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Best SCT set-up for visual observation of galaxy clusters

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#1 ABQJeff

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Posted 20 October 2021 - 10:51 PM

One of my favorite objects to visually observe are galaxy clusters. Think Markarian’s Chain, Fornax-Eridanus Group, Leo Triplet, even tried and true Bode’s Nebula.

The challenge is that to see galaxies really well, you want a big aperture, but to see multiple you want a decent field of view (I found on order of .95-1 degree works well). For SCTs these are definitely orthogonal desires.

So what js the optimum SCT set-up for the popular galaxy clusters? I ask because I am wondering if or how I could do better with another SCT set-up than with my C9.25 Edge on Atlas Pro (which gives awesome views)? Would I do better with a C11 Edge and 0.7x focal reducer (but then reducer adds extra glass and won’t be at the ideal spacing when used for visual vice AP), do I just get an NV device to use with my C9.25 and other scopes instead of $3600 C11 Edge scope plus $700 reducer (but NV I have read is not ideal for galaxies). Seems a C14 would be too narrow a field to fit in 6, 7, or even 8 galaxies into FOV.

Thoughts?

Thanks!

CS!

Jeff
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#2 Taosmath

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Posted 20 October 2021 - 11:38 PM

Is there anything wrong with an 8" SCT with a 0.63 focal reducer?  (I have a 8" F6.3 Meade which I got recently and I like so far)

 

With a 24mm Panoptic you get a TFOV of 1.25 degrees and about 53x magnification, and a 3.8mm Exit pupil.  

 

A C9.25 & FR reducer changes that to 62x/1 degree and 3.8mm EP.

 

Even with a 6.3x reducer (do they make 6.3 reducers for C14's??)  a C14 would give you 92x, 0.7 degrees & 3.8mm EP.

 

Limiting magnitude for a C8 is 14, 14.4 for a C9.25 and 15.3 for a C14 (but much bigger mount is needed of course)

 

Just my 2cents.


Edited by Taosmath, 20 October 2021 - 11:39 PM.

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#3 Bob4BVM

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Posted 21 October 2021 - 12:27 AM

The real answer is what you brushed on and brushed over in one breath:  "big aperture,"

 

hunting distant galaxy clusters is some of my favorite observing for many reasons...

 

That being said i would never box myself  into a single scope type  to accomplish the task.  SCT's for all their attractive features, become commercially unavailable beyond 16 inches.  That is exactly the point where another scope design is just beginning to pick up steam ( as well as photons)

CS

Bob


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#4 maroubra_boy

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Posted 21 October 2021 - 01:49 AM

REALLY???!!!

 

navel-gazing.jpg


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#5 luxo II

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Posted 21 October 2021 - 01:50 AM

OP you had better don the flameproof suit…

Def the wrong horse for this course… Just wait till the big dob users wake up to this thread …. LOL…


Edited by luxo II, 21 October 2021 - 01:54 AM.

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#6 bobhen

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Posted 21 October 2021 - 06:35 AM

You will see more galaxy clusters and detail in galaxies using you current SCT and adding an astro camera to do short exposure (40-60 second) EAA. You can reduce an SCT down to F5 and even faster. These cameras can be somewhat inexpensive ranging from $299 on up. You will be observing using a screen but nothing visual will touch what a camera will do, even with very short exposures. Don’t be afraid of observing using a screen the views will still amaze.

 

For purely visual, get the largest SCT you can and reduce it to the fastest you can.

 

You will be able to see more galaxies with Night Vision with any SCT than you will without using Night Vision. Night vision is like adding some aperture to you scope. However, Night Vision is expensive at around $4,500. But it does offer many other enhanced observing opportunities.

 

I have used SCTs ( 8, 10 and 11”) visually, with a camera doing EAA and using Night Vision. Generally...

 

1. The most details and deepest penetration goes to the camera and EAA. Although dark is always better, you do not need to travel to a really dark sky. 

 

2. The best, enhanced “visual views”, while still “retailing the visual experience” goes to Night Vision. Although dark is always better, you do not need to travel to a really dark sky.

 

3. The purest view goes to visual but you will want to move up to a the largest SCT you can handle and you should observe in a really dark sky.

