Moose asked:
"In exposures measuring from 10s of minutes to hours, what difference
does mirror lock-up make?"
----------------------------
Answer: None
However, not all astrophotos are hours long. Lunar and planetary stuff
is in the right range to be affected by mirror and aperture arm vibration.
Although I wrote the praise of the OM-1 for its mirror lock-up the
lock-up feature is actually a pain to use. At the high magnification
required for planetary and some lunar photography, by the time you quit
fiddling with that teeny-tiny mirror lever the scope is not likely
precisely on the target any more and you can't see through the
viewfinder to verify whether it is or not.
What I would actually do is use the "hat trick". Cover the end of the
scope with a hat or cloth, open the shutter, remove the cloth for the
duration of the exposure, replace the cloth at the end of the exposure
and the close the shutter.
Actually, what I would actually do is none of the above. I gave up
astrophotography as too damned much trouble a year or two after buying
the OM-1 in the '70's. Replacing my Miranda GT with an OM-1 didn't make
me a better or, more importantly, a more patient astrophotographer :-)
Then Fernando said:
"Battery drain is nonsense, how many times shall I write this."
Well, after being on this list for about four years I don't ever recall
Fernando writing this. On the other hand, as my wife frequently reminds
me, I don't recall much of anything these days. So I ran off to check
the bodies immediately at hand. Removed the batteries and fired them
all on "B". OM-2n and OM-2sp are totally mechanical in "B". Clearly,
battery drain is not an issue. OM-PC/40 is not mechanical in "B". With
no batteries it locks up and needs to be reset. Is this a
"single-digit" body characteristic only? My guess is that the "G" might
work OK as well. I'll have to go find one and check it out.
Chuck Norcutt
Woburn, Massachusetts, USA
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