Re: [APML] OT: 240 Galaxies in 3 square degrees of Virgo

[Jerry Lodriguss <lists3@astropix.com>]

Hi Don,

I don't know for sure what's causing the elongated stars in the upper left, 
but I have a guess...  It's  not field rotation for sure, I spent an hour 
drift aligning and the exposures were only 7.5 minutes.  It's not 
atmospheric differential refraction.

I think it's astigmatism because the camera's focal plane was not perfectly 
coincident with the focal plane of the scope.  The camera is very heavy and 
I have an Astro-Physics 2 inch adapter with EOS T-mount. There is a LOT of 
slop and play in the EOS T-mount adapter the AP is using, and I just think 
the weight of the camera pulled that corner down.

At least that's my guess right now.

The AP adapter also vignettes, even with the smaller size chip than a piece 
of 35mm film, so I'm looking for other solutions to this problem right now.

Jerry


At 12:03 PM 4/18/2005, you wrote:
>Jerry,
>
>That's simply amazing to see so many galaxies in one view.  I'm looking 
>forward to trying a DSLR with my scopes.  You show what's possible.  BTW, 
>do you know what is causing the elongated stars in the upper left?  With 
>the short exposures it shouldn't be FR nor ADR.
>
>Thanks,
>Don
>
>>
>>I've just posted a picture of the heart of the Virgo Cluster that shows 
>>240 galaxies in a 3 square degree field.
>>
>>It's at:
>>
>>http://www.astropix.com/HTML/SHOWCASE/VIRGO.HTM
>>
>>The field of view is 2.5 x 1.25 degrees in a 5 inch refractor working at 
>>f/6 taken with a Canon 1D Mark II DSLR camera.
>>
>>10 individual exposures of seven and a half minutes each were averaged 
>>together in a single image.
>>
>>I've also posted the full-resolution image with an overlay at:
>>
>>http://www.astropix.com/IMAGES/SHOWCASE/VIRGO240.JPG
>>
>>Warning!  It's a 540kb JPEG that opens up to a 23mb file!
>>
>>There is also an enlargement of galaxy M87 where the jet coming out of 
>>the galaxy's nucleus is visible.
>>
>>Thanks for looking,
>>
>>Jerry
>>
>>Photoshop for Astrophotographers
>>http://www.astropix.com/PFA/PFA.HTM
>
>
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