times
Double stack (Quark + PST etalon):
Test_Limb_DS.jpg
Test_Limb_DS.jpg (12.04 KiB) Viewed 1141 times
Very best,

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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Tue Jan 01, 2019 8:59 pm

Hrm,

So now I'm curious, why use the PST etalon after the Quark? I wonder if I could place it, or a different etalon, in front of the Quark instead? Be it something like a Lunt 35mm, 50mm or other? Also curious if I can simply just put a narrowband filter instead of a 2nd etalon here to shave the skirt?

Just thinking of the results so far, it makes me wonder about the PST etalon as I would think it would easily shave off the skirt of the transmission profile, given the Quark is operating with a tight bandwidth and not see the double limb. But, the limb is there, so it's not achieving what a typical double stack should be able to do. It's helping a little, but it's not taking out the continuum.

Or heck, what about a combo Quark inserted into the other Quark?

Very best,
Last edited by MalVeauX on Tue Jan 01, 2019 9:35 pm, edited 1 time in total.

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Re: PST Etalon with a Quark, Log & Results

Post by marktownley » Tue Jan 01, 2019 9:07 pm

If you put a different etalon infront of the Quark it wouldn't be in a telecentric beam and wouldn't work. Quark after Quark won't work - the etalons are polarised and would work to make virtaully zero transmission.
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Tue Jan 01, 2019 9:36 pm

marktownley wrote:
Tue Jan 01, 2019 9:07 pm
If you put a different etalon infront of the Quark it wouldn't be in a telecentric beam and wouldn't work. Quark after Quark won't work - the etalons are polarised and would work to make virtaully zero transmission.
Interesting thanks,

I saw that Jozef managed to put a Quark & Quark Combo together and posted images. How did that work then? I never saw how the limb looked, just active regions.

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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Tue Jan 01, 2019 11:18 pm

Marty,
I find there are PST etalons and there are GOOD PST etalons.
It could be your etalon has a bandwidth <1A ( "Acceptable " to Coronado/ Meade) but wouldn't do much to suppress the "Foot" of the DS bandwidth.
Just a thought.
You could put the lenses back on the PST, set it at the -200mm inside focus and follow it by the Quark...The PST works at f10 so with the x4 in the Quark you'd end up at f40....
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Tue Jan 01, 2019 11:42 pm

Thanks,

That is true, maybe this is a so-so PST etalon.

I decided to try to use it because when I imaged full discs with it, it seemed decent. I was not having issues with surface contrast and filaments were dark and ARs were contrasty. Figured it was at least an ok etalon.

Ex from this etalon when it was in the PST:

Image

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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Tue Jan 01, 2019 11:49 pm

Marty,
Yeah, that looks good for a PST.....
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Wed Jan 02, 2019 12:01 am

Do you think there needs to be something after the PST etalon?

I've always though it strange that the train was Quark (with a blocking filter) -> PST Etalon -> no lenses, no glass, no blocking filter -> camera sensor.

It's close to cutting the skirt down, just not quite there.

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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 12:03 am

I use my Lunt DSII unit (intended for an LS80, about 35mm aperture) before my Quark in my 155mm f/7 scope. I cannot visually detect a double limb at all double stacked. With the lone Quark, the double limb is very bright. I estimate my Quark in the 0.5-0.6A range. No idea what the DSII is because I never use it alone.

Therefore, I agree with the above, I would put the collimators back in and place the PST before the Quark. I have two focusers in my rig, so I can adjust the distance of the DSII from the objective and then the Quark from the DSII. I find it is very insensitive to placement of the DSII despite the theory of needing exact placement. So definitely go for it.

Oh, of course I have an ERF (front-mounted DERF) before the DSII unit or I would burn that out.

George

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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 12:06 am

(I agree after the Quark you would want bare etalon. And before the Quark you need collimation and enough energy reduction but no other blocking. George)

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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Wed Jan 02, 2019 12:15 am

Thanks,

Does the PST etalon require the collimating lenses for a native F10 beam already? Or are they there to create the F10 beam? I'm curious when it comes to putting the PST etalon into a SCT design telescope. I will soon be trying this on my fully blocked C8 Edge, F10, so I could potentially move things around and put the PST etalon (with or without) its lenses first, then the Quark last. Or something different?

I'm also very curious about things like a Lunt etalon. I've seen a few people using them in large scopes, like Harald's unigraph, he's just using a 35mm Lunt etalon and a double stack module with a pressure tuner in some kind of configuration and it seems to cut away that double limb no problem and keeps fairly high transmission. I suppose eventually I'll explore something like the Lunt 35 and Lune 50 etalons. The idea of a double stack using those is not too costly and they are high transmission.

Right now, I'm just trying this out for fun since I already have the Quark and already had the PST.

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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 12:31 am

Others are more expert on the PST, but yes I think the lenses you removed are the lenses that allow it to work with the f/10 objective of the PST. So you'll need them if you use the PST etalon before the Quark.

I assume on the C8, you will need the collimating lenses. That's a little more complicated because the beam has already been amplified by the secondary mirror and you will have larger angles than for a native f/10 refractor.

After the Quark, you are over f/30 and don't need the lenses.

The Lunt 35 will require some kind of additional collimating lenses. The DSII unit (which also happens to be 35mm but is a different thing) is an etalon plus a pair of collimating lenses (just like your PST), so I didn't have to mess around with additional collimators. I just stuck it in the f/7 beam (it is designed for f/7 but can work fine with something longer if placed correctly). I already had the DSII unit, so it was a no brainer.

George

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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Wed Jan 02, 2019 12:40 am

The PST etalon assembly is designed to accept an f10 input beam and when positioned at the correct -200mm presents a collimated beam to the etalon.
One issue, which would impact on the performance would be the blocking filter bandwidth in the Quark.
I recently tested a PST blocker and it was close to 6A FWHM.
I don’t know what the Quark blocker FWHM is.
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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 1:31 am

Won't the Quark etalon itself will serve as the blocking filter for the PST? That is, even if the Quark blocker were 20A (i.e., seemingly too wide), the etalon would block spikes for example 8A away from its centerline. Is the concern that the etalon has high shoulders and won't block enough of the off-band spikes?

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Re: PST Etalon with a Quark, Log & Results

Post by MapleRidge » Wed Jan 02, 2019 1:58 am

Hi George...

Interesting that you have a Quark after the DSII module, something I have been meaning to try to setup as a DS on my 150mm, F8 OTA + DSII. Which version of the quark are you using, and I'm curious how far behind the DSII does the Quark reach focus? I tested a friends Standard Chromosphere model with the built in telecentric and had to add a lot of extenders to reach focus on its own. I did not get a chance to try it as a DS on the modded scope before I had to return it.

I'd be interested to see some example images and setup pics/details if you can share?

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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 2:46 am

Hi, Brian. I have a classic Quark chromosphere (i.e., not combo). As I said, pretty narrow at around .5-.6A. I don't image, but I can describe the visual. No more double limb. Prominences have varied brightnesses, some are same as the solar disk and some are dimmer, leading to a slight filaprom where it hits the surface. It looks a lot like a high-magnification processed image when seeing is great. And contrast looks almost similar to my LS80 DSII, which has great contrast.

I put the DSII (from LS80) just a centimeter or two back from where it should be just because the pressure tuner keeps me from inserting it too far up the 4" focuser. An LS100 DSII might go up further. But I don't see much of a difference between where it currently is and even a few centimeters further back, so it doesn't seem to matter much. Then I have a 2"-long Lunt spacer and a Feathertouch 2.5" draw tube focuser, then the Quark, then a 1.25" diagonal, then a binoviewer. And with all that, I still need to pull it back a little further, so I can either shove in an extra 2" extension or just pull the DSII about half a centimeter further back from the objective and that just makes it. And remember that a binoviewer takes up a lot of back focus.

Therefore, it doesn't surprise me that you need all the extensions. Sometimes I just throw on one or two diagonals to soak up extra space.

Let me look for an image of the setup.

