Coma correctors for fast newts

[pmrid]

There's the MPCC of course - something of a standard - but when backfocus problems make the MPCC unworkable, you go looking for alternatives. I need to find a corrector that will give me another 5 or 6mm to play with. What do others use on their fast newtonians (if anything)?

Peter

[Alchemy]

I found an MPCC gave me some extra back focus on my 12 inch, it appears its not enough for you though.
other alternatives are.
1. A low profile focuser, ..... Somewhat problematic I found due to less support in the mechanism led to heavy cameras pitching and becoming off axis.
2. Cutting the tube and relocating the mirror further up the tube, by an amount that you can buy as an extender ( I think I ended up doing a 50 mm cut)

[Alchemy]

I found an MPCC gave me some extra back focus on my 12 inch, it appears its not enough for you though.
other alternatives are.
1. A low profile focuser, ..... Somewhat problematic I found due to less support in the mechanism led to heavy cameras pitching and becoming off axis.
2. Cutting the tube and relocating the mirror further up the tube, by an amount that you can buy as an extender ( I think I ended up doing a 50 mm cut)

[Tandum]

Peter, if your looking for more space between the corrector and sensor then a keller corrector might be it. http://www.astrosysteme.at/eng/correctors.html

Get your wallet out :)

[gbeal]

Before I shelled out for the big ticket Kellor, I'd be looking to "modify" the MPCC. Any competent machinist could gain you 5-6mm I reckon.
Gary

[pmrid]

I was just looking at the OPT site and in paticular at their instructions for using the set of adapters Baader sell as an accessory for their MPCCs. The instructions indicated a tolerance of +/- 3 mm in that 55mm distance. I wonder if anyone has found the MPCC does in fact have a margin of error of that magnitude.
Peter

[gbeal]

I'm sure mine does, and the AT2FF does as well.
My TRF2008 on the other hand does not, it limes about 50mm, not the documented 55mm. One way to find out..........
Gary