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New camera for EAA- which way to go?

CMOS EAA dso equipment imaging
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13 replies to this topic

#1 GazingOli

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Posted 17 September 2020 - 07:55 AM

Hello EAA connaisseurs,

 

I am planning to purchase an additional camera. Actually I was heading for an ASI 533 but an alternative came to my mind which could be advantageous.

 

My scopes are a C8 and a custom apo 80/480. With the C8 I am using a 6.3 reducer.

 

The alternative to just buying an ASI 533 would be:

 

- get a Starizona Night Owl reducer 0.4 for the C8

- get a reducer 0.79 for the apo refractor

- buy an ASI 178 instead of the ASI 533

 

The money spent is about the same. The advange would be that I get faster scopes. The FOV would be about the same.

 

Anything I oversaw? What would you think is the better way to go?

 

CS.Oli


Edited by GazingOli, 17 September 2020 - 08:01 AM.


#2 MrRoberts

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Posted 17 September 2020 - 08:31 AM

Bought my 294MC earlier this year due to its larger pixels and have not looked back. Although not cooled, the shorter exposer times (<30s) seem to negate some otherwise negatives. I will have to let others chime in on your thoughts on choices as I have had no experiences with other asi units. From what I've seen from others there is no doubt that if you ever want to try longer exposer ap the cooled units are the way to go.



#3 jprideaux

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Posted 17 September 2020 - 09:04 AM

The night-owl gives a 16mm imaging circle which pairs nice with the 16mm diagonal of the ASI533.  The ASI178 only has about a 9mm diagonal.   So one question to ask yourself is if you ULTIMATELY want to get both a night-owl AND and an ASI533 (or other larger diagonal camera)?  If you do, then purchasing a ASI178 might be a bit of a waste unless you want the smaller pixel size for smaller objects.  

The ASI178 has a bit bigger diagonal (but smaller pixels) than the ASI224 (but not as big of a diagonal as the ASI533).  


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#4 garyhawkins

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Posted 17 September 2020 - 09:34 AM

Hi Oli,

 

If you're going to stick solely with EAA then your second option looks good.  However, the Night Owl may not be available for a while - I know it's out-of-stock in the US and is not expected back anytime soon.

 

As you know I have the 533MC.  I purchased this in case I decide a little astro might be fun, or I wanted to play around with narrowband EAA that requires longer exposures.  It's a nice camera, and I'm very pleased with it - the imaging circle matches well with a C8/0.63 combination.

 

That being said, currently I don't have a second piggy back scope. I must admit the one failing with my current system is the ability to do wide field EAA.  Bigger targets are just out of reach, but I figure there are plenty of smaller ones to keep me busy :).

 

CS Gary


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#5 GazingOli

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Posted 17 September 2020 - 12:29 PM

Thanks for your advice. The AND is not an option at the moment. And with my CPC longer exposures are not in reach unless I purchase a wedge which I do not intend to. So I might end up with version 2... we will see. I am not really in a hurry. EAA just started for me and there is a lot I can do with what I have.

 

Tonight I will start testing with high gain...

 

Gary, a scope with a shorter focal length is a nice thing but I must admit that I use the C8 more than the Olifractor at the moment. However with a bigger sensor I could also observe the big nebulae which I cannot at the moment.

 

CS.Oli



#6 alphatripleplus

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Posted 17 September 2020 - 03:50 PM

As you have a small sensor camera, you could try using your existing f/6.3 reducer with the refractor - I do this and use about 0.8x focal reduction, taking the ST80 from f/5 to f/4. Of course, the SCT reducer is not designed for this purpose, and the flattening aspect of the reducer is designed for a f/10 SCT, not a f/5 refractor. However, with a small 1/3 inch sensor, there are no additional aberrations visible to me when reducing from f/5 to f/4 on my 80mm achromat. For a bigger sensor, I doubt it would work out well.

 

If you want to try this experiment, you will probably need an adapter that takes SCT  threads on one end, and converts to whatever threads are on the back of your refractor.


