Any evidence of mirror "flop" in SCT?

[Merlin66]

What I'm looking for is an image ruined by the mirror "flop" movement in an SCT. Can you help?

Yes, I know there can be mirror "slop" during focusing, but during imaging - does the mirror actually "flop" around to be a real problem.

(I should say I've asked this question before and got no real evidence...)

Another Urban Myth - for the Mythbusters????

[earth titan]

I'm interested in this as well. Just started doing some imaging using a 200mm sct without mirror lock. No evidence as yet - will let ya know..

[Earl]

I hear that flop can occur when crossing the meridian, however I have not experienced this.

[budski]

Earlier this year I ran a series of tests on my C11 to determine if mirror movement (slop/shift) occured when the 'scope was slewed to the horizon or during focusing. The glassware, especially on an 11 or 14 inch unit, constitutes most of the instrument's weight but is less of an issue with the 8 or 9.25 models. In practice there was enough play in the teflon greased sleeve to ruin collimation (set at near zenith) and the backlash on the native focuser also affected alignment. For that reason I added a MoonLite Crayford focuser and manufactured an adjustable mirror locking system.

[Tim]

I've never noticed it Ken.

I have always made sure to do the final focus adjustment anti-clockwise, (I think thats the right way), but have never had a problem with the mirror going off. And that is true even when imaging at F10 (2350mm fl), where it would show up immediately.

Tim

[Merlin66]

Budski,

I don't think slewing the scope around is a good measure of the effects of flop during imaging.

The attached write-up make give some insight.

Conclusions:

You don't need a Crayford for focusing

The average flop is much less than thought and can be guided out without a problem

SCT mirror flop.doc