09/03/2023 – 2.5 Hours of The Elephant’s Trunk Nebula

During my EAA session on 09/02/2023 I observed the Elephant’s Trunk region of IC 1396, but it was not framed very well. Last night I decided to capture some more data centering on IC 1396A to frame the nebula better and to hopefully see more details in this dark dusty nebula. This was not an EAA session, though I did periodically check a live stack which I had running in SharpCap. I captured the data and then processed it using Siril and GIMP.

I planned to shoot 3 minute exposures so I shot some 3 minute darks. I captured an hours worth of darks (20 x 180 seconds, sensor cooled to -5 C) and created the Master Dark in SharpCap (this was just for the live stack, a new master was created from these frames in Siril). I did not reshoot flats (but I should have), I am using the ones I shot the night before.

Once the Sun set I verified plate solving and ran the Ekos Polar Alignment routine. Plate solving was calculating the focal length to 699.8 mm. The mount was pretty well aligned from the previous night, so it only needed minor adjustments.

Primary (Imaging) Secondary (Guiding)
Scope: SVBONY SV503 102ED, UA Field Flattener
Camera: ZWO ASI294 MC Pro, Cooled to -5 C
Focuser: ZWO EAF
Mount: Sky Watcher EQ6-R Pro
Scope: SVBONY SV106 60mm Guide Scope
Camera: Orion Star Shooter Autoguider (OSSAG)

The plan for the evening was to use 180 second exposures to capture at least 2 hours of data. I ended up collecting 2.5 hours of IC 1396A data – 50 x 180 second exposures at 121 gain, 30 offset, and bin 2×2. I started the capture sequence at 8:50 PM. A few high thin clouds rolled through around 9:30 PM, but it cleared back up pretty quick. I was guiding and the RMS value stayed between 0.7 and 0.9. I deleted 2 frames from the sequence due to airplanes flying through them, so at the end of the sequence I added an addition 2 frames to get a total integration of 2.5 hours.

This morning I processed the data with Siril to create this image of the Elephant’s Trunk Nebula.
IC 1396A, Elephant's Trunk Nebula, 50 x 180 seconds, 09/03/2023
I processed this image of the Elephant’s Trunk Nebula (IC 1396A) in Siril following this tutorial: From Raw to Finished: A Siril v1.2.0 Tutorial for Beginner Astrophotographers. I did this a few times to get the above results. I learned a lot from the video and realize I am going to need A LOT more practice.

Better framing and a lot of interesting details compared to the captures during the previous EAA session on 09/03/2023. The longer exposures and more integration time definitely made a tremendous difference.

There are 2 places where the flats did not quite calibrate correctly. There is a dusk mote in the lower right, and another just above the Elephant. I am going to try to shoot some new flats later today and reprocess.

Here is an overview of the processing workflow I used in Siril (which is covered step-by-step in the tutorial):

  1. Create biases, flats, darks, lights, and process folder in working directory.
  2. Drop the captures into the associated directories (Darks in darks, Flats in flats, Lights in lights). I do not have bias frames, so I edited the OSC Preprocessing script to not use them.
  3. Run the OSC Preprocessing script.
  4. Background extraction to clean up gradients in the background.
  5. Photometric Color Calibration – Make sure the focal length and camera pixel size settings are correct.
  6. Remove Green Noise
  7. Remove Stars… select the pre-stretch linear image
  8. Asinh Transformation – Adjust stretch factor to where you can just see the object.
  9. Histogram Transformation – Adjust black and white sliders. Make sure there is no clipping of data.
  10. Use Star Recomposition to add stars back.
  11. This is not covered in the tutorial but I used this Automated Star Reduction script to remove some of the background stars.

Before covering the scope I collected some Moon light. The Moon is this capture is 79% and waning. This was captured around 11:30 PM, 09/03/2023. I captured 200 x 0.000032 second exposures of the Moon and stacked the best 20% in AS!3, then made some adjustments in GIMP.
Moon, 79% Waning, 09/03/2023, 40 x 0.000032 secs
I’ll keep practicing… I will probably tinker with this one a bit more as well.

Over all a fun night and decent (IMHO) results. Back to EAA for the next session…

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