Hi
It would be helpful if you could tell me what my camera's gain and offset are.
Would you be able to tell me where I can find this information?
Thank you |
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Maybe this will help. See page 10. It will also depend on the capture software you use. Microsoft Word - QHY9 CCD camera user guide.doc |
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Gain is an amplification of the original signal, like a volume control. Your camera will have a range of gain settings, it's up to you to choose what the best one depending on camera performance and your needs.
The easiest way to think about offset is a shifting of the entire histogram to the right. It controls what the lowest black value can be. If it's not set correctly you'll clip useful data at the far left edge of the histogram. Because of the random nature of signal you want to have enough padding there so that you don't loose data
Keep in mind that all of these adjustments will change things like read noise and dynamic range. Take the time to study the performance curves for your camera and learn what each of the curves represent.
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Bob Lockwood:
Maybe this will help. See page 10. It will also depend on the capture software you use.
Microsoft Word - QHY9 CCD camera user guide.doc Thanks Bob and sorry fot the delay. I know this doc.
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Tony Gondola:
Gain is an amplification of the original signal, like a volume control. Your camera will have a range of gain settings, it's up to you to choose what the best one depending on camera performance and your needs.
The easiest way to think about offset is a shifting of the entire histogram to the right. It controls what the lowest black value can be. If it's not set correctly you'll clip useful data at the far left edge of the histogram. Because of the random nature of signal you want to have enough padding there so that you don't loose data
Keep in mind that all of these adjustments will change things like read noise and dynamic range. Take the time to study the performance curves for your camera and learn what each of the curves represent. Thanks Tony. I'm looking for a method to know what gain is the optim to my Qhy9.
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I couldn't find the performance curves for this camera so I can't say anything specific. It is a CCD the the CMOS rules we mostly talk about here don't apply. Read noise is high so you'll want to make longer sub-exposures. There are calculators for this but I would guess that 300 to 600 sec. would work well. Try that at gain zero and see what you get. Take a close look at the left edge of your histogram and make sure you're not clipping the shadows. If you are you'll need to increase offset, 100 would be a good starting point as this seems to be a common number used with similar cameras.
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The QHY9 was/is powered by a Kodak KAF8300 sensor. The basic gain setting is at around unity gain, as typical for CCD cameras. Read-out noise is typically high at 16e rms (at zero gain) and so is thermal signal. Using MaximDL or similar programs of the CCD era should allow setting the gain and offset. The full datasheet of the sensor is here: APPLICATION NOTE |
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Gain along with ISO does not increase or decrease the sensitivity of the chip/pixels. That can not be altered. Instead, it alters the number of levels/steps needed to reach saturation. There for an increase in gain decreases the full well depth. Here is an excellent article explaining this: cloudbreakoptics.com/blogs/news/astrophotography-pixel-by-pixel-part-3Since the QHY9 uses the CCD Kodak 8300 chip, there will more likely be no gain or offset adjustment. As far as know, all CCD chips gain was set by the manufacture. There is no need to worry about gain settings with CCD. Connect and expose. The 8300 had low QE by today's standards. It was around 50%. It was also fairly noisy and will require good dark frame substraction. It was very popular in its day, and in my openion why CMOS was so celebrated. On the other hand' Sony CCD chips such as the ICX694AL & ICX814AL (3.67 nm pix, read noise of 3e) have performance close ,in my openion, to today's CMOS, such as my IMX571. Accept for size. Lynn K.
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andrea tasselli:
The QHY9 was/is powered by a Kodak KAF8300 sensor. The basic gain setting is at around unity gain, as typical for CCD cameras. Read-out noise is typically high at 16e rms (at zero gain) and so is thermal signal. Using MaximDL or similar programs of the CCD era should allow setting the gain and offset. The full datasheet of the sensor is here:
APPLICATION NThanks Andrea. |
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Lynn K:
Gain along with ISO does not increase or decrease the sensitivity of the chip/pixels. That can not be altered. Instead, it alters the number of levels/steps needed to reach saturation. There for an increase in gain decreases the full well depth.
Here is an excellent article explaining this:
cloudbreakoptics.com/blogs/news/astrophotography-pixel-by-pixel-part-3
Since the QHY9 uses the CCD Kodak 8300 chip, there will more likely be no gain or offset adjustment. As far as know, all CCD chips gain was set by the manufacture.
There is no need to worry about gain settings with CCD. Connect and expose. The 8300 had low QE by today's standards. It was around 50%. It was also fairly noisy and will require good dark frame substraction. It was very popular in its day, and in my openion why CMOS was so celebrated. On the other hand' Sony CCD chips such as the ICX694AL & ICX814AL (3.67 nm pix, read noise of 3e) have performance close ,in my openion, to today's CMOS, such as my IMX571. Accept for size.
Lynn K. Thanks Lynn
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