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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Eclipse Lunar
From: Paul Hirose
Date: 2017 Aug 22, 13:14 -0700
From: Paul Hirose
Date: 2017 Aug 22, 13:14 -0700
On 2017-08-21 12:48, Greg Rudzinski wrote: > The moment of extinction of the 21 August 2017 eclipse is captured by a Canon Rebel DSLR with 200mm Super Takumar Pentax lens. The lunar distance is almost zero as seen in the image (about 0.3' to go by pixel measure). The picture appears to be almost the end of the eclipse. In the screenshots the observer data are N34 10.5, W119 13.8, +7 ft height eye, 75 F, 29.98 inches Hg, 18:41:29 GMT. (Temperature and pressure have no effect on lunar distance if the limbs are practically in contact.) With the JPL HORIZONS online calculator I get: Date__(UT)__HR:MN:SC.fff Azi_(a-appr)_Elev Ang-diam 2017-Aug-21 18:41:29.000 *m 136.6403 61.4166 1897.471 (Sun) 2017-Aug-21 18:41:29.000 *m 135.7496 61.1050 1955.369 (Moon) The "UT" time in this case is UTC. Elevation is the airless (unrefracted) angle. Angular diameter is arc seconds. The "*m" means it's daytime and the Moon is above the horizon. I calculate center to center distance = .5296°. After subtracting semidiameters and converting to arc minutes, I get lunar distance = -0.33, i.e., the Moon is inside the Sun's limb. It's much easier to use the Lunar4 program, which does all that automatically and also says -0.33.
