26 September 2007

I have occasionally noticed differences in the data reported by various programs about celestial bodies. I decided to compare the data provided about the Moon by my primary astronomy tools to see how big the difference actually is.

For the following table I set each program to todays date at 1545 EDT, the time of Full Moon. For consistency I set all the program to 00 seconds past the minute. This was a pain for Starry Night Starter since the Moon was below the horizon at that time and it told me the moon didn't rise until 18## EDT and then reset the time to 01## tomorrow when the moon transits. To get at the information I wanted I had to lock the center and lock on the Moon and then step the time back to the time I wanted.

  

	Virtual Moon Atlas	Planetarium	Starry Night Starter	Cartes du Ciel
R.A.	0h10m20,8s	0h10.6m		0h10m19.87s
Dec.	+2°44'46"	2.8°		+2°44'18.9"
Distance	363,475 km	364*103 km 1.2s		363,508 km
Apparent Diameter	32.88'	32'52"	33'	32.9'
Colongitude	92.5°	92.6°
Phase	0.1°	2.3°		0°'
Lunation (age)	15.29 days	15d7h00m	14.8d
Illumination	100.0%	100.0%	99.98%	1.000
Solar Inclination	-0.7°			-0.72
Libration in Latitude	-02°13'			-2.21
Libration in Longitude	-02 22"			-2.49
Position Angle	-22.1°			-22.1
Azimuth	+55°00'	54.7°	54°38.869	+54°43'27'
Altitude	-30°08'	-30.3°	-30°20.509'	-29°46'02"
Rise	18:35	18:10	1836
Transit	00:12	00:12	01:06
Set	06:25	6:26	07:42
Rise Azimuth	87.54°	93.9°
Transit Altitude	+53°	+47.4°
Set Azimuth	269.72°	270.8°
Phase		Full	Full
Magnitude		-12.8	-12.84	-12.70
JD		2454370.3229
LMST		15h10m
Equation of Time		8m38s
Siderial Day			27.3217d
Solar Day			29.5307d

The Moon is bright enough that I can usually find it, except maybe at first or last crescent, so most of these differences are not important practically. But I often have to get some of the data I like to record from different programs because no one program has everything. I rely primarily on Planetarium and secondarily on Starry Night Starter. But Starry Night Starter seems to be at odds with most other data sources most of the time. Virtual Moon Atlas doesn't work well under Vista (actually it works fine, it just doesn't want to shut down properly). Some of these programs may have some of the data that is missing in the table, but I haven't found a way to get to it and haven't spent time slogging through the instruction manuals/help files for any of them but Planetarium and Starry Night Starter.

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Observing Location	MetOval
Observational Period	2200-2400 EDT
Atmospheric Conditions	Cloud Cover Clear Temperature 79° – 77° F Wind Light Breeze Humidity Moderate Feels Like Mild It was really close before and when I came out at 2100 EDTbut a front must have moved through around 2130 EDT because the temperature and humidity both seemed to drop at that time. I couldn’t see any clouds but could hardly see any stars either. There was no appreciable ring around the Moon. Seeing was rock solid again tonight. There was no boiling at all on the Moon. Transparency Poor Seeing I
Instruments	SAR: Coulter CT-100 Newtonian reflector - Charlie Celestron Omni 20mm (21.6x) Celestron Omni 2x Barlow
Observing Party	Charlie Ridgway

Target Moon Constellation Psc Category Lunar Time yyyymmdd.hhmm 20070926.2200 EDT Comments Lunation 1048 Phase Waning Gibbous Full + 6h15m Age 15d13h15m Distance Light Time (from earth) 357,024 km 1.19s Elongation 175.5° W % Illuminated 99.8% Morning Terminator Colongitude (λ E) 95.7° Evening Terminator Colongitude (λ W) 285.7° Libration in Latitude -2°41’ Libration in Longitude -1°53’ Magnitude -12.8 Angular Size 33'34" Altitude 36.2° Virtual Moon Atlas graphicThere is a tiny libration arrow that you can hardly see that is down near 7:15. I tried identifying terminator features but the lighting was so flat on the rest of the Moon that I was having trouble finding features to use as reference points. There was lumpiness around the western limb from Mare Crisium to beneath Tycho. There is a nick in the limb about at the top of Lacus Autumni, which was seen with difficulty. I can see a couple of indentations of the terminator in the SW that I think are Boussingault and Boguslawsky I found Lacus Excelentiae I saw a dark splotch that was Schicard and another that was Wargentin. Further to the south was another dark spot that should have been Schiller and the unnamed plain below it. Continuing from Schiller to the limb there was a broad double notch in the limb that would be either Bailly or Hausen and Le Gentil, depending on the amount of libration. Ansgarius, Behaim,Hecataeus, and Humboldt look like they have a little bit of space between them and the terminator. Abel is in the terminator. Lyot

I tried to star hop from the Moon through the up through the Bass, over to the Water Jar, and down to the head to find the star field containing Pluto (a suggestion from Peter the last time we were out) and got lost coming out of the Water Jar and into the body.

Next I tried for Neptune but couldn’t make the stars match up with Planetarium and when I eventually moved around and found Cassiopeia I discovered that I had been starting my hop off of Altair rather than Deneb Algedi as I thought.

It is hard to hop to anything when you can’t see enough stars to tell where you are starting from.

About this time the Sci-Fi guy came by. He reads a lot of Sci-Fi and watches Nova and always has weird questions that are kinda there but not that close.

While the Sci-Fi guy was there a guy came up and asked if we were just taking it easy. Then he wanted to know if we were police or worked for the development (I had my radio clipped to my belt). Finally he asked if we were doing drugs. I don’t know if he was looking to make a buy or what. When we told him where the rent-a-cop shack was he said he knew and walked off in the other direction. It was bizarre (even the Sci-Fi guy thought so).

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Here is another one of those inconsistencies in Planetarium.

It says that the Moon was full today at 1546 EDT and it shows it as 100% illuminated at that time. But it also says that it continues to wax until 1549 EDT. I did some exploring and found that it becomes 100% illuminated 2h09m before it is Full and remains 100% illuminated for 1h35m after it is Full.

Time	Illuminated	State	Notes
1336	99.9%	waxing
1337	100.0%	waxing
1344	100.0%	waxing
1545	100.0%	waxing	time of Full Moon
1546	100.0%	waxing
1549	100.0%	waxing
1550	100.0%	waning
1719	100.0%	waning
1720	99.9%	waning

I don’t see how the Moon can get any more illuminated than 100%. Once it reaches 100% it should be shown as full for however long it is at 100%. The way it is now it never appears to be full on either the summary screen or on the status screen.