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


Jack et al,

Wish I could have been there... With the 10" properly collimated and the
primary squeaky clean, I have been itching to get out; and from what I read,
the 5x Powermate would have seen some long over-due action.  For good seeing
conditions, Eagle Eye is shinning a .500 record for me, and your report is
encouraging.  Unfortunately, Eagle Eye's distance makes it a less-favorable
destination for those in the east valley.

Regarding high magnification use: 50x per inch under good seeing conditions
sounds right for planetary observing, but with well figured optics, I think
one could get away with 60-70x/inch+ and maintain a detailed and contrasty
image.  Unfortunately, my eyepiece selection gives me a range of
magnifications leading up to 560x, and then a sudden jump to 998x, which I
have only used two or three times with success.  I wish I could put this
theory to the test.

For deep sky, I certainly agree, however an object's surface brightness
plays a substantial role in effective high power uses.  I find planetaries
to be the most rewarding under high power.  NGC 2440 is an example which
gets better and better with every step of magnification.  There are a few
PNes in Cygnus that also fit this bill, for example NGC 7027.

Funny how magnification helps resolve fainter stars, though.  I would be
interested in comparing limiting magnitude under skies with good
transparency against good seeing.  And speaking of M57, Brian Skiff has a
great magnitude chart to guide such an experiment.  My hypothesis is seeing
out-weighs transparency, so far the faintest I've gone with the 10" using
Skiff's chart is 16.1 at the All AZ SP last year.  I also think there was a
topic on amastro discussing seeing vs. transparency when resolving M57
central star.

Let's hope the rain pours, but clears for the weekend.

-FRANK



-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx]On Behalf Of Jack Jones
Sent: Monday, July 08, 2002 7:08 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [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



--
This message is from the AZ-Observing mailing list.  See this message's
header if you want info about unsubscribing or the list's archive.

This is a discussion list.  Please send personal inquiries directly to
the message author.  In other words, do not use "reply" for personal
messages.  Thanks.


--
This message is from the AZ-Observing mailing list.  See this message's
header if you want info about unsubscribing or the list's archive.

This is a discussion list.  Please send personal inquiries directly to
the message author.  In other words, do not use "reply" for personal
messages.  Thanks.

Other related posts: