Re: [APML] Tech Pan/Ha filter focusing

["Richard Payne" <astropix@msn.com>]

Scott, you can only use a different filter to focus your Ha filter if it is
the exact thickness as the Ha, which
you can bet it's not. I have gone through this with my Schmidt camera. I use
a holder machined specifically
for a Lumicon Ha. The easiest way would be to use a good dial indicator and
shoot a series of 1 or 2 minute exposures
and rack it out .002" at a time and scan and select the best shot and
reshoot to confirm. Then you merely focus
with a knife edge and indicate it the correct distance. Probably sounds
harder than it really is.
Don't try using a dial caliper because it won't be as accurate. Let me know
if I can be of further assistance.

Richard Payne
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