Believe it or not, this is a characteristic of the camera's sensor, sometimes Canon accounts for this in the camera's firmware. Normally, this isn't an issue for terrestrial photography because the signal easily swamps out this noise, but in astrophotography we are not using the sensor in the way Canon intended when it was designed. This is what happens sometimes when we use the camera at the edge of its design envelope. What we are seeing is a picture of the sensor and the underlying electronic signal.
The fact that the Moon was out didn't help either.
Canon EOS Rebel XS (full spectrum mod)
Astronomik CLS CCD
Orion thin off axis guider
QHY5L-II M guide camera
Celestron CGX,Edge HD 8,0.7x focal reducer
Optec TCF-Leo focuser
This was a single image, so there is no processing done on it yet. The temp was 60F last night and I had not been running it that long. I'll have to see if all images have it, or if it showed up at some point.
In the past, I saw it in one set of images after processing, but not in the raw image itself.
Hopefully it was just a fluke and the next session goes better.
- Scott V
Canon Rebel T6i (unmodified)
William Optics ZenithStar 73, 0.8x Flattener, ZWO EAF, ZWO ASI120MM Mini Guide
Astronomik CLS Light Pollution Filter
This was a single image taken directly from the camera. I did not get a chance to take darks last night.
It looks like that data is stretched pretty aggressively. Canon sensors are notorious for banding however I have never seen it to that extreme.
Take bias frames and see if you notice the same pattern when you stretch them as aggressively.
I was taking photos last night and saw that there are horizontal bands in the image. At first I thought it was because I was trying to push 180 second (see attached image), but the bands remained even with a 60 second image.
I have seen this previously with the camera, but not always occuring. This is with a stock Canon Rebel T6i.
Skywatcher HEQ5 Pro mount