ZWO Camera comparison

[Maideneer]

I have a 224MC that I've been using but little birdies have been telling me all over the place that a different camera may be in order since I am just starting my journey with my new C9.25 HD scope.  Someone advised I should use the 224 as my guide cam for use with an OAG.

So I start to compare cams and I have almost no idea what I'm looking at (I'm not a technological person, it's like hieroglyphics to me), even though I've watched countless Youtube tutorials on what does what.  I'll put it this way, if it were YOU...what camera would you get (for technical reasons with a 9.25HD, not cost)?  I've included a comparison chart below displaying cooled cams, it seems that's the most popular route but I may be wrong too.

 

 

Edited July 26, 2021 by Maideneer

[AstroMuni]

What are you proposing to use the C9.25 HD for - planets or DSO?

Have you tried using https://astronomy.tools/calculators/field_of_view/  to find out what kind of images you will get within your FOV? Then you can decide whether you need a camera with a bigger sensor or 224mc is good enough.

If its DSO's you are after ,then you will need to look for cameras with a bigger sensor as your scope has a large focal length. Then depending on your budget you could go for a cooled or uncooled version of camera.

Edited July 26, 2021 by AstroMuni

[Davey-T]

You need something with decent sized pixels to achieve a reasonable image scale, images can be binned although it works better with mono cameras.

I use an Atik 314L that has 6.4um pixels and bin those with 10"SCT.

At the top of this page under resources there is a calculator where you can enter your scope and camera to see what image scale it will give, to see if it's under / over sampled.

Dave

[Maideneer]

5 minutes ago, AstroMuni said:

What are you proposing to use the C9.25 HD for - planets or DSO?

Sorry I always forget that teensie little detail when asking questions!  For now, mainly planets but I really would like to shoot the odd DSO target every now and again and by that I mean nothing complex.  I don't wanna spend 4 days capturing data if you get my drift.  I just eventually want the usuals - M31 (I know my scope will be too much FL), M16, M45 you get the idea.

[Maideneer]

13 minutes ago, Davey-T said:

You need something with decent sized pixels to achieve a reasonable image scale, images can be binned although it works better with mono cameras.

I use an Atik 314L that has 6.4um pixels and bin those with 10"SCT.

At the top of this page under resources there is a calculator where you can enter your scope and camera to see what image scale it will give, to see if it's under / over sampled.

Dave

And that's my trouble, when someone says 'decent sized pixels'...I have trouble processing what that means because it's a relative term.  I'll try the calculator, thank you!

[AstroMuni]

3 minutes ago, Maideneer said:

For now, mainly planets but I really would like to shoot the odd DSO target

Then the FOV of the ASI224mc with your scope should be sufficient. And its brilliant at DSOs as well (esp the types you are looking for). I use the same camera so can vouch for it with DSOs. See the link in my signature of my journey. I dont have a lovely scope like yours but still managed to get decent images. As mentioned above use the FOV calculator and be the judge

[Davey-T]

This from Astronomy tools, using .63 reducer and binning gets somewhere near a good sampling rate but as above given the FOV of your scope your current camera is fine.

Dave

[Maideneer]

7 minutes ago, AstroMuni said:

Then the FOV of the ASI224mc with your scope should be sufficient. And its brilliant at DSOs as well (esp the types you are looking for). I use the same camera so can vouch for it with DSOs. See the link in my signature of my journey. I dont have a lovely scope like yours but still managed to get decent images. As mentioned above use the FOV calculator and be the judge

[Maideneer]

14 minutes ago, Davey-T said:

This from Astronomy tools, using .63 reducer and binning gets somewhere near a good sampling rate but as above given the FOV of your scope your current camera is fine.

Dave

I have the Edge HD (or will)...does that make a difference over the regular SCT?  Also, I'll be using the .7 reducer

Edited July 26, 2021 by Maideneer

[The Lazy Astronomer]

11 minutes ago, Maideneer said:

And that's my trouble, when someone says 'decent sized pixels'...I have trouble processing what that means because it's a relative term.  I'll try the calculator, thank you!

