[AZ-Observing] Re: Mag sequence was:(Saturn's Rings)
- From: "Tom Polakis" <polakis@xxxxxxxx>
- To: Reply-To:az-observing@xxxxxxxxxxxxx
- Date: Thu, 18 Oct 2001 12:28:48 -0400
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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