Comments on: Copeland’s septet (Hickson 57) http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/ Occasional observations about astronomy, astrophotography, and software Tue, 18 Nov 2008 15:11:06 +0000 http://wordpress.org/?v=2.3.2 By: Vern http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-353 Vern Fri, 21 Apr 2006 22:35:19 +0000 http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-353 The longest time the Stellacam2 can expose is about 8.5 seconds. The 8.5 second exposures can be stacked to decrease noise. I typically image an object for about 20 minutes, so I take about 150 images in that time. With Registax3 I then use the "rotation" button to align the images and eliminate any rotation which might result from having the equatorial mount not exactly north. As I recall, there was a very slight amount of rotation evident with a motor driven alta-azimuth mount with 8.5 second exposures. However, you can get just about as deep with only 4 second exposures. I often switch to 4 second exposure (occasionally 2 second) if its a bit breezy. I think you should be able to get very good images on an alti-azimuth mount if it was solidly built. The Stellacam2 is an amazing device -- with my 11 inch Nexstar I can get to nearly 17th magnitude here in a light polluted Denver suburb. That is as visually deep as a 30 inch can go at a dark sky site! Not as much resolution, a 30 inch is still preferred -- looking at a notebook screen is not the same as looking though an eyepiece. The longest time the Stellacam2 can expose is about 8.5 seconds. The 8.5 second exposures can be stacked to decrease noise. I typically image an object for about 20 minutes, so I take about 150 images in that time. With Registax3 I then use the “rotation” button to align the images and eliminate any rotation which might result from having the equatorial mount not exactly north.

As I recall, there was a very slight amount of rotation evident with a motor driven alta-azimuth mount with 8.5 second exposures. However, you can get just about as deep with only 4 second exposures. I often switch to 4 second exposure (occasionally 2 second) if its a bit breezy. I think you should be able to get very good images on an alti-azimuth mount if it was solidly built.

The Stellacam2 is an amazing device — with my 11 inch Nexstar I can get to nearly 17th magnitude here in a light polluted Denver suburb. That is as visually deep as a 30 inch can go at a dark sky site! Not as much resolution, a 30 inch is still preferred — looking at a notebook screen is not the same as looking though an eyepiece.

]]> By: peter http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-352 peter Fri, 21 Apr 2006 21:02:04 +0000 http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-352 I get dark sky envy when I see all these images of galaxies. Great grabs. I am not familiar with how the stellacam works. Do these shots require a motorized equatorial mount and long exposure times? Could one use a Stellacam on non-motorized and then stack images? peter I get dark sky envy when I see all these images of galaxies. Great grabs.

I am not familiar with how the stellacam works. Do these shots require a motorized equatorial mount and long exposure times? Could one use a Stellacam on non-motorized and then stack images?

peter

]]> By: Andrew http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-351 Andrew Fri, 21 Apr 2006 18:25:56 +0000 http://www.raben.com/weblog/2006/04/20/copelands-septet-hickson-57/#comment-351 I'll see if I can image this with a DSLR...Probably not but,it is worth a try!!!. I’ll see if I can image this with a DSLR…Probably not but,it is worth a try!!!.

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