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Old 17-07-2009, 12:48 PM
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Which Astro Camera to Buy

I am looking to upgrade my Canon 300D to something that can take longer exposures with less noise.

My budget is limited to around $1000.00 for a camera.

So far, I have narrowed the choice down to the new Atik 16IC Cooled Astro Camera and The Canon 40D DSLR.

I guess my main questions are:

1. Will the 40D enable long exposures with low noise. 10 minutes would be great but 20 minutes even better.

2. Would resampling the images taken with a 40D to a smaller size remove most of the noise.

3. Would I be better off getting the cooled Atik, even though it has a smaller chip and lower resolution. The Atik should be capable of 20 min exposures with no noise.

I am leaning towards the Atik, as it is a dedicated astro camera and also has an autoguider port for later use as an autoguider if need be.

Cheers,
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Old 17-07-2009, 01:12 PM
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Originally Posted by Astrobserver99 View Post
I am looking to upgrade my Canon 300D to something that can take longer exposures with less noise.

My budget is limited to around $1000.00 for a camera.

So far, I have narrowed the choice down to the new Atik 16IC Cooled Astro Camera and The Canon 40D DSLR.

I guess my main questions are:

1. Will the 40D enable long exposures with low noise. 10 minutes would be great but 20 minutes even better.

2. Would resampling the images taken with a 40D to a smaller size remove most of the noise.

3. Would I be better off getting the cooled Atik, even though it has a smaller chip and lower resolution. The Atik should be capable of 20 min exposures with no noise.

I am leaning towards the Atik, as it is a dedicated astro camera and also has an autoguider port for later use as an autoguider if need be.

Cheers,
Hi Rob

I am certainly no expert, although i will throw in my tupence worth'

1. The 40D will let you do longer exposures with lower noise, this answer is based on a few points. firstly its a newer camera than the 300D, and i know its "quieter" as a result. 10 mins without noise on an unmodded DSLR just isnt gonna happen, in the winter, you can get away with a few minutes tops, especially if your gonna stack images, i have taken a 10 min exposure with my 1000D (i know its not the same camera) it was really noisey, so forget 20 mins for defo, and in the summer it will be even shorter, i am guessing 90 secs to 2 mins, although again this very much depends on ambient conditions, so no, i would forget 10 or 20 mins subs with an unmodded DSLR.


2. No. it wouldnt remove it, but it might make it harder to see, there really is no substitute for darks to remove noise, and even at that, depending on conditions you will will need several if stacking, people say you need a few darks for every few subs, TBH i have had my best results when taking MORE darks than subs, but its up to you


3. That Atik might well be able to do the exposure lenghts you desire, as i believe its peltier cooled, and a quick look around 'tinternet shows thats its a very well recieved product. Although using a CCD has its own pitfalls, one of them being a very steep learning curve, especially if its not the "one shot colour" type, and mono with filters. At the end of the day its buyers market and up to you, but i am sure our more learned members will chime in with more advice for you.


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Old 17-07-2009, 01:26 PM
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Thank you Duncan. If an unmodded DSLR is capable of around 2 min exposures, what would a modded DSLR be capable of?
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Old 17-07-2009, 01:35 PM
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Thank you Duncan. If an unmodded DSLR is capable of around 2 min exposures, what would a modded DSLR be capable of?

Hi Rob

have a look here

http://glogg.jupiter-io.net/300D/

The user shows before and after mod images, and before and after mod darks, the difference is quite impressive, he also has single 45mins subs, with his modded camera, i chose this one, as its your current camera.

hope this helps


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Old 17-07-2009, 01:54 PM
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The mods on this site look impressive, but I doubt there would be anyone in Australia willing to do such modifications. They look beyond the scope of an amateur.

Cheers,
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Old 17-07-2009, 02:01 PM
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The mods on this site look impressive, but I doubt there would be anyone in Australia willing to do such modifications. They look beyond the scope of an amateur.

