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TS 2" Field Flattener for Visual

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#26 Messyone

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Posted 02 February 2018 - 08:51 PM

Just bought a used 5” f5 acro at 600mm fl. Interested to see if the FF works with this scope as well as the 80x600 achro with Pan 35....



#27 Usquebae

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Posted 25 April 2018 - 06:51 PM

I just received the TS2 Flattener and would like to run some tests indoors.  Will the distance to the object of focus impact optimal spacing of the reducer?  Maybe it's a silly question but I expect these are intended for use at infinity focus.



#28 Sarkikos

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Posted 25 March 2019 - 05:50 AM

I ordered a TSFlat2 from TS last night.

 

Mike


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#29 jeffmac

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Posted 26 March 2019 - 10:30 AM


Mike, looking forward to your results.
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#30 mrsjeff

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Posted 03 May 2019 - 08:33 AM

I ordered a TSFlat2 from TS last night.

 

Mike

Just wondering if you've had a chance to try this out. 


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#31 Sarkikos

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Posted 03 May 2019 - 09:50 AM

Not yet.  Last weekend I took my 10" Dob to a dark site, so no time spent there with my refractors.  Skies have been cloudy at home.  But I intend to give the TSFlat2 a test soon.

 

My C80ED and ST120 are probably the best candidates.  Both have a 600mm focal length, which is what the flattener seems to like, judging from comments I've read about it.

 

I'm especially interested to see how the ST120 performs with the TSFlat2.  Has anyone else tried it on that scope yet?

 

Mike


Edited by Sarkikos, 03 May 2019 - 10:00 AM.

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#32 Peter Besenbruch

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Posted 03 May 2019 - 06:10 PM

My C80ED and ST120 are probably the best candidates.  Both have a 600mm focal length, which is what the flattener seems to like, judging from comments I've read about it.

 

I'm especially interested to see how the ST120 performs with the TSFlat2.  Has anyone else tried it on that scope yet?

I have mine semi-permanently parked on my GSO 2" diagonal in my C80ED. For critical, high power viewing, I tend to get better results with the 2" TSFlat removed.

 

One thing I would be interested to hear about in your testing on the ST120 is the impact of the TSFlat on color correction.


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#33 Sarkikos

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Posted 03 May 2019 - 08:07 PM

I expect the TSFlat to flatten the field in the ST120.  Better color correction would be icing on the cake.  Is that possible?

 

Mike



#34 Peter Besenbruch

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Posted 08 May 2019 - 04:59 PM

I expect the TSFlat to flatten the field in the ST120.  Better color correction would be icing on the cake.  Is that possible?

Color correction would be nice, but I suspect that it might go a little bit the other way. :(



#35 Sarkikos

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Posted 09 May 2019 - 05:43 AM

I don't observe planets or the Moon with my ST120, so color correction is not a big deal for me.  I don't really care if Jupiter is smeary or Venus is colorful.  I have other telescopes for themt.  But I would like a flatter field for wide-field low-power deep sky views.

 

If I'm concerned about color correction for bright stars, I guess I could always screw on the 495 Longpass.  TSFlat2 plus 495 Longpass might be a good combination for the ST120.  But the 495 Longpass introduces a yellow shift, which would not be good for appreciation of colored doubles. 

 

Mike


Edited by Sarkikos, 09 May 2019 - 06:52 AM.


#36 jeffmac

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Posted 09 May 2019 - 09:36 PM

Not yet.  Last weekend I took my 10" Dob to a dark site, so no time spent there with my refractors.  Skies have been cloudy at home.  But I intend to give the TSFlat2 a test soon.
 
My C80ED and ST120 are probably the best candidates.  Both have a 600mm focal length, which is what the flattener seems to like, judging from comments I've read about it.
 
I'm especially interested to see how the ST120 performs with the TSFlat2.  Has anyone else tried it on that scope yet?
 
Mike


Mike, please try it with the AT72. I have a Skywatcher 72 and am thinking of buying the TSFlat2, if it is noticeably advantageous.

#37 Sarkikos

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Posted 10 May 2019 - 06:36 AM

I'll eventually try the TSFlat2 with several telescopes.  But the focal length of the AT72 is only about 432mm.  Judging from some of the posts here, 600mm seems like the optimal focal length for the TSFlat2.  

