Eliminating vignetting on a full frame.

avandonk · #1 10-02-2008, 03:52 PM

A full frame camera suffers from vignetting even with a 2 inch focuser. I managed to pick up another Astro Physics 2.7 inch focuser and had Luke Bellini from Starstuff make an adapter to suit the 150mm F5 Achro. He also made two adapters that allow me to connect Borg bits to either focuser without having to use a 2 inch nose piece. The only thing now that even starts to limit the clear view of the full frame to the whole of the 150mm objective is the 48mm filter near the camera. The Borg bits have an ID of 53 to 55 mm.

I am getting a side by side unit to hold all of my scopes from Starstuff. This will allow the use of the fridge with either the 100ED or 150mm achro and allow rotation to get better framing.

Bert

robgreaves · #2 10-02-2008, 04:11 PM

Looks good - a nice job of adapting that great AP focuser.

That should help with vignetting, but surely the ongoing problem will be off axis coma and spherical aberration? How flat is the field of your achromat? What are the stars like at the corners of your (now un-vignetted!) full frame?

Regards,
Rob.

avandonk · #3 10-02-2008, 04:30 PM

Rob here is an earlier thread on this setup.
http://www.iceinspace.com.au/forum/s...ad.php?t=23971

Below is an image produced by HA and O3 data at an ISO of 1600.

The Borg or Hutech FR/FF flattens the field nicely. Turns the 150mm F5 into an f/4.5. The AP FR/FF should also work quite well and then we will have a 150mm f/3.75!

Bert

robgreaves · #4 10-02-2008, 07:42 PM

Hi Bert

Thanks for posting that - your setup definitely works! Nice to see stars pinpoint to the edges.

Regards,
Rob.