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Help me select a small widefield imaging refractor; analysis-paralysis has taken hold...

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#1 SimonIRE

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Posted 03 October 2020 - 12:26 PM

Hi All,

 

I am looking for a very good quality portable wide field refractor and I seriously need opinions...

 

  • It's got to be fast - f5 or lower (preferably lower)
  • It's got to have an imaging circle that will cover a full frame sensor (QHY367)
  • Aperture 85mm or less. 
  • Portable
  • It's got to have a significantly greater FOV than the FSQ106 which I have (and it's going to a remote dark site).

 

This is what I have been looking at:

 

1. Tak FSQ 85 possibly with the focal reducer (negatives - price and I will probably feel compelled to upgrade the focuser)

 

2. Tak 60CB possibly with the focal reducer - (negatives - doublet, not sure I am really considering this)

 

3. Williams Optics GT 81mm (negatives - not sure there are any?)

 

4. Borg 55FL f3.6 - (positives - FT focuser, widest FOV here, can't think of any stand out negatives but it's hard to get info on these scopes)

 

 

I fully accept this is a mixed bunch. If you think the FSQ is the clear winner, then say so, but tell me what you would pick from the other three if you had to. The FSQ requires several other upgrades (focuser and reducer) making it more than double the price of the others. 

 

Simon


Edited by SimonIRE, 03 October 2020 - 12:27 PM.


#2 CounterWeight

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Posted 03 October 2020 - 12:50 PM

Confused here, I thought the 106 image circle was wider than the 85 ?



#3 snommisbor

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Posted 03 October 2020 - 12:58 PM

You want fast and wide get a camera lens with an adapter to attach to your camera. Heck an Nikon Canon take your pick 85mm f 1.8 would be fast. Plus the manual ones tend to have a focus stop at infinity so you would be perfectly focused. 


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#4 SimonIRE

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Posted 03 October 2020 - 01:03 PM

Confused here, I thought the 106 image circle was wider than the 85 ?

 

The image circle is bigger but the FOV isn't given the same sensor size. My 106 is going to a remote dark site on the other side of the planet. I would like something wider (and cheaper) for my home observatory. 


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#5 SimonIRE

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Posted 03 October 2020 - 01:04 PM

You want fast and wide get a camera lens with an adapter to attach to your camera. Heck an Nikon Canon take your pick 85mm f 1.8 would be fast. Plus the manual ones tend to have a focus stop at infinity so you would be perfectly focused. 

 

Thanks for this; I looked at if for a while but it's probably too wide. I was hoping for a high quality refractor solution. 


Edited by SimonIRE, 03 October 2020 - 01:05 PM.


#6 junluo168

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Posted 03 October 2020 - 01:19 PM

That list covers a wide range of focal length and prices... I current have both Tak FS-60CB and FSQ-85EDX. For imaging, I did decide to upgrade to feather touch. If you are patient, there are feather touch focuser for these scope from time to time listed. The upgrade is definitely worth it.

FS-60CB is much lighter(portable), although a doublet, provides excellent view for imaging. Maybe it’s the fluorite magic? It just looks good! Not sure if it can adequately cover large frame sensor though.

FSQ-85EDX is much heavier compared to the baby Tak. It’s not as portable of course but optically it’s superb. Very flat and even better with the 1.01X flattener. If cost and weight is less of a concern, this would be my choice.

I only used WOZ73. Very solid but no Tak.

From what I read Borg is ultra light and should perform like a FS-60CB optically.

Recently I had seen Askar line of ultra wide. Askar 200mm is like a lens. Portable but not sure if you like the focusing. Had not used it.

#7 SimonIRE

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Posted 03 October 2020 - 01:55 PM

That list covers a wide range of focal length and prices... I current have both Tak FS-60CB and FSQ-85EDX. For imaging, I did decide to upgrade to feather touch. If you are patient, there are feather touch focuser for these scope from time to time listed. The upgrade is definitely worth it.

FS-60CB is much lighter(portable), although a doublet, provides excellent view for imaging. Maybe it’s the fluorite magic? It just looks good! Not sure if it can adequately cover large frame sensor though.

FSQ-85EDX is much heavier compared to the baby Tak. It’s not as portable of course but optically it’s superb. Very flat and even better with the 1.01X flattener. If cost and weight is less of a concern, this would be my choice.

I only used WOZ73. Very solid but no Tak.

From what I read Borg is ultra light and should perform like a FS-60CB optically.

Recently I had seen Askar line of ultra wide. Askar 200mm is like a lens. Portable but not sure if you like the focusing. Had not used it.

Very helpful; many thanks

Edited by SimonIRE, 03 October 2020 - 01:56 PM.


