View Full Version here: : First serious Galaxy imaging attempt
24-03-2012, 03:12 PM
Last night was a nice clear night so I decided to give my first real attempt to polar align the CGEM as accurately as I could and attempt to image my first galaxy using autoguiding and multiple subs. I took a photo of the Sombraro Galaxy back in June, but that was a last photo taken just as I was packing up, no guiding, no serious attemtion and all I had was a blur.
Last night I started with the Jewel Box in Crux... 5x30sec subs and 5x1 min subs... then I moved onto M96, took 10 x 1 minute subs and 10 x 5 minute subs. Last of the night I found M100 and took 5 x 5 minute subs and 1 x 10 minute sub before I had to packup to get ready for work.
I processed and stacked the images in Nebulosity 3, then shrunk the images in photoshop to try and make the images look sharper.
Both Galaxy exposures were taken through a Celestron UHC/LPR filter, and all images were taken with a unmodded Canon 40D, f6.8 focal reducer/CC on the NexStar 8SE.
My stars look fuzzy and not sharp points of light, I'm quite sure that I was in focus. I used a Bahtinov mask to focus before exposing.... I would greatly appreciate if anyone can give me any advise on how to improve on these images so they actually look like galaxies and not just smudges.
24-03-2012, 09:18 PM
for long exposures the polar alignment needs to be really spot on for the stars to remain nice, also they look a little dark for the time put into them
24-03-2012, 09:46 PM
What ISO setting are you using?. Are you guiding?
25-03-2012, 11:42 AM
Thank you for the replies.
The ISO i was using was ISO800, through a Celestron UHC/LPR filter which does darken the image a bit. I had to use it because otherwise I got the milky orange sky glow on the exposures, and even with the filter I still had to play with the blackness in nebulosity and fair bit.
I was guiding using a DMK41au02, through a f3.3 recucer connected to a 80mm f6.25 (500mm) refractor and that was feeding the laptop running PHD, the controler I used was the GPUSB back to the guide port on the CGEM.
I didn't get streaking or loss of guide star at all for the duration of the exposures (One was for over an hour and the second for almost a hour) so I assumed that my polar alignment was very close... as with everything, there is always room for improvement in my polar alignment.
I wish I had more opportunity to use the gear since practise makes perfect, the weather was horrendous, and this being the first serious attempt, to be honest I didnt expect too much... Not too long ago I was getting advise on planetary imaging and with a bit of practise I got a couple deascent pics... no where near as some I seen here, but a lot better then my first attempts.
Do you think its dark for the exposure time because of processing, sky glow.... combination of both??
25-03-2012, 08:01 PM
Take a 5 second single image and see if the stars are sharp, if not then your focus may be off.
26-03-2012, 01:12 AM
Your images are excellent for first attempts. It is not easy to image these galaxies and you will need a lot longer imaging time in the order of 3-4 hrs worth of data as well as setting yourself up for guiding your mount.Might i suggest APT if you are using a Canon DSLR for image capture and do it from a dark site so that you can get rid of the LP filter.
Also pick something bright such as M42 or the Eta Carina nebula to image. Keep on imaging these until you get your focus spot on using APT and a Bahtinov mask and really look at each image to be sure you are focused. Then goto your object and get 5min subs and a lot of them. Then stack and look at the resultant image.
Its a long hard road to go down but very satisfying.
26-03-2012, 09:01 AM
I am only new to this whole thing myself. Have you tried guiding without the reducer? The m95 image shows some signs of drift. Just experiment using different combinations. And like others have said, start with the bright stuff to hohn your skills.:thumbsup: Great start though..
27-03-2012, 11:28 PM
Thank you for the responses, great and encouraging feedback and advise, I greatly appreciate it.
I used a bahtinov mask to focus, so I thought that focus was spot on, the polar alignment might need a bit more attention. Especially if I need to expose, or gather subs, for a total of 3-4 hours!!!
Next time I'll try to guide with out the reducer as suggested by Starcrazzy, I guess it would pickup more of a drift to correct while guiding if it was f6.25 rather then, with the f3.3 on a f6.25 refractor, is f2ish...
Now just to get another clear dark night where I don't need to work the next day...
27-03-2012, 11:38 PM
Looking at the images again, your stars are all 'fuzzy' in a given direction, it looks like an alignment issue to me.
Definitely lose the reducer, it has serious distortion which will throw your guiding out the window.
28-03-2012, 11:08 AM
28-03-2012, 11:11 AM
Is the the bright star on the bottom of the m95 the supernova? Lucky shot of it is;)
29-03-2012, 10:03 AM
It's the M96... Supernova??? Either a supernova or a over active pixel :D
02-04-2012, 10:13 PM
I got a copy of APT as recommended by Allan Gould...
Thanks Allan, the program is great.
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