C11 SCT mirror flop potential fix? Advice please?

[newbie alert]

1 hour ago, oymd said:

One last question please

How does the Croyford Focuser play with the Celestron f/6.3 reducer?

Can they work together?

Many thanks

 They have the same thread

[RT65CB-SWL]

58 minutes ago, newbie alert said:

 They have the same thread

...like this --->

[Merlin66]

I regularly use the C11 for spectroscopy...

I've fitted a JMI focus motor to get "best" focus...

The mirror slop/flop is generally caused by the grease on the baffle being "thinned out" by the mirror always sitting in roughly the same position...

Wind the focuser through full travel (about thirty turns) each way  every month or so to re-spread the grease on the baffle. This helps. And always approach final focus from the same direction.

I don't find the slop/flop to be an issue. (The Celestron focuser design is MUCH better than the Meade SCT's , which I had for many years!)

 

[oymd]

5 hours ago, Merlin66 said:

I regularly use the C11 for spectroscopy...

I've fitted a JMI focus motor to get "best" focus...

The mirror slop/flop is generally caused by the grease on the baffle being "thinned out" by the mirror always sitting in roughly the same position...

Wind the focuser through full travel (about thirty turns) each way  every month or so to re-spread the grease on the baffle. This helps. And always approach final focus from the same direction.

I don't find the slop/flop to be an issue. (The Celestron focuser design is MUCH better than the Meade SCT's , which I had for many years!)

 

Many thanks for that.

Can you please explain what you mean by: "always approach final focus from the same direction"?

I do not get that?

Also, do you know which direction does the mirror mover with clockwise and anticlockwise rotations?

Would like to know which direction moves the mirror backwards?

Many thanks

Ossi

[Merlin66]

When focusing, make the final focus movement by turning the focus knob anti-clockwise....If I remember correctly this moved the mirror down the baffle tube towards the rear cell.

Easy to check, just look into the front and watch the mirror movement....

 

[m.tweedy]

On my C11  (that i recently sold) I had the big threaded nut that is screwed in front of the mirror(for want of a better word) tightened. It did involve removing the corrector plate to do. Juergen who did it for me reduced the mirror flop a lot by tightening it up. It did not remove it completely even though i had a Starlight micro focuser instead of the stock focuser. I ended up buying one of the large format Crayford Focusers which meant the reducer screwed inside the actual Crayford. I then attached a cheap motor control (an Orion or Skywatcher) to stop the extreme vibration caused when trying to focus. At 2.7 metres any slight vibration is quite obvious.

It performed brilliantly.

I only sold it to enable me to buy an Ioptron CEM120.

You can of course do this. 

http://www.darkatmospheres.com/music/C11_Project/

Edited April 2, 2020 by m.tweedy
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