I agree Don, and that's what I was alluding to. It's an excellent shot. Bloated stars are a sign of soft seeing. On Jan 28, 2014 5:14 PM, "Don J. Colton" <djcolton@piol.com> wrote:
I think the bloating was more a function of the seeing. I couldn't get as tight of focus as normal even with short exposures. Usually FWHM is about 2-3 on 6th mag stars but I was getting about 5 at best.
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Tuesday, January 28, 2014 2:35 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Longer Focal Length Imaging
The stars are a tad bloated Don, but even so, that is an excellent image. Keep going, and well-done!
On Tue, Jan 28, 2014 at 2:16 PM, Don J. Colton <djcolton@piol.com> wrote:
I have been experimenting with imaging at longer focal lengths using the SBIG STT-8300 with FW8G-STT, filter wheel with built-in-guider. I have been using the Mewlon 250 with the Astro-Physics .67 focal reducer. This gives a focal length of 2010 mm or 79.13 inches. At this focal length a guide scope is difficult to use without getting flexure. Using off-axis guiding is the most effective way. The new SBIG filter wheel intercepts some of the light with a small off-axis pick off mirror and passes it through a focal reducer before going to the separate built in guide camera bypassing the filters so you always guide with unfiltered light.
This setup allows long guided exposures at relatively high magnification. On Saturday I took 9 - 15 minute luminances and 8 each 5 minute RGB images and combined them for the image of M 51 (see below link). Not one image had any star trailing, which I find quite amazing. The seeing was not very good which I think affected fine detail.
http://www.slas.us/gallery2/main.php?g2_itemId=5755&g2_imageViewsIndex =1
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