# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Daytime Venus Lunar
From: Antoine Couëtte
Date: 2012 Aug 14, 02:31 -0700

Kermit,

I can do one better for you. I have taken a digital photo using a 200 mm lens set at ISO 200, 1/250 sec, f 11 on infinite focus. The minutes of arc per pixel has been previously calibrated at .0975 minutes of arc per pixel. Measured pixels from Venus center to Moon near limb is 403 pixels for a measured angle of 39.3'

Attached is a rather spectacular result considering how close Venus is to the Moon.

If you inspect the image it is apparent that Venus is oval and yes I did measure from the center of the oval on the previous sextant measurements.

Greg Rudzinski

*********************************************************************************

Well done again Greg. Superb picture !!!

So ... I did computations again.

*******

Not taking in account phase correction, you "should" have observed 0°39'387, hence a difference of 0'087 with your own value of 0°39'3

If I enter 39'387 into Frank's Computer, I am getting an error in Lunar 0'0 with Error in Longitude 1'2

*******

If now taking phase correction in the calculations , you "should" have observed 0°39'308 : here an insignificant difference with your observed value of 0°39'3

If I enter 0°39'308 into Frank's Computer, I am getting an error in Lunar -0'1 with Error in Longitude 1'6

*******

The effect of phase correction on Lunar Distance is 4"74 (vs 5"04 yesterday).

Result's with Frank's computer are much closer to-day. I had time this morning to use my standard checking method, while yesterday I used a short cut which likely led me to wrong conclusions in my comparison for this specific example (no time now to dig this further for the time being).

And finally, from results observed yesterday and to-day, I would favor the fact of taking in account Phase Correction in the Computations of Lunars.

Of course, any third party again warmly welcome to check results here-above.

Best Regards again

Kermit

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