To help point you in the right direction: the atmosphere will limit the resolution it's possible to obtain with long-exposure DSO imaging. It's generally accepted that the resolution limit for most people is 1"/px (in reality, it's likely to be quite a bit higher, but let's take the best case of 1"/px for now).  To achieve 1"/px with your scope at its native focal length you'd want pixels of ~11um. If you used the 0.7x reducer, then you'd want pixels of ~8um. Smaller pixels than that will just lead to oversampling - that is, you won't be capturing any finer detail (because your resolution is limited by the atmosphere), rather, you'll just be spreading the detail out over more pixels. Also, attempting deep sky imaging as a beginner* with such a long focal length will be PAINFUL.

However, all that sampling nonsense above goes out of the window for very short exposure planetary imaging. You are no longer as limited by the atmosphere as you're using exposures of tens of milliseconds rather than several minutes. A general rule of thumb for a decent sampling rate for planetary is to take your focal ratio and divide by between 5 and 7 - this will give you an ideal pixel size in um. Note that high resolution planetary imaging is usually done at very long focal lengths, so ditch the reducer and go for a 2x or 3x Barlow instead. If you used a 2x Barlow, this would give you an f ratio of 20, divide that by 7, and you'd be looking at wanting pixels of ~2.9um. Note also that cooled cameras are not needed for planetary.

*I assume you're new to this, apologies if not. 

[Maideneer]

3 minutes ago, The Lazy Astronomer said:

To help point you in the right direction: the atmosphere will limit the resolution it's possible to obtain with long-exposure DSO imaging. It's generally accepted that the resolution limit for most people is 1"/px (in reality, it's likely to be quite a bit higher, but let's take the best case of 1"/px for now).  To achieve 1"/px with your scope at its native focal length you'd want pixels of ~11um. If you used the 0.7x reducer, then you'd want pixels of ~8um. Smaller pixels than that will just lead to oversampling - that is, you won't be capturing any finer detail (because your resolution is limited by the atmosphere), rather, you'll just be spreading the detail out over more pixels. Also, attempting deep sky imaging as a beginner* with such a long focal length will be PAINFUL.

However, all that sampling nonsense above goes out of the window for very short exposure planetary imaging. You are no longer as limited by the atmosphere as you're using exposures of tens of milliseconds rather than several minutes. A general rule of thumb for a decent sampling rate for planetary is to take your focal ratio and divide by between 5 and 7 - this will give you an ideal pixel size in um. Note that high resolution planetary imaging is usually done at very long focal lengths, so ditch the reducer and go for a 2x or 3x Barlow instead. If you used a 2x Barlow, this would give you an f ratio of 20, divide that by 7, and you'd be looking at wanting pixels of ~2.9um. Note also that cooled cameras are not needed for planetary.

*I assume you're new to this, apologies if not. 

Def new to the explanation you provided lol, cheers!

[vlaiv]

Camera that you have - ASI224 is one of the best planetary cameras out there.

Planetary imaging is very different to regular imaging as it consists of taking video with very short exposure - like 5-6ms exposures at high gain and then processing that video in special way.

ASI224 has 3.75µm and that means that you want around F/15. You'll need x1.5 barlow with your scope (as it is F/10) for best resolution.

There is actual equation that gives you optimum F/ratio for given pixel size as far as planetary imaging goes.

For long exposure imaging, well, yes, since you are using long FL instrument - you'll probably need to bin your pixels. To answer original question, with 9.25 EdgeHD scope, if money was not issue, I would choose ASI6200 mono with filters. I would not use reducer with this combination.

[Maideneer]

4 minutes ago, vlaiv said:

Camera that you have - ASI224 is one of the best planetary cameras out there.

Planetary imaging is very different to regular imaging as it consists of taking video with very short exposure - like 5-6ms exposures at high gain and then processing that video in special way.

ASI224 has 3.75µm and that means that you want around F/15. You'll need x1.5 barlow with your scope (as it is F/10) for best resolution.

There is actual equation that gives you optimum F/ratio for given pixel size as far as planetary imaging goes.

For long exposure imaging, well, yes, since you are using long FL instrument - you'll probably need to bin your pixels. To answer original question, with 9.25 EdgeHD scope, if money was not issue, I would choose ASI6200 mono with filters. I would not use reducer with this combination.

I have a 3x Barlow but more than happy to pick up a 1.5 if that would suit it best.  lol at the ZWO price - it's the same amount the Edge cost haha.  Maybe in future years when I get good at what I am doing!