 

Do some extensive research on the above and then choose the best path for your observing goals, budget, portability needs and your observing style. 

 

Bob


Edited by bobhen, 21 October 2021 - 06:36 AM.

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#7 ABQJeff

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Posted 21 October 2021 - 07:14 AM

Wow!  I go to bed and wake up with all these great inputs, thank you!

 

I have only briefly scanned the inputs, so some quick initial responses from me.

 

1) regarding a dob, yes those are perfect for this   I do plan to get something like an 18” Obsession in 5-10 years, but for now I have my Atlas Pro and living life observing “from the back”.   That is why I focused on SCTs.

 

2) as Bobhen just alluded to, I am debating for next ~$4000-4500 in purchases: C11 + reducer or EAA set-up or NV, but didnt want to constrain or influence inputs.  (I will get all eventually, but in what order?)

 

(Note: Parents/retired neighbors all want me to get EAA first as their vision is going and want me to show them snaps of what I see, but I enjoy the ‘photons in eyeballs’ and prefer not to spend time at a computer screen.  I will get it at some point as it is a common request.  EAA is somewhat ‘live’ wouldn’t be too post processing intensive).

 

I will go back to reading, thanks again!!

 

Jeff


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#8 ABQJeff

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Posted 21 October 2021 - 07:21 AM

OP you had better don the flameproof suit…

Def the wrong horse for this course… Just wait till the big dob users wake up to this thread …. LOL…

Dob users: Yes I do plan to get a dob (like an 18” Obsession), just not at present time.



#9 alphatripleplus

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Posted 21 October 2021 - 07:37 AM

How dark are your skies? If you are set on doing visual deep sky observing of galaxies under heavy LP, you may well be disappointed regardless of how big a scope you have.

 

I used to live under Bortle 8 skies, and was severely limited with galaxy observing using my C8. EAA was definitely the way for me to go.  Under Bortle 4 skies, EAA stills shows more than visual when looking at galaxies, but the skies are dark enough to do visual on galaxies with my C8.


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#10 ABQJeff

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Posted 21 October 2021 - 08:19 AM

How dark are your skies? If you are set on doing visual deep sky observing of galaxies under heavy LP, you may well be disappointed regardless of how big a scope you have.

 

I used to live under Bortle 8 skies, and was severely limited with galaxy observing using my C8. EAA was definitely the way for me to go.  Under Bortle 4 skies, EAA stills shows more than visual when looking at galaxies, but the skies are dark enough to do visual on galaxies with my C8.

I live under Bortle 4-5, get to Bortle 3 for quick observing trips (<4 hrs) to local dark sky site (1 hr away), Bortle 1-2 for all nighters 2 hour drive away.

 

I saw 7 galaxies at once in Fornax-Eridanus in my 9.25 Edge on Bortle 1 skies during Oct New Moon…thought “Yes, more of this please!”

 

CS!


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#11 Bill Barlow

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Posted 21 October 2021 - 10:25 AM

I would think a standard C11 would begin to show you more members of galaxy groups and clusters.  I have one and it shows a bit more than the C9.25 I previously owned.  However I once owned a C14 and this size SCT opened up a whole new world when viewing galaxies.  I found many Hickson, Abell and Arp galaxy groups with this scope.  I’m glad I got to use one for three years or so before the weight became too much for me to handle safely.

 

Bill


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#12 WadeH237

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Posted 21 October 2021 - 11:38 AM

The challenge is that to see galaxies really well, you want a big aperture, but to see multiple you want a decent field of view (I found on order of .95-1 degree works well). For SCTs these are definitely orthogonal desires.

For cruising through galaxy clusters, I like to use my C14.  For seeing large galaxy clusters in context, I like my 4" refractor.

 

If I want to do both at the same time, I use my 14" F/4.6 Dob with a Paracorr.

 

The problem is that, while SCT's provide a nice compact package for large aperture, their design inherently limits the field of view.  Refractors have the opposite problem.  They have a great field of view, but become unwieldy (are stunningly expensive) when you get into apertures that will challenge large SCT's.  Newtonians can run with (and exceed) SCT's for aperture, and with coma correction, they can have a wide field of view at the same time.

 

Don't get me wrong, I love my SCT's - especially my C14 - but they are the wrong tool for this particular mission.