Cheers,

probably right, but it all depends on the person, i work at a component level with hardware in the IT industry, and it doesnt look to difficult to me, Ultimate DSLR's have premoded and pre-cooled camera that you can buy, although they are a bit pricey. I only mention this, as i guess like me, your looking to get a lower SNR ratio, longer exposures with lower, or not much increase in noise, and the only way to do this ona DSLR is cooling, there are other methods of cooling, that are less effective, although every bit helps, i know there several members on here who have moded cameras, as for modding a DSLR with a peltier, that would be a hard, as the ones i have worked with where not the sturdiest of things.

Its swings and roundabout. but if your less bothered about appearance, then there are more options. I have a copper heatsink at home from a Radeon 4850 that i am tempted to crack onto the back of the sensor on my 1000D.

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Old 17-07-2009, 02:04 PM
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Originally Posted by Astrobserver99 View Post
Thank you Duncan. If an unmodded DSLR is capable of around 2 min exposures, what would a modded DSLR be capable of?
Just the same , the modification makes no diference to the cooling or lack of it. The fact that a DSLR generates heat during exposureis the main reason noise is created on the image.

Most modern DSLR's are capable of 5 minute exposures with ease but do require darks to be taken. You will need to take a good number of exposures and stack them to get the best result.

As to which camera? I would go for the new DSLR. It has a much bigger CCD/CMOS and is very capable of producing great images.
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Old 17-07-2009, 02:10 PM
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Good point Doug. I was thinking of a modded DSLR with cooling. Even with cooling, there will be greater heat on a DSLR chip than CCD Astro because of the larger chip...

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Originally Posted by Hagar View Post
Just the same , the modification makes no diference to the cooling or lack of it. The fact that a DSLR generates heat during exposureis the main reason noise is created on the image.

Most modern DSLR's are capable of 5 minute exposures with ease but do require darks to be taken. You will need to take a good number of exposures and stack them to get the best result.

As to which camera? I would go for the new DSLR. It has a much bigger CCD/CMOS and is very capable of producing great images.
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Old 17-07-2009, 02:21 PM
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Just the same , the modification makes no diference to the cooling or lack of it. The fact that a DSLR generates heat during exposureis the main reason noise is created on the image.

Most modern DSLR's are capable of 5 minute exposures with ease but do require darks to be taken. You will need to take a good number of exposures and stack them to get the best result.

As to which camera? I would go for the new DSLR. It has a much bigger CCD/CMOS and is very capable of producing great images.

Hi Doug

Please dont think me an idiot, but i am confused, how would a cooling mod make no difference to the cooling, or lack of it?

am i missing something?

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Old 17-07-2009, 03:17 PM
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OK, I'm probably going to upset some people here but...

WRT noise in astrophotography you have to understand that the noise apparent in a photo, or sub exposure comes from several different sources
  • Sensor noise (dark current, temperature and exposure time dependant)
  • Skyglow (always present, stronger during fuller phases of the moon)
  • Light pollution (depends on where you're taking the shots)
  • Read noise (always there, but varies from shot to shot)
  • Others that I've forgotten about for the minute
By far the greatest of these for long exposures in or around major population centres is ... Light pollution.

Unlike most of the other sources of noise, LP is not subtractable, nor does it behave like other random noise, in fact it is better classed as unwanted signal. This and this alone, within 50km of a major city in Australia limit your subs from a DSLR to maybe 5 minutes maximum. You'll not gain a great deal (if anything, you may lose S/N) by going longer.

So, what to do to combat this? You can move to a darker site, temporarily, like what Greg does with his dark sky site. This reduces the N part of the S/N calculation. LP filters also do this to an extent, but are less effective. Or you try to increase the Signal part of the S/N, by using a more sensitive sensor, again this is better at a dark sky site and LP filters can help when at home. Narrowband filters and a nice sensitive CCD makes a huge difference in and around the city.

So, which is better, a cooled CCD or a modded DSLR, I'd go for the CCD everytime.

There's a handy calculator to work out the optimum exposure time based on the CCD and your background levels from a test exposure at
http://starizona.com/acb/ccd/calc_ideal.aspx

It doesn't list DSLR's, but I think one of the QHY cameras has a similar type of OSC chip in it?

Cheers
Stuart
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Old 17-07-2009, 03:22 PM
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OK, I'm probably going to upset some people here but...


WRT noise in astrophotography you have to understand that the noise apparent in a photo, or sub exposure comes from several different sources
  • Sensor noise (dark current, temperature and exposure time dependant)
  • Skyglow (always present, stronger during fuller phases of the moon)
  • Light pollution (depends on where you're taking the shots)
  • Read noise (always there, but varies from shot to shot)
  • Others that I've forgotten about for the minute
By far the greatest of these for long exposures in or around major population centres is ... Light pollution.

Unlike most of the other sources of noise, LP is not subtractable, nor does it behave like other random noise, in fact it is better classed as unwanted signal. This and this alone, within 50km of a major city in Australia limit your subs from a DSLR to maybe 5 minutes maximum. You'll not gain a great deal (if anything, you may lose S/N) by going longer.

So, what to do to combat this? You can move to a darker site, temporarily, like what Greg does with his dark sky site. This reduces the N part of the S/N calculation. LP filters also do this to an extent, but are less effective. Or you try to increase the Signal part of the S/N, by using a more sensitive sensor, again this is better at a dark sky site and LP filters can help when at home. Narrowband filters and a nice sensitive CCD makes a huge difference in and around the city.

So, which is better, a cooled CCD or a modded DSLR, I'd go for the CCD everytime.

There's a handy calculator to work out the optimum exposure time based on the CCD and your background levels from a test exposure at
http://starizona.com/acb/ccd/calc_ideal.aspx

It doesn't list DSLR's, but I think one of the QHY cameras has a similar type of OSC chip in it?

Cheers
Stuart

You never upset anyone mate, and there is some good info there for sure, personally i would go with the CCD ... but i just tried to address the OP's points, and it seems to have detracted from that somewhat

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Old 17-07-2009, 03:35 PM
Hagar (Doug)
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Good point Doug. I was thinking of a modded DSLR with cooling. Even with cooling, there will be greater heat on a DSLR chip than CCD Astro because of the larger chip...
Now that is a diferent kettle of fish..... A cooled DSLR such as the Astro DSLR's from Central DS are way diferent from a standard DSLR and will allow exposures in the 20 minute range without problem. The thing to remember is that no cooling or camera really lets you go without taking calibration files also. My QHY8 has a cooling delta of about 45 degrees C and uses a Sony low noise CCD but still benifits greatly from Flats, darks and bias file calibration.

The big plus for the cooled DSLR is the processing already done by the camera. This can and does make the initial processing much easier. There was a 450D Astro DSLR for sale on this forum and can recommend these cameras. The results are very good. Paul Haese has used a Central DS cooled 40D and his results speak for themselves. It is a bit more than your budget but would serve you well as a great imaging camera.

http://www.iceinspace.com.au/forum/s...ad.php?t=46440

Good luck with your choice.
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Old 17-07-2009, 03:49 PM
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You never upset anyone mate, and there is some good info there for sure, personally i would go with the CCD ... but i just tried to address the OP's points, and it seems to have detracted from that somewhat

No I think the posts here represent discussion on the topic "which is better?" as the OP posted, also there was talk of noise, particularly in relation to camera noise. I was simply reminding people that although the camera contributes some noise (in some cases a lot of noise) it is not the only source of noise to contend with. Even with my ST-10 and a LP filter shooting at Zenith I can rarely go past 10 minutes unless I'm shooting narrowband. So as the OP (and others) have suggested, going to 20 minutes on a DSLR would be impossible from the 'burbs. So to pick a camera on the basis of lower noise over 20 minutes rather than five is ill advised for most people here.

Oh, and I do upset people here, mainly because I disagree with them from time to time...

Cheers
Stuart
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Old 17-07-2009, 09:27 PM
Hagar (Doug)
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Hi Doug

Please dont think me an idiot, but i am confused, how would a cooling mod make no difference to the cooling, or lack of it?

am i missing something?

I won't think you an idiot, you idiot. The original post was with reference to a Canon 40D DSLR and was not for a cooled DSLR. Read the original post again!
The reference to cooling was for an Aitik cooled CCD.

The Aitik 16 has a pretty small CCD at 782 X 582 pixels not even .5 of a megapixel.
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