Thursday, December 18, 2014

M42... Required Image

So I've been taking pics of this nebula since I started astrophotgraphy sometime in the late 80's.  Back then, I was using a 8 inch Meade Schmidt-Cassegrain that my mom bought for me.   (Well, I asked and she okay'd it.)   Astrophotography was done with film and there were many choices.   Invariably, the results were blurry smears of red.  Guiding was done through a finder scope with a reticle eyepiece.  I shot many rolls of film, but nothing really came out to my satisfaction.

I didn't realize at the time that guiding a 2000mm focal length scope through a 60mm guidescope was never going to really work.  I tried lots of combinations, but the end result was always disappointing.

Anyhow, fast forward 25 years and I got this image of M42, the Orion Nebula, and NGC 1977, the Running Man nebula.

I had to devote several nights to getting the exposures to make this image.   This was shot on the nights of Nov 24, 25, 30, then Dec 14 and 15.   I used 31 x 15 min exposures, 46 x 5 min exposures, 35 x 2 min exposures, 35 x 15 seconds, and 35 x 5 seconds.   That's about 13 hours of exposure.  I actually shot about 17 hours of total exposure, but I only used the best 80% of the shots to process the image.   Scope:  Takahashi TSA102S w/Televue .8x focal reducer/flattener.  Mount:  Used AP1200.   Misc:   Guided w/Orion 50mm guidescope and QHY5II-L autoguider.

It's kind of a mandatory shot for any astrophotographer, but I wanted to do it because I knew I would get something worthwhile as it's so bright.

There are issues with the image.    The darker dust structures around the edges of the brightest parts are noisy.   I got those structures from those longer 15 min subexposures, but I think I need like 3-4 times the number of 15 minute exposure which means another 3+ nights of imaging this object.   Getting extra 15 minute shots would increase the signal-to-noise ratio which translates into less noise and more structure.

I was sorta lazy with using layer masks (a technique in Photoshop) and some of the stars are not the right brightness (too large) relative to other stars.

Sharpness is an issue.   Overall, I think the image is a little blurry - except near the core of the Orion nebula where the Trapezium is located (the tiny grouping of 4 stars near the center).   And that Trapezium is weirdly detailed with respect to everything else.

The overall color is little garish to me.   I know this object gets overly saturated by most people and I ended up doing the same thing.

Also, there is some curvature in all the corners, but most obviously in the upper right and left respectively.   I've known about this for awhile, but I haven't bothered to address it.  *I think* it's focuser tilt as the curvature seems to be different depending on the orientation of the camera.  I also picked up some spacers to place between the flattener and the camera.   More crap to address.

If you look closely to the bottom edge, just to the right of the center you can see some artifacts from the constant parade of satellites I had to deal with.   Actually the satellites aren't moving, there's a bunch of geostationary satellites that happen to be located in M42

Overall, to me, it's a "meh."   But I'm glad I did it.

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