For the last year or so some of my images using the same bias, dark, and flat frames show significantly different noise levels, even when take one after the other. A summary image showing the effect is here: https://eccssw.com/AstroIssues/Noise/ as are the raw and calibrated FIT files. When I apply PixInsight's "Linear Defects Correction" to remove the bad columns that aren't removed by the darks, the "noisy" images that are to be integrated have pattens - different shapes and sizes of boxes, for example. Sequence Generator Pro was used for image capture. No settings were changed between shots. The camera is one of the first STXL-16200. Is it possible something in the camera is going flaky?
That's what I did. Download links are not valid. You get a 50 byte file containing only the following: Not sure where you're going, but you're not there!
Interesting. Must be different browsers since I could right click and download it. Regardless, I added a MIME type for fits to the server. When I left click on a link now it brings up the downloads dialog box. The "Not sure where..." message is my 404 message.
I uploaded the dark and flat masters which were used by both frames. https://eccssw.com/AstroIssues/Noise/ If it makes any difference, the sensor (Class 1) has a lot more column defects now than it did a year ago and a much more pronounced dark band at the top 1/3 than it had when new. Thanks in advance for looking at this.
I can't use images processed by PixInsight; it does weird scaling to them. I wanted a raw dark frame. Also, I recommend reshooting your darks periodically. Sensors will gradually accumulate cosmic ray damage, resulting in new hot pixels. Taking fresh calibration frames periodically will help mitigate that effect.
@Doug, I added a "Single Dark Frame". I have newer darks and regularly take them. I looked for two images using the same dark master that were taken back-to-back where one had lots of noise and the other didn't, and the first example is what I used. I didn't know about cosmic ray damage - that's interesting, thanks.
I'm not really seeing an increase in noise on one frame compared to the other, doing a simple dark frame subtraction. Images can often look noisier or smoother if they aren't contrast stretched on the display the same way. Going by the numbers I don't see much there. I think you will benefit by making a new calibration set. Personally I redo them every few months.
