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Re: Watching a star for IE: an obturator trick?
From: Brad Morris
Date: 2019 Dec 9, 21:03 -0500
From: Brad Morris
Date: 2019 Dec 9, 21:03 -0500
Tony
The trick I use for this is to overlay the sun image with itself. Its quite easy to see when they don't perfectly overlap and when they do.
It is then straightforward enough to adjust your (metal) sextant to IE=0 with zero side error.
Try it. You can always try the stars, the horizon or a far off steeple again if you are unhappy with the result.
Brad
On Sun, Dec 8, 2019, 11:17 PM Tony Oz <NoReply_TonyOz@fer3.com> wrote:
Hello!
The ongoing discussion of the star-to-star angle as the sextant sanity check has reminded me my efforts to eliminate the IE (and side error too).
For me it is not so easy - even with the 7x (Keplerian) scope - to tell if both images of a star coincide perfectly. I have to move the index arm slightly to see where each image is.
Last time I did the adjustments I asked a friend to move his palm infront the horizon and index mirrors thus blocking temporarily either of the view paths. With the images (alternatively) blinking I can see the [non]coincidence much more clearly. I think some sort of fan propeller could be used as an obturator. Will try next time I take my sextants to the shore.
Please comment.
Warm regards,
Tony
60°N 30°E
