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From: Bill (no email)
Date: Sun Apr 24 2005 - 18:42:38 EDT
Fred
I am envious of your standard deviations, especially with the larger angles.
To date every Sun/moon I have shot had the Sun to the west of the moon
(April 13, 2005 and on), and I prefer separating, so did try some
set-and-leave shots for separation.
What I find interesting is despite different methodologies, scopes,
instruments and locations we both wind up over shooting the target
consistently (and it would appear we both saw the same Sun and moon in April
;-)
What time(s) of day did you make your April 05 observations? As I noted
before, while my STDEV's of error were horrible, the observations I made
when the Sun and moon had Hc's over 40d turned out remarkably well, with
mean errors in the 0.25' to 0.5' range. The "easy" shots with the moon high
in the sky and the Sun in the 15d-25d range all had sub 0.2' STDEV error
means, but error means were in the 0.5' to 1.0' range. Admitted the
instrument in in the hands of a novice, and I don't have enough data points
to justify a firm conclusion, but it appears the lower the Sun gets the more
I overshoot. There is not enough flattening of the Sun by refraction to
account for the trend. If you are using Franks calculator, I recall he did
have a correction for Sun/noon flattening, then disabled it. I do not know
if he has plugged it back in. Either way flattening could only account for
0.1' or so.
If memory serves, Alex had run test using the Sun for IE with both his
Galilean and inverting scopes, and saw little or no significant difference.
Still stumped
Bill
> I mentioned that my sun-moon lunars were markedly inferior to other
> lunars. Here are some data on that. For a while, I thought I was
> failing to converge the objects in the center of the glass, so I bought
> a Russian 7x (6x ?) inverting scope with wires in the field of view, so
> that I could center the objects (and get greater magnification than
> offered by my 4x star scope). This didn't seem to help, as indicated
> below. In general, the sun lunars show a gap of about 1.2' to 1.4' of
> arc, while the star and planet lunars show no gap. The one difference
> that remains to be explored is that the sun lunars have much larger
> distances than the star lunars, so that arc eccentricities or failure
> to maintain the sextant in the plane of observation may be occurring.
>
> I haven't used the inverting scope very much yet, so I'm far from
> proficient with it. But the bias appears to persist with it, and
> appears to be .
>
> Date Telescope Objects Mean(clrd
> D) N(delarc') Mean(delarc') StdDev(delarc')
> 09/22/2004 4xGalilean Moon,Antares 38 2 0.1 0.38
> 04/18/2005 7xinverting Moon,Jupiter 58 7 0.5 0.21
> 04/20/2005 4xGalilean Moon,Jupiter 21 6 -0.1 0.28
> 10/06/2004 4xGalilean Moon,Venus 49 7 -0.2 0.26
> 10/07/2004 4xGalilean Moon,Venus 38 6 -1.1 0.23
> 09/20/2004 4xGalilean Moon,Sun 80 6 1.2 0.37
> 09/21/2004 4xGalilean Moon,Sun 92 6 1.3 0.49
> 10/05/2004 4xGalilean Moon,Sun 97 6 1.4 0.15
> 10/06/2004 4xGalilean Moon,Sun 87 8 1.2 0.34
> 10/08/2004 4xGalilean Moon,Sun 66 10 0.7 0.38
> 11/07/2004 4xGalilean Moon,Sun 62 6 1.7 1.28
> 04/16/2005 7xinverting Moon,Sun 93 6 1.4 0.15
> 04/17/2005 7xinverting Moon,Sun 103 8 1.2 0.24
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