#8 Hesiod

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Posted 03 October 2020 - 01:59 PM

I would throw in also the Vixen FL55.
Focuser is way better than on fs60, and has an excellent flattener and reducer, for ca 240mm or 310mm focals.
Also, unlike most Taks, you have not to enter into an adapters' nightmare, as all parts screw directly between themselves.

Anyway, I would make my choice depending on the tracking device/mount you plan to use: the FL55 works very well even with a diminutive Polarie, so its overall portability is quite amazing.
If move a larger mount, maybe could just get the reducer for the fsq106, since seems to recall that the difference in focals between the two fsqs was pretty small (60mm?)

#9 Cometeer

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Posted 03 October 2020 - 02:06 PM

I have a FS-60CB. It works fine for planetary and lunar imaging in Q mode, but false color is visible in CB mode. I’ve used it with a generic flattener, not the Tak branded one, so I can’t say how the official flattener may improve things. It made more economical sense to just buy a different 60mm scope for imaging. 



#10 HydrogenAlpha

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Posted 03 October 2020 - 11:47 PM

I owned both the FSQ85 and FS60. Both are optically excellent. I eventually sold both to upgrade to a 5-incher, but eventually bought the FS60 back. Btw, the Borg 55FL is also a doublet. 

 

IME CA on the FS60 is not a big deal, but some people find it a problem. But I've never used it with a full frame sensor, so I cannot comment on that.

 

As for the FSQ85, I think it goes without saying that it is essentially optically perfect at this aperture. The FSQ85's focuser is pretty decent, so you may not need to change it to a feathertouch unless you've gotten a lemon. 



#11 Sebriviere

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Posted 16 October 2020 - 02:52 AM

The image circle is bigger but the FOV isn't given the same sensor size. My 106 is going to a remote dark site on the other side of the planet. I would like something wider (and cheaper) for my home observatory. 

You can approach teh ASKAR vendor (sometime on this forum)... They do have the ASKAR FRA400, and just released the FRA 600.

The FRA400 is in between the 61 and 76 EDPH with 44mm image circle, the FRA600 is more like your FSQ106 (at 108mm) with 66mm image circle.

I use a FRA400 with ASI533MC-P, EAF Focuser and ASI462MC.... so all this being ZWO, an ASIAir PRO to control all that.

The FRA400 is a petzval Quintuplet, at 5.6, going down to 3.9 with reducer.

Unsure on FRA600 reducer availability yet.


Edited by Sebriviere, 16 October 2020 - 02:56 AM.


#12 rbish237

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Posted 16 October 2020 - 05:09 AM

I have and like the FS60 - I use it with the Tak reducer and my Fuji cameras (not full frame) for quick grab and go unguided imaging.    

 

Sample image w/ the reducer and the Fuji XT1: https://www.astrobin.../full/266515/0/

 

I haven't tried it, but don't think its image circle is big enough to handle a full frame sensor.  Also, I never use it as a true doublet - I either use it with the reducer (F4.3-ish) or with the Q module (F10) for lunar/planetary.  There is also a flattener available, but I haven't tried that.    

 

Don't have any experience with the other scopes on your list, other than to know that the FSQ85 should handle full frame w/o any problem.  But it is a much heavier scope.  



#13 Sebriviere

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Posted 16 October 2020 - 08:58 AM

https://www.astrobin...6gte5a/?nc=user

link M31 FRA600
link M31 FRA400 reducer
https://telescopius....alaxy/by-cheman

Edited by Sebriviere, 16 October 2020 - 09:10 AM.

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#14 SimonIRE

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Posted 16 October 2020 - 09:08 AM

 

That's a really great image. Incidentally, how do you find those Antlia filters? - they are very competitively priced. 



#15 Sebriviere

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Posted 16 October 2020 - 09:17 AM

That's a really great image. Incidentally, how do you find those Antlia filters? - they are very competitively priced.

https://www.cloudyni...owband-filters/
and google can help you for vendors.

None are my photo, nor I use this filters. Just posted these to help you with ASKAR FRA quality and FoV...

You probably l9ved the Tak quality, which is why it is going remote to a dark side (of the force?).
The FRA600 is the same in spec on the paper... mostly not in optical quality, but possibly for 1/2 the price if the tak...
and you are almost in known terra.
Always balance between optic/price/weight... and Sharpstar/Askar build for others... (Raptor 61, is a boosted 61EDPH MrkII...)

I originally was looking at a Redcat... hard to find at descent price with Covid-19 supply chain issues...
Found the FRA400, same price in EU as the RC51, wider and better... no regrets.

Edited by Sebriviere, 16 October 2020 - 09:28 AM.

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