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Refractors for imaging nebulae and galaxies

Astrophotography Beginner Imaging Refractor
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#1 Srinivas

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Posted 24 November 2022 - 10:49 AM

Hello! I am looking to purchase an apochromatic refractor for the ASI533MC Pro. I have selected Gran Turismo 71 APO, Astro-Tech 80mm ED Triplet, TS Optics AP 80/560 ED and the Omegon 61/335 Triplet ED. As of this moment I have no idea which one is better for deep-sky photography, as I want to image nebulae and large galaxies.

Can anyone point me in the right direction. Thank you laugh.gif

 

Edit- My mount will be a skywatcher eqm 35 pro 


Edited by Srinivas, 24 November 2022 - 10:53 AM.

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#2 Adluginb

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Posted 24 November 2022 - 11:44 AM

I use the GT71 and the 533 for ap and it works great!

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#3 jsmithsd

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Posted 24 November 2022 - 11:47 AM

The AT80mm ED triplet would be a fine match with the ASI533MC camera. With the 0.8x reducer/flattener you would have a resolution of 2.02 arc-seconds on the Sky and a field of view of 1.69 x 1.69 degrees.  Very slight under sample but with usual seeing conditions would produce great images.


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#4 jsmithsd

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Posted 24 November 2022 - 11:49 AM

That is a fine rig you have, love the gold color. I have the same GT71 but in the red color. I love that little telescope and find it is the one I use the most as it is very light weight and produces awesome images. 


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#5 Spaceman 56

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Posted 30 November 2022 - 03:07 AM

 

Edit- My mount will be a skywatcher eqm 35 pro 

I would go more up market than the EQM-35

 

for astrophotography an 80mm refractor an AZ/EQ5 or an EQ6 is a better choice.

 

I got a Stellarvue 80mm Doublet F7, and with my AZ/EQ5 pro I get pretty good images.

 

Rosette Nebulae
 
Omega 11th May 2022
 
Alnitak 23rd Feb.
 
so to assist you by summarising, an 80mm doublet and a good mount is what you need.
 
best wishes Spaceman

 

 


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#6 Jeff B

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Posted 30 November 2022 - 11:55 AM

The good old and plentiful Orion 80ED F7.5 doublets, or the SW equivalent, with reducers/flatteners and a good aftermarket focuser has proven to be up to the task.  Won't break your wallet either.


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#7 Skywatchr

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Posted 01 December 2022 - 09:59 AM

Hello! I am looking to purchase an apochromatic refractor for the ASI533MC Pro. I have selected Gran Turismo 71 APO, Astro-Tech 80mm ED Triplet, TS Optics AP 80/560 ED and the Omegon 61/335 Triplet ED. As of this moment I have no idea which one is better for deep-sky photography, as I want to image nebulae and large galaxies.

Can anyone point me in the right direction. Thank you laugh.gif

 

Edit- My mount will be a skywatcher eqm 35 pro 

Any one of your current scopes will be fine for most Nebulae and bright galaxies/clusters with the 80mm gathering the most light.  But a 102mm (or larger) will be better for fainter galaxies. Although it will be on the edge for weight limit of the EGM 35.  If all is calm with no winds, it should still handle a 102mm for guiding.



#8 SilverLitz

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Posted 01 December 2022 - 03:28 PM

My response is more general than you requested, as I glanced over your large galaxy objective.

 

Think about FoV and target size.  Larger FoV can be had with shorter FL scope (w/ large image circle) and large sensors; this is what most nebula targets need.  For galaxies (except the large M31 and M33) and planetary nebulas, the objective is almost the opposite, e.g. you need a fine image scale for the detail on heavily cropped, tiny targets.

 

What you are zeroing in on is much more a nebula setup, with your biggest challenge being the small size of the 533 sensor.  The GT71 w/ FR/FF will have a FoV of ~111x111 arcmin, with an image scale of ~2.2"/px.   This resolution is fine for targets that ~ fill the FoV, but is too coarse for cropping in on a small galaxy.  This combo will be great targets the size of: Lagoon Nebula, Orion Nebula + Running Man, Rosette Nebula, and Elephant Trunk Nebula.  To get larger targets, you will need to either mosaic or get a larger camera (FoV with APS-C IMX571 cameras are ~230x150 arcmin).  M31 would require mosaic (or IMX571), while M33 would fit (with breathing room around the galaxy).

 

The 533 camera would pair nicely with longer FL scopes for the small targets.  With a 130mm, f/7 scope, the 533 would have smaller FoV of ~42x42 arcmin, with a finer image scale of ~0.85"/px.   This fine image scale can handle significant cropping of tiny targets, and may provide all the resolution your seeing allows.  This uncropped FoV is great for targets for targets of the size of: M101 Pinwheel galaxy, M20 Trifid Nebula, NGC-2174 Monkey Head Nebula, and M17 Omega/Swan Nebula.


Edited by SilverLitz, 01 December 2022 - 03:43 PM.



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