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ZWO cameras and pixels, reducer and barlow

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#1 clarnibass

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Posted 16 July 2019 - 12:29 AM

Hi

 

I want to improve planetary photos and I'm going to buy a few things, including a ZWO camera. I tried Jupiter for the first time a few days ago with my APSC DSLR camera (see other thread if interested).

I read this very good article https://agenaastro.c...yers-guide.html

A few things are still confusing me...

 

For example, looking at the ASI178MC and ASI183MC. The article marks the former as best for planetary and the second as best for DS and ok for planetary. Both have 2.4 pixels. They have approx 6MP and 20MP respectively. The sensor of the former is obviously smaller. Using a x2 barlow on the latter gives roughly the same frame. They have 60FPS and 19FPS at max resolution respectively. The ASI183 specs list lower resolutions at faster FPS, but I'm not sure if this is binning or cropping.

 

At max resolution on both, would 60FPS vs 19FPS make a very significant difference? If I understand, pixels on target would be the same. The 183 would just have a lot more sky around it (waste basically).

 

Some of the advantages of a camera like the ASI183 could come later, when I try some DS objects or anything that would gain from the higher resolution and larger sensor.

I'm trying to understand if there are disadvantages that I'm missing for using the ASI183 and not the ASI178, ignoring the higher price and the 2" vs. 1.25" mounts.

 

Maybe the ASI183 would just give the same results, so the ASI178 would be better, and when I decide to try DSO later, I should get a camera that would be better for that. Better than the ASI183, or my ASPC and FF DSLRs?

 

I'm using these models as examples that I think best illustrate what I'm trying to figure out.

 

FWIW my telescope is a Meade SCT 8" 2000mm.

 

Thank you



#2 Tulloch

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Posted 16 July 2019 - 01:09 AM

Hi there, most people use the ASI224 or 290 cameras for planetary imaging (mind you, I'm still using my Canon DSLR smile.gif ). They are small sensors so will not be so good for large DSOs.

 

Have a look at what is possible using these cameras here and here , and a series of excellent videos for how to take planetary images here.

 

Hope this helps

 

Andrew


Edited by Tulloch, 16 July 2019 - 01:13 AM.


#3 Stelios

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Posted 16 July 2019 - 01:39 AM

For DSO, you want a *cooled* camera. So you would want the ASI183MC-Pro. *BUT*, that's assuming you understand the mono vs color tradeoffs and other features/issues of the ASI183. NOT something to rush into while just trying to image Jupiter smile.gif  There are many alternatives for DSO, and you need to match well to your equipment (the ASI183 would *not* match well with the Meade *for DSO*).

 

For planetary you want the ASI224MC or ASI290MC as already recommended, or the slightly larger sensor of the ASI385MC. You do NOT need the cooled versions. 

 

Check the ZWO Camera Comparison page. Note that ZWO gives only the three cameras listed above 5 stars for planetary. They should know wink.gif  The most important thing for planets is frame rate. You need to get as many frames as you can in the relatively short time before the planet rotates and hides some features. 



#4 clarnibass

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Posted 16 July 2019 - 04:10 AM

Thanks. The ZWO chart is helpful but I'm still confused about something... it is the "why". Leaving the 183 out of this (seems no real or any advantage for planets over the 178), I'm comparing the 178, 385, 290 and 224 (all MC since I'm not getting a mono camera for now).

 

The 178 has a couple of differences such as 14 bit and IR-CUT which I don't know how much if any difference these would make.

The others have a much higher frame rate at full resolution (120FPS to 170FPS). The 178 has more pixels on the target. A question is whether using lower resolution crops the sensor (I assume that is what it means?). If that's the case, I can use cropped mode, for example 2048×1080 at 116fp and still get "more pixels on the target". However this is at 10 bit. 14 bit is half the frame rate.

The 385 and 224 pixels are pretty much the same as my APSC DSLR, but of course in video the DSLR uses the entire frame for 1920x1080.

The 290 has even higher frame rate and smaller pixels (so more pixels on the target).

 

What I know from using many DSLRs with various sensor sizes and resolutions, more pixels on target sometimes mean better and sometimes not. A photo from my ASPC at 24MP is significantly better than the FF camera if cropped to ASPC Size at 10MP. However the difference is less than exactly x2.4 better because the result from the FF camera sensor is better. I don't know what the technical reason for this but it's as if the pixels are "better" (because they are bigger or whatever reason).

 

So... how do I know what resolution, sensor and pixel size, frame rate, etc. would give the best overall results with my telescope?

 

I'd like to get the "best for me" right now and add another camera if/when I start with DS (I'd need an equatorial mount first anyway). Best for me is within budget (which all of these are) and less hassle (which for now means the MC models). Anything up to approx $700 is ok.

 

Thanks again


Edited by clarnibass, 16 July 2019 - 04:17 AM.


#5 Tulloch

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Posted 16 July 2019 - 05:09 AM

Hi there, it can be confusing at first. Have a look at this video, it will help answer your questions. Once you've watched this one, have a look at some of the others in the series.

https://www.youtube....h?v=4CEJVSkayYw

 

Also, your questions would be better asked on the solar system imaging forum here

https://www.cloudyni...ing-processing/

 

Forget all you know about imaging with a DSLR, planetary imaging with a ZWO camera is a completely different ballgame smile.gif . Nearly all the advanced planetary imagers use either 224 or 290 cameras on their 14"+ telescopes.

 

Good luck.

 

Andrew

 



#6 Tulloch

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Posted 16 July 2019 - 05:15 AM

Also, read this thread, take special note of the Kokatha Man's reply #9. He is an expert in this field, and has forgotten more about creating amazing planetary images than you and I will ever know.

 

https://www.cloudyni...lp-appreciated/

 

Andrew




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