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Upgrading to Wider FOV System for EAA

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#1 YossiZ

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Posted 18 April 2021 - 12:03 PM

Hello,

I have a maksutov 150mm, f/6.3 reducer and ASI178MC camera that yields a field of view of 22.4x15.1'. This is good for most objects but not enough for the moon and sun, M33, leo's triplet together, M42, the flame nebula and more.

I want to get aproximately 60x40' FOV and considering two options:
1. Adding ASI294MC-Pro
Pros: A camera suited for DSO (cooled, memory buffer, less amp glow, better full well capacity), one time expanse
Cons: Staying with slow f/7.8 system
2. Adding apo refractor in the price range of the 294MC-Pro such as WO GT 71 triplet
Pros: Faster f/5.9 system
Cons: Staying with the 178MC planetary camera (not cooled, amp-glow, no buffer memory...), will probably lead to further expanses such as solar filter, flat panel and who knows what else

I will really appreciate your opinions. Thank you.

#2 barbarosa

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Posted 18 April 2021 - 01:18 PM

Wide field is nice and refractors are good. I owned but no longer have MCTS and SCTs from 90mm to 11". Then I was loaned an 85mm f/7"semi-apo" which for a long time I thought was a triplet. I promptly bought the dedicated flattener-reducer and generally us it at f/5.6 and less often with a Barlow at f/14.

 

I bought a 120mm f/7 triplet and recently added the factory flattener-reducer for an f/5.4 option and this is an excellent combination. I sold the last SCT in order to buy an f/2 RASA 8.

 

Cameras recommended to me by people more skilled than I am, and owned or used by me-

 

ASI183 color cooled on the RASA (I liked it and still have this camera)

ASI 294 color cooled on everything (now stays on the 85mm)

ASI533 color cooled on the RASA and the 85mm (impressive so I sold it and  bought the 2600)

ASI2600 color cooled on the RASA and the 120mm (this is a very good camera, no amp glow, smooth but not as sensitive as the 294)

 

I think that I will sell the 183 now that I have the 2600. The high pixel count on these cameras gives you good zoom options and they bin well.

 

There are some very good ED doublets to be had. WO scopes are made at least some of them by SharpStar or so I read. It could be worth your while to look at SharpStar as well as AstroTech (slight discount for CN members). The SW EvoStar ED doublets have a good reputation and a decent optional reducer is available.

 

Now what should you do? Well if wide field is important to you and you post suggests that it is, then you need need a refractor or a RASA or maybe an imaging Newt. Your post implies a $1k USD budget. My suggestion would be to buy the scope and use the 178 until the sinking fund is replenished. 

 

There are always additional costs in this hobby, something like a yacht but smaller. The items you listed are trivial, discretionary and can be postponed as long as needed. 

 

Good luck.


Edited by barbarosa, 18 April 2021 - 01:20 PM.

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#3 JMW

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Posted 18 April 2021 - 01:53 PM

There are trade offs of focal length, focal ratio, camera sensor size that will impact EAA. In my light polluted backyard observatory, I need enough aperture and focal length to overcome the sky glow so I use a f/4 10 inch newtonian. Under dark skies I prefer to use my refractors for the wider fields of view. 

 

The mount used may also limit the size of the scope.


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#4 Jeff Lee

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Posted 18 April 2021 - 02:31 PM

I have a 4" Es102 triplet and my trusty old C8. For small stuff nothing beats a large scope, even in EAA. for large stuff and many nebula's nothing beats a faster/wider 4" (my runs at 560mm /f5.6) IMHO.


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#5 alphatripleplus

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Posted 18 April 2021 - 02:55 PM

I have an ATEDII 72mm f/6 FPL-53 glass doublet APO, that I can recommend for EAA use with and without a reducer. I also have a 102mm f/12.7 Maksutov and rarely use it for EAA even with a reducer - I'd recommend going the APO route for wide field views.


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#6 YossiZ

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Posted 19 April 2021 - 12:53 AM

Thank you all for the useful info.

Looks like there is an agreemant that buying a fast apo refractor is more beneficial then a DSO camera for the same FOV.

After comparing many doublets and triplets up to ~1000$, I am leaning towards the WO GT71 at 885$. I may later add the 0.8 FR to get even faster and wider (f/4.7, 1.27x0.85°). Sharpstar 76 is also a good candidate so I will try to find head to head comparison between the two.
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#7 GazingOli

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Posted 19 April 2021 - 01:07 AM

If you really want more FOV, the apo is the better choice.

 

However I can tell you that I got a combo of a CPC800 and a 80/480 triplet apo and I am using 90 % CPC800 and 10 % apo, because I like the smaller objects. It is simply a question of taste.

 

All together with ASI 178 MM and 178 MC.

 

CS.Oli


Edited by GazingOli, 19 April 2021 - 01:11 AM.

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#8 alphatripleplus

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Posted 19 April 2021 - 08:11 AM

Yes, I also have a combo of a short focal length APO and a C8, and agree that they are complementary as Oli suggests.


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