25 January 2007

Mercury & Venus - Daylight Obs.

Date: 25 January 2007 U.T.
Time: 18:40 - 19:08 U.T.
Telescope: 102mm SCT
Magnification: 120x
Seeing: Fair to Poor
NELM: Daytime
Temperature: +45 F (+7 F)


The above sketches show Mercury to the left and Venus to the right. West is up in these mirror-reversed sketches. The phases of both planets were close to full. The terminators (border between day and night) of both planets are to the East (down in the sketches). The terminators were slightly darker than the rest of the limb region on both planets; but more so for Mercury than for Venus. Some subtle shading was suspected on Mercury -- to the northeast. None was suspected on Venus. Both planets appeared to be white or almost white in color.

Venus was considerably brighter and appeared to be about double the apparent size of Mercury.

Both planets were quite small as viewed in the telescope's eyepiece. Both are currently on the far side of the Sun from Earth; and both are currently east of the Sun in the sky.

A note on "go-to" telescopes: Some people might consider a "go-to" telescope to be a necessity for pointing a telescope at planets in the daytime; but observers made daytime planetary observations long before the invention of electronic computers and self-pointing telescopes. None of my telescopes or mounts have the ability to point themselves at astronomical objects. I've found no need for the technology and have managed to do fine without it. I prefer to point my telescopes myself -- even at planets in the daytime sky. For myself, part of the joy of amateur astronomy is 'driving' the telescope myself.

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