[AZ-Observing] Re: Eagle Eye this past Sat.

After I cracked out my 2.5 Barlow for 500X with the 9mm, Lynn and I were
able to spot the central star in M57 (not M51 - are you sure you are ready
for the H400, or should you go back again to review the M Objects? :-) ) We
could have gotten even "stupider" and doubled that power. You were "only" at
45X/inch and I was at 35X/inch with my 14.5". That's rather "low" high power
and 100X/inch could very well have been tried with the seeing at 7/8 and no
wind in dark skies. The 50X/inch guideline limit usually quoted is for the
Moon and planets. For deep sky you can go a lot higher for detail and faint
star detection. It's easier to see detail if the object is larger and more
spread out (to a point, that is, and then you start losing it, so experiment
with each object), and the background becomes darker, which also helps. The
contrast doesn't really get better, since you are magnifying both the object
and the background, but the eye has an easier time detecting faint objects
and detail with the darker background. An individual star is just plain
easier to see at lower background luminance. For point sources, with high
power the sky's the limit! Roger Clark in "Visual Astronomy of the Deep Sky"
says up to 330X/inch (!) can be used in detecting individual stars in a
nebulous background. That's under very special conditions, but you can see
why Mike Spooner and Frank Kraljic like to go for those super-high powers. I
also think that is why those with small apertures can even get thru the
H400, because smaller scopes love higher powers/inch a lot more than larger
ones.

Jack Jones
Saguaro Astronomy Club
Lunar List Awards and
Messier Marathon Co-coordinator
Phoenix AZ
spicastar@xxxxxxxxxxxxxxx


>...Chuck and I were determined to spot M51's central star, and I was able
to declare a victory after Jack prodded us to bump up to "stupid" power
around 780x.  I declared victory as the thing kept blinking in and out in
the same spot several times.  I imagine that this one will be a bit easier
higher up, so I'll keep trying.
>Thad



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