Good focal reducers for Quark?

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Brett
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Good focal reducers for Quark?

Post by Brett » Tue Jul 28, 2015 1:54 pm

There are a couple of cheap brand focal reducers on the market to use with the Quark, but are there any reducers that will be better in terms of dispersion and spherical abberation that would go well with the Quark and a cmos camera? Also, would a 1.25 inch or 2 inch reducer be better fitted to the Quark?



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Re: Good focal reducers for Quark?

Post by grimble_cornet » Tue Jul 28, 2015 10:22 pm



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Re: Good focal reducers for Quark?

Post by Valery » Wed Jul 29, 2015 7:39 am

There are really no good reducers for Quark. Most of them are just a achromat doublet lenses with their own
sets of aberrations. The worst are field curvature, field astigmatism and spherical aberration.

I noticed that if I focus the system for the center, then field edges are softer and wise versa.

And the slower the telescope you do use with Quark, the better a given reducer works - as expected.



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Re: Good focal reducers for Quark?

Post by Astrograph » Wed Jul 29, 2015 5:11 pm

As I have told many customers, the cheap reducers are not made for tele-centric beams like the Quarks. The only one I know of is the Baader 0.7x Tele-compressor. These are not cheap (£209) but work. They have 2" threads. Unfortunately they are very hard to get hold of



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Re: Good focal reducers for Quark?

Post by marktownley » Wed Jul 29, 2015 5:56 pm

I have and use the Baader Solar Telecompressor. It is great and shows none of the uneven field illumination, curvature and softness towards the edges like the cheapy 0.5x version I first tried. I whole heartedly recommend it.


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Re: Good focal reducers for Quark?

Post by Dennis » Thu May 02, 2019 7:39 pm

Hi,
what about this for the Quark? anybody tried the daystar 0,5x / 0,33x reducer with 4 lenses? sounds like a relevation for Quark users..

https://www.astroshop.de/flattener-korr ... r_0_select



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Re: Good focal reducers for Quark?

Post by skyhawk » Fri May 03, 2019 12:36 pm

grimble_cornet wrote:
Tue Jul 28, 2015 10:22 pm
This might be of interest: http://solarchat.natca.net/viewtopic.ph ... al+reducer


Link does not work please check it when posted thanks


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Re: Good focal reducers for Quark?

Post by Dennis » Fri May 03, 2019 3:09 pm

the link works fine for me..

here is another one:

https://www.bhphotovideo.com/c/product/ ... 0_33x.html

but can also be found on google: "daystar reducer 0.5x"



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Re: Good focal reducers for Quark?

Post by skyhawk » Sat May 04, 2019 8:41 am

Many thanks

Looks good but a high cost


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Re: Good focal reducers for Quark?

Post by sulcis2000 » Mon Dec 28, 2020 2:09 pm

marktownley wrote:
Wed Jul 29, 2015 5:56 pm
I have and use the Baader Solar Telecompressor. It is great and shows none of the uneven field illumination, curvature and softness towards the edges like the cheapy 0.5x version I first tried. I whole heartedly recommend it.
Hi Mark

how did you put Baader Solar Telecompressor in Quark Filter?
Can you show us a picture?

Thank you

Ale


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Re: Good focal reducers for Quark?

Post by marktownley » Mon Dec 28, 2020 3:07 pm

Hi Ale.

I use a Quark to T2 adapter in place of the usual eyepiece holder https://www.firstlightoptics.com/adapte ... to-t2.html

The Baader solar telecompressor goes onto this.

Then I have a Baader 1.25" click lock holder at the other side of the compressor.

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Re: Good focal reducers for Quark?

Post by sulcis2000 » Mon Dec 28, 2020 4:30 pm

i Mark

thank you a lot.
I read that the working distance of the Baader Solar Compressor 0,7X is of 110mm (Distance to the camera sensor)
Do you respect it? So you have to add an adapter (T2 female Female thread to a M48 Male thread) and then the Baader Solar Compressor and then 110mm of back focus...is it right?

Ale


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Re: Good focal reducers for Quark?

Post by LTHB » Mon Dec 28, 2020 10:10 pm

Hi Ale,

the 110mm distance given for the 0,7x Baader Telecompressor is not very critical; the working distance between Telecompressor and sensor can differ from 110mm by quite a margin, with good results. Just try it out - that is also, what Baader tells you when you ask them (which I did a while ago).

Unfortunately Baader's website is not as informative and helpful in this point as it could be: They are stating the 110mm as the "ideal" or "correct" distance from reducer to sensor, but they also state that you can get different reduction factors by varying the distance reducer-sensor: A detailed report (unfortunately in German only) can be found here: https://www.baader-planetarium.com/de/b ... -spectrum/ (see the table in the paragraph titled "Die Ergebnisse"); the point is also briefly mentioned on their English website here: https://www.baader-planetarium.com/en/b ... essor-0-4/

What I found even more puzzling is the question how to focus a telescope when I am using a Telecompressor: The Telecompressor is designed for use behind a telecentric lens system. In order to make the light path really telecentric you will (also according to Baader) use the telescope's focuser to put the focus point at a specified distance behind the telecentric system (the exact distance depending on your telecentric system), and having done that, the focuser position should stay fixed. NOW adding to your system a telecompressor WITH A CAMERA SENSOR EXACTLY 110mm BEHIND obviously raises the question where to put another (helical or whatever) focuser - or how else to focus.

The practical approach seems to be a healthy dose of tinkering and trial and error... - or at least I did not get a more precise answer from Baader.

Frank



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Re: Good focal reducers for Quark?

Post by marktownley » Fri Jan 01, 2021 2:49 pm

sulcis2000 wrote:
Mon Dec 28, 2020 4:30 pm
i Mark

thank you a lot.
I read that the working distance of the Baader Solar Compressor 0,7X is of 110mm (Distance to the camera sensor)
Do you respect it? So you have to add an adapter (T2 female Female thread to a M48 Male thread) and then the Baader Solar Compressor and then 110mm of back focus...is it right?

Ale
I used the setup yesterday Ale for my Ha full disk image

ImageHa-FD-DS-bw by Mark Townley, on Flickr

I found a picture of the setup from earlier in the year.

Imageimage by Mark Townley, on Flickr

There is a SCT to T2 adapter at the back of the compressor which will take some optical path (10mm?), then the Baader 1.25" clicklock https://www.firstlightoptics.com/adapte ... hread.html (38mm optical path), I then have some extension tubes on the camera c-mount nose piece (~40mm optical path), and then whatever the standard distance for a flir camera to chip is. So, I guess i'm close to 110mm, maybe less.

I have measured before and I reckon i'm running at about a 0.73x reduction factor, would make sense if i'm under the 110mm quoted distance.

Mark


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