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Which 10"-12" scope for planetary nebula and galaxies?

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#1 ClownFish

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Posted 28 January 2020 - 08:38 PM

Just checking in again, to see what people suggest for long focal length photography (galaxies and planetary nebula).

I have an CEM120 EC2 on the way for my home observatory, so portability is not a requirement.
My skies are really nice.  I live at 6800 feet in NM.

 

Price below $4500.

 

- TPO or Astro-Tech 12 inch F/8 RC?   Truss or enclosed tube?

- Celestron C11 Edge HD?

 

Your Advice?

 

 

 

 



#2 james7ca

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Posted 28 January 2020 - 08:45 PM

Are you planning on using an ASI1600MM (your signature says "ASI600")?


Edited by james7ca, 28 January 2020 - 08:47 PM.


#3 RogeZ

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Posted 28 January 2020 - 10:08 PM

Truss-RC with 3” FT

#4 ClownFish

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Posted 28 January 2020 - 10:53 PM

Are you planning on using an ASI1600MM (your signature says "ASI600")?


I will use the 1600mm binned 2:2 until I figure out a better camera.

#5 carolinaskies

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Posted 29 January 2020 - 04:49 PM

Personally I'd go with an SCT over RC, the F/10 or F/8 12" ACFs by Meade specifically unless you planned to do any F/2 imaging in the future with the purchase of a Hyperstar.   The FOV is small regardless of which you choose given the focal lengths involved.  

Every telescope design deals with it's own pro vs con scheme.  

The truss design itself has the inherent issue of both chance off-axis light though that's less likely in an observatory(a shroud can be used though), you also need to protect the optical surfaces with covers to prevent dust and other contaminants getting onto them even if using a shroud.  You'll need to learn how best to colimate an RC, but like with any other telescope it's something we have to do, so that's not a particular con.  

An 11" Edge is under 30lbs(slight more than that with a good Losmandy dovetail), while the ACFs are 40-42 w/Losmandy dovetails, The 12" RC are 44lbs 
The actual size of a 12" RC physically is larger than the SCTs due to the necessity of truss design and the addition of the rear focuser.  

You might slide over to Astrobin and look at some of the various images there using the 12" RC vs 11" Edge & 12" ACFs.  
 


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#6 jgraham

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Posted 29 January 2020 - 04:53 PM

The Meade ACFs are wonderful! From what I have heard the Celestron Edge HDs are also very nice. Sooo, from your two scopes I'd take a hard look at the Edge HD. I'm setting up an older non-Edge C11 for planetary imaging and it shaping up to be a fine scope, though I don't plan on using it for deepsky since the field isn't as flat as I'd like (hence the interest in the ACF/Edge HD scopes).

 

Enjoy!


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#7 Stephen Kennedy

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Posted 29 January 2020 - 11:18 PM

I would go with the GSO RC12 which is available either as a truss or solid OTA.  It also has fixed mirrors with no refracting elements so you will not have to worry about chromatic aberration or mirror flop like you would with an SCT.



#8 james7ca

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Posted 29 January 2020 - 11:39 PM

I will use the 1600mm binned 2:2 until I figure out a better camera.

Okay, but your signature says "ASI600" which I guess is just a typo.

 

In any case, I hope you have good seeing conditions because going to either of the scopes you mention will require above average seeing to reach anything close to their full potential. I image at 0.75 arc seconds per pixel and there are only a few nights each year when I can really take advantage of that kind of image scale. As for New Mexico, YMMV. See this thread by John Hayes:

 

https://www.cloudyni...o/#entry9844804



#9 ClownFish

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Posted 30 January 2020 - 01:38 AM

Good point James.  Climate change is certainly affecting NM, and seeing is taking a big hit in many places due to the shifting jet stream I heard.   I live far enough from Albuquerque and Santa Fe where we usually have different weather.  Wind can be brutal here, so a dome is the direction I am moving.  But as far as scope - I have not decided where I want to go - so I picked a mount that would grow with me no matter what I decide to do.  I may go the RASA route, and just grab wide field images.  I will have to wait and see how everything pans out and make adjustments to my expectations as I go.  The god news is I am now able to devote full time to this hobby now - so no wasted good nights due to work or travel.  :)



#10 carolinaskies

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Posted 30 January 2020 - 06:32 PM

I would go with the GSO RC12 which is available either as a truss or solid OTA.  It also has fixed mirrors with no refracting elements so you will not have to worry about chromatic aberration or mirror flop like you would with an SCT.

CA? CA is an issue to refractors, not to SCTs and mirror'd scopes in general and not created due to a corrector. 

Mirror Flop is not something common to the current generation of SCTs, it's time to let those old ideas lay in the waste bin where they belong. 

The upgrades to the central baffle & focus systems has remedied this issue along with included mirror locks.   

SCTs were subject to coma and field curvature, however both Edge and ACF scopes have dealt with that issue extremely well.

I believe earnestly that either design RC or SCT is quite capable of the intended use. 


  

    



#11 james7ca

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Posted 30 January 2020 - 07:45 PM

I have a 9.25" EdgeHD and while it doesn't have any significant problems with chromatic aberration at the f/10 focus it certainly does have mirror flop. With its built-in mirror locks the problem isn't too bad (but movement in the primary mirror can still occur). However, it can have notable issues with mirror flop if you don't tighten down the locks.

 

In terms of CA, well, the EdgeHD series is pretty well corrected although its off-axis spot diagrams do show differences between red, green, and blue (at its native f/10). Furthermore, Celestron's EdgeHD 0.7X reducer almost certainly introduces some amount of CA, although not nearly as much as you'd see with a typical ED refractor.

 

All that said, I think the EdgeHD series performs very well. I do have some reservations about the smaller, 8-inch model (it's kind of an EdgeHD "lite"), but that scope is relatively inexpensive in comparison to the larger models.


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