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Getting started w low budget EAA setup

EAA beginner dso equipment
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#1 GazingOli

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Posted 20 February 2020 - 05:59 AM

Hello fellow stargazers,

 

I am new to this board and I hope I did not oversee any threads with similar content.

 

Trying to get started with a low budget EAA setup in addition to pure visual astronomy with my CPC 800, I am thinking of putting a small Fraunhofer 80/400 equipped with a camera on top of the CPC.

 

My goal is mainly to catch a better view of DSO from my location which is fairly lightpoluted due to an airport in the North. I do not want to capture perfect images but learn to see more through the telescope. So I want to use both – visual and EAA – besides each other.

 

I figured out the following setup:

  • Achromatic refractor 80/400 (Skywatcher, Omegon, Orion… ) OTA
  • Altair GPCAM3 224C USB3
  • SharpCap PRO Software for live stacking

In astronomy.tools it seems to fit quite well, both images of M1 for example are in the same FOV when using my favourite 25 mm 2” eyepiece 70° on the C8. I am aware that I will only be able to reach objects about this size with that equipment which would be fine with me. I am mainly targeted at PN and galaxies (not applicable for M31, sure).

 

C8 mit 80400Camera.jpg

 

Anything I oversaw or comments on this idea? I am a beginner (approx. 1,5 y of experience in astronomy) and first time thinking about EAA. Any commet would help. Also any source for more information.

 

CS.Oli


Edited by GazingOli, 20 February 2020 - 06:11 AM.


#2 jprideaux

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Posted 20 February 2020 - 07:53 AM

It is possible to see more with the 80mm aperture (400mm FL) scope with small camera than the 200mm aperture (2000mm FL) with 2.5mm eyepiece if you collect and stack images with ENOUGH total integration time. For example, the following link shows what the Stellina can do which is also 80mm (400mm FL) using a small (but different) camera.

https://support.vaon...m1-crab-nebula/

The picture shown in that link had 607 stacked 10 sec images.
(1 hour 41 minutes integration time). As you reduce total integration time, the resulting image quality goes down. Each person decides the appropriate balance between image quality and how long they want to wait. For conventional astrophotography people are willing to wait a LONG tine and do lots of post-processing to get the best image quality they can. For “near-real-time” EAA, people are willing to accept a much lower quality image (than conventional AP) but get it much faster and with no post-processing. Of course having more telescope aperture (and focal-length reduced) helps get higher quality faster but that tends to drive the cost up.

Edited by jprideaux, 20 February 2020 - 07:57 AM.


#3 cmooney91

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Posted 20 February 2020 - 08:16 AM

That should work, but you will have a lot of chromatic aberration and star bloat. the camera is very sensitive, even into near IR, so it will pick up a lot more CA than you can see visually. Filters can help with this. The user DragonMan has done a lot of EAA with achromats.

 

I started with a little camera lenses then moved to a $130 Meade Mini LightBridge 114mm F4 Newtonian. It was a great match for the IMX224 sensor.  The Altair GPCAM3's slim body fits down into the focuser, so there is no modification needed to reach focus. The reflecting Newtonian telescope has no chromatic aberration, but it does have Coma. The good news is the small IMX224 sensor only samples the central sweet spot, so the worst of the coma does not show up.

 

The faster F4 speed is very beneficial for EAA. The down side is the small cheap newt needs a little collimation every time it's transported. It doesn't take long to do. 

 

Another issue is this visual newt has an undersized secondary for camera use (even 1/3"), so careful mechanical alignment, and flat frames are very beneficial. 

 

Here is an album of my 114mm F4 and IMX224. I used that combo for 1.5 yrs and loved every second of it.

 

It's a great low cost synergistic match up. 

 

I'd say the pluses and minuses probably make the achro vs newt choice a toss up, it depends on your preferences, either one will probably serve you well.

 

For the smallest planetaries, it might be good to have a focal reducer to enable you to use the camera with the CPC800 occasionally. 


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#4 GazingOli

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Posted 20 February 2020 - 09:45 AM

A friend of mine already mentioned that I might be troubled by chromatic aberration and I was not aware that Stellina is using an ED refractor. eVscope is a Newtonian, maybe for that reason.

 

But even a small Newtonian will not fit on top of the CPC system which I intend to use as a GoTo system. So I will try to find a suitable ED refractor and use it together with a reducer.

 

Thank you!




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