FreeLists / az-observing / [AZ-Observing] Re: Mag sequence was:(Saturn's Rings)

["Frank Kraljic" <fjkraljic@xxxxxxxx>]

> Frank Kraljic did the same thing for a similar length of time with his
> 10-inch Spooner Newtonian, also on a tracking platform.  He was able to
> see the magnitude 16.1 star.

The 16.1 magnitude star was difficult to mark, requiring high magnification
(400x), definitely requiring averted vision.  The first thirty minutes, I
struggled to concretely identify a 15.7 mag star just west of M57, and a
15.6 star south of the PN; 15.4 was consistently visible, however once
noticed, the 15.7 remained apparent over 50% of the time.  I am amazed at
the difference in faintness based on tenths of magnitudes.  Obviously, the
difference is more vast the fainter one goes.

Two things I would like to point out:

1)  Shrouding my head over the eyepiece with a blanket made a vast jump (in
tenths) in magnitude classification.

2)  I wonder if M57's surface brightness effects dark adaptation.  Would
16.1 be easier to spot if not in the same FOV as the Ring?

I remember Brian Skiff has a chart of optimal and expected magnitudes for
various apertures.  Does anyone (Brian) have a link to that data?

-FRANK



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