C11 Questions

[mtodman (Matt)]

I'm looking at picking up a used Cll XLT OTA to satisfy my planetary & deep space needs (especially imaging galaxies) and have a few questions:

1) Has anyone come up with an effective way of locking the primary mirror so as to avoid mirror flop? I've seen a few methods available but I'd like to know if anyone on these forums has sucessfully achieved this?

2) Field curvature & Coma - Which reducer / corrector should I be looking at? Would the standard Meade f/6.3 reducer do the job? Are there other ones out there better suited to the C11?

3) Piggybacking - I would probably look at piggybacking my FSQ106. Do you think the C11 OTA is solid enough for this?

4) Cooling - How important is this? I would like to get back into some planetary imaging. I've seen Paul Haese's Peltier cooling mod. Do I need to go this far? What advantages does peltier cooling have over installing fans alone?

Many thanks

Matt

[multiweb (Marc)]

Originally Posted by mtodman

I'm looking at picking up a used Cll XLT OTA to satisfy my planetary & deep space needs (especially imaging galaxies) and have a few questions:

1) Has anyone come up with an effective way of locking the primary mirror so as to avoid mirror flop? I've seen a few methods available but I'd like to know if anyone on these forums has sucessfully achieved this?

Yes - 3 bolts at 120 degrees will do the job. You need to drill the mirror cell and insert threaded aluminium nipples to accommodate for the bolts. You also need to fit some flat aluminium piece at the back of the mirror glass. I used a compound that bonds to glass, alloys and steel.

Originally Posted by mtodman

2) Field curvature & Coma - Which reducer / corrector should I be looking at? Would the standard Meade f/6.3 reducer do the job? Are there other ones out there better suited to the C11?

I'm testing this corrector. Just received it so will keep you posted. For planetary you wouldn't need it but for deepsky imaging and wider field yes.

Originally Posted by mtodman

3) Piggybacking - I would probably look at piggybacking my FSQ106. Do you think the C11 OTA is solid enough for this?

With proper dovetail and mounting yes. Will your mount take all the weight though?

Originally Posted by mtodman

4) Cooling - How important is this? I would like to get back into some planetary imaging. I've seen Paul Haese's Peltier cooling mod. Do I need to go this far? What advantages does peltier cooling have over installing fans alone?

Very important. I use straight fans and it's good enough for me. Paul does planetary at long FL so it's more important to get the mirror cooler in his case.

Originally Posted by mtodman

Many thanks

Matt

No worries - PM me if you need more details & pics.

[casstony]

There are two different styles of rear cell which may be an important consideration if you're thinking of cutting/modifying it - the flat Celestron style like Marc has, or the scalloped Skywatcher style (still a Celestron branded scope)

[multiweb (Marc)]

Here's a pic of the mirror and the cell. While you're at it fit two extra handles on the sides (bunnings bathroom section ) Top one is the original one. As PMd there's only one way all this can go on a C11 as there's not much room. The back of the cell has reinforcements in the cast as well which you don't want to drill into so it doesn't give you much choices about where you are going to drill the holes for the fans and the three bolts.