George

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Re: PST Etalon with a Quark, Log & Results

Post by george9 » Wed Jan 02, 2019 2:58 am

Here is my setup. The main scope is a 155mm f/7. You see a 4" focuser, a Precise parts adapter, the DSII unit from an LS80, a spacer, an adapter to the Feathertouch, a 2" Feathertouch focuser with 2.5" draw tube (racked all the way out), the Quark chromosphere (with 4.2x), a Baader T2 prism, and a 32mm Plossl. You'll notice that the 4" focuser is racked out about a quarter inch. That obviates the need for me to add yet another spacer, but I would rather than it were all the way in for better theoretical placement of the DSII.

Next to that is a 130mm f/6.3 with a Lunt 2" Herschel wedge and my Denk II binoviewer with 21MM Denk eyepieces. And the third scope is a 70mm f/6.8 with a Lunt B1200 CaK filter and an R2 video camera. All on an AP1100 mount.
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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Wed Jan 02, 2019 4:47 am

George,
Fair comment.
It would depend how how “matched” the transmission curves are and how close they are in CWL.
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Re: PST Etalon with a Quark, Log & Results

Post by Bob Yoesle » Wed Jan 02, 2019 3:44 pm

Very nice implementation George!
After the Quark, you are over f/30 and don't need the lenses.
RE: PST etalon. Remember, an air spaced etalon is a different beast than a solid spaced etalon, and suffers from the decreased refractive index of air compared to a solid spaced etalon, and field and instrument angles will not be as easily optimized when placed after the objective. It will work better in a collimated system versus a telecentric system. With say an f33 telecentric system (f8 refractor feeding the Quark), it will likely perform no better than if it were "naked" in about an f10-15 light cone, and therefore the bandpass and transmission curve would be considerably widened. This is probably why Marty can't get completely rid of the double limb, and why George can - George's air-spaced DSII etalon is located in the ideal collimated beam of the DSII, and the smaller Quark etalon following it is located in its telecentric system which is better suited for small solid spaced etalons.

So Marty should indeed try the collimating and refocusing lenses with the PST etalon, then follow with the Quark - which indeed will act as both a blocking filter and etalon for double stacking the PST etalon - and see what happens...
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Wed Jan 02, 2019 5:49 pm

Interesting!

Can anyone speak to the placement of the PST etalon (with collimating lenses) with an F10 SCT? Will it need to have extensions or how does one measure things out there? I know they're used with SCT's commonly, but I'm not sure how the focus system is handled, compared to the refractor system with the -200mm and all that for the PST etalon. I will be switching to SCT in February or so, and if that means putting the PST etalon (with its lenses) first, and then the Quark, and if that kills the double limb, I'd be happy with that for the time being until I can figure out something better that is affordable.

I was looking at this:

viewtopic.php?t=24283

Looks doable. Can't quite tell what every part there is. But I assume the PST etalon can be put right into the visual back, the primary mirror can move to allow focus there, and the Quark would slide in after that, has the blocking filter built in, and set? Though I'm curious if I would still need potentially a blacking filter after the PST etalon to ensure the same issue like now isn't happening?

I assume this is a simple answer question, but, if it's simple to put a PST etalon behind a F10 SCT, where is the complication with respect to double stacking with two PST etalons?

Thanks!

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Re: PST Etalon with a Quark, Log & Results

Post by Bob Yoesle » Wed Jan 02, 2019 7:28 pm

Hi Marty,

"... and if that kills the double limb, I'd be happy with that for the time being until I can figure out something better that is affordable."

What do you consider affordable?! "Better" H alpha performance (especially double stacked) and "affordable" is kind of working at odds with each other. A PST etalon and Quark are at the top of the list of affordability. Anything else is likely to be more (way more) expensive. Unless you can hand-pick a PST or Quark filter from multiple samples (ala Valery), something better will be a larger Lunt or Coronado etalon in a collimator lens system, or Solar Spectrum or DayStar SE/PE grade filter with a Baader or custom BelOptik telecentric...

My personal choice would be to place a SolarSpectrum or Daystar SE/PE filter in a Baader or BelOptick telecentric system, and as Apollo/SkyBurner did have Chroma Tech or another fitler maker produce a bunch of 0.1 nm or less hard-coated H alpha filters to double stack with it. That should do the trick. Christian and I would certainly buy one or more of these...

