Well, in that case You don't have precise temperature control built into the camera. AFAIK Altair hypercam has only a cooler, not a precise controlled peltier (like ZWO, QHY) and that is why You cannot get rid of thermal pattern, as temperature changes during photosession.
Actually that statement is incorrect , ( get rid of thermal patterns) i can completely remove the Starburst in Pixinsight and DSS4.1.1. and Nebulosity 4.
the problem at this point is the way APP interprets the darks and flats as it calibrates the light frame.
thank you for your input , 🙂 Mabula will have a look at this when he has a minute..
Actually that statement is incorrect , ( get rid of thermal patterns) i can completely remove the Starburst in Pixinsight and DSS4.1.1. and Nebulosity 4.
the problem at this point is the way APP interprets the darks and flats as it calibrates the light frame.
thank you for your input , 🙂 Mabula will have a look at this when he has a minute..
Micth
Oh, glad to see there's a solution for thermal patterns, i suspected the temperature control to be "guilty" 😉
Improved, data calibration of severe Amp Glow, amp glow does not behave linearly so it's always important to not use dark scaling if your sensor has significant amp glow. You need to create darks of the same offset, gain/ISO, temperature and exposure time as your lights, to properly deal with amp glow. Now, in cases of strong amp glow, it can happen that the glow is so strong when compared to the real photon signal and noise in our data that a large part of these pixels will be calibrated to zero if we subtract a suitable dark frame. This will happen in each frame for different pixels and that will have a cumulative effect in image integration. The statistics of the pixelstacks will actually be skewed to the upside still showing residual amp glow in some cases. In 2) Calibrate, there is now a new option that will adaptively solve this for data were this happens. It's called Adaptive Data Pedestal. If you enable this, it will prevent severe clipping on the black point in calibration, and will therefore prevent skewed pixel statistics in image integration. It's an adaptive algorithm, so it takes a little bit more time in calibration. A case were you probably need to enable this is strong Amp Glow with camera's like the ZWO ASI183. For most camera's and datasets, this setting will have no effect, but in cases where severe black clipping in calibration does occur, for whatever reason, this setting will prevent it and will ensure precise calibration and no-skewed statistics in image integration.
Example of an integration of ZWO ASI183mm-c Oxygen-III data provided by Warren Landis @orangemaze, with and without the setting enabled in calibration:
In this case, the amp glow is not calibrated out with the Adaptive Data Pedestal disabled, because the amp glow simply overpowers the real OIII data on the location of the amp-glow. By enabling the Adaptive Data Pedestal, the amp glow is properly calibrated.
I received a nice Hydrogen-Alpha data set from Mitch of IC405. Details are:
60x180sec lights
40x180sec darks to calibrate the lights
50x flats to calibrate the lights
60x bias to calibrate the flats. (not used for the light frame calibration)
To see the extreme amp-glow problem of this sensor, this is the stretched MasterDark:
You can see the extreme amp-glow on the right side of the sensor, and a little bit in both bottom corners of the sensor.
These are the results with and without the Adaptive Data Pedestal enabled in calibration, off course, highly stretched to show the data calibration performance in an integration of 60x180 seconds Hydrogen-Alpha frames (3 hours total exposure time):
Without Adaptive Data Pedestal:
With the Adaptive Data Pedestal enabled, where is the Amp-Glow ?? 😉 :
Direct comparison:
What happens without the Adaptive Data Pedestal: the residual amp-glow that you see in the integration without the adaptive data pedestal enabled, is the result of skewed data integration (to the upside) due to black clipping of the light frames after the subtraction of the MasterDark. This means that the provided lights are not sufficiently illuminated for this sensor. This sounds strange perhaps for such a BSI cmos sensor, but the illumination really is not enough to have the light/photon signal overcome the severe amp-glow on the right side of the sensor. The Amp-Glow signal is so strong, that after subtracting a masterdark from the light frames, a lot of pixels are still black clipped... The Hydrogen-Alpha signal (in this case) is too weak to overcome the Amp-Glow. This has a degrading effect on the data, once properly calibrated with the Adaptive Data Pedestal enabled, the image data will always have worse noise characteristics in the areas where the Amp-Glow resides on the sensor.
The Adaptive Data Pedestal is an adaptive algorithm that will prevent the black clipping of pixels after masterdark subtraction and therefore the integration results are no longer skewed to the upside, thus properly removing the amp-glow signal if the provided darks are of the same temperature, same exposure and same gain + offsett as the light frames.
This post was modified 5 years ago 2 times by Mabula-Admin
I agree , WOW , thank you for making a program that will allow us to push the envelope on this new Sony BSI chip without fear of horrible amp glow and damaged data sets.
More data and images to come in the coming weeks processed with APP.
