15 December 2007

Fairy-Land Dim vales- and shadowy floods- And cloudy-looking woods, Whose forms we can't discover For the tears that drip all over! Huge moons there wax and wane- Again- again- again- Every moment of the night- Forever changing places- And they put out the star-light With the breath from their pale faces. About twelve by the moon-dial, One more filmy than the rest (A kind which, upon trial, They have found to be the best) Comes down- still down- and down, With its centre on the crown Of a mountain's eminence, While its wide circumference In easy drapery falls Over hamlets, over halls, Wherever they may be- O'er the strange woods- o'er the sea- Over spirits on the wing- Over every drowsy thing- And buries them up quite In a labyrinth of light- And then, how deep!- O, deep! Is the passion of their sleep. In the morning they arise, And their moony covering Is soaring in the skies, With the tempests as they toss, Like- almost anything- Or a yellow Albatross. They use that moon no more For the same end as before- Videlicet, a tent- Which I think extravagant: Its atomies, however, Into a shower dissever, Of which those butterflies Of Earth, who seek the skies, And so come down again, (Never-contented things!) Have brought a specimen Upon their quivering wings. Edgar Allan Poe

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Observing Location	PSC
Observational Period	1300-1315 EST
Atmospheric Conditions	Cloud Cover Scattered Clouds Temperature 32°F Wind Light Breeze Humidity Low Barrometric Pressure 30.47” Hg Steady Feels Like Cold 27°F Wind Chill It is cold but not really uncomfortable. The wind is barely perceptible. Transparency Good Seeing II
Instruments	Brunton 8x21 compact binocular w/Welco gold shade 14 welder's filter - Charlie Golden Gate 7x35 binocular w/Welco gold shade 14 welder's filter - Charlie
Observing Party	Charlie Ridgway

Target Sunspots Constellation Oph Category Solar Time yyyymmdd.hhmm 20071215.1300 EST Comments Distance Light Time 0.984 AU 8m 11s Angular Size 32' 33.2" Altitude 24.7° Heliographic Latitude (B0) -0.95° Heliographic Longitude (L0) 175.21° Position Angle (P) 10.05° Carrington rotation number (CR) 2064 Group 978 is still there but I can’t find it.   Groups Spots R North 0 0 0 South 0 0 0 Total 0 0 0 R = (Groups * 10) + Spots)

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I have graphed some information about Mars for the period November through December 2007 to see how magnitude, diameter, distance and percent illuminated are related.

As is to be expected, the planet subtends the greatest diameter when it is closest to Earth.

Its maximum brightness spans the period when it appears largest and when it is most fully illuminated, which is a function of where it is in its orbit in relation to the Sun and Earth (fully illuminated when it is at opposition). Most of that period is also when it is closest to Earth (because that is when it appears biggest)

The unexpected thing is how slowly the planet approaches its maximum brightness and how quickly at fades after.

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Last night I found a table that I was working on a good while ago that might be useful in dealing with maps for occultations. It indicates what size an inch or centimeter represents at different map scales. Some of the scales are what you will find on printed maps and others are ones that I calculated that would result in useful figures for interpreting the map and are only applicable if you have mapping software that can create them.

Scale	1" =	1 cm =
1:100	~3'	1 m
1:1,000	~30'	10 m
1:1,200	100'	12 m
1:2,400	200'	24 m
1:4,800	400'	48 m
1:5,000	~150'	50 m
1:6,000	500'	60 m
1:6,336	0.1 mi
1:7,920	1/8 mi' 600'	~80 m
1:9,600	800'	~100 m
1:10,000	~800'	100 m 0.1 km
1:12,000	1000'	120 m
1:15,840	1/4 mi	~160 m ~0.4 km
1:20,000		200 m
1:24,000	2,000'	240 m 0.8 km
1:25,000		250 m
1:31,680	1/2 mi	~320 m ~0.8 km
1:31,960	.75 mi	~1.2 km
1:50,000	~0.8 mi	500 m 0.5 km
1:62,500	~1 mi	~630 m
1:63,360	1 mi 1760 yards 5280' 63360"
1:75,000	~0.5 mi	0.75 km
1:100,000		1 km
1:125,000	~2 mi	1.25 km
1:126,720	2 mi	~1.25 km
1:150,000		1.5 km
1:200,000		2 km
1:250,000	~4 mi	2.5 km
1:253,400	4 mi	~2.5 km
1:316,800	5 mi	~3 km
1:400,000		4 km
1:500,000	~8 mi	5 km
1:506,880	8 mi	~5 km
1:633,600	10 mi	~6.25 km
1:1,000,000	~16 mi'	10 km
1:1,013,760	16 mi	~10 km
1:1,267,200	25 mi
1:3,168,000	50 mi
1:2,000,000		20 km
1:2,500,000	~15	25 km
1:5,000,000	~30 mi	50 km