Friday, December 22, 2023

Improving Coarse Adjustment on Polaris

Getting the Losmandy mount properly aligned no True North was possible but not easy.  The field of view in the Polar Alignment Scope is a bit narrow.  Someone on Cloudy suggested that I put a laser pointer in the polar axis use the beam to get a coarse aim at Polaris.  This would get the Polar Alignment Scope close enough for fine adjustment.

Fine idea so I machined an adapter to hold the laser pointer centered in the polar axis where the Polar Alignment Scope (PAS) normally sits.  That tube is 22mm diameter so I found some scrap aluminum that I could turn down to 22mm.  It is not a tight fit but then again I do not want friction impairing the fit of the PAS in the polar axis.

The laser pointer barrel is 16.6mm.  My largest twist drill that does not look like a prop from the 1960s terrible Land of the Giants series is a 1/2" bit.  My boring but is not long enough to bore out the needed length.  Yes, I came up with a clever workaround a week or so ago.  But better was to find a 17mm twist drill.  If one exists that is not made in the PRC, I could not find it.  Fortunately I found an American-made 9/16" bit which is about 17.2mm.  Close enough.  I do not want a press fit.

The steady-rest served its function as I drilled the 1/2" hole large enough for the laser pointer to easily slip in place.  My original plan was to put the laser pointer in the hole butt-end first but to get the on button to a useful position required enough cutting to take a different approach.  I put the business end into the 17.2mm hole turned the laser up to 1 MW and bored out a hole in the other end.  No, really I drilled a .157" hole in the far end so the beam goes out.  It slides into the base of the PAS bore and I can press the on button.  

The laser pointer will still fall out of the adapter and both fall out of the bore.  Tomorrow, I will drill and tap a 1/4"-20 hole in the side of the adapter and use a set screw to keep the laser pointer in position.  (This should not push the laser pointer too far out of center.  Even .6mm offset should be fine.,). I will put some masking tape on the outside of the adapter so it sticks in place at least approximately.

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