M42 Orion Nebula

Canon 500D camera with EF-200/2.8L lens on EQ6 equatorial mount guided by a QHY5 camera and  PHDGuiding. Stacked 5 frames in Deep Sky Stacker, total exposure ca 5 minutes. Shot on Sat-Sun night 23-24 Jan 2010 in cool -18 C but calm weather. Would have wanted longer exposures and more frames, but the guiding wasn't working very well, and Orion is pretty low, hiding behind trees from my site. The dark thing on the right is a tree 🙂

Same image but cropped:

A nice improvement over my 2008 December attempt on M42.

Orion nebula (M42)

It seems like ages since the skies were clear last time. Must be around 2 months I think. Last evening however was good for astrophotography again. My target was the Orion nebula, or M42.

I took 40 sub-exposures, each 60s long, but half of them were out of focus :(, and a couple of the remaining ones had star-trailing due to vibration or me pushing the mount or something. The end result is a stack of 14 images, so 14 x 60s = 14min total exposure time. There is software out there to help with focusing, I'm looking at Nebulosity in particular. A DewNot dew-heater worked really well, no more problems with dew or frost on the lens.

Canon 20D wtih 70-400/4L lens set to 200mm and F/5.6: Unguided EQ-6 mount. Stacked with DeepSkyStacker with 10 dark frames (no flats or bias frames). The image above is a 100% crop, below is the full frame:

This site is about a 35min drive away. It allows exposing for 1-4 minutes at F/5.6. That's almost good enough, if you look at the "why autoguide" slides of Craig Stark's talk (especially the SNR plot at ca 7:20), it's clear that single exposures of a few minutes are required to reach good SNR.

The noise is supposed to be 1/sqrt(14)=3.7-fold lower in the stack above, but I'm not very impressed by how it looks compared to this single 60s frame: