NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
A Jupiter lunar etc.
From: Peter Hakel
Date: 2010 Aug 28, 01:24 -0700
From: Peter Hakel
Date: 2010 Aug 28, 01:24 -0700
This evening (Pacific Time zone) provided me with a nice opportunity to shoot a Jupiter lunar. It was a far limb observation with a Davis Mark 15 from my backyard. Considering a number of mitigating circumstances (no visible horizon to get altitudes for clearing, being too tired/lazy to get my artificial horizon out, using a plastic sextant, having essentially zero lunar-shooting experience…) I was planning on getting just a quick and rough agreement between the calculation and the measurement. The index error was "zeroed out" by adjusting the mirrors so the two Jupiter images coincided. The time was marked with my radio controlled digital clock. This is what I got:
UT: 28 August 2010, 06h 33m 15s
Moon: GHA 63d 57.6', Dec N 10d 08.0', SD 14.8', HP 54.4'
Jupiter: GHA 72d 47.8', Dec S 0d 52.1', SD 0.4'
Observed lunar distance (far limb): 14d 20.0'
I read the altitudes of the two bodies from the pUniverse app on my iPhone as 33d for the Moon and 31d for Jupiter. I took these altitudes as both Ha and Ho so that really rendered the clearing part of my spreadsheet inactive (another mitigating circumstance). Further considering that my telescope could not reliably resolve the 0.4' semidiameter of Jupiter and knowing the rather large amount of "play" that my sextant has in determining its index error, I certainly did not expect agreement better than a few minutes of arc. To my surprise both the calculated and measured lunar distance came to 14d 05.1'! (See the two yellow cells in the attached screen capture and their gray companions just below.) Definitely fortuitous, nevertheless pleasant to see, so I figured I'd share this with NavList. :-)
The pUniverse app also placed Uranus very close to Jupiter in the sky; indeed at the same UT for this planet I got:
GHA 74d 47.8', Dec S 0d 54.0', magnitude 5.7
So I pulled out my binoculars. The Moon surface looked spectacular. Jupiter appeared as a little disk and (despite the shaking of the image) I could make out two of its moons. I looked in the direction of where Uranus should be. I believe that one of the specks of light I saw was it (and one did seem to have a blue color to it) but in the absence of further study I cannot say for sure.
With the extra observations and writing of this message this evening turned out to be a bit longer than I originally expected; now it's well past midnight here.
Peter Hakel
UT: 28 August 2010, 06h 33m 15s
Moon: GHA 63d 57.6', Dec N 10d 08.0', SD 14.8', HP 54.4'
Jupiter: GHA 72d 47.8', Dec S 0d 52.1', SD 0.4'
Observed lunar distance (far limb): 14d 20.0'
I read the altitudes of the two bodies from the pUniverse app on my iPhone as 33d for the Moon and 31d for Jupiter. I took these altitudes as both Ha and Ho so that really rendered the clearing part of my spreadsheet inactive (another mitigating circumstance). Further considering that my telescope could not reliably resolve the 0.4' semidiameter of Jupiter and knowing the rather large amount of "play" that my sextant has in determining its index error, I certainly did not expect agreement better than a few minutes of arc. To my surprise both the calculated and measured lunar distance came to 14d 05.1'! (See the two yellow cells in the attached screen capture and their gray companions just below.) Definitely fortuitous, nevertheless pleasant to see, so I figured I'd share this with NavList. :-)
The pUniverse app also placed Uranus very close to Jupiter in the sky; indeed at the same UT for this planet I got:
GHA 74d 47.8', Dec S 0d 54.0', magnitude 5.7
So I pulled out my binoculars. The Moon surface looked spectacular. Jupiter appeared as a little disk and (despite the shaking of the image) I could make out two of its moons. I looked in the direction of where Uranus should be. I believe that one of the specks of light I saw was it (and one did seem to have a blue color to it) but in the absence of further study I cannot say for sure.
With the extra observations and writing of this message this evening turned out to be a bit longer than I originally expected; now it's well past midnight here.
Peter Hakel
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