Astrometry

I created a very simple observing planning spreadsheet for use in Microsoft Excel. For any given dates or locations, it calculates:

· Time of sunset, end of astronomical twilight, start of morning astronomical twilight and sunrise.

· Time of moon set and moon rise, so it gives an idea of the duration of true darkness. The times are within a few minutes Naval Observatory times.

· Position, elongation, diameter, brightness, rise, transit and set times of the planets

To run the spreadsheet, you must set your Excel security settings to "trust macros". If asked, when the file opens, you must “enable macros” or “enable content” (depending on your Excel version). The workbook is locked except for the light green shaded cells. If you know Excel well and want to revise it for your needs, you can remove the sheet and workbook protection. Nothing is password protected.

The spreadsheet can only handle dates between 1/1/1900 and 1/1/2050. The planet calculation errors are large outside of this range.

The visual magnitude estimates include phase angle effects. However, the estimate for Saturn does not include the rings, so it will generally under estimate Saturn's brightness.

At the bottom left, NGC object numbers can be entered. They must be entered in the form of “M42” or “NGC1976” (no spaces). Then, it will show a limited amount of information about the object, such as what Sky and Telescope chart number shows that object. More importantly, it shows the object’s rise time, time of transit and set time. I also added the time when the object is at least 45 degrees above the east horizon and 45 degrees above the west horizon. I try to plan my imaging when objects are above those angles. If those time are within the “darkness” times, they are highlighted as light blue.

I populated the object list with all the Messier objects and all the NGC objects. I also populated a few example locations (on the “Locations” tab). You can edit or add locations. They must be entered as decimal degrees.

I did this primarily to learn more about Excel VBA and the astronomy calculations. I’ve tested it, but I’m sure there are some bugs I haven’t worked out. If you find some, let me know.

Entry cells are generally shaded in green. All other cells are locked. To unlock the entire spreadsheet for editing, type "ctrl+W".

The spreadsheet is posted in the "Documents" library.

References

Astronomical Algorithms, Second Edition, Jean Meeus, Willmann-Bell, Inc., 2009
http://en.wikipedia.org/wiki/Sunrise_equation
http://users.electromagnetic.net/bu/astro/sunrise-set.php
http://ssd.jpl.nasa.gov/?ephemerides