M27 - the elusive outer shell (just)

[turfpit]

The data was from 10th October 2024, reprocessed with my ever evolving processing experience. I had tried 300s & 600s exposures but finally settled on 1200s to overcome the sensor noise of the Atik 314E. 1200s - not bad for a Celestron AVX mount. Processed with Pixinsight and Starnet++ with a final run through Starfixer https://www.starfixer.org/. Integration time 2h 20m.

M27_Ha-7x1200s.jpg (564.32 KiB) Viewed 550 times

Data: 100 bias, 18 darks, 30 flats, 10 lights (3 rejected by PixInsight as affected by the Aurora) guided.
Equipment: Celestron AVX mount, Vixen 81s refractor, Vixen 0.67 reducer/flattener, Altair 7nm Ha filter in ZWO mini wheel, Atik 314E camera.
Software: SharpCap, Pixinsight, Starnet++, Starfixer

What started off as a 10 frame capture was interrupted by the magnificent Aurora display of 10th Oct 2024 (captured with an iPhone).

Aurora_10_Oct_2024_scaled.jpg (128.19 KiB) Viewed 548 times

Processing was:

• Calibration/integration with WBPP

• Delinearisation

• Export as 16-bit TIFF

• Starnet++ to create starless image

• PixelMath for image - starless = starsonly

• RangeMask

• Inverted RangeMask to apply LocaHistogramEqualisation

• CurvesTransformation, slight 'S' curve

• PixelMath to recombine starless and starsonly

• HDRMultiscaleTransform with mask to tame the centre of M27

• TGVDenoise

• Export to Starfixer for star reduction + denoise

I did try a HOO version using 300s OIII and 600s Ha but the exposures were not long enough to show the outer shell.

M27_HOO.jpg (71.47 KiB) Viewed 550 times

This year the weather was poor when M27 was in the best position for capture. Try again next year ....

Dave

[admin]

Hi Dave,

nice images, really pulling out the faint detail with the long exposures and the processing. Could you mix the luminosity from the longer exposures with the narrowband data perhaps? I don't know if the different orientation of the images is an insurmountable problem or not?

I think we mostly missed out on the October aurora down here in the south, maybe that was the one that seemed to fizzle out just before midnight and then came back to life about 2am when everyone had given up?

cheers,

Robin

[turfpit]

Robin

I did try mixing the 1200s with the 300 & 600s but the orientation did for me. With the autocrop, M27 was off to one side of the frame. I had to remove the camera for some reason between sessions and didn't quite get the gear back together the same. It was the last session of 8 where I tried the 1200s exposures.

Dave