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Should I worry about coma on fast newt and ASI183?

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#1 Jkaiser3000

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Posted 12 April 2021 - 05:33 PM

Hi,

 

I have the option of locally sourcing a used Orion 8” astrograph. The scope comes barebones: no coma corrector or collimator. I’m hoping to get into DSO imaging with it and plan on using an ASI183 camera so, should I worry about coma on such small sensor (compared to APS-C or full frame)? Is there any way I could simulate the appearance on an image? 
 

Maybe I should’ve started with this question but, is this scope a good option for starting in AP? It’ll be riding on a losmandy gm811 mount so that “should” be no problem. My reasoning was, it’s about the same price as a good 80mm refractor but, much faster and with a bit longer reach for smaller objects. That is, as long as I don’t need to account for a coma corrector lol.gif

 

So, thoughts on this?

 

thanks



#2 mashirts

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Posted 12 April 2021 - 05:41 PM

On their field if view calculator I match up the sensor diagonal view with an eypiece view and use an eyepiece to see what the sensor will see.

 

https://astronomy.to.../field_of_view/



#3 Jkaiser3000

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Posted 12 April 2021 - 06:12 PM

Thanks mashirts. I used that site extensively when I was deciding what camera to get and, still use it to drool at what I coulda, shoulda woulda got if money were no issue lol.gif

 

Sadly it doesn’t show what the effects of coma on such a fast scope are for a smallish sensor. I’d rather know before i spew out the 400 bucks for the scope wink.gif . I’m debating on whether I should get this scope or a small refractor. Decisions decisions, the bane for us geminis bawling.gif



#4 LuscombeFlyer

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Posted 12 April 2021 - 06:17 PM

I think the Orion 8" astrograph is an outstanding choice in its price range. Though I'd suggest you'll probably want to invest in a coma corrector as soon as the budget allows. But as you're just getting started in AP, you'll have other challenges to overcome before want of a coma corrector becomes the limiting factor.

Also, Stellarium will allow you to enter the specifics of your telescope and sensor to see pretty much exactly what the FOV will be



#5 Stelios

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Posted 12 April 2021 - 06:59 PM

aybe I should’ve started with this question but, is this scope a good option for starting in AP? It’ll be riding on a losmandy gm811 mount so that “should” be no problem. My reasoning was, it’s about the same price as a good 80mm refractor but, much faster and with a bit longer reach for smaller objects. That is, as long as I don’t need to account for a coma corrector lol.gif

 

IMO you will need collimation tools, a coma corrector, and possibly more (I don't know the exact scope you are getting, if it is an "astrograph" it *should* have an adequate focuser and rigid enough body (*should* is the operative word here). 

 

The scorned small ED refractor + flattener is simple and wonderful. Sometimes the common advice has it right.




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