On Dec. 1, 2007, an error in lunar terminator colongitude code that returned incorrect results during leap years was corrected. Persons who downloaded a copy of the spreadsheet prior to 12/1/2007 should redownload the corrected spreadsheet.

Quick Start

• Download the Excel spreadsheet. 7.5 megabytes. Open the spreadsheet and allow macros to run.
• In worksheet "SetObservingPoint" in the blue highlighted cells, enter the terresterial longitude and latitude for your observing point in integer degrees, minutes and seconds.
• In worksheet "TerminatorLocation", set the observing date year, Month, Day and integer UTC hour in blue highlighted cells B19 throug B22. Wait 10-20 seconds for all the worksheets in the spreadsheet file to recalculate.
• Note the computed lunar terminator longitude at the observing date and integer UTC hour.
• Go to worksheet "MainLunarCatalogue". Filter the table on the field "Long_dec" for a one or two degree frame around the lunar terminator position, e.g. - Long_dec is greater than or equal to 20 AND Long_dec is less than or equal to 22. The main catalogue will filter for objects on or near the terminator.
• Go to worksheet "PlanAnnualOpportunities". Filter the table on the field "Long_dec" around an object of interest. The table will filter to show the altitude and arcsec size of the Moon when the lunar terminator will be at that location during a four hour time frame on each day during the next 12 months.
• Charts in worksheets "PlanAnnualGraphical" and "PlanDateGraphical" show these favorable observing dates and times for the next year.

Summary

This project is an observation planning spreadsheet implemented in Microsoft Excel (2003) suitable for beginner or intermediate lunar observers. The spreadsheet contains a catalogue of approximately 2,600 lunar objects which can be sorted and filtered by the current position of the lunar terminator. Utilities are provided to predict on what dates and times a particular terminator position will occur in the 12 months following the current date and time. It is designed to quickly answer the question "What's on the terminator tonight?" The spreadsheet is not internationalized and assumes a Microsoft Windows U.S. date system. While this spreadsheet contains a good utility for locating favorable observing times for objects near the terminator on the Moon's near-side face between 0 and 90 degrees East or West lunar longitude, this spreadsheet is not suitable for high-precision planning for observing objects in libration areas on the lunar limb.

This lunar observing spreadsheet will be of interest to instructors of introductory college astronomy courses, astronomy club lunar party organizers, and intermediate and beginner lunar observers. By using the full power of Excel's drill-down data filter feature, a variety of interesting lunar tours can be developed, e.g. - by geologic period, by crater size, by feature type, by bright ray crater, by dark halo crater, by dark-floor craters, by fractured floor craters, etc.

A better existing alternative is the popular freeware Virtual Atlas of the Moon (VAM) by Patrick Chevalley and Christian Legrand. A nice java-based simple planner is Tom Talbott's 2002 Moon Calculator.

Purpose

To observe the Moon efficiently, like deep sky observing, is dependent on having a good catalogue of interesting objects and the ability to determine the current location of objects. Typically, this may involve reviewing several books and guides for appropriate targets applicable to a particular night. Finding the right targets is confounded by the numerous lunar targets on the Moon's near-side. In the United States Geologic Services Gazetteer of Planetary Nomenclature - Moon Nomenclature Tables, there are approximately 10,000 near-side lunar features. Several guides and observing lists are available to help the beginner and intermediate to select a few targets for an applicable night. Popular printed guides include Wood's The Modern Moon: A Personal View and his LPOD website, Antonin Rukl's An Atlas of the Moon and John E. Westfall's Atlas of the Lunar Temrinator. The outstanding freeware Virtual Atlas of the Moon (VAM) by Patrick Chevalley and Christian Legrand includes cross-reference indexing to Wood's Modern Moon, Rukl's Atlas and Westfall's Atlas. Using VAM, it is possible to filter for craters and other features currently on or near lunar terminator and then easily look up the book and chart cross-references. Features are included in VAM to filter and sort craters by an interest rating.

However, VAM requires the user to have the VAM program installed on a computer available to the user. Sometimes this is not possible.

This project's lunar observing spreadsheet was created out of a desire to have an observing tool that was more generic and flexible than VAM and that could be carried around with the user on a data device like a jumpdrive. I was also interested in study astronomical math algorithms. The implementation vehicle chosen was Microsoft Excel. Excel is widely distributed in office environments. Thus, during a workday break, it is possible using this spreadsheet to quickly select a few objects for after work observing or to plan a lunar astronomy club party.

This project's lunar obseving spreadsheet also was created out of a desire to have an observing list of intermediate size, e.g. - something between the Wood's Lunar 100 that is not large enough to sustain a lifetime observing program and the information overload of the 10,000 plus entries for nearside lunar features in the USGS Planetary Gazetter. A more reasonable catalogue size of around 2,000 objects with heavy indexing and organization around feature characteristics and lunar geologic history was seen as desirable.

Other features included in this lunar observing spreadsheet are a means to quickly move target lists to HTML tables for redistribution over the web.

Before embarking on an observing program, beginners are urged to go to your local college library and read two short sections in the first chapter in Westfall's Atlas entitled "Observing Programs and Visibility Cycles" and "Illumination near the terminator" regarding low sun-angle observing. Contrast that with the bright ray objects in Rukl's list of 50 showcase objects in the back of Rukl's Atlas. Typically, bright ray craters are observed closer to the full Moon. The Royal Astronomy Society of Canada (RASC) Annual Observer's Handbook also has a good overview section on the technique of lunar observing.

Catalogue Description

The lunar observing spreadsheet catalