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Greg,

Sorry, but I think your following comparison is not really valid:

3. Precision 0.4' vs 0.1' of a sextant.

Assuming that you estimate your H.E. to +/-20% and the timing is exact
to +/-1 sec you have a resulting observational error of +/-0.6 moa
which is independent of the instrument you use. From your results I
would conclude that the photometric errors are smaller and contribute
only marginally to the final result.

I indicated previously that the observations should be analysed the
same way as the calibration has been done. Were the 3093 pixels
derived the same way as you used for your calibration measurements,
e.g. the mean of 6 individual measurements?

Regarding your conclusion "... with the bonus of improving photo
editing skills". I hope you don't edit your photos too much before
measuring ;-) However it is true that changing brightness and/or
contrast influence the measurement. That's at least partially the
reason for obtaining slightly different results when we compared our
measurements, which were taken from the same photo, but using
different programs. It looks like the different programs had different
default settings for showing a photo.

Marcel

   

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