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

Mike is referring to the magnitude sequence that appeared in Brian Skiff's
article in the September issue of S&T.  I spent a half hour or so with my
20-inch Dobsonian on a tracking platform (a necessity for this kind of
observation).  I was disappointed to only reach magnitude 17.1.  If I
remember correctly, there was a magnitude 16.8 star, and I was able to see
it all of the time.  I put 17.1 as the limit, as I could only see it about
one-fourth of the time.  I think the next one down in the sequence was
17.4 or 17.6, and I had no luck with it.

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.  If you simply take the square of the ratio
of our two apertures, my mirror should gather 4 times as much light as
Frank's.  he should see 1.5 magnitudes fainter [(2.512)^1.5 ~ 4].  So
Frank should be able to see a magnitude 17.7 star in my scope.  I
attribute my disappointing result to:

1 - Poor optics in the 20-inch, which were demonstrated later that night
by a lousy view of Saturn.  At 400x, the star discs are larger than they
could be with good optics, so you can't see as faint.

2 - Frank's eyes are 17 years younger than mine.


I want the answer to be #1, of course.

Tom


> Hi Tom,
> Meant to ask how your survey of Brian's magnitude sequence around M57
worked
> out. I was going to try this also after hearing you mention it but got
busy
> visiting and forgot. :) It would be interesting to know if viewing
Jupiter
> or Saturn with bigger aperture affects dark adaptation to a noticeable
> degree that could be determined by the sequence survey.
> --Mike Spooner


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