NGC 7662 Blue Snowball Nebula (lucky imaging experiment)

[Menno555]

Since my Zwo ASI294MC Pro is back to the dealer for a check, I only have my non-cooled planetary Zwo ASI385MC to play with.
I did read about the lucky imaging technique for DSO, so of course I had to experiment with that. The real short exposures (100 ms) did not really work but with 500 ms it did work.
The Blue Snowball nebula was a nice object for it with mag 8.5.
And the result is okay. It's a really other discipline to work with: with this camera a lot of horizontal banding appeared, but SharpCap has a setting to counter that effect.
Also finding the balance between exposure, gain and brightness (offset) was different. And no (dark) flats are needed, only darks.
And just way to few stars for DeepSkyStacker to work with so I used Planetary System Stacker for that. This stacking program can give great results, better then AutoStakkert. For those interested: https://github.com/Rolf-Hempel/PlanetarySystemStacker
All in all a fun something to experiment with. For sure going to see what it can do with the ASI294.

The Netherlands, Bortle 7/8
Meade LX200 8" f/10 ACF OTA
Ioptron CEM25EC mount (no guiding)
Optolong L-Pro filter
Optec Lepus Standard 0.62x reducer
Zwo ASI385MC camera

Captured with SharpCap Pro
6000 x 500 ms / Gain 300 / Offset 30 / White balance R50/B50 / Dark frame applied

Stacked in Planetary System Stacker
Best 600 lights (10%)

Processed in SiriL + Photoshop
Siril: photometric color calibration, histogram
Photoshop: levels, curves, color, reduce noise.

[admin]

Hi Menno,

an interesting experiment – the 385 is a very nice sensor, but I do wonder if you might be read noise limited at such short exposures on a faint target. If you have the sensor analysis done for that camera then you should be able to read off the e/pixel/s for the actual nebula to see if you are getting to the 10 times read noise squared level that you would want to be at.

Thanks very much for including the information about PSS – it looks very interesting… Going to have to give that a go on some old data to see how it does

Cheers, Robin

[Menno555]

Thanks Robin!
And yes, the noise is a lot in this case due to the high gain and offset. The master dark is riddled with pixels and banding and glow.
I did try the Brain but that didn't work, it gave a message that is could not not work with the short exposure times.
And that " .. getting to the 10 times read noise squared level that you would want to be at." is still meaningless to me
The workflow for me was first to see how short the realistic exposure time could be without going to extremes in gain and offset. That turned out to be 500 ms. And after that it was finetuning of the gain and offset. All this pure visually.

And yes, PSS is just great. The stacked result really is remarkably better then AutoStakkert.

Menno