But back to your original question - for a C8 double stack system, and speaking only from a "theoretical" point of view:

First I would optimize the focus of the C8 via the mirror lock at its ideal position. This will feed the PST collimator the best possible f10 light cone. You would then place the PST collimator lens at the requisite 200 mm inside the C8 focus (measured using the Moon, etc). This system would remain essentially fixed (add machining cost for adapters). Then add a focuser like George did with his refractor. The PST refocusing lens will then output another f10 light cone to the Quark, and it's telecentric lenses would give the etalon an optimized f43(!) light cone (EFL 8.6 meters). Needless to say even with a 0.5 x focal reducer we are talking very narrow hi-res imaging only under very good seeing conditions.

"... where is the complication with respect to double stacking with two PST etalons?"

This would involve a figuring out, just as with a single PST etalon, how to tune them individually (tilt? mechanical pressure? make your own vacuum tuning module using optical windows x 2?) Likely a very custom machining job. But it can be done ;-) And don't forget intra-etalon reflection suppression.

There generally are no easy, or inexpensive, solutions when dealing with optimized (no double limb) narrow band and double stacked filter systems. Check out the ISOON https://www.semanticscholar.org/paper/S ... 3/figure/0 system here:

isoon_optics.png
isoon_optics.png (32.91 KiB) Viewed 1077 times

Now that's what I call a "better" project to go for, but it definitely is not "affordable" :-)
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Wed Jan 02, 2019 8:03 pm

Thanks Bob,

Good point, affordability is definitely relative.

I would love to just get two Quantums at 0.6A or 0.7A and call it a lifetime, but, that isn't happening... ever, unless someone wills them to me or I find an amazing estate auction that no one else made it to. So might as well explore other options.

So, from my perspective, affordability going from something like a Quark and/or PST setup, or a combination of either of them, would be to look at some of the Lunt options. I've seen how Harald has his unigraph setup with a Lunt DS module and a basic Lunt 35mm etalon in his big folded refractor and there's no double limb there. And those two Lunt etalons are cheaper than a single new tight Quantum (which won't even eliminate a double limb on its own even at 0.3A). I would consider a $4k investment in something like that to be affordable considering what it can do.

Unaffordable for me would be a new Quantum or similar.

Following all of Christian's documentation, I'd love enjoy having a good 0.5~0.6A etalon and have a second filter that is around 1A to shave the skirt, but finding that with high transmission is no simple task, also not inexpensive, but way more affordable than two Quantums or similar combinations.

So that leads back to maybe something like the Lunt etalons and/or combination of a Lunt etalon followed by either a PST or Quark, but ultimately I would think long term it would just make more sense to eventually have two Lunt etalons configured and a big blocking filter.

Until then though, still tinkering with the entry stuff since I already have them.

I can support a 4m to 8m effective focal length in Florida. Before the storm season, I routinely image at 4200mm with good seeing.

Currently looking to setup it up so that the C8 + Quark (with or without the PST etalon depending on how things turn out) with a 0.5x focal reducer with the ASI174MM will have me right back at 4200mm where I'm already imaging often.

And I mainly only want the double stack effects for the limb, for ARs and spots, I'm fine with just the Quark (at least this Quark that is).

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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Wed Jan 02, 2019 9:23 pm

I occasionally have the PST etalon assembly double stacked on the SM60/ED80 (which gives an f10 beam) and BF15..
The image below was taken on 31 Dec 2018 using an ES x3 extender (for the first time) and the ASI 174 (excuse the NR - forgot to add the T2 tilter!)
I'd like to think that this combo effectively suppresses the Photospheric edge....
053.jpg
Sm60/Pst DS
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Re: PST Etalon with a Quark, Log & Results

Post by MalVeauX » Wed Jan 02, 2019 9:43 pm

Hrm,

It seems the limb is still present there too. It's not as stark, but you can see the transition as it's mostly without spicules and texture and has a blur to it. I have similar on my double limb. The super obvious double limb line goes away, but you can still see some kind of continuum leaking through. Interesting.

Thanks for the example!

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Re: PST Etalon with a Quark, Log & Results

Post by Merlin66 » Wed Jan 02, 2019 9:51 pm

Marty,
Yeah, you're probably correct....better seeing and better focus might show it more clearly....
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