Heart and Soul

The Heart and Soul nebulae (IC 1805 and IC 1848) are in Cassiopeia and are high enough above the horizon to start shooting relatively early in the evening, so I set up and shot 51 x 5 min for 255 minutes of total exposure.

The longer exposure made processing this much easier. The signal-to-noise ratio is way better, fainter parts of the nebula don’t fall apart and become grainy when I do the contrast enhancement.

My first impression was that there are too many stars compared to all the images I’ve seen online. But then I found this comparison, by Trevor Jones who runs the AstroBackyard YouTube Channel. He shows an image from a modified DSLR (similar to mine) and another using an H-alpha filter. The latter shows fewer stars. And most of the images I’ve found online are done with narrow-band filters which allow specific wavelengths from ionized gas clouds, but little starlight. So yeah, there are really that many stars in the field.

Here’s a bit of fun on what PixInsight is doing under the hood when I ask it to do the integration of those 51 frame but to also do pixel-level statistical rejections.

Those long lines crossing the frame are satellite trails. If I walk through the frames one-by-one, I can spot a couple of the brighter ones (the above image has been severely stretched). Additionally, there are two small lines that look suspiciously like faint meteor trails that were also removed. THe horizontal banding is something I need to look into more, but that appears to be structure in the DSLR sensor itself that calibrations failed to remove. I can see similar banding in the master bias frame. I suspect the issue is that because the camera temperature floats with the environment, that the darks and lights don’t quite match leaving the above residual banding.