M42 - The Great Orion Nebula

A tip of the hat to Baz for the stacking tutorial.

32 1min lights, 10 darks, Vixen 80mm f/5 Refractor, 50D ISO 1250. Unguided.

Great job! Very clear image. Last summer's attempt looks great too.

Good Job!
BAZ has always been helpful with many things. He has helped me a lot when it came to time lapse.

The only things I would suggest however, would be use a lower ISO. I have found that ISO 800 is the optimal setting for the 50D under most conditions. However if you're not auto-guiding and you want more saturation in less time then I can understand that. 1 minute is plenty exposure time even at ISO 800. That way you won't be blowing out the core/trapezium so much.
At the ISO you were using I might have used a 1:1 ratio of Darks, flats and bias frames to light frames(Subs).

I also notice your stars show some drift. There are methods you can use in post processing to help with that. I haven't tried them myself, and I don't know if Bud Guinn uses these forums or not, but he has a good method for correcting elongated stars.
http://www.budguinn.co​m …als/star%20elon​gation.htm

One more thing. There is a problem many of us have a hard time with when it comes to post-processing our image data. Over Clipping the dark points! Keep in mind space is not actually black, especially areas surrounding nebulous regions such as the orion nebula.

Just my 2 cents. Hope it helps.
Oh Yeah, I might have turned the camera sideways on this one.

Here are some more links you might find useful when it comes to image processing.

http://www.astropix.co​m/HTML/J_DIGIT/TOC_DIG​.HTM
http://www.astronomyph​otos.com/PhotoshopTech​niques1.htm
http://www.astronomyph​otos.com/PhotoshopTech​niques2.htm
http://www.danielmccau​ley.com/tutorials.html
http://www.iceinspace.​com.au/projects.html

That's real nice Jeff!

tkerr: thanks for the 50D tips and info/links, I'm off to do some reading!

Well done, Jeff, crisp and sharp.

I'm guessing you didn't use flats, since the corners are darker than the rest. You should try them, they really do make a difference.

Don

i know this is an old post....BUT....how do you guys get these images if they arent guided? wouldnt everything be trailed?

There are two terms - Guiding and Tracking.
Tracking is when a motor is used to move the mount at the same rate as the stars. Guiding is when you have another camera watching the stars and adjusting the tracking to keep the star centered. Open loop versus closed loop in engineering speak.
Guiding accounts for atmospheric effects like refraction, mechanical errors like gear noise and to some extent, polar alignment so you get much better results (but it costs more).

just for interest sake, what does one have to pay for a "reasonable" quality guiding system?

That depends on what you already have. You can get pretty good results from a butchered webcam and a 50mm binocular objective or finderscope if you like to tinker, have a laptop and a mount that can communicate with a PC. If you're not the tinkering type, you can buy finderscope/guide-camera as ready-to-go system for about US$300 I think.

SteveInNZ wrote in post #13500502
There are two terms - Guiding and Tracking.
Tracking is when a motor is used to move the mount at the same rate as the stars. Guiding is when you have another camera watching the stars and adjusting the tracking to keep the star centered. Open loop versus closed loop in engineering speak.
Guiding accounts for atmospheric effects like refraction, mechanical errors like gear noise and to some extent, polar alignment so you get much better results (but it costs more).

So in the case of the OP...he mentions that the photos were taken 'unguided'. So...how did he take the photos? If it was not tracked...and it was unguided...what method was used? Logic will tell me that neither method was used in this case. Sorry I am just a bit confused on that.

If someone says 'unguided', in these circles it's taken as meaning tracked, but not guided. So it was taken on an equatorial mount with a motor (tracking) but no further computer assistance (guiding).

Thank you. That is what I was wondering.

ok, thanx for the clarification as well....i understand now

Excellent image Jeff. M42 is one of my favorite celestial objects.