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DSLR OUT...........CCD IN.


MARS1960
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Hi all, it's about time i made the jump to CCD imaging.

I have a limited budget and i will be wanting to stay with OSC for now.

I have seen a QHY8L for £600 or an Atik 314L plus for £450.

I will be using my ED80.

I understand the much smaller FOV with the atik, this isn't an issue as i still have a DSLR if i want to image the larger targets.

Are either of these substantially better than each other in IQ? will i need to buy anything else like field flatteners/reducers?

TIA.

Edited by MARS1960
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Hi 

I'd recommend the x0.85 FF/FR with the ED80 and the QHY8L - it's a great camera with very low noise - here are a couple of shots taken purely with the 8L from a dark(ish) site 

M42-QHY8L-RLD.thumb.jpg.1dac2563e348500f6b89408f5b9a82d1.jpg

M31-rld-2.thumb.jpg.f13f93d24424d6cd8dc88cb7a1e205b5.jpg

Edited by RichLD
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15 minutes ago, RichLD said:

Hi 

I'd recommend the x0.85 FF/FR with the ED80 and the QHY8L - it's a great camera with very low noise - here are a couple of shots taken purely with the 8L from a dark(ish) site 

M42-QHY8L-RLD.thumb.jpg.1dac2563e348500f6b89408f5b9a82d1.jpg

M31-rld-2.thumb.jpg.f13f93d24424d6cd8dc88cb7a1e205b5.jpg

Very nice those Rich.  I'm beginning to wish i'd never asked, decisions decisions :undecided:.

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For info.  What duration of exposures are we talking about with those images @RichLD   ?   They are spectacularly good.  I have recently  acquired a QHY 8 pro and have yet to stretch it's legs. These are so good they give me goose bumps.

@MARS1960 One thing to think about is that a smaller FOV will probably amplfy any guiding or mount issues.  Have a look at the potential targets that you may want to image and see how many can be bagged by your present scope(s).

This is a good resource.   ( http://www.blackwaterskies.co.uk/imaging-toolbox/  )

 

Edited by Craney
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5 minutes ago, Craney said:

 

@MARS1960 One thing to think about is that a smaller FOV will probably amplfy any guiding or mount issues.  

 

 

No, there's no connection between FOV and guiding precision. The connection is between pixel scale and guiding precision. In a given scope, the smaller the pixels the better you need to guide. A small chip does not 'get you closer' than a large one as is sometimes assumed.

Olly

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14 minutes ago, Craney said:

For info.  What duration of exposures are we talking about with those images @RichLD   ?   They are spectacularly good.  I have recently  acquired a QHY 8 pro and have yet to stretch it's legs. These are so good they give me goose bumps.

@MARS1960 One thing to think about is that a smaller FOV will probably amplfy any guiding or mount issues.  Have a look at the potential targets that you may want to image and see how many can be bagged by your present scope(s).

This is a good resource.   ( http://www.blackwaterskies.co.uk/imaging-toolbox/  )

 

Mmm, yeah that's one of my concerns.

I have bought the Atik, the HEQ5 should be here mid next week and i'm now seeking out guide/finder scopes and cameras, think i'll just go with a 9x50 finder with an SPC 900 attached and use PHD2.

Thx for the link, i'll take a look.

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17 minutes ago, Craney said:

What duration of exposures are we talking about with those images @RichLD

Thanks for the kind words! M42 was around 1.5 hrs in 600s, 300s and 60s subs to try and capture the DR of the object. The M31 is 10 x 600.

Rich

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9 minutes ago, ollypenrice said:

No, there's no connection between FOV and guiding precision. The connection is between pixel scale and guiding precision. In a given scope, the smaller the pixels the better you need to guide. A small chip does not 'get you closer' than a large one as is sometimes assumed.

Olly

The struggle is real. I've been having the same dilemma lately. I love my Canon for having a local storage and no need for a laptop in the field (as I usually go to a dark site and am battery operated), but I upgraded my mounts and am thinking of gathering Ha data from my lightpolluted garden. 

I'm looking at the ZWO ASI (currently I'm thinking about the 1600 MM pro, but the 294 mc pro has the edge when I choose a color camera over a filter wheel).

But the more I look into it, the more I get lost. 

I've looked into that calculator too, both give me a "green" reading, but I still don't know what way to go or what will make the ultimate argument. 

 

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2 hours ago, MARS1960 said:

Hi all, it's about time i made the jump to CCD imaging.

I have a limited budget and i will be wanting to stay with OSC for now.

I have seen a QHY8L for £600 or an Atik 314L plus for £450.

I will be using my ED80.

I understand the much smaller FOV with the atik, this isn't an issue as i still have a DSLR if i want to image the larger targets.

Are either of these substantially better than each other in IQ? will i need to buy anything else like field flatteners/reducers?

TIA.

The 8L all the way. The sensor on the Atik is tiny, whereas the 8L uses a DSLR sensor (same as used in some older Nikon DSLRs if I recall correctly).  Just check that the DIN cable fits snugly...it's a heavy old cable to have hanging off that port.

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9 minutes ago, Zakalwe said:

The 8L all the way. The sensor on the Atik is tiny, whereas the 8L uses a DSLR sensor (same as used in some older Nikon DSLRs if I recall correctly).  Just check that the DIN cable fits snugly...it's a heavy old cable to have hanging off that port.

Thanks, i've just bought the Atik lol.

But heyho, it is going to be used for those small planetary nebula and clusters etc.

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41 minutes ago, ollypenrice said:

No, there's no connection between FOV and guiding precision. The connection is between pixel scale and guiding precision. In a given scope, the smaller the pixels the better you need to guide. A small chip does not 'get you closer' than a large one as is sometimes assumed.

Olly

Thanks for the correction.    

I always thought that if I was imaging with same guide cameraand guide scope, then any mount corrections applied would appear as bigger movements in the final image on the imaging camera with the smaller field of view. ie  1 sec of arc etc will be a bigger proportion of the final image.

I need to sit down with a pencil, a note pad  and a whiskey and think some more about this.

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You have just bought an ATIK..... !!!....  

I needed a stiff drink after buying the 414ex mono.   ...  but in fairness, not cheap but it has been an absolutely fantastic camera, and it still keeps on giving me those 'wow' moments.  It worked straight out of the box, even with a complete numptie like myself in charge of it.

I hope you get a lot of satisfaction from the purchase, and enjoy the firewater as well.

 

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1 hour ago, Craney said:

Thanks for the correction.    

I always thought that if I was imaging with same guide cameraand guide scope, then any mount corrections applied would appear as bigger movements in the final image on the imaging camera with the smaller field of view. ie  1 sec of arc etc will be a bigger proportion of the final image.

I need to sit down with a pencil, a note pad  and a whiskey and think some more about this.

The best way to think about it, I believe, is this: a given scope will project an image of a certain size in mm onto whatever chip you put in there. Now, how big are the pixels of your chip? The smaller they are, the more pixels the chip puts under the projected image, meaning the resolution improves (if the seeing and guiding support it.) The more resolution you are aiming for, the better your guiding needs to be.

Olly

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On 04/11/2018 at 16:34, ollypenrice said:

No, there's no connection between FOV and guiding precision. The connection is between pixel scale and guiding precision. In a given scope, the smaller the pixels the better you need to guide. A small chip does not 'get you closer' than a large one as is sometimes assumed.

Olly

Hi Olly, can you expand on that as I struggle to get these types of things in my head..I understand that in this situation that the qhy8 has the larger fov and won't make the target any bigger  but struggle with pixel scale and guiding, is it you're looking for guiding at half your pixel scale of the the particular setup? How do you find this out,or is there a equation to use?

As another question while we're on the same subject  the atik 314 and 4284ex has the same sensor size but the 428 has smaller pixels, will that give better resoution or does the 428ex need better guiding to achieve that resolution?  

Edited by newbie alert
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39 minutes ago, newbie alert said:

Hi Olly, can you expand on that as I struggle to get these types of things in my head..I understand that in this situation that the qhy8 has the larger fov and won't make the target any bigger  but struggle with pixel scale and guiding, is it you're looking for guiding at half your pixel scale of the the particular setup? How do you find this out,or is there a equation to use?

As another question while we're on the same subject  the atik 314 and 4284ex has the same sensor size but the 428 has smaller pixels, will that give better resoution or does the 428ex need better guiding to achieve that resolution?  

No problem. Let's start at the beginning with the important idea of what 'full size' means when we present an image on screen. It means that one pixel on your camera chip is given one pixel on your PC screen. Unless your chip is very small this means you won't be able to see all the image at once on the screen. You'll need to move the image around on the screen to 'visit' all of it. The image file name will be followed by '100%' in Photoshop. Keep this definition of 'full size' or '100%' in your mind for what follows.

Next we imagine shooting M27 in the same scope but with two cameras, camera A and camera B. They have the same chip size but camera A has 9 micron pixels (large) and camera B has 4.5 micron pixels (small.) The projected image from the scope as it lands on these chips is identical but camera A puts only a quarter as many pixels under this projected image as camera B. (Camera B has twice as many across and twice as many up and down so 4 times as many altogether.)

Now think about these two images presented at full size or 100% on you PC screen. Camera B's image is going to be 4x bigger by area on the PC than camera A's image because it will need 4x as many screen pixels. Not only will it be bigger but it can carry more details (with a caveat to follow.)

So two things determine the final size of an image and the detail it can carry. 1) The size of the object's image projected by the scope. This is entirely determined by focal length and nothing else. 2) The number of pixels onto which the same image is projected. This is entirely down to pixel size and nothing else.

Finally let's take two cameras with the same size pixels but different chip sizes (say the Atik 4000 and the Atik 11000. The 4000 has the same size pixels but a smaller chip.) We try these cameras in just one scope on M27 again. M27 will fill the frame in the 4000 but be sitting in a wide field of stars in the 11000. However, M27's projected image is landing on precisely the same number of pixels in both cases so, seen at full size, M27 will be identical in both cameras, both in size and in detail resolved. Many newcomers mistakenly believe that the M27 filling the frame is somehow more 'zoomed in on' than the one in the wider starfield. It isn't. All that's happened is that your PC is fitting the images to your PC screen size, showing one at, say, 100% and the other only at 66%.

The caveat is that three other things limit your workable resolution. 1) The atmospheric seeing. 2) Your guiding. 3) The optical resolution of your telescope. (You cannot use an ever tinier scope with ever tinier pixels and hope to match the resolution of a larger scope because tiny scopes can't resolve enough detail optically. However small scopes with small pixels can, in many cases, rival bigger scopes remarkably well, as I hope I demonstrated in a recent Astronomy Now article.

You can use an online calculator like this to find your imaging pixel scale. http://www.12dstring.me.uk/fov.htm PHD lets you key in your guider FL and guide cam pixel scale after which your guide RMS will be in arcseconds. If your guide RMS is half or less than your imaging pixel scale you should be OK.

Hope that's helpful.

Olly

 

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On 04/11/2018 at 15:04, RichLD said:

Hi 

I'd recommend the x0.85 FF/FR with the ED80 and the QHY8L - it's a great camera with very low noise - here are a couple of shots taken purely with the 8L from a dark(ish) site 

Holy cow, Rich.  For OSC and relatively limited data that M42 is insanely good.  Bravo, Sir!

(M31 isn't so shabby either, mind).

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19 minutes ago, ollypenrice said:

No problem. Let's start at the beginning with the important idea of what 'full size' means when we present an image on screen. It means that one pixel on your camera chip is given one pixel on your PC screen. Unless your chip is very small this means you won't be able to see all the image at once on the screen. You'll need to move the image around on the screen to 'visit' all of it. The image file name will be followed by '100%' in Photoshop. Keep this definition of 'full size' or '100%' in your mind for what follows.

Next we imagine shooting M27 in the same scope but with two cameras, camera A and camera B. They have the same chip size but camera A has 9 micron pixels (large) and camera B has 4.5 micron pixels (small.) The projected image from the scope as it lands on these chips is identical but camera A puts only a quarter as many pixels under this projected image as camera B. (Camera B has twice as many across and twice as many up and down so 4 times as many altogether.)

Now think about these two images presented at full size or 100% on you PC screen. Camera B's image is going to be 4x bigger by area on the PC than camera A's image because it will need 4x as many screen pixels. Not only will it be bigger but it can carry more details (with a caveat to follow.)

So two things determine the final size of an image and the detail it can carry. 1) The size of the object's image projected by the scope. This is entirely determined by focal length and nothing else. 2) The number of pixels onto which the same image is projected. This is entirely down to pixel size and nothing else.