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#13 carolinaskies

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Posted 21 October 2021 - 02:57 PM

For galactic clusters you'll need aperture and fast focal ratios.  Visually for SCTs you want native focal ratios lower than F/10 if you can get them (LX600 Meade's are F/8, older LX200s that are F/6.3).  With EAA you can use some of the fast reducers like the old Meade .33x if you can find one and use it with a 1" sensor.  Yes you can use focal reducers for visual, but they simply are not the same as native focal length.  

If you really wanted to study them visually you need to look into a 20" F/4 truss dob or larger.  

I remember a number of years ago looking through a 36" Obsession at distance chains... but these days really going with an EAA is I think much wiser... LOL. 


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#14 Bean614

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Posted 21 October 2021 - 08:20 PM

I'm under Bortle 4 skies, and for several years had a NexStar 11 GPS on my rear deck, under a TG365 cover year round (in New England!).  No reducer, no EAA, strictly Visual.  Clusters like Stephan's Quintet,  7331 & Friends, several groups within the Virgo Cluster,  etc., were Marvelous! Each one mentioned was in one FOV.  A few days either side of the New Moon best.

  With good transparency,  high mags, with LOTS of detail, were eminently possible.  They've provided some of my fondest astronomical memories.


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#15 ABQJeff

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Posted 21 October 2021 - 08:36 PM

 

 

Don't get me wrong, I love my SCT's - especially my C14 - but they are the wrong tool for this particular mission.

Completely agree, alas a dob is not in my near term plans.  I am thinking EAA with the C9.25 until I get the big Dob (when I get more space and a more permanent locale for my scopes, ie an observatory).  



#16 ABQJeff

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Posted 21 October 2021 - 08:47 PM

but these days really going with an EAA is I think much wiser... LOL. 

Yeah I am thinking EAA (for now)  

 

The C11 would ride on my Atlas Pro nicely for visual, but $4500 (with 0.7x reducer) to only go up (280/235)2= 42% brightness gain, it is worth it?  (lots of CN threads on that)   I will eventually get a C11, bc why not?, but in the priority list, I could use EAA or NV gear with my other scopes and since half my viewing is from home those won't be affected as much my light pollution.    And as for EAA vs NV, I can share pretty color snaps with EAA with the family.



#17 ABQJeff

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Posted 21 October 2021 - 08:50 PM

I'm under Bortle 4 skies, and for several years had a NexStar 11 GPS on my rear deck, under a TG365 cover year round (in New England!).  No reducer, no EAA, strictly Visual.  Clusters like Stephan's Quintet,  7331 & Friends, several groups within the Virgo Cluster,  etc., were Marvelous! Each one mentioned was in one FOV.  A few days either side of the New Moon best.

  With good transparency,  high mags, with LOTS of detail, were eminently possible.  They've provided some of my fondest astronomical memories.

Question: Are you able to fit the whole Leo Triplet and both Bode's Nebula into a FOV with a ES82-30/31 Nagler or ES68-40/41 Panoptic?

 

The C11 would ride on my Atlas Pro nicely for visual....and I do love those raw photons going into my eyes, and dark skies are not far away...decisions, decisions...



#18 Cpk133

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Posted 21 October 2021 - 08:53 PM

Completely agree, alas a dob is not in my near term plans.  I am thinking EAA with the C9.25 until I get the big Dob (when I get more space and a more permanent locale for my scopes, ie an observatory).  

You can use google image search instead of eaa if you just want to see something on a screen.  


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#19 ABQJeff

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Posted 21 October 2021 - 08:57 PM

You can use google image search instead of eaa if you just want to see something on a screen.  

Love it!  Ugh, you are pulling at my heart strings.   I love being one with the sky and telescope...

 

But that puts me back to where I started: EAA vs NV vs slightly bigger aperture...

 

CS!



#20 Bean614

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Posted 21 October 2021 - 08:59 PM

I like the higher mag views, so usually an ES 24/68* was the lowest I'd go for Galaxy Clusters, like those I mentioned.  With that EP, it wouldn't be possible.  However..... I had an Orion 38mm Q70 for a while, and a 40 Pan, and it was Possible to grab those in one FOV. 