[vlaiv]

2 minutes ago, Maideneer said:

lol at the ZWO price - it's the same amount the Edge cost haha.  Maybe in future years when I get good at what I am doing!

Are you referring to 6200? Well - it is in your comparison table and EdgeHD has about 42mm of corrected and illuminated circle - so it would be waste not to use full frame sensor on it.

You can get smaller camera, but I think you'll be happier with both shorter FL scope and smaller camera as combination.

If you want very decent starting setup - why not go for 150PDS coupled with decent coma corrector and 4/3 size camera like ASI294? These are all relatively cheap items that fit nicely together.

Yellow is 150PDS + 294 camera - more FOV - fits more targets better - no need to worry about binning - just use super pixel mode for debayering and you'll be spot on.

[Maideneer]

1 hour ago, vlaiv said:

Camera that you have - ASI224 is one of the best planetary cameras out there.

Planetary imaging is very different to regular imaging as it consists of taking video with very short exposure - like 5-6ms exposures at high gain and then processing that video in special way.

ASI224 has 3.75µm and that means that you want around F/15. You'll need x1.5 barlow with your scope (as it is F/10) for best resolution.

There is actual equation that gives you optimum F/ratio for given pixel size as far as planetary imaging goes.

For long exposure imaging, well, yes, since you are using long FL instrument - you'll probably need to bin your pixels. To answer original question, with 9.25 EdgeHD scope, if money was not issue, I would choose ASI6200 mono with filters. I would not use reducer with this combination.

Can you suggest a 1.5x barlow for this scope model?  Not sure if those are so common as the other ones.

[vlaiv]

41 minutes ago, Maideneer said:

Can you suggest a 1.5x barlow for this scope model?  Not sure if those are so common as the other ones.

Any barlow that has removable barlow element will work as x1.5 barlow if you get correct distance (closer to sensor - smaller magnification - further away from sensor - larger magnification).

If you want the best barlow out there - look at Baader VIP barlow. If not - then even something like this:

https://www.firstlightoptics.com/barlows/baader-classic-q-225x-barlow.html

will do.

GSO made x2 barlow that had removable 1.25" element with filter thread - you can use one of those as well.

[The Lazy Astronomer]

25 minutes ago, Maideneer said:

Can you suggest a 1.5x barlow for this scope model?  Not sure if those are so common as the other ones.

You could just stick with your 3x one for now. It would give you a sampling rate of ~0.11"/px, which is pretty much right on the limit of what's possible, so you'd need excellent conditions to take full advantage of it, but I assume you could just bin/downsample in post processing software (in the same way you can with deep sky images) if the conditions on the night didn't support the very high resolution.

The disclaimer here is I've never actually tried software binning planetary images - it may be that it doesn't give you the same benefits as doing it on DSO images... maybe someone cleverer then l can confirm. 

[Shimrod]

12 hours ago, Maideneer said:

I have a 224MC that I've been using but little birdies have been telling me all over the place that a different camera may be in order since I am just starting my journey with my new C9.25 HD scope.  Someone advised I should use the 224 as my guide cam for use with an OAG.

So I start to compare cams and I have almost no idea what I'm looking at (I'm not a technological person, it's like hieroglyphics to me), even though I've watched countless Youtube tutorials on what does what.  I'll put it this way, if it were YOU...what camera would you get (for technical reasons with a 9.25HD, not cost)?  I've included a comparison chart below displaying cooled cams, it seems that's the most popular route but I may be wrong too.

 

I was one of those birdies! And this was in a conversation about guiding - with the suggestion that the ASI224 was retained for guiding duties. If you want to do DSO you are still going to need something for guiding, so from my perspective it would make more sense to get an imaging camera with a larger sensor if you can afford it. With a small sensor you will face challenges getting the target on sensor, although you may be planning on using plate solving software to deal with that.

[Maideneer]

27 minutes ago, Shimrod said:

I was one of those birdies! And this was in a conversation about guiding - with the suggestion that the ASI224 was retained for guiding duties. If you want to do DSO you are still going to need something for guiding, so from my perspective it would make more sense to get an imaging camera with a larger sensor if you can afford it. With a small sensor you will face challenges getting the target on sensor, although you may be planning on using plate solving software to deal with that.

