[vsnet-chat 3073] Re: saving observing time

[Taichi Kato <tkato>]

Re: [vsnet-chat 3062] saving observing time

Dear Timo and all,

> ...moonlight and light pollution. My observations with 17.5" dob
> may be divided into 3 classes with respective limiting mag:
> 
> 1) low power - takes about 30 seconds
> 2) high power: obs with change into 6 to 12 mm eyepiece takes a minute,
> more if I let the field drift in
> 3) high power and readaptation - takes about two minutes.

  (Though the strategy will not apply to a large scope), after my
experience in late 1980's, I learned not to use low power eyepiece
in order to save time and not to lose adaptation.  I constantly used
magnitications with an exit pupil of ~1 mm (x100 for a 10-cm scope, and
x200 for a 20-cm scope).  Unless there was particular necessity (e.g.
observing bright novae), I never changed the magnification.  Using this
exit pupil, the sky background was suppressed low enough to maintain dark
adaptation throughout 1 or 2 hour runs.  The exit pupil of my finder was
3 mm, so I had to care not to break the adaptation by spending too much
time (longer than tens of seconds) in manually introducing variables
through this low-power finder.  I once tried a constant magnification
of x400 for a 20-cm scope, but it proved to be too difficult (and
inefficient) to introduce variables into this small field of view.

Regards,
Taichi Kato

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