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Re: AH: windproof shades material
From: Igor S.
Date: 2021 May 19, 16:00 -0700

Hello Modris,

Thanks for your reply. I am using Astra IIIB sextant. Yesterday I was also testing it with the GPS anti spoof app of Frank Reed (http://reednavigation.com/GPSAntiSpoof/) which I found very handy. The difference was as expected very small < 0.5'.

Plastic wrap is indeed very thin ~ 10 um ( https://en.wikipedia.org/wiki/Plastic_wrap ) compared to the typical 4mm float glass.

I was also thinking of making a side door in one of the walls, so that I don't have to disturb the food film whenever I want to place there a tray with water or to get rid of the condensate.

kind regards,

Igor

Hello, Igor!
I am realy happy that someone else have experimented with this AH “design”. I have checked many times: these small waves does not afect Sun’s image quality, because food film is very, very thin (of course, film shuld not be loose; in your pictures it looks like that the film could be streched more on the lower ends of the curved surface. The waves on the top, where the film is tensioned, are OK. I have examined it for hundreds of times ). But your position results show that everything works perfect. I can achieve average accuracy of position lines 0.1-0.2 minutes of arc (my sextant: soviet SNO-M; what is your sextant model?).
The only disadvantage in your design is that you have to take off the film to access the basin. It would be more convenient to make a hole in the bottom plate.
Modris

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