Beginner Astroimages

Peter.M · #1 13-09-2011, 01:27 PM

Hi all, I recently resparked my interest in astronomy and decided that I wanted to get into deep space astrophotography. After reading countless guides, forums and the like I bought a GSO 8 inch f4 Newtonian reflector. I mounted it on a HEQ5 pro and decided on the orion mini autoguider to keep the weight down. I spent the first night learning polar alignment using the starshoot autoguider with DEC turned off in PHD. The second night I quickly got the mount aligned and slewed over to the trifid nebula.

I had a few issues to contend with on the night. I had to guess the point of focus and take test shots because I have no focusing aid at the moment. The moon was full and very close to the target when I was finishing sub exposures. I also have a street light about 10 meters from me. I am happy with the result as what is the first time I have used this equipment.

The final image is 27 30 second sub exposures at 800 iso on my nikon d3100. 10 dark frames 5 flat frames and 50 bias frames were used. I have cropped to frame the nebula, I have no coma corrector at the moment and the edges of the frame are ruined because of it.

Any feedback fellow beginners have as well as more experienced people is very welcome.
http://i47.photobucket.com/albums/f1...tos/trifid.jpg
Thanks, Pete

asimov (John) · #2 13-09-2011, 01:35 PM

Well you have the data there Pete. Yes, I think you should seriously consider a coma corrector/field flattener as one of your next purchases.

A23649 (Nathan) · #3 13-09-2011, 04:01 PM

that's fantastic well done

jjjnettie (Jeanette) · #4 13-09-2011, 06:49 PM

I have the same scope and mount.
Well done!!
Yep, a coma corrector is certainly the go.
I've not done any imaging with mine yet as I don't have one.

RobF (Rob) · #5 13-09-2011, 07:49 PM

Congratulations Pete! What a stunning effort for your first post and pic

Most of us are happy to get stars in the centre looking as good as your slightly coma affected outer stars. I wouldn't be calling that "ruined"

Peter.M · #6 13-09-2011, 08:18 PM

Thankyou for your kind remarks everyone, the image that I uploaded is far better than the overall image coma wise because it is a centered frame that I have cropped. I am happy with the small coma present in the cropped version also.

jjjnettie (Jeanette) · #7 13-09-2011, 09:34 PM

are you using Photoshop?
You can artificially remove the coma by doing this...
go to ..... filter - distort - lens correction
then move the "remove distortion" slider over to the left to around -20.
It's only a band aid cure but make for a more pleasing image for now.

renormalised (Carl) · #8 14-09-2011, 10:01 AM

That is a great shot for a first!!!!

Well done

Peter.M · #9 14-09-2011, 11:56 AM

For this photo I used lightroom because I find that If I dont require major editing such as masking it is alot easyer to use than photoshop. I do however have photoshop should I want to use it and I will give that lens distortion a go soon.

Last night I thought I would try something a little harder to photograph. I am still unsure what will be a good target for my gear level and light polution combination. I decided on giving NGC 6744 a go. I have always wanted to photograph galaxies, just the thought that you are taking a photo of billions of stars, and that the photons that you are capturing have been in space for millions of years before we capture them with a camera.

The limiting visual magnitude in that area of the sky was about 4-5. I took some test shots and decided on an exposure of 1 minute, later when processing I wish that I had chosen 2-5 minutes. I took 41 useable frames, and stacked them into this photo.

I read somewhere that nikon cameras had an inbuilt noise correction feature where they would take a dark frame after every exposure and subtract it. I went looking and found that it had been on for all of my images so far. Because I planned to take my own dark frames later I decided to turn it off to speed up light frame capture. The time it takes to make one exposure halved, however I think one of the artifacts of this was the red noise in the image.

Being a beginner I am happy that I got anything at all from what is a fairly dim target, I think I even captured its companion galaxy ngc6744a in the top right of the frame. However I am somewhat of a perfectionist and would love to improve this effort.

Any guidance on a better target to shoot, or simply in the exposure time would be greatly appreciated. (the image was 60 seconds at iso 400)

Cosmic (Daniel) · #10 14-09-2011, 01:27 PM

Great images, your off to a good start there

Peter.M · #11 15-09-2011, 01:48 PM

Reprocessed version.