 

Something like this might be better for the AT72 or SkyWatcher 72:

 

William Optics 2" 0.8x Apo Reducer / Field Flattener 6

https://agenaastro.c...-p-flat-f6.html

 

Though I don't know how good the WO would be for visual.  What it does for AP means nothing to me.

 

(Unfortunately, the WO R/FF is discontinued.)

 

But in any case, the weather here has not been cooperating.  The one night it was clear, there was an emergency at home I had to deal with.  frown.gif

 

Mike


Edited by Sarkikos, 10 May 2019 - 06:55 AM.


#38 jeffmac

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Posted 10 May 2019 - 05:12 PM

I'll eventually try the TSFlat2 with several telescopes.  But the focal length of the AT72 is only about 432mm.  Judging from some of the posts here, 600mm seems like the optimal focal length for the TSFlat2.  
 
Something like this might be better for the AT72 or SkyWatcher 72:
 
William Optics 2" 0.8x Apo Reducer / Field Flattener 6
https://agenaastro.c...-p-flat-f6.html
 
Though I don't know how good the WO would be for visual.  What it does for AP means nothing to me.
 
(Unfortunately, the WO R/FF is discontinued.)
 
But in any case, the weather here has not been cooperating.  The one night it was clear, there was an emergency at home I had to deal with.  frown.gif
 
Mike


It may not be optimal at 430mm but I'd sure like to know how it performs on the 72mm. I've never seen an SCT FF/Reducer produce perfection across the field either but it does help the visual view.

Edited by jeffmac, 10 May 2019 - 05:13 PM.

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#39 Der_Pit

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Posted 13 May 2019 - 09:14 AM



I expect the TSFlat to flatten the field in the ST120.  Better color correction would be icing on the cake.  Is that possible?

I assume it largely depends on the scope, too.

I'm using the TSFlat2 on an (old) AP Stowaway.  I agree this (450mm f/5) is at the limit of its specifications.  It does do a good job on flattening the FOV of my ASI1600, but color is really bad. The scope itself is basically color clean, with the TSFlat I do have strong focus difference for the RGB filters, to the point that I don't do L images with it - they are just much less sharp than the narrow channels....



#40 Sarkikos

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Posted 09 July 2019 - 07:38 AM

The TS2FF works very well on my C80ED and Bresser AR-102xs.  For both, I screwed the TS2FF onto the barrel end of a Baader 2" mirror diagonal.  Field curvature is corrected.  I don't need to refocus for center of field vs edge of field.  The usual eyepieces still come to focus, no problem.  These include a 13, 6 and 3.7 Ethos, as well as a Leica Zoom.

 

However, the TS2FF does not work well on the ST120.  At least, just screwing the TS2FF onto the barrel end of a 2" diagonal does not work.  Obvious field curvature is still visible. 

 

Mike


Edited by Sarkikos, 09 July 2019 - 07:44 AM.


#41 Sarkikos

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Posted 28 July 2019 - 11:18 AM

Last night I took out my ST120, 10 Ethos, 8 Ethos, Baader 2" ClickLock Mirror Diagonal and TS2FF.  I removed the barrel of the diagonal, exposing the SCT threads.  I attached an SCT-48mm ring adapter to the diagonal, and then screwed on the TS2FF.

This setup produced a flat field in the ST120, through both the 8 Ethos and 10 Ethos.  The field stop of the 8 Ethos is 17.8mm below the shoulder.  The field stop of the 10 Ethos is 6.9mm below the shoulder.  (These are Tele Vue specs from their website.)  The 10.9mm difference between the field stop locations of the two eyepieces didn't appear to make any difference in the flatness of the field.

The total optical length w/o the diagonal barrel for the 8 Ethos is 112mm - 18mm = 94mm.  The total optical length w/o the diagonal barrel for the 10 Ethos is 112mm - 7mm = 105mm.

The total optical length with the diagonal barrel for the 8 Ethos is 138mm - 18mm = 120mm.  The total optical length with diagonal barrel in place for the 10 Ethos is 138mm - 7mm = 131mm..

The TS2FF w/o the diagonal barrel flattened the field nicely.  The TS2FF with diagonal barrel did not.

According to TS, the optimal spacing for a refractor with a 600mm focal length (like the ST120 or C80ED) is 113mm.  This is 19mm greater than the spacing w/o diagonal barrel for the 8 Ethos, 8mm greater than for the 10 Ethos.  Would inserting a 19mm or 8mm spacing ring in the setup make any visible difference in field flatness?  I doubt it. 

Keep in mind that the C80ED - which also has a 600mm focal length - showed a flat field with the TS2FF with the diagonal barrel left on.  Would the C80ED show a visibly flatter field with the diagonal barrel removed?  I doubt it.  

Use the specs that these companies give you as general guidelines.  But decide what you want to do based on what you actually see in the field.

Mike


Edited by Sarkikos, 28 July 2019 - 12:11 PM.

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#42 tony_spina

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Posted 29 July 2019 - 06:19 PM

Mike can you post a picture of the assembly 



#43 Sarkikos

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Posted 30 July 2019 - 09:40 AM

I took the C80ED out again, this time attaching the TS2FF via ring adapter directly to the 2" diagonal without the diagonal neck.  Sharp stars from edge to edge of the field.  

 

Actually, without the TS2FF the C80ED does not have extreme field curvature.  The ST120 has more FC, and the AR-120xs has a boat load.  But in the C80ED, with TS2FF connected to the diagonal barrel, FC was improved.  With TS2FF connected directly to the diagonal without the diagonal barrel, correction for FC was optimal.

 

Mike 



#44 Sarkikos

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Posted 30 July 2019 - 09:49 AM

Mike can you post a picture of the assembly 

 

Here are the two setups I'm using:

 

(A) Baader 2" ClickLock mirror diagonal with diagonal barrel + TS2FF

 

(B)  Baader 2" ClickLock mirror diagonal w/o diagonal barrel + SCT/48mm ring adapter + TS2FF

 

 

(A) works best with AR-102xs f/4.5, ST80, AT72EDII

 

(B) works best with ST120, C80ED

 

These results agree with the spacing advised by TS.

 

The location of the eyepiece field stop does not appear to affect the field flattening for 10 Ethos vs 8 Ethos, which have an 11mm difference in field stop location.

 

I saw the greatest improvement in flatness of field for the AR-102xs f/4.5 and the ST120.  Those two telescopes had the greatest degree of FC before using the TS2FF.

 

Mike


Edited by Sarkikos, 30 July 2019 - 07:31 PM.

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#45 Sergey Stern

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Posted 31 July 2019 - 05:36 AM

Mike,

did you check the TS2FF with Nagler 31 T5 (or other long focal widefield eyepieces) on ST120? Would it vignette?

Sergey

#46 Sarkikos

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Posted 31 July 2019 - 06:49 AM

No, I didn't want to bother with the weight of the 31 T5, 21 Ethos or even 13 Ethos when testing these small telescopes on a grab-n-go alt-az mount.  I would probably need to stick a counterweight somehow on the sky-end of the dovetail to compensate.  

 

But the TS2FF is designed primarily for AP, where I hear vignetting is a big deal.  I don't think there will be any vignetting for visual.  

 

In any case, my main purpose in testing was to look for improvements in FC, which is why I used Ethos eyepieces.  The 10 and 8 Ethos are comparatively light compared to the other Ethos eyepieces.

 

Mike


Edited by Sarkikos, 31 July 2019 - 07:27 AM.


#47 Bagwell

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Posted 31 July 2019 - 07:50 AM

Did they change the name of the TS2FF ?  It doesn't show up on Teleskop website as "TS2FF" for some reason.  I remember seeing it somewhere listed that way in the past but for some reason it doesn't now.  

 

Vaughn



#48 ji4m

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Posted 31 July 2019 - 08:11 AM

Agreed.  The closest model I found is TSFLAT2.



#49 Sarkikos

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Posted 31 July 2019 - 09:26 AM

TS2FF is just a fast way of typing the name.  It is the name used in the opening post of this thread:  TS 2" FF.  No use getting hung up on labels. 

 

Yes, it is the TSFLAT2.  

 

The best way to resolve uncertainties is to provide a link:   https://www.teleskop...-Anschluss.html

 

Mike


Edited by Sarkikos, 31 July 2019 - 09:29 AM.

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#50 areyoukiddingme

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Posted 31 July 2019 - 11:52 PM

Tried mine last night with 80mm F6, and it did remove a good bit of FC in the 21 Ethos. 

 

Saw some astigmatism at the edge, and I wonder if the flattener is adding that, or if it is just a matter of optimizing the distances.


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