C11 general enquiry

[multiweb (Marc)]

I'm going to have access to a C11 soonish and I'm starting to do a bit of reading having never used an SCT. The idea is to do a bit of long FL imaging and close up. I'll be using the QHY8 and a Losmandy G11. Anyone has experience with that kind of rig? I'm thinking of using an off axis guider (QHY5) as to minimise the weight or any flexure issues. I'm aware SCT are prone to mirror flop and coma. Is there any Field Flattener out there recommended for the C11? I currently have a Baader MPCC but I doubt it would do the job of such a long FL. As always thanks for any help and pointers.

[33South (Chris)]

Marc,
The Baader is no good for the C11 only fast scopes to f6.
Celestron have (had?) an f3.3 for imaging and f6.3 for visual and imaging which as far as I know are basically the same as the Meade 4000 series.

Bintel advertise the Meades at A$195 and A$179

[netwolf]

The Mogg reducer is cheaper and has shown very promising results. The F6 reducer can be reduced to F3 with a Extension tube that is also sold by Mogg. But at F3 this is would have vigneting for a sensor the size of the Qhy8.

[gbeal]

I looked at this when you first posted, and considered you were looking at a field flattener, not a reducer, is this correct?
If so, and assuming you have both pieces, try the MPCC. OK, as some suggest it is designed for a faster instrument, it "could" work, so try it. I know this from personal experience, having used mine for removing the coma on an 80mm refractor, where others said it won't work.
I alkso have an AP 67CCD Telecompressor, which if I had known about a week or two ago could have let you try, as it was on holiday in Ozzie, but has since returned.
Bear in mind the flattener or MPCC will require a specific distance from the chip, and the OAG will be part of this distance perhaps. I looked at trying an OAG a while back, but gave up, it was just too hard. I cannot see what a decent low mounted guide-scope will be any worse than the OAG, and in fact prefer this to a side by side. YMMV.
Gary

[multiweb (Marc)]

Thanks for the feedback guys.

Originally Posted by gbeal

I looked at this when you first posted, and considered you were looking at a field flattener, not a reducer, is this correct?
If so, and assuming you have both pieces, try the MPCC. OK, as some suggest it is designed for a faster instrument, it "could" work, so try it. I know this from personal experience, having used mine for removing the coma on an 80mm refractor, where others said it won't work.
I alkso have an AP 67CCD Telecompressor, which if I had known about a week or two ago could have let you try, as it was on holiday in Ozzie, but has since returned.
Bear in mind the flattener or MPCC will require a specific distance from the chip, and the OAG will be part of this distance perhaps. I looked at trying an OAG a while back, but gave up, it was just too hard. I cannot see what a decent low mounted guide-scope will be any worse than the OAG, and in fact prefer this to a side by side. YMMV.
Gary

Yes, I'm worried about the field not being flat. I guess I'll have to do some testing. As for the OAG I thought in case my G-11 doesn't take the C11 + one guide scope (ED80) it would be the prefered solution but reading further I hear people being able to handle the weight.

[gbeal]

And don't go past building a plate to have the ED80 (or whatever) closer to the RA axis. It will require some thought, and a little ingenuity but having the guide-scope right in close brings the weight down and closer, two good scenarios. I have never been a fan of the SBS system simply because of the extra weight.
Gary

Yes, I'm worried about the field not being flat. I guess I'll have to do some testing. As for the OAG I thought in case my G-11 doesn't take the C11 + one guide scope (ED80) it would be the prefered solution but reading further I hear people being able to handle the weight.[/QUOTE]