Winter is coming and this also means that Orion the Hunter is again showing up on in the sky.
After three weeks of mostly clouds skies I got my APO Refractor out to do some imaging. In the meantime I also learned that ma problems with guiding and blurry stars also seem to come from very poor seeing over Innsbruck.
The following images have a sharpness value (FWHM) of 7 arcseconds for stars. Astrophotographers in better regions of the world don't bother shooting if this value goes over 4. Looking back at old images I found out that the sharpest I got from my Garden location was 3 arcseconds.
But anyway here are the three images I processed from this session. The pictures were done in true RGB color.
The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of 1,344 ± 20 light years and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light years across. It has a mass of about 2000 times the mass of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
If your mount is not aligned perfectly to the polar star, even with good guiding, this puts strong constraints on your exposure times. Even off axis guiding does not solve this problem. If you miss aligned just 1', the guiding star is 2 degrees away from your image and you're 60 degrees above the horizon, field rotation will accumulate on a 30 min exposure to about 5 pixel on my Atik 490ex.
As I build and tear down my setup for every session, there is a limit of time I'm willing to spend for alignment. All Star Polar Alignment on my mount gives me about the 1' precision mentioned above. For now I will limit the exposure times, depending how far up I'll look.
For the future I may investigate drift alignment and how good I'm able to streamline this process.
Anyway, here's my latest result based on things learned from all the previous mistakes. I especially looked for tracking errors, exposure times and focus.
3x15 min each in Ha, OIII, SII; 3x2 min each in RGB for the star colors
I decided to give the North American Nebula a try with my new APO.
First setup was my unmodified EOS M3 with the 480 mm APO and the flattener from my light polluted garden. The nebula was close to the zenith which makes the sky a little bit darker. Total integration time was about hour.
The signal was really weak. Below is the result after pulling all my post processing skills.
Next night I tried it with my Baader H-alpha filter. As my current setup for the APO does not work with flattener AND filter, I had to make the pictures without the flattener which is painfully visible at stars in the corners. The image below has almost 2 hours of integration time.
Again it shows the bad sensitivity of the unmodified EOS M3 to H-alpha frequencies.
I'm now really considering getting one of the dedicated CCD cameras, even if you've to sell your house to get one.
Surprisingly there was a clear sky for a few hours last night over Innsbruck. Moon was half up, but otherwise it was as good as it can get in city conditions.
I wanted to try a few things. First use my very cheap Skywatcher StarTraveler 80mm refractor to make a wide image of M31. Second I wanted also to check out my new Astronomik CLS filter to reduce these pesky city lights. And thirdly I wanted to use off axis guiding through the scope.
With the off axis guiding I failed miserably. I have to try to get focus and light during day. I fell back to use my 9x50 finder as guiding scope.
The Astronomik CLS filter is a mixed bag. I seem to get a little more contrast with it (which is needed because of the short focal length of 400mm). On the other hand you get blueish images with almost no red channel in it. I took 12x5 min 1600 ISO subs and still there was almost no information there.
The StarTravel ST80 is amazing for the amount of money it costs. Of course there are distortions off center, purple fringe effects are very visible around stars and focus is not really clear cut on the full frame. But for 100 euro it is still amazing.
So here's the final image 12x5 min ISO 1600 subs with an EOS M3. No dark frames, no flats, noise reduction was completely done in Photoshop.
Yesterday was a surprisingly clear night in Innsbruck.
For a change I tried to do some Planetary Nebulas from my light polluted garden. I chose M27 and M57 because they where high in the sky and therefore showed less problems with the background glow over Innsbruck.
M57 is even with the 2000 mm focal length of my EdgeHD SCT a little small. Also guiding becomes a challenge in these bright skies.
Imaging was done with an unmodified EOS M3 at 1600 ISO. I chose exposure times of 2 and 3 minutes to help with the guiding and to keep the background glow under control. Stacking was done with DeepSkyStacker and Photoshop.
And again, I'm actually quite happy with the result.