I've been working on astrophotography for about a month. I started from basically ground zero, so the learning curve has been STEEP!!
I'm in the "I don't know what I don't know" phase of learning, so unfortunately I don't know exactly what to ask to help with my current issue.
Nebula photos have LOTS of noise in them.
Here's my current acquisition project: The cone nebula:
The above image is after pre-processing in Pixinsight. Here's what I've done so far:
I captured 60 images at 119s exposure with the camera gain at 96 and offset at 20 (ZWO ASI071MC Pro). The camera sensor was cooled to -10C. The gain and offset values came from a Sharpcap image sensor analysis. The exposure time came from the Sharpcap Smart Histogram recommendation after measuring the night sky and using the image sensor analysis results. The OTA is a WO GT81IV using the WO Flat6AIII 0.8 flattener/reducer.
- Subs brought into Pixinsight
- Subs were calibrated using a superbias and master flat
- Subs were cosmetic corrected with a master dark
- Subs were debayered
- Subs went through the subframe selection process and weighted based on a score taking FWHM, eccentricity and SNR ratio into consideration (the Light Vortex tutorial weighting scheme)
- Subs were registered and then stacked based on their weights, drizzle data was generated
- Local normalization was generated
- Drizzle files with local normalization were integrated
- Integrated image went through background neutralization
- Image was then photometric calibrated
- Image then went through DBE (dynamic background extraction)
The image in the link above was also quickly cropped and then stretched just so you could see it.
I like the colors. BUT, the nebulosity has a LOT of noise. It's very, very grainy.
- The expected amount of noise for 2 hours of exposure?
- Is it reasonable or unreasonable to expect to get smooth nebulosity from this image using Pixinsight noise reduction processes (TGVDenoise, MLT Transform)?
- Should I even bother trying to get this image to look good (smooth nebulosity)? Am I better off not trying to process this data yet and add additional subs before trying to process?
- I know there's no hard and fast rule for how much exposure is needed. But given that the above image is two hours of exposure, how much more exposure should I expect to need before I can reasonably expect to get smooth nebulosity in my image (after Pixinsight processing)?
I can't get this image to look good, and I'm not sure if it's my Pixinsight limitations, my data limitations or my capture method is flawed. Do I need to invest more time in more exposure, or is this enough data to get a decent result if I get better at applying noise reduction techniques in Pixinsight?
Eventually, I want to combine this with RGB data. I also have 75 subs of RGB at 30 seconds exposure each. That data is also noisy.
Thoughts? Next Steps?
I'd REALLY appreciate someone who's been through this talking me through the recommended next steps.