RBA Premium Astrophotography

Messier 20, The Trifid Nebula

Posted: August 6th, 2008

Original size: 3859x2550

August 6st, 2008, 11:00pm to 2am PST

Exposure: 12 x 8 minutes
Focal: 2160mm, f/21.6

Imaging Scope: NP101is with Powermate 4x barlow
Camera:Canon 40D IR/UV filter
Guide camera: StarShootAutoGuider
Guide scope: Orion Short 80mm
Mount: Takahashi EM-400

Site: Fremont Peak, CA
Transparency: Average

Stacking: DeepSkyStacker
Processing: PixInsight + Photoshop

Third attempt with the Powermate x4. The nebula came up nice - at least the emission part of it - but for obvious reasons (only 12x8 minutes shots with a f/21.6 focal ratio through a 4" scope) all the detail surrounding the nebula is missing. Just look at the resulting image from the calibration + stacking and you'll see how much I had to stretch this one. In fact, in order to bring the nebula out of the background I had to prepare some custom flats, otherwise when stratching the histogram, the whole background was coming up at a similar intensity as the nebula itself. It would have been nice to get a bit more reflection nebula, but again, at this focal ratio and with an DSLR (in a very warm night I may add) I should be happy with the results.

That's of course until you notice how terrible the stars in the corners look. Or more accurately, the stars all over the field, getting worst as we approach the corners. I don't think it's caused by the default optics of the Powermate (it didn't happen with the previous two shots of the Lagoon and the Bubble nebulas). I'm betting it could be that when connecting the Powermate, the camera might move off the optic axis, causing this unwelcoming effect.

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