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Hello Paul and Marcel,

This Post in reply to your last 2 posts :

******

To you Paul,

RE : http://fer3.com/arc/m2.aspx/Low-Alt-Refraction-Hirose-apr-2013-g23719

Thanks for specifying a Formula published in the "new" Explanatory Supplement (ES). It shows up as Formula (3.282-2) in the ES 1992 Edition.

Your remark prompted me into closer searching the "older" (Sep 1977) ES version for any actual information on Refraction at 0° apparent height. Apart from the Standard -34' value used for the SUN and MOON risings and settings, the only additional information in Section 2E is a reference to Chauvenet's "Manual of spherical and practical astronomy" (1960 reprint) and another reference to Smart's "Text-Book on Spherical Astronomy" (1944 reprint).

In Smarts's Sixth Edition (1977 / 1980 reprint) : again ... apart from the standard -34' refraction value, I fail to see any more specific mention to any Low Altitudes Refraction Values.

*******

RE : http://fer3.com/arc/m2.aspx/Low-Alt-Refraction-Tschudin-apr-2013-g23724

Hello Marcel,

First of all, sorry for a few typos which I had mistakenly printed in my post RE : http://fer3.com/arc/m2.aspx/Low-Alt-Refraction-USCG-Student-Example-for-Low-Altitude-Couëtte-apr-2013-g23718

Please find here-after a few comments where applicable.

QUOTE

Reference #3: The air pressure is given. I do not know what the water
pressure relates to.

UNQUOTE

REPLY : It means "Water Vapor pressure", i.e. Humidity 0%, or Air entirely dry.

*******

QUOTE

Reference #6: Could this have been a typo and the value been in
degrees, still requiring to add the sun diameter?

UNQUOTE

REPLY : This is a typo . Sorry again. This value actually reads - 34.0' which is most probably a simple copy/paste of the Standard -34' value used in the US/UK N.A.'s for SUN/MOON risings/settings.

*******

QUOTE

References #10 and #11: It looks like being the same formula. There
seems however to be a slight difference. Was #11 not copied correctly?
(I do not have the original reference.)

UNQUOTE

I do not hold a copy of such original formula either ...

*******

Best Regards to both of you

Kermit
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