Slight issue with home made 8" F4 astrograph

[chrissuddell]

Hi,

I have recently completed (appart from the baffling and flocking), a bitza home made F4 8" scope using a GSO 8" F4 scope as the doner for the optics, custom tube, rings, primary support, secondary support and GSO monorail focuser.

DSCN4265 by chrissuddell, on Flickr

DSCN4263 by chrissuddell, on Flickr

DSCN4262 by chrissuddell, on Flickr

DSCN4261 by chrissuddell, on Flickr

DSCN4260 by chrissuddell, on Flickr

Flat Newt by chrissuddell, on Flickr

I beleieve the collimation was very good, but I'm getting some odd shaped stars on the top left of my test image.

M101-6-5-min-Sig by chrissuddell, on Flickr

Alkaid by chrissuddell, on Flickr

The setup was 8" F4 scope, MPCC and QSI583, this image is 6x5 Minutes L for M101 and 6x2 minutes on the bright star just to test the secondary, very little processing because its just a scope test.

I wondered if anyone has any ideas what this issue could be, I'm begining to think its the MPCC, I have this image with a different scope and optics still an 8" F4, with a DSLR and the same MPCC? IMG_0592 | Flickr - Photo Sharing!

Any thoughts or comments would be appreciated.

Chris

[Macavity]

No technical thoughts (or solutions!) but some impressive modifications.

And something (ultimately) worthwhile re. these "interesting" scopes.

[Moonshane]

your secondary is not central based on the pic. not sure if this would produce the bloated stars though.

[terrym2002uk]

Have you tried doing a star test to check the pattern?

[nytecam]

Have you tried rotating camera 180 deg to see if effect swaps to opposite corner? If so it would point to camera/ccd placement.

[chrissuddell]

Hi,

I don't think its the camera CCD placement, I took this recently and I think the stars are on in the far corners with this image. This is without the corrector on a Tak at F4.5.

Chris

m78 LRGB Lighter by chrissuddell, on Flickr