Thursday, January 21, 2010

CGEMs, CGEMs Everywhere!

Tonight was a bit of a laugh. The forecast was for very clear and steady skies despite the moon which was at around 36% illumination. I headed to the local, popular observing spot to explore my CGEM mount again. Well, I was joined by four others with their CGEMs! All had different scopes mounted on top of them, but it was certainly quite funny to see five CGEM mounts out under the stars together. It looked like a Celestron commercial!

Tonight I went through the entire setup procedure again, including the two-star alignment procedure, adding calibration stars, polar alignment and periodic error correction. Again, the CGEM mount left me speechless! I was done with the initial alignment process in a couple of minutes, the mount places the first and second alignment stars well within the field of view of my 12mm illuminated reticle eyepiece. Polar alignment was complete withing about five minutes, and I checked for drift and hardly noticed any over a two-to-three minute period. Then, I went into the Periodic Error Correction (PEC) menu and watched the playback, and it looked like it did indeed remember the PEC settings I made last time I was out, just like the manual said it would!
It really is an amazing mount to use, and you can be observing and taking relatively decent photos in very little time at all.

I took a quick snap of the moon. It looked gorgeous and beckoned to be imaged. The shot is below. It's quite nice and the AstroTelescopes ED80mm handled and resolved it quite well.

I took several images this evening. Despite the moon, I really wanted to see how well the mount tracked without guiding. I went to the Double Cluster, which is a useful object because it is bright and contains tons of stars, making it a good subject for mount testing, in my opinion! Anyway, I took a series of two minute exposures, and the result was very impressive (see below). Ignore the shoddy focusing job! The stars themselves are very sharp and rounded, showing little signs of polar drift. With guiding, this mount is going to be amazing!

Image Details:
  • Nikon D40 DSLR
  • AstroTelescopes 80mm ED Refractor
  • Celestron CGEM, unguided
  • 6 * 2 minute light frames
  • 4 * 2 minute dark frames
  • 20 bias frames
  • Processed in Deep Sky Stacker
  • Tweaking in IRIS

Next week, or thereabouts, I'll write up a more detailed review of the CGEM mount and the AstroTelescopes 80mm ED OTA that I now own. Next month, I'll take this awesome rig out toe the dark sky site, where I hope to try my hand at guiding and capture some faint fuzzies!


Anonymous said...

Way to Go Phil,Brent here in Orlando,FL aka HelloBozos online...I switched out my Nexstar8se mount to the CGEM as well.I put the 8SE's tube on it.I have my CGEM 80mm PHD guided.I can "Set-it an Forget-it"..heh..pardon the informercail pun..all night..I just stop exposing to spin the filter wheel an then press the blub of the CanonT1i's remote an away the exposers go again...I only lack dew heaters an house for it all now


Phil said...

Hi Brent!
Thanks for the post! Yeah, I really like this mount and it has far surpassed my expectations of it already.
I am hoping to use PHD next month. Let me ask you - what mount do you select for the CGEM within PHD?

Polaris B said...

Nice Double Cluster, Phil! I'm excited for your longer exposures. The mount looks like a winner. I hope it is as responsive to PHD as it is to its internal electronics.


Phil said...

Thanks, Val! Me too! I have seen folks use it with PHD successfully so hopefully next month I'll give it a go...

Jeff said...

Hi Phil,

I'm curious - are you using any software to control or focus your D40? Do you use an IR remote?

Phil said...

Hi Jeff,

Well, I don't use any focusing aids yet. My method right now consists of:
1. Goto a bright star close to the object I am imaging
2. Focus, take a 20 second exposure
3. Examine picture on back of camera, zooming way into stars to look for sharp image and near equal distribution of pixels, adjust focus if needed
4. Keep taking shots and reviewing until happy with outcome
5. Goto desired object
6. Take 1 minute exposure
7. Examine image carefully as per step 3 above, adjust if necessary
8. Start long exposures once satisfied

I pick an object close to the star because I think that focusers do travel a little bit while slewing to other objects. Thinking of it now, I really should just use my focus lock knobs *slaps forehead*

I think my images are okay, focus-wise. What I would like to do is get some focus assistance software (Nikon D40s are fairly limited in this degree) OR build one of those fancy focus masks...

I do use the IR remote. I have Nikon Capture Control software that I could use to control the camera, for some odd reason the software decides to delete frames at random due to them being "out of focus", which is annoying. So for now, I sit around and shoot the camera with my IR remote. It's good exercise for the arms...

The D40 isn't designed with astrophotography in mind. I bought it because it was a good priced entry-level DSLR with d ecent features and very good reviews. Having said that, with a bit of work and tweaking, it can produce decent astro images.


PS Great blogs!!!! I like aviation, too - always looking up!

Donald said...

Hi Phil. I just purchased a CGEM with 8" HD. Unfortunately after having the mount for 2 days I was experience alignment issues where the mount experienced "RA Runaway." Celestron is replacing the mount. Anyway, after you do the All Star Polar Alignment do you check to see through Drift Alignment to see if the process worked well? I'm interested to see your pictures with you use the auto-guider. Thanks. Great pictures!!

Phil said...

Hi Donald,

Thanks for visiting, and for the compliments on the photos!

So, my process is thus:
1. Initial alignment on Pole Star using the polar alignmnet scope
2. Turn on mount
3. Enter/Confirm date and location
4. Do a two star alignment
5. Go straight to Calibration process, using as many stars as you can.
6. THEN do Polar Alignment process (follow exact instructions on screen)
Voila, that is it. I use a barlowed reticle eyepiece to insure precise alignment on stars, and after step 6 above I watch it for a while to see if I can find any drift. Usually I don't (thus far)

This is good enough to get the autoguiding going. I went for a full spin under dark skies two weekends ago, shooting M51 and M81/M82 with my 80mm ED refractor. The results are on my newer blog entries and I am pretty happy with them.

Sorry to hear about your misfortune. Let me know how it goes...