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Old 09-08-2018, 10:05 AM
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Merlin66 (Ken)
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Join Date: Oct 2005
Location: Junortoun Vic
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The mechanical focusing mechanism used for the SCT's - both Meade and Celestron are used to move the main mirror up/ down the central baffle tube.
The very fine gap between the baffle tube and the mirror "boss" can cause some mirror flop - the is the same for both. Re-spreading the grease regularly by running the focus through the full travel a few times help reduce this flop.

In the Meade the focus knob joins the rear of the mirror support with a pin (the Celestron use a fixed threaded rod) and this can cause some extra focuser movement - you quickly learn to finally focus from one direction.

To ensure mimimum slop/flop (while using the spectrograph) I resorted to fitting a mirror lock (MAPUG design) which allowed the mirror/ focuser to be "locked" into position after focusing. This worked well for me, especially on the 12".

Nothing to be really concerned about, just need practise and you'll quickly come to terms with it.
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