Another Quark/Lunt DS question

[edwyun]

Hello,
I have a question for the collective brain trust. I'm putting together a Quark chromo/Lunt etalon double stack for a refactor. A lot of good information on this site about that. In selecting the Lunt etalon, is there any reason to get the LS50FHa over the LS40FHa? I would be using a RAF Camera adapter to mount the Lunt. From what I've seen, the LS40 seems to work just fine. Is there any benefit to getting the LS50?

My sense is that the limitation is with the Quark chromo and not the Lunt in terms of aperture. Thanks.

Ed

[DavidP]

Hi Ed.
I was waiting for a more knowledgeable response, but since there’s been none, I’ll chime in.
You didn’t mention your refractor aperture or focal length, but using a Lunt 40 shouldn’t restrict your light cone if it is positioned correctly, nor would the 50 improve light throughput or resolution over the 40. So likely no real improvements using the 50.
The air-spaced etalon should go after the solid one.
Generally this combo creates a pretty dim image. I’ve used a similar combination, and though I’ve never looked through it visually, it requires problematically long exposure times or high gain.

[edwyun]

David,

Thanks for your thoughts. The Quark>Lunt DS would primarily be for a 92mm f6 scope. But potentially could be used on a 130mm but unlikely. This would be for visual and imaging with an ASI174mm sensor. I agree with your thinking about the 50 versus 40. I think I would be more limited by the Quark given that it has a 12mm BF (although the Quark Combo has a 25mm BF). But I just don't know if there are any other things to consider when choosing between the two Lunt etalons for this type of setup.

Based on your post, it looks like I also need to consider whether it will be too dark for visual. I guess there is only one way to find out.

Ed

[DavidP]

Based on your post, it looks like I also need to consider whether it will be too dark for visual. I guess there is only one way to find out.

Ed

No! There are other ways to find out. That’s why we have this forum so that you don’t need to reinvent the wheel.
Hopefully someone with a similar set-up will speak up. I can put mine together and put an eyepiece in, but I’m not so sure how relevant it will be to you since my solid etalon is a SolarSpectrum .3A

[Dennis]

David,

Thanks for your thoughts. The Quark>Lunt DS would primarily be for a 92mm f6 scope. But potentially could be used on a 130mm but unlikely. This would be for visual and imaging with an ASI174mm sensor. I agree with your thinking about the 50 versus 40. I think I would be more limited by the Quark given that it has a 12mm BF (although the Quark Combo has a 25mm BF). But I just don't know if there are any other things to consider when choosing between the two Lunt etalons for this type of setup.

Based on your post, it looks like I also need to consider whether it will be too dark for visual. I guess there is only one way to find out.

Ed

Technically there is no advantage over the Lunt 40 in this case. The larger blockfilter of the combo will not give you more field of view then with the chrom. version since in both cases you are limited by the clear aperture of the etalon. So of the 40mm clear aperture of the Lunt 40 ~20mm will usable because of the Quark etalon.

There might be an advantage if you assume the etalon quality of the 50 is better over the 40 though. Or the sweet spot behaviour in a collimated configuration. For the Quark Lunt 40 ds combination i would say the 50 doesnt give you an advantage considering the price difference.

[Oak]

Based on your post, it looks like I also need to consider whether it will be too dark for visual. I guess there is only one way to find out.

Ed

No! There are other ways to find out. That’s why we have this forum so that you don’t need to reinvent the wheel.
Hopefully someone with a similar set-up will speak up. I can put mine together and put an eyepiece in, but I’m not so sure how relevant it will be to you since my solid etalon is a SolarSpectrum .3A

My quark+Lunt40 is very nice for visual. At f40 and above it starts to get a bit dim, but still usable with a sun shade for the binoviewers.

[edwyun]

Technically there is no advantage over the Lunt 40 in this case. The larger blockfilter of the combo will not give you more field of view then with the chrom. version since in both cases you are limited by the clear aperture of the etalon. So of the 40mm clear aperture of the Lunt 40 ~20mm will usable because of the Quark etalon.

That was my thinking as well. Thanks.

There might be an advantage if you assume the etalon quality of the 50 is better over the 40 though. Or the sweet spot behaviour in a collimated configuration. For the Quark Lunt 40 ds combination i would say the 50 doesnt give you an advantage considering the price difference.

Thanks also.

[edwyun]

My quark+Lunt40 is very nice for visual. At f40 and above it starts to get a bit dim, but still usable with a sun shade for the binoviewers.

Thanks for your first hand experience. I believe I read several of your threads about this particular combo. So I will have a go and try things out. I have most of what is necessary for the DS, except for clear sunny skies!

[Oak]

I hope it goes well and you are able to get an etalon. The only reason to go with a 50mm one over a 40 would be fo a larger aperture "small" scope. If you do go that route, you need the 50mm version with the white housing (internal tilt mechanism). I don't know how easy it would be to ass compression tuning to the 50, probably not as simple as in the 40 though.

[edwyun]

The quark/lunt worked visually, though I needed a blanket over my head to see well. I am still dialing things in. But it got me thinking. How about an external D-ERF (which I have for a different project) > scope > telecentric (like a powermate 2x or 4x) > two internal LS40FHa (only have 1 so far) > blocking filter? Thoughts?

[KMH]

The quark/lunt worked visually, though I needed a blanket over my head to see well. I am still dialing things in. But it got me thinking. How about an external D-ERF (which I have for a different project) > scope > telecentric (like a powermate 2x or 4x) > two internal LS40FHa (only have 1 so far) > blocking filter? Thoughts?

Check out this thread:

https://www.cloudynights.com/topic/9198 ... refractor/

Kevin

[Oak]

Or this one:

viewtopic.php?p=429729