QHY10 gain and offset settings someone know how to do it?


#1

Hello everyone.

I have like over a year my account but I didn’t post anything.

But today I have a question and I hope someone can answer me.

I just got from a friend a QHY10 OSC camera but I find out in the QHY website that I need to set up the Gain & Offset before use it.

QHY has an horrible program to do it but to be honest I don’t get nothing at all.

So, I was wonder if anybody here know how to do it in SGP!?

I try almost 2 weeks already and I start to give it up.

Please if somebody know how to do it please let me know.

Thanks you a lot to all for the time.

PS. Sorry for my English.


#2

Install the native and ASCOM drivers for the camera (as Administrator). Then select the camera in SGPro. Finally, click on the “settings” icon next to it. This will launch the QHY app and allow you to customize gain and offset to your liking.


#3

I did that already And SGP can see the camera. But I mean this:

I will copy and paste from the QHY website.

Set on the GAIN and OFFSET

GAIN is the pre-ADC programmable gain amplifier setting. OFFSET is the ADC voltage offset setting. The correct setting of OFFSET and GAIN can change the CCD’s system gain,to make the CCD output signal range match the ADC quantization range, so as to get the best dynamic range.

Suitable for most of the GAIN and OFFSET Settings:

1.Set the gain=0,set the exposure time to 0,cover the lens ,then shoot a BIAS frame.

2.Watch the local average value of the captured images(you can use the Noise Analyze function of EZCAP,image process->noise analyze).The ideal average value is around 500 to 1000.If the value is higher ,then you should reduce the OFFSET.If the value is lower ,then you should increase the OFFSET.Repeat steps 1-2 to obtain the ideal OFFSET value.

3.Open the lens cover,increase the exposure time ,then use the uniform light source to take a saturated exposure image.Watch the local average value of the captured images.If the value is less then 60000,you should increase the value of GAIN.If the value is 65535 ,you should reduce the value of GAIN. Repeat this step to obtain the appropriate GAIN value.

4.Under this GAIN value ,repeat steps 1-2 to obtain more accurate OFFSET value.

Note:For some QHYCCD products when you use bin modes of 22,33,4*4,images may reach 65535 even the gain is 0,so you just set the gain to 0.

Anyone has done this before on SGP?


#4

You had to do this with EZCAP. Terrible software. You must select Noise Analysis from the top menu as instructed.
I have setup my new QHY10 using this method apparently successfully but am getting poor results. I am hoping to get some expert help tomorrow from our club members. Will report back if they come up with a better system of calibration.
I ended up with setting of Gain 5 and Offset 117 but this varies with each camera but may be a good starting point for you. A club member with a QHY8 has had good results with Gain 5 and offset 120 so it seems in the ballpark.

Hope this helps a little.


#5

You can do this in SGP. You’ll need the Image Statistics window open. Connect the camera and cool it to your desired temperature. Once cooled, cover the camera opening and take a bias frame, or simple take a frame and focus exposure at 0 seconds. Look at the mean value in the Image Statistics window. You want that value to be between 500 and 1000. To adjust, click on the tools icon for the camera and adjust the offset. If the mean is below 500, adjust the offset up, and vice versa if the mean is above 1000. Keep taking images and adjusting until you get it set.

Once that is done, take the cap off of the camera and point it at a brightly lit wall and take a 5 second or so exposure. The idea here is to fully saturate the sensor. Look at the Image Statistics window and note the mean. You want that number to be between 60,000 and 65,535. If it is less than 60,000, turn the gain up, and if it is 65,535 (it will never be higher), turn the gain down. I like to shoot for about 63,000.

Once you have it set, check the offset again to make sure it hasn’t changed. If it has, repeat both steps.

Once you have them set, you never need to chance them.

Tim


#6

I meant to add that you want to make sure binning is 1x1 and that readout mode is normal.

Tim


#7

Just did this with my QHY11 in SGP, naturally :slight_smile:

The steps @spokeshave lists are exactly how it’s done. Just make sure to set your Gain = 0 when adjusting your offset in the first step. Also the “Tools” menu that is referred to is the settings icon for the camera next to the connect button. NOT the Camera Control Panel settings (just in case this was unclear)

Thanks,
Jared


#8

I have consulted our club members and despite following the manufacturers procedure my gain setting of 5 is too low. Our other club member with the QHY8 found the same and is now set at 17 for gain. It seems the Offset setup works as there is no light source involved. I was advised to ensure that full saturation occurs as “spokeshave” has mentioned. This was apparently the case when I followed instruction but clearly did not resulting in the correct setting. I may try a brighter light source today.


#9

After much trial and error. The recommended setup seems a bit hit and miss. Fortunately I found this link which explain why and how to setup the camera in detail.

http://www.astropixel.gr/uploads/7/8/3/5/7835053/scientifically_determining_ccd_gain_and_offset.pdf

The answer for all QHY10 users I think.

Hope this sort your problem too.


#10

spokeshave, I have this same CCD and have seen 2 different ways of setting gain. one place is telling me that the MAX should never hit above 65535, another is saying that the MEAN/average should be between the 60k and 65535.

guess I just want to make sure im setting the camera up correctly, and not sure which rule I should use… should I be adjusting gain based on the MEAN, or the MAX? (IE- is it ok that the max is hitting 65535 but the mean is below? or should it not be maxing out at 65535 at all?)

I appreciate any confirmation here! I am also seeing slightly different image stat values between SGP and EZCAP, not sure which one would be best to go by.


#11

I don’t think it really matters. The idea is to set the gain such that a saturated pixel maps to an ADU value of slightly less than 65535. Assuming that your exposure is long and bright enough to saturate the sensor, almost all of the pixels will be saturated with the exception of a very small number of very cold or dead pixels. You know that the max value represents the fully-saturated pixel output, so this is probably a good place to start. The mean should be very close to the same number. If it isn’t, it means that the exposure isn’t bright enough or that your sensor has a lot of dead pixels that are skewing the mean. So it is probably not a bad idea to look at both. Ideally, you want the gain set such that both the mean and max are close to, but no more than 65535. It is better to err on the low side than the high side. If your mean ends up at, say, 55000, you are still using 15.75 bits of the 16-bit image container and you can be certain that every pixel value gets a unique ADU value. On the other hand, if you err on the high side, you will get some pixels maxxed out at 65535, but you will have no idea how many are maxxed out, or by how much they are maxxed out.

Tim


#12

some of that is some what confusing to me still as im … new to the CCD imaging world. I think my exposure is long and bright enough, I was testing on a white wall from about a foot or so away, with a fluorescent light over head, I also tested about a foot away from a blank white computer monitor, (is that too bright?) and I was using 5 second exposure times.

ill double check my numbers, but with that type of exposure test that I just stated, if my mean is above 55000 and my max is hitting 65535, that should be sufficient? but the closer I can make the mean to the max the better? - so mean of 63000 and max of 65535 would be better than 55000/65535

thanks for your fast response, the help is appreciated!
-Tyler


#13

Tyler:

I’m sorry, I think I’m making something that is fairly simple into something more complex than it needs to be. The point is that you want the gain set such that virtually all of the pixels are close to 65535 without going over. If you have a couple of pixels that are “stuck on” or very hot, they will get to 65535 very quickly. That’s why you can typically ignore the max value as long as the mean or median are in the range you want. If both your median and mean are a few thousand ADU below 65535, you should be fine even if you have a max of 65535. Why don’t you take a test white shot and post your min, max, median and mean? That would help me understand how close you are.

Tim


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