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#7 mikenoname

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Posted 17 September 2020 - 04:00 PM

Oli,

 

If you haven't already, I would highly recommend you run these different combinations you are considering through the Astronomy Tools site to compare FOV, image scale, resolution etc.

 

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

 

That should provide some insight.



#8 GazingOli

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Posted 17 September 2020 - 06:55 PM

Interesting idea to try the Celestron FR on the apo refractor. That would - in my case - mean to get from 2" SC thread to 2" filter thread and back. Instead I got a 0.5x FR from a friend for testing. It goes into the 1,25" nose piece of the camera.

 

ASI533vsASI174wReducers.jpg

 

CS.Oli


Edited by GazingOli, 17 September 2020 - 06:58 PM.


#9 alphatripleplus

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Posted 17 September 2020 - 08:42 PM

Interesting idea to try the Celestron FR on the apo refractor. That would - in my case - mean to get from 2" SC thread to 2" filter thread and back. Instead I got a 0.5x FR from a friend for testing. It goes into the 1,25" nose piece of the camera.

 

attachicon.gifASI533vsASI174wReducers.jpg

 

CS.Oli

I have tried both the f/6.3 SCT reducer and a 0.5x 1.25inch reducer with my 80mm f/5 ST80. The issue with the 0.5x reducer is that this reducer has a pretty short focal length, which means I get too much focal reduction unless the reducer is very close to the camera sensor. If I place my 0.5x reducer at the end of a 1.25inch nosepiece, I get almost the full 0.5x reduction taking my f/5 achro to f/2.5, which is too much in terms of the induced aberrations.

 

In order to get a 0.8x reduction factor to f/4 with my ST80, the 0.5x reducer must be placed much closer to the camera than the end of a 1.25inch nosepiece - unless you have a really, really short nosepiece.



#10 GazingOli

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Posted 17 September 2020 - 08:59 PM

so, if I use the 0.5 FR on my 80/480 apo at the nosepiece of the ASI camera I would get f/3. I remember I tried this once and noticed very strong halos around the stars... I want to try it again and use a IR/UV cut filter... you think this might help?

 

I got a set of adaptors which might work to get the FR right to the housing of the camera. I will figure it out and post photos and detailed infos on the type of adaptors if it works.

 

CS.Oli



#11 GazingOli

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Posted 17 September 2020 - 09:54 PM

ok, I figured out a way to get the reducer closest to the sensor:

 

reducer1DSC03304.jpg

 

reducer2.jpg

 

reducer3.jpg

 

Link to the TS adaptor: https://www.teleskop...ow-profile.html

 

CS.Oli


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#12 GazingOli

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Posted 17 September 2020 - 10:00 PM

As for the original question:

 

if this cheap FR works well I will probably use it and buy the ASI 178 - saves a lot of money smile.gif

My main issue is to get more FOV for the 80/480 apo. The C8 is mainly for small objects where I will only use the .63 reducer, if any.

 

CS.Oli


Edited by GazingOli, 17 September 2020 - 10:09 PM.


#13 GazingOli

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Posted 19 September 2020 - 04:31 AM

I had the chance to test the effect of the reducer last night:

 

VglNGC6888OlifraktorReducer.jpg

 

seems to be a reasonable factor - no halos on the stars no more. Thank you Errol for the tip where to place the reducer!

 

CS.Oli


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#14 GazingOli

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Posted 19 September 2020 - 05:02 AM

As for the original question

 

this would mean that with the ASI533 the image scale would be (and also is with the ASI224) 2.31 arcsec per pixel, which is undersampling which is to be avoided.

 

Means that I should anyway purchase a camera with 2.4 micron pixels makes an image scale of 1.47 arcsec per pixels.

 

-> ASI178, ASI183

 

BUT these are probably not a good match for the C8 ... and sometimes it would be nice to have a little more FOV at the C8 for the ease of software alignment for stacking.

 

CS.Oli




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