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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2018 Sep 27, 13:23 +0200
Dear Antoine,
thanks for your comments. Interesting, as always.
“Opinions about publishing Planets GCL's instead of Planets GCM's in the Nautical Almanacs ?”
I prefer GCM è
For Venus 1977/03/18
· phase angle φ = 139°
· illumination = 12.09 %
· SD = 0.42 moa
The attached simulation on how Venus appears is taken from Stellarium.
So I would have been tempted to use the lower limb and correct for SD.
Easier than a phase correction.
When the illumination of the Moon is near “Full Moon”, at night the line of the horizon could be false due to the reflections. Great error.
As this case of Venus, I try to avoid these kind of weird sights.
“If you eye is sharp enough and ones can see the spot of light, or the limb it is not necessary, isn't it?”
I mean:
If you eye is sharp enough and one can see the spot of light, or the limb; the phase correction is not necessary, isn't it?
Yesterday I was cheking:
| Date | UT1 | Body | GHA | Dec | SD | HP | RA | Illumination | Zn | Hc |
| 26/09/2018 | 18:16:17 | Venus | 64º 46.9' | -20º 39.5' | 0.36 | 0.38 | 14:19:09 | 21.01 | 237 | 03º 58.67' |
| 26/09/2018 | 18:16:17 | Mars | 331º 48.5' | -23º 10.6' | 0.14 | 0.26 | 20:31:03 | 89.08 | 151 | 17º 56.74' |
| 26/09/2018 | 18:16:17 | Jupiter | 50º 29.4' | -17º 20.1' | 0.27 | 0.02 | 15:16:19 | 99.52 | 228 | 14º 49.57' |
| 26/09/2018 | 18:16:17 | Saturn | 6º 27.0' | -22º 45.0' | 0.14 | 0.01 | 18:12:29 | 99.75 | 184 | 23º 48.41' |
My applications calculate the SD for planets and the user could choose limb = UL/C/LL. User decision…
But to be honest, when I shoot planets, I always treat them as a spot, as my eye, till now, is able to discern and interpolate the center, and no correction for SD is taken into account.
