#81  
Old 09-12-2009, 10:26 PM
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People have been telling me the sbig has 2 stage cooling but the web site says single stage cooling. How can it achieve -40delta cooling with a single stage tec? I believe the colder these KAF chips are the better the perform.
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  #82  
Old 09-12-2009, 10:29 PM
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Originally Posted by AlexN View Post
As do I mwahahha!!!
Alex I am sure you try another 4 or 5 cameras before Christmas .

Mark
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  #83  
Old 10-12-2009, 06:04 AM
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Quote:
Originally Posted by Peter Ward View Post
The number of active pixels defines how many pixels end up in the image. The rest are used for engineering purposes and are rather moot.

KAF8300's are an 8.3 megapixel sensor. I look forward to seeing one sometime shortly after Christmas
This is true, but they are very useable (at least in the monochrome version). There are 40 extra rows and 40 extra columns outside the defined Active Area which according to Kodak docs:

"These pixels are light sensitive but they are not tested for defects and non-uniformities. The response of these pixels will not be uniform."

Flat-fielding takes care of the non-uniformities.

Terry
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  #84  
Old 10-12-2009, 08:41 AM
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I downloaded a single frame dark frame (fits file) from QHY forums. Fits dark frame had dimensions of 3584 x 2574 pixels = 9225216 pixels = 9.2 MegaPixels.

I don't understand how the dark frame fits file I downloaded has more pixels than the image sensor's total pixels? Can someone shed light on this for me please?

Edit - one thing I can see from the raw dark frame is exactly how many pixels are usable at least. The active area is defined, then I can see the area Terry is talking about (55 columns, no rows), as these pixels are brighter than the rest, but still capturing data. There are pixels near the edge that are either black or just single columns that would not be usable.

From a rough calculation I see approx 3425 x 2569 usable pixels (with the use of a flat frame) = 8.8 MP

I got the dark frame fits file from this page.

Last edited by Kal; 10-12-2009 at 09:17 AM.
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  #85  
Old 10-12-2009, 09:39 AM
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3584*2574=9225216
9225216/1024/1024=8.79 MP.

3544*2534=8980496
8980496/1024/1024=8.56 MP.

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Humayun
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  #86  
Old 10-12-2009, 10:06 AM
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Originally Posted by Octane View Post
3584*2574=9225216
9225216/1024/1024=8.79 MP.

3544*2534=8980496
8980496/1024/1024=8.56 MP.

Regards,
Humayun
You aren't converting bits to bytes, so mega is a pure representation of 1 million. Therefore 1 million pixels = 1MP, there is no conversion that needs to be done.

That is why on the specifications for the CCD it states:

Active pixels: 3326*2504(8.3mega pixel) 3326x2504= 8328304 = 8.3MP
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  #87  
Old 10-12-2009, 12:14 PM
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Woops, you're right. :blush:

Pre-breakfast posting!

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Humayun
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  #88  
Old 12-12-2009, 11:17 PM
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Kal my frames are 3326 x 2504 which is equal to 8328304 or 8.3 mega pixels. Darks are the same as are flats and bias frames.
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  #89  
Old 12-12-2009, 11:35 PM
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Originally Posted by Tandum View Post
People have been telling me the sbig has 2 stage cooling but the web site says single stage cooling. How can it achieve -40delta cooling with a single stage tec? I believe the colder these KAF chips are the better the perform.

I missed this post earlier..

They are a single stage TEC as the website says. -40c Δ is not difficult to achieve with a single stage TEC depending on the power consumption of the element. A sufficiently power hungry single stage TEC could achieve almost any ΔT. However I think manufacturers of astro CCD's have to stick with lower power TECs in order to reduce both electrical noise, and power consumption of the camera.. Sure it would be nice to achieve -60C Δ T, but if it required 12v 10A to do it you probably wouldnt be so impressed..

Dark frames I've seen from a few different KAF8300 based cameras seem to indicate that anything below -10c gives very acceptable results, and anything much lower than -20c seems to make little difference.. I've seen dark frames from the ML8300, QHY9, Apogee U8300M and QSI583 at varying temps from 0c to -30c...
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Old 13-12-2009, 03:11 PM
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Originally Posted by AlexN View Post
I missed this post earlier..

They are a single stage TEC as the website says. -40c Δ is not difficult to achieve with a single stage TEC depending on the power consumption of the element. A sufficiently power hungry single stage TEC could achieve almost any ΔT. However I think manufacturers of astro CCD's have to stick with lower power TECs in order to reduce both electrical noise, and power consumption of the camera.. Sure it would be nice to achieve -60C Δ T, but if it required 12v 10A to do it you probably wouldnt be so impressed..

Dark frames I've seen from a few different KAF8300 based cameras seem to indicate that anything below -10c gives very acceptable results, and anything much lower than -20c seems to make little difference.. I've seen dark frames from the ML8300, QHY9, Apogee U8300M and QSI583 at varying temps from 0c to -30c...
Yeah -20C sounds about right Alex. It would be interesting to see your power settings to achieve this with a single peltier though. Last night was about 20c and Maxim showed camera temp at -20C and power settings varying between 58 -61% on my QHY9.

Mark
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  #91  
Old 13-12-2009, 05:01 PM
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Originally Posted by Paul Haese View Post
Kal my frames are 3326 x 2504 which is equal to 8328304 or 8.3 mega pixels. Darks are the same as are flats and bias frames.
OK, thanks for that info Paul. The fits I downloaded from QHY with higher res must be from a pre-release driver or something where Qui didn't discard the edge data, which probably explains how it came out to too many MP in the first place.
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  #92  
Old 13-12-2009, 07:01 PM
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Mark, I would assume the ST8300 would be at 85~90% power to achieve that sort of delta temp.. Pure speculation obviously but I'll let you know as soon as I do!
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  #93  
Old 27-12-2009, 10:44 PM
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Looks like a few SBIG 8300 have hit the ground in the States. This is an interesting thread for those who were quick enough to bag the QHY9 in it's early days with a few teething problems. Just a quick look at this thread looks like SBIG might have a few problems to overcome as well.


http://www.cloudynights.com/ubbthrea.../o/all/fpart/1
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  #94  
Old 27-12-2009, 11:22 PM
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Just a quick look at this thread looks like SBIG might have a few problems to overcome as well.....
I'd put it down to user error.
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  #95  
Old 27-12-2009, 11:30 PM
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I'd put it down to user error.
The next thing will be that it's a faulty camera. Come on Peter, how hard is it to take a dark frame. It appears he managed to take darks with a DSLR.

From memory I didn't have this sort of problem with the QHY9 but it seemed very correct for some to post very old teething problems we had with the original QHY9. Whats more the problems which were experienced were all fixed here in Australia without loss of warranty.
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  #96  
Old 27-12-2009, 11:35 PM
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Hey Doug, He was taking darks through a thin plastic 2" cap on the end of the nose piece in a fully illuminated room... Those plastic caps, they are not light proof...

I had a near on identical looking dark frame from my ST10 when I did the exact same thing, thinking that the cap would be enough considering the camera had a shutter.. Not the case... I then put the camera into my scope and took darks with the metal cap on the scope - problem solved...
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  #97  
Old 27-12-2009, 11:43 PM
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I might add, upon reading the most recent post by the original poster, he took darks in a dark environment and the problem was solved..
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  #98  
Old 27-12-2009, 11:49 PM
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Originally Posted by AlexN View Post
Hey Doug, He was taking darks through a thin plastic 2" cap on the end of the nose piece in a fully illuminated room... Those plastic caps, they are not light proof...

I had a near on identical looking dark frame from my ST10 when I did the exact same thing, thinking that the cap would be enough considering the camera had a shutter.. Not the case... I then put the camera into my scope and took darks with the metal cap on the scope - problem solved...
You are making a lot of assumptions there Alex. He states only that the camera was cooled with the shutter closed and the camera covered. At no point does he mention a plastc cover. Assuming it was a plastic cover the light patern would likely be something other than a straight line away fom the edge of the frame.

You were certanly quick enough to cast up teething problems with he QHY9 dating back to when it was released. And just as quick to make excuses in this case.

Let see what happens, I can take daks in a fully lit room with the qy8pro covered properly and I would assume hat this gentleman has sed a DSLR and would know how to take a dark. But you never know.
The ST is adverised as having a shutter for taking Dark Frames???
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  #99  
Old 27-12-2009, 11:51 PM
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i might add, upon reading the most recent post by the original poster, he took darks in a dark environment and the problem was solved..

sounds like a light leak to me
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  #100  
Old 28-12-2009, 12:03 AM
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Believe it or not. Astro cameras are designed to be used in the dark... Shutters in astro cameras are not generally designed to be 100% light proof, come to think of it, I don't think there is a way you could make a 100% light proof shutter that could operate at high speed..
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