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#21 ABQJeff

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Posted 21 October 2021 - 09:19 PM

I like the higher mag views, so usually an ES 24/68* was the lowest I'd go for Galaxy Clusters, like those I mentioned.  With that EP, it wouldn't be possible.  However..... I had an Orion 38mm Q70 for a while, and a 40 Pan, and it was Possible to grab those in one FOV. 

Thanks, I was wondering because my C9.25 (with filter wheel) just fits Bode's nebula in the FOV (with some spaceing from the edge) with a 30-82, and that is .05 degrees bigger than what a C11 would do in the same set-up with a 40-68.  I guess I could get a Pentax 40XW or 41 Panoptic to squeeze out a few more tenths of a degree...that would save me price of the Edge reducer...


Edited by ABQJeff, 21 October 2021 - 09:22 PM.


#22 WadeH237

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Posted 22 October 2021 - 07:16 AM

Completely agree, alas a dob is not in my near term plans.  I am thinking EAA with the C9.25 until I get the big Dob (when I get more space and a more permanent locale for my scopes, ie an observatory).  

You can do great stuff with EAA on a C9.25.

 

But even that won't do what you are asking in post number 1.  EAA will help with the "aperture" part of the equation, but the C9.25 will still have a narrow field of view.  If you want to get a wide field for galaxy clusters, then you would want to do EAA with a refractor (the Altair 102 in your signature would be a good candidate).  Then you would have the wide field, plus the dim details available with EAA.


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#23 ABQJeff

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Posted 22 October 2021 - 10:51 AM

You can do great stuff with EAA on a C9.25.

But even that won't do what you are asking in post number 1. EAA will help with the "aperture" part of the equation, but the C9.25 will still have a narrow field of view. If you want to get a wide field for galaxy clusters, then you would want to do EAA with a refractor (the Altair 102 in your signature would be a good candidate). Then you would have the wide field, plus the dim details available with EAA.


Yes to get entirety of clusters (Fornax-Eridanus/Markarians Chain), several degrees wide, I would certainly need to use my refractors, a good sized dob doesn’t even do 3 degrees+. I wasnt thinking that big an FOV at first as I was focusing on visual of a handful of galaxies. But if I go EAA, as mentioned the other scopes come into play as does capturing entirety of clusters (not just a portion).

#24 Bill Barlow

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Posted 22 October 2021 - 11:31 AM

Question: Are you able to fit the whole Leo Triplet and both Bode's Nebula into a FOV with a ES82-30/31 Nagler or ES68-40/41 Panoptic?

 

The C11 would ride on my Atlas Pro nicely for visual....and I do love those raw photons going into my eyes, and dark skies are not far away...decisions, decisions...

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


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#25 ABQJeff

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Posted 22 October 2021 - 02:28 PM

Yes to get entirety of clusters (Fornax-Eridanus/Markarians Chain), several degrees wide, I would certainly need to use my refractors, a good sized dob doesn’t even do 3 degrees+. I wasnt thinking that big an FOV at first as I was focusing on visual of a handful of galaxies. But if I go EAA, as mentioned the other scopes come into play as does capturing entirety of clusters (not just a portion).

And using “Astronomy Tools”, I just reminded myself (not doing any EAA or AP at present) that a nice small-mid size (quick image dumping) CMOS sensor has a much, much smaller FOV than visual EPs.  So the comment by WadeH237 was spot on.  Base FOV with my 102 F/7 and using an ASI-533 (for example) is 0.91 degrees which closely matches my C9.25 and a 30mm-82 degree (including 2” filterwheel which makes actual F/L ~2600mm).  (I know there is the F/2 Hyperstar option, but for switching between EAA and visual as I would do, it wouldn't be the most convenient, which is the whole point of EAA - enhanced visual vice involved AP).

 

So my current thinking/assessment:

If I go EAA, it would be most entirely with my ED80, 102 F/7 or 140 F/6.5 (using ROI or Barlows to match FOV of visual field of C9.25 as a natural vs enhanced view).  I would use CMOS on C9.25 probably for planets and individual small DSO….which is not the point of this thread.

 

So because of FOV limits for EAA CMOS, if I want to enhance my visual-like galaxy cluster experience JUST with an SCT I am looking at larger aperture (with potential for add on reducer) or NV (eg afocal TV system).




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