Elephant's Trunk Nebula (IC1396A) 2025

The Elephant’s Trunk Nebula is part of a large emission nebula called IC1396 in Cepheus. The nebula is approximately 2,400 lightyears away, and the namesake “elephant’s trunk” is about 20 lightyears long.

Just out of frame is the bright-red Garnet Star, which was very helpful for finding my target. The Garnet Star is one of the largest known stars at around 1,000 times the radius of the Sun.

This image represents my longest total exposure time (nearly 8 hours vs. my usual 2-3) and my best astrophoto to date. The dark nebulae turned out really well, and I am happy with the contrast and color range. The bright regions are a little noisy, but that is really the only complaint I can make.

Ultimately, I think this is among the highest caliber of astrophotos that can be taken using my current equipment. More hours of exposure can always be taken and better processing techniques can always be used, but this result was astonishingly good for an old DSLR, an inexpensive achromat telescope, and one of the smallest/most basic star trackers on the market.

On to the technical discussion:

I shot this over 3 nights (11/22-11/29/2025), so it was finally time to graduate from Siril’s provided preprocessing/stacking scripts and learn to process the data manually. For those unfamiliar, a manual workflow was necessary in order to apply corrections to each night separately and then stack the 3 corrected datasets. I learned a lot of useful details about how Siril works, and I think I will continue to use a manual workflow in the future for the additional control it provides.

I also applied my recently-improved histogram stretching skills to bring out a lot of detail and contrast. I ran through several iterations of stretching and star recombination, but I have not yet found a combination that cuts down on the color noise surrounding the trunk region. In the future I may try again if I can identify a possible solution.

I opted to correct using bias frames and not dark flats, as it seems my previous approach of using dark flats but not bias frames was based on outdated information. The new consensus seems to be that dark flats are mostly useful if the exposure time of the flats is very long (5 or 10 seconds). As my flats are typically 1 second, the dark flats were not likely contributing much. On the other hand, my camera can probably benefit from bias correction, and bias frames are required because Nikon has apparently not published a bias offset for the sensor.

GIMP seems to work better for star recombination than Siril’s built-in tool, but it struggles with noise reduction. I found that to see meaningful noise reduction in GIMP, small, swirling triangular artifacts are introduced. For this reason, I used PSX for the final denoise instead.

Technical details:

• Lens: Sky-Watcher StarTravel 120
• Camera: Nikon D3200
• Mount: Sky-Watcher Star Adventurer 2i
• Optics: Explore Scientific Field Flattener
• Filters: SVBONY UHC
• Exposure: 956x30s at ISO800
• Corrections: 50+50+50 darks, 25+13+50 flats, 50 bias
• Stacking: Siril
• Post-processing: Siril (stretch, gradient removal, color calibration, star mask), GIMP (star recomposition, brightness/contrast), PhotoScape X (denoise)
• Bortle: 4

Notes for improvement:

• As mentioned above, investigate processing strategies for reducing color noise, especially in bright regions