Finally let's take two cameras with the same size pixels but different chip sizes (say the Atik 4000 and the Atik 11000. The 4000 has the same size pixels but a smaller chip.) We try these cameras in just one scope on M27 again. M27 will fill the frame in the 4000 but be sitting in a wide field of stars in the 11000. However, M27's projected image is landing on precisely the same number of pixels in both cases so, seen at full size, M27 will be identical in both cameras, both in size and in detail resolved. Many newcomers mistakenly believe that the M27 filling the frame is somehow more 'zoomed in on' than the one in the wider starfield. It isn't. All that's happened is that your PC is fitting the images to your PC screen size, showing one at, say, 100% and the other only at 66%.

The caveat is that three other things limit your workable resolution. 1) The atmospheric seeing. 2) Your guiding. 3) The optical resolution of your telescope. (You cannot use an ever tinier scope with ever tinier pixels and hope to match the resolution of a larger scope because tiny scopes can't resolve enough detail optically. However small scopes with small pixels can, in many cases, rival bigger scopes remarkably well, as I hope I demonstrated in a recent Astronomy Now article.

You can use an online calculator like this to find your imaging pixel scale. http://www.12dstring.me.uk/fov.htm PHD lets you key in your guider FL and guide cam pixel scale after which your guide RMS will be in arcseconds. If your guide RMS is half or less than your imaging pixel scale you should be OK.

Hope that's helpful.

Olly

 

Very nicely explained.  You could have been a teacher ?

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30 minutes ago, ollypenrice said:

No problem. Let's start at the beginning with the important idea of what 'full size' means when we present an image on screen. It means that one pixel on your camera chip is given one pixel on your PC screen. Unless your chip is very small this means you won't be able to see all the image at once on the screen. You'll need to move the image around on the screen to 'visit' all of it. The image file name will be followed by '100%' in Photoshop. Keep this definition of 'full size' or '100%' in your mind for what follows.

Next we imagine shooting M27 in the same scope but with two cameras, camera A and camera B. They have the same chip size but camera A has 9 micron pixels (large) and camera B has 4.5 micron pixels (small.) The projected image from the scope as it lands on these chips is identical but camera A puts only a quarter as many pixels under this projected image as camera B. (Camera B has twice as many across and twice as many up and down so 4 times as many altogether.)

Now think about these two images presented at full size or 100% on you PC screen. Camera B's image is going to be 4x bigger by area on the PC than camera A's image because it will need 4x as many screen pixels. Not only will it be bigger but it can carry more details (with a caveat to follow.)

So two things determine the final size of an image and the detail it can carry. 1) The size of the object's image projected by the scope. This is entirely determined by focal length and nothing else. 2) The number of pixels onto which the same image is projected. This is entirely down to pixel size and nothing else.

Finally let's take two cameras with the same size pixels but different chip sizes (say the Atik 4000 and the Atik 11000. The 4000 has the same size pixels but a smaller chip.) We try these cameras in just one scope on M27 again. M27 will fill the frame in the 4000 but be sitting in a wide field of stars in the 11000. However, M27's projected image is landing on precisely the same number of pixels in both cases so, seen at full size, M27 will be identical in both cameras, both in size and in detail resolved. Many newcomers mistakenly believe that the M27 filling the frame is somehow more 'zoomed in on' than the one in the wider starfield. It isn't. All that's happened is that your PC is fitting the images to your PC screen size, showing one at, say, 100% and the other only at 66%.

The caveat is that three other things limit your workable resolution. 1) The atmospheric seeing. 2) Your guiding. 3) The optical resolution of your telescope. (You cannot use an ever tinier scope with ever tinier pixels and hope to match the resolution of a larger scope because tiny scopes can't resolve enough detail optically. However small scopes with small pixels can, in many cases, rival bigger scopes remarkably well, as I hope I demonstrated in a recent Astronomy Now article.

You can use an online calculator like this to find your imaging pixel scale. http://www.12dstring.me.uk/fov.htm PHD lets you key in your guider FL and guide cam pixel scale after which your guide RMS will be in arcseconds. If your guide RMS is half or less than your imaging pixel scale you should be OK.

Hope that's helpful.

Olly

 

As ever superbly well explained..thanks very much once again

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1 hour ago, RayD said:

Holy cow, Rich.  For OSC and relatively limited data that M42 is insanely good.  Bravo, Sir!

(M31 isn't so shabby either, mind).

You're too kind sir, many thanks! Yes, good skies make all the difference with OSC I find - I also suspect that the QHY8L is a good match for the ED80.

TBH it was a pig to process though ?

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