Re: [APML] More New Images Posted

["John C. Mirtle" <spampit@shaw.ca>]

Thanks Dean,
    I have not shot with the f6 compressor and I doubt that I will. I have
been using an 8" f6 Newtonian since 1987 and I wanted a "change of scenery".
There are some issues with the compressor. The biggest is that it changes
the back focus point. You cannot use an off-axis guider with the compressor,
you must use a guidescope. At least with this design, there is no mirror
flop to complicate using a guidescope. From what I understand, the field is
still flat but vignetting is increased.
    I plan to use it with a CCD, mostly to image really small objects. With
my ST237a, I need 2 frames to get M51! It should work out nicely for
planetary nebula but at this time I do not have any CCD images.

John Mirtle
Calgary, Ab. Canada

----- Original Message ----- 
From: "Dean Jacobsen" <deanjacobsen@earthlink.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Monday, July 28, 2003 8:17 PM
Subject: Re: [APML] More New Images Posted


Both shots are very nice John.

The Vixen tube looks to be a winner.  Have you had a chance to take any
shots in the f/6.4 configuration or with a CCD?

Dean Jacobsen
www.astrophoto.net

At 06:27 PM 7/28/2003 -0600, you wrote:
>     It's been a while since I have done this, but - I have some new
images!!
>These are my first-light images on a new mount with a new optical tube.
>Manfed Wasshuber got me interested in the Vixen VC200L as a way of getting
a
>longer focal length without all the "gotcha's" of an SCT. Last night's
>effort bore fruit, and all 3 would have been worth posting if I didn't
>insist on manually guiding one of them. :-)
>     The Vixen really does appear to be flat field, I cannot see any
>difference in the star images from centre to edge with tech pan. Vignetting
>is minimal, diffraction spikes included and focus is easy at F9! I used an
>ST4 to guide using a Lumicon NEG. The off-axis images focus up nicely to
>points, instead of the comatic blob found in Newtonians. As a result, it
was
>very easy to set up and focus with the ST4 through the NEG. The background
>is a bit uneven with the NGC891 shot, due to my tech pan being over 1 year
>old. Comments welcome......
>
>http://members.shaw.ca/jmirtle/n891.htm - full frame
>http://members.shaw.ca/jmirtle/m71.htm - cropped 50%
>http://members.shaw.ca/jmirtle/equip.htm - Vixen photo at bottom of page.
>
>John Mirtle
>Calgary, Ab. Canada
>
>_______________________________________________
>Astro-Photo mailing list
>Astro-Photo@seds.org
>http://seds.org/mailman/listinfo/astro-photo


_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo

_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo