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Best SCT set-up for visual observation of galaxy clusters

SCT Celestron Catadioptric NV DSO Observing
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#26 Jon_Doh

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Posted 26 October 2021 - 09:10 AM

Yes on both galaxy groups using a C11 with a 40mm ~70 degree FOV eyepiece.  I’d take a C14 over a 14” Dob any day.  The 14” Orion Dob I saw once was massive compared to my C14.  A very high percentage of galaxy groups will fit in the FOV of a C14. 
 

Bill

And you can always use a focal reducer to fit more groups in the fov :)


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#27 Bill Barlow

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Posted 26 October 2021 - 10:11 AM

I never tried one out when I had the C14.  Don’t they reduce the light throughput some?

 

Bill


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#28 ABQJeff

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Posted 26 October 2021 - 06:48 PM

I never tried one out when I had the C14.  Don’t they reduce the light throughput some?

 

Bill

Yes, I found that to be the case with my MCT 150 and the Antares 0.63 reducer, ~10% cut in light throughput, but get wider FOV with 1.25" EPs (about same as with 2" EPs)...no free lunch.   

 

Jeff


Edited by ABQJeff, 26 October 2021 - 09:11 PM.


#29 gnowellsct

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Posted 29 October 2021 - 01:13 PM

And you can always use a focal reducer to fit more groups in the fov smile.gif

Not really.  Using the standard f/6.3 reducer, you won't get more (un-vignetted, which is critical) field than you would in (for example) a 70 degree 40mm Pentax XW.  

 

Now if you want to do astrophotography and have fastar options, that's a different matter.


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#30 gnowellsct

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Posted 29 October 2021 - 01:15 PM

I never tried one out when I had the C14.  Don’t they reduce the light throughput some?

 

Bill

I hope we are talking about vignetting which is what happens when you try to make a scope do what it can't do.   Vignetting takes the form of a dark ring around the field of view, so one might call it "reduced light."   "Light throughput" usually means the loss of light that occurs when it goes through glass.  That is not really an observing consideration.

 

Greg N



#31 gnowellsct

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Posted 29 October 2021 - 01:30 PM

This is a good galaxy cluster setup.  Really, you need the aperture more than the field of view.  This rig does very well with the Perseus cluster.  The refractor gets you wide field views that the C14 can't.

 

I will put in a word for Newtonians f/6 and below.  The best view of M81-M82-NGC 3077 that I've ever had was through my 10" f/6 (since sold).  Nothing else I had comes close.  The C14 can't do the full field, which is about 1 1/3 degrees if you leave a little edge in to frame it all. Even the c8 can't do that.   Some would say well toss in a reducer.  But that's the point.  The reducer will spoil the view with a vignetted edge.

 

The 3 to 5 inch refractors at my disposal can easily do the field but can't match the image brightness.  I did get a very good view of this trio though my 5" refractor earlier this summer, and I was satisfied that all things considered I had the observing capabilities I want to have.  But the fact is my own (former) ten inch Newt, and my friends' eight, ten, and twelve inch Newts, give a more yowee view of the same field.

 

So it seems to me that Newtonians are a great option for galaxy clusters.  Nonetheless they're not MY option for galaxy clusters, I prefer as a general tool a refractor paired with an SCT. 

 

C14+CFF at Chimney mountain 6-20.jpg

 

 


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#32 ABQJeff

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Posted 29 October 2021 - 01:59 PM

I hope we are talking about vignetting which is what happens when you try to make a scope do what it can't do.   Vignetting takes the form of a dark ring around the field of view, so one might call it "reduced light."   "Light throughput" usually means the loss of light that occurs when it goes through glass.  That is not really an observing consideration.

 

Greg N

In my case (Antares on my 150 MCT) it seemed to be more throughput than vignetting.   Adjusting for exit pupil/image size in the comparison and using same brand EP, the center of image seemed a little dimmer with the reducer than without.  I guess 10% because it was enough to notice but not grossly dimmer.


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