Elephant trunk (jackfrost373)

Elephant trunk

Revision title: Full 2 days

Subject: IC1396 (wider) Elephant trunk [170' x 140', M+5.59], Cepheus

I might have been a bit too optimistic in trying to capture this target. The first night I managed to get ~40 minutes of data before it went below the horizon, and I changed the night's focus on the Heart nebula. The trunk itself is starting to become visible, though the surrounding nebula is faint as you can tell from the zeroth revision. After making it the main goal of the second night, I got three more hours in (1st revision). But the nebulosity is still hard to find. This is not the beginner friendly target I naively thought it would be.

The (wider) Elephant trunk does fit perfectly in my 400mm frame, and seeing the beautiful reds from the lesser magnitude Heart nebula (M+6.50) I thought this was going to be a walk in the park. In hindsight, the intensity is spread out over the larger solid angle - a quick&dirty calculation for my setup results in 1.9 signal photons/pixel/s for the Heart, and only 0.7 photons/pixel/s for the wider Elephant trunk. That's a factor 2.7 less signal to get above the noise threshold per pixel, so no wonder it appears fainter. A lesson learned.

Still, valuable to put it online as reference for the future, when I might manage to get to a lower Bortle zone, obtain a dedicated (Ha-sensitive) astrocam, a proper large aperture telescope, or a narrowband Ha filter.

I saw some banding in the first night, so I manually adjusted the position throughout the second night a few times. Looking forward to dithering with guiding in the future. I think the pattern noise was due to a thin layer of ice appearing on the lens at some point in the night - perhaps I should consider a dew heater as well for nights like these. For combining the sessions, I just threw all images into one 'lights' folder and re-used the same darks/flats/biases as the first night.

Anyway, I'm loving Hershel's garnet star in the top right - a red supergiant like Betelgeuse and one of the largest stars in our sky, 100.000x brighter than the sun.

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Title: Full 2 days

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Revision title: Full 2 days

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