|
Hi Paul,
I also have the Meade focal reducer, and have used it succesfully with the SBig. The pics you're showing look like it's outside the focal distance for the FR. How do you have it attached to the SBig? Do you have a CFW as well?
When I use mine it's attached to a cheap 1.25" VB, which is about an inch long and has t-threads on the 1.25" end, these screw directly into the CFW. Then the FR is screwed on the front and a 2" SCT adapter on the front of the FR into the focusser. I get some coma towards the outer edge of an ST10 chip, which is far bigger than your ST7 chip. I used to have an ST7, don't remember any problems using it. I generally use an Optec f5 reducer now (bought from IIS), the back focus distance is set for ST camera with CFW, it's great for an ST7 sized chip, but the ST10 presents it with some problems. I have double stars on the guide chip (don't ask me why, but it happens with the Meade FR as well, so I think it's just getting towards the edge of the FR range).
The optimum FR to CCD distance varies depending on who you talk to, but 87mm is the current best thinking, closer seems to be OK, further away is not on from my experience.
Cheers
Stuart
|