OSC Purchase

[peeb61]

Folks,

I'm thinking of purchasing a OSC CMOS cooled camera to take images through my 1000mm F/L MN190.

Been onto Bintel asking about the ZWO ASI183MC Pro Cooled Camera which I thought was a decent price, They said it would be 'camera is good, You are slightly over sampling but nothing Major.'

What is oversampling? And what will the drawbacks be?

Many thanks in advance.

Paul

[Nikolas]

Depends on the type of telescope you are using.
https://www.cloudynights.com/topic/300919-undersampled-oversampling-an-image/

[Wavytone]

If you can wait for a new model, the one I'd buy for that scope is the ZWO ASI533, slightly larger square sensor and larger pixels, should be a good match.

[Startrek]

Paul
Sampling in general terms is how well your image train can resolve levels of detail in objects at various atmospheric conditions using a specific pixel matrix on the camera sensor via your focal length / focal ratio
To see if your over sampled or under sampled you need to work out your image scale or pixel scale of your image train ( telescope and camera )
Formula for image scale or pixel scale (P) expressed in arc sec per pixel is -
P= pixel size of your imaging camera ( in microns uM ) x 206.3 divided by your telescopes focal length in mm

Over sampling is < 1.0 arc sec / pixel
Under sampling is > 2.0 arc sec / pixel
In good seeing conditions 0.80 to 1.0 arc sec/ pixel is OK stars will be round and sharp
In average to poor seeing conditions 0.80 to 1.0 arc sec/ pixel will produce slightly fuzzy or bloated stars
It’s most cases and conditions is probably better to be slightly over sampled or around the 0.80 to 1.20 arc sec per pixel mark ( but not critical as atmospheric conditions vary so much )
NB: DSLR’s are generally only useful in telescopes with focal lengths less than 1200mm or > 0.80 arc sec per pixel

Hope the above answers your question about sampling

[gregbradley]

Nice summary Martin.

Greg.

[doppler]

Here is a handy calculator
http://astronomy.tools/calculators/ccd_suitability
Rick

[peeb61]

Thanks Nikolas, using the scope mentioned in my post! Interesting reading on the CN link you gave me, many thanks.



Had a look at that, looks interesting and competitively priced! Looking for something a little bit more than 9 mp, I'm using a QHY8L at the moment running at 6Mp, images are good but feeling I could a little better with overall resolution? Do you think I'm asking too much? Does it matter?



Certainly does help Martin...so the ZWO ASI183MC Pro with 2.4um will give me 0.5 resolution and will oversample because of the cell size but the ZWO ASI533 with 3.76um will give me 0.78 which would be better? So the bigger the um will give me a better match? Forgive me if I have it a bit mixed up! :lol:

I have to agree with Greg, great summary!





Rick, thanks for this, really helped!

[Nikolas]

If the images are undersampled then use drizzle to fix the blockiness. Drizzling is really a good tool to use if you do it right

[Atmos]

Paul, having a imaging resolution around 0.8”/pixel is good. You ideally want to try to get your stars to be, under average seeing, 3 pixels across.

[peeb61]

Thanks Colin for your valued input, never thought buying a new camera would end in migraines! LOL!

Been looking at the ZWO ASI533 because of the 0.78 size or ASI294MC Pro which is close to 0.95, I know you can't comment and I respect that but would any of these be best suited to my setup?...Hypothetically?

Many thanks
Paul

[Startrek]

Paul
The next question is what do you want to image ?

Moon and Planets
Or
Deep Sky objects ( clusters , galaxies , Nebula etc )

The ASI1533 ISC Camera maybe more suited for planetary imaging at only 9 megapixel and it has a very small sensor size

If you want to image DSO’s the following cameras maybe more suitable -
ASI1294MC sensor size 19mm x 13mm Resolution 11.7 megapixel Pixel size 4.63uM
ASI 071MC sensor size 23mm x 15mm Resolution 16 megapixel Pixel size 4.78uM

Both these cameras will achieve sampling rates of around 0.90 arc sec per pixel at your focal length of 1000mm ie: slightly over sampled

The ASI183MC is another option but at a pixel size of only 2.4uM you would be way over sampled at your focal length of 1000mm ( not a wise option, more suited to a shorter focal length telescope )

Choices , choices but in the end it’s what you can afford

In the end for DSO imaging some of the specs to look for is a pixel size to get you slightly over sampled for your focal length 0.80 to 1.20 arc sec per pixel , medium to large size sensor , high ADC bit say 14bit or 16bit and a high QE 80% or higher

Hope some others can chime in who know a lot more than me about dedicated Astro cooled OSC cameras

Good Luck

[peeb61]

Thanks Martin yet again! :thumbsup:

Deep sky objects is my aim and hopefully my outcome. At the moment I'm using a QHY8L with a 7.8uM and seems to match my scope well? I was just after an upgrade, newer technology, more MPs etc. So confusing, but its all starting to come together, I think it was the Bintel email that has thrown me or woke me up to the fact that there's more than just picking a camera and away you go, the valued answers in this post has certainly opened my eyes big time.
At a 1000mm F/L my imaging scope is proving a little bit on the tricky side to make this the right choice to get it right and what you have added has made it more clearer and I thank you for that.

I will look at the ASI1294MC and read up a bit more on the reviews and look at some of the images this camera is taking, it will give me some indication on its performance and hopefully find someone with a setup close to mine. Who knows my prime imaging scope may change and it may be better suited to the newer one with a shorter F/L.

Many thanks Martin!

[The_bluester]

I have an ASI294MC Pro. I think it is a good beginning OSC but they have some issues in flat fielding. You generally need to shoot lots of subs to smooth out the background to let you stretch data really hard to find it, but they seem to have an incurable colour cast around the edges. Very carefully shot and processed flats help but I have not found anyone who has eliminated the issue altogether. Cooling issues on that chip seem to be the cause most often thought of.

There seem to be some interesting new cams on the roadmap for next year. I am thinking of heading down the mono road but the microlens diffraction issue in all the cams with the same chip as the ASI1600 would really irritate me and I think 20,000 electron wells are a bit shy. I am sitting tight to see how some of the new stuff performs in the wild before I update.

I think the ASI294 is OK as a beginners to intermediate OSC cam and probably a great EAA camera.

[peeb61]

Thanks Paul, I think you have a strong and valid point, maybe I should wait as well and see what appears on the horizon as well.

Paul

[peeb61]

Thanks all for your input to this post, I have gone and put an order in for a ZWO ASI071MC.

Will be looking forward to the day it arrives.

Thanks again.

Paul

[The_bluester]

Have fun. And 071 would probably actually be a better match for the scope I am using now that my 294, but with enough subs shot, drizzle processing recovers the star shapes pretty well.

[peeb61]

From a Paul to a Paul,

Many thanks! :thumbsup:

[ChrisV]

You'll love it. A great camera!