thutchison
Active member
Hi all:
I have been using PI for some time, but I have been using a CMOS camera that did not include an overscan area. I recently purchased a QHY600m camera that does include overscan. I am confused by the ImageCalibration process as it applies to overscan. I have combed through the other articles on this forum, but I am still quite confused.
The definition of the overscan area is a trivial matter. I completely understand how to define the image area and the overscan area(s). My area of confusion is in the procedure for using it.
With my prior camera, I took no bias frames. I took dark frames, flat frames, and flat dark frames. The dark and flat darks were integrated separately without calibration into master_dark and master_flat_dark images. The master_flat_dark image was used in ImageCalibration with the flat frames to create a master_flat_frame. The master_dark and master_flat were used in ImageCalibration for the light frames. "Calibrate" remained unchecked in all cases, as did optimize on darks because of glow in the sensor.
The QHY600m includes the overscan area and suggests that it should be used to combat bias drift. My questions are many, but include the following:
1. Should bias frames be taken rather than using flat dark frames and building a master_flat_dark?
2. Should I calibrate each set of calibration images (bias, dark, flat) using the overscan area separately, or should I integrate the calibration images as before and only select the "overscan area" option when calibrating the lights? If each should be done separately, I believe that PI will truncate (remove) the overscan areas from the output image, in this case the master... frames? Would this not cause an issue when attempting to calibrate the light frames (incorrect geometry)?
It would seem to me that the correct procedure would be to integrate the bias, dark, and flat frames without calibration and, when integrating lights, select the overscan area and select "calibrate" for each, allowing PI to subtract the average value of the overscan area from each respective master before calibrating the masters with each other and subsequently, the lights. I'm not sure if I have this correct and would GREATLY appreciate any assistance that can be offered.
Thank you.
Tim.
I have been using PI for some time, but I have been using a CMOS camera that did not include an overscan area. I recently purchased a QHY600m camera that does include overscan. I am confused by the ImageCalibration process as it applies to overscan. I have combed through the other articles on this forum, but I am still quite confused.
The definition of the overscan area is a trivial matter. I completely understand how to define the image area and the overscan area(s). My area of confusion is in the procedure for using it.
With my prior camera, I took no bias frames. I took dark frames, flat frames, and flat dark frames. The dark and flat darks were integrated separately without calibration into master_dark and master_flat_dark images. The master_flat_dark image was used in ImageCalibration with the flat frames to create a master_flat_frame. The master_dark and master_flat were used in ImageCalibration for the light frames. "Calibrate" remained unchecked in all cases, as did optimize on darks because of glow in the sensor.
The QHY600m includes the overscan area and suggests that it should be used to combat bias drift. My questions are many, but include the following:
1. Should bias frames be taken rather than using flat dark frames and building a master_flat_dark?
2. Should I calibrate each set of calibration images (bias, dark, flat) using the overscan area separately, or should I integrate the calibration images as before and only select the "overscan area" option when calibrating the lights? If each should be done separately, I believe that PI will truncate (remove) the overscan areas from the output image, in this case the master... frames? Would this not cause an issue when attempting to calibrate the light frames (incorrect geometry)?
It would seem to me that the correct procedure would be to integrate the bias, dark, and flat frames without calibration and, when integrating lights, select the overscan area and select "calibrate" for each, allowing PI to subtract the average value of the overscan area from each respective master before calibrating the masters with each other and subsequently, the lights. I'm not sure if I have this correct and would GREATLY appreciate any assistance that can be offered.
Thank you.
Tim.