Inferior Planets Greatest Elongation and Brilliances Scripts
Version 3.0
Files
1) Mercury
- Greatest Elongations.ssc
2) Venus - Greatest Elongations.ssc
New in version 3.0
1) Greatest Brilliancies for Venus.
2) Screen Saver Mode
3) Rise and Set times
4) Elongation, magnitude, ride high/runs low and phase angle calculations
5) More Menu choices
6) Direct calculations for display times
Instructions:
1) Download zip file
2) Extract the files
3) Run Stellarium
4) Run scripts
5) Run file
6) From Main Menu choose the event(s) you wish to view
7) When running
Press + to go to the next Elongation
Press - to go to the previous one
Press [ to start over (at the original date)
Press ] to go back to Main Menu
General Notes:
I could have taken the easy way out and just set these scripts for one location, but instead I wanted a script that would display these events using the users home location. So what these scripts do is "attempt" to calculate the best time at your location to view the events. To do this the scripts calculate sunset, sunrise, starrise, starset and midday transits at your location and from those it "guesses" the time best to view the eventss.
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Unfortunately there's no "Get latitude" or "Get longitude" functions in Stellarium scripts, so when you 1st run any of the scripts, they will first attempt to calculate your position and your offfset from UTC. It won't get your location exactly, but it should be close enough that the set and rise times won't be significantly different.
It calculates lat by your angle to the North Star
It then calculates long by starting at "12 noon" UTC and then seeing when Solar Noon is at your location. The difference is your longitude.
If you find this annoying or want more accuracy, you can open any of the script files in notepad (or equivalent) and manually enter your lat and long where it says lat and long.
When you 1st do this you will notice the initially lat and long numbers don't make sense, this is done on purpose.
If lat and/or long are in there normal ranges (lat is anything between -90 and 90 and long is between -180 and 180) then the program will use those values, if the lat and/or long are out of range then the program will attempt to determine them.
You have to enter lat and long in decimal form. There are many online coversions out there or to convert from Degrees, minutes, seconds to degress in decimals
Degrees + minutes/60 + seconds/3600
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As such, if you let the script estimate lat and long, Rise and Set times can be off by up to 10 minutes.
If manually put your exact lat and long in the script file, rise and set times are accurate to 1 to 2 minutes.
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Greatest Brilliancy or Illumination is when the Planet is brightest as seen from Earth. Due to quirks in Venus' orbit, Venus' Greatest Brilliancy occurs about a month before it's morning/western greatest elongation and about a month after it's evening/eastern greatest elongation.
Mercury's Greatest Brilliancy occurs at it's superior conjunction, so it's invisible behind the sun so I didn't include it.
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It seems every source you look at has a different greatest brilliancy date for Venus, the likely reason for this variability is the week Venus reaches it's greatest brilliancy the changes in magnitude are only in the 100ths or even 1000ths decimal places, so slight differences in rounding will give slightly different days, so everyone's is different and the dates I use are no better or worse than eveyone else's.
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The time the planet is displayed is not the exact time of the Greatest Elongation but the best time on that date that the planet is visible at your location.
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These numbers are not calculated by the Stellarium program but are calculated
in the script itself or my program where I determined these dates. These
numbers are calculated the exact time of the event not the "best view" time
being displayed on the screen.
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Elongation: The seperation in degrees between the planet and sun.
Magnitude: The brightness of the planet. Depending on what source you use magnitude values vary from source to source. For example some sources claim Venus max brightness is -4.4 while others have it at -4.9 and everything in between. As such my calculations for Venus and Mercury are slightly different than Stellarium. For example where as in Stellarium Venus' brightest magnitudes are about -4.55 mine are about -4.85. I base my calucations off the JPL Horizons site and my magnitudes seems to match theirs.
Rides High / Runs Low: This is the declination difference between the sun and planet. When the planet rides high it is above the sun, runs low it is below. In the Northern Hemisphere when the planet (especially inferior ones) "rides high" it is more easily viewable and when it runs low even though it might have a large elongation from the sun it could be hard to view. In the Southern Hemisphere the opposite is true so "runs low" is better.
Illumination: This is the percent the planet that is sunlit as visible from earth.
Phase Angle: This is the angle from the planet to the sun and earth. Range is from °0 to 180°. If it's zero the planet appears "full", if it's 90 degrees it appears "half", and if it's 180 degrees it appears "new". Only the Moon and Mercury and Venus can have phase angles exceeding about 50 degrees. Interestingly the phase angle is also the elongation from the sun the earth would be if you were on the planet.
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There are two modes to select Key Press Mode and Screensaver Mode
Key press mode, the conjunction will display until you press one of the + - [ ] keys
Screen Saver Mode the script will behave LIKE a screensaver.
Keyword LIKE, it doesn't work exactly like a screensaver,
When you select screensaver mode, up will pop the 1st event, the program will hold for 3 seconds (This is the default time, you can edit this time in the script file if you wish) and then go to the next event and again hold for 3 seconds and then the next event and on and on.
To leave the screen saver, unlike "real" screensavers pressing any key or moving the mouse will not cause the screensaver to end, with these scripts only changing the date by pressing the dates keys will cause the screensaver to end.
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All these scripts will start at the next up coming Greatest Elongation
For example with Venus program file
On 1/1/2010 it should start with the Greatest Elongation on 08/20/2010
On 08/20/2010 it should still start with the Greatest Elongation on
08/20/2010
But on 8/21/2010 the program will then start with the Greatest Elongation
on 1/8/2011
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No I didn't type all these years and times out. I wrote a computer program based on Paul Schlyter's work at
http://www.stjarnhimlen.se/comp/ppcomp.html
which produced all these values.
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My dates I calculated do seem to match other dates from a wide variety of sources, but I make no guarantee on accuracy.
I'm sure accuracy decreases the further back or forward in time any given script goes.
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I can be emailed at qam1@aol.com