I feel like I talk to so many people I don't remember who said what anymore!  That's what dad brain does to someone I guess.  So I think what I'm going to do here is get my new scope setup, learn the thing first visually and then see what is and isn't possible on the 224 and then make a determination on guiding and imaging cam.

And I have to learn what plate solving is haha and how software can accomplish that.

[vlaiv]

10 hours ago, The Lazy Astronomer said:

You could just stick with your 3x one for now. It would give you a sampling rate of ~0.11"/px, which is pretty much right on the limit of what's possible, so you'd need excellent conditions to take full advantage of it, but I assume you could just bin/downsample in post processing software (in the same way you can with deep sky images) if the conditions on the night didn't support the very high resolution.

The disclaimer here is I've never actually tried software binning planetary images - it may be that it doesn't give you the same benefits as doing it on DSO images... maybe someone cleverer then l can confirm. 

Problem with oversampling is down to read noise.

With F/30 and 3.75µm pixel size one really over samples by factor of x2. That spreads the light more and effect of read noise becomes more important. If you bin to get to actual resolution - you put 4 pixels together and that makes final sample have 4 "dozes" of read noise.

Only difference between one long exposure and bunch of short exposures is in read noise and since in planetary imaging we keep exposure very short to freeze the seeing (at about 5-6 milliseconds) - stack is very sensitive to level of read noise. That is why ASI224 is good camera in the first place - it has lowest read noise of the bunch.

[AstroMuni]

11 hours ago, vlaiv said:

If you want the best barlow out there - look at Baader VIP barlow. If not - then even something like this:

https://www.firstlightoptics.com/barlows/baader-classic-q-225x-barlow.html

+1 to that. I have the Q225x 🙂

Edited July 27, 2021 by AstroMuni

[ollypenrice]

It would be well worth stepping right back from the fine details and camera specifics to understand a small number of underlying concepts. Get these clear in your mind first, then get into the specifics. That's the only way to avoid buying the wrong kit. 

Long focal length means small field of view and potentially higher resolution of detail. Planets are small, lots of deep sky objects are vast.

Fast focal ratio means shorter exposure time but only compare focal ratios when the focal lengths are the same or very similar.

Rough guide to pixel sizes:  small pixels, 3 micron or less. Large pixels 7 micron or more. They are getting smaller, especially with CMOS cameras.

Sampling rate: how much sky area lands on each pixel. More sky per pixel means more light/faster exposure but less resolution of detail. Unit is arcseconds (of sky) per pixel. For deep sky imaging, below about 1 arcsecond per pixel the seeing (atmospheric blurring) will kill finer detail. Above about 3.5"PP stars risk looking blocky and pixelated.

High resolution (arising from long focal length and/or small pixels) requires more accurate guiding and more accurate focus and better seeing, so is more difficult. So imaging at 1 arcsec per pixel is much more demanding than imaging at 3.5 arcsecs per pixel.

Olly

[vlaiv]

3 hours ago, ollypenrice said:

Above about 3.5"PP stars risk looking blocky and pixelated.

Why is everyone constantly saying this? I'm yet to see blocky and pixelated star.

Here, this is 5"/px:

Are any of these stars blocky and pixelated?

[ollypenrice]

1 hour ago, vlaiv said:

Why is everyone constantly saying this? I'm yet to see blocky and pixelated star.

Here, this is 5"/px:

Are any of these stars blocky and pixelated?

I say it because in the image below, Tak Baby Q with reducer and Atik 4000 CCD, I had to blur the stars. The reducer took the system beyond 3.5"PP and the stars were certainly blocky. The image was undersampled and did not meet my house standard, if you like. It depends on other factors, too. You may get some natural blurring from the seeing, small stars may be worse affected than large, and so on. I like to be able to present images at 100% (ie full size) and beyond 3.5"PP I cannot do that to my own satisfaction. This is based on many years of imaging. Larger stars sort themselves out, as you demonstrate. I find that smaller ones don't.

Olly

[david_taurus83]

2 hours ago, vlaiv said:

Why is everyone constantly saying this? I'm yet to see blocky and pixelated star.

Here, this is 5"/px:

Are any of these stars blocky and pixelated?

Tbf vlaiv, there's a few square stars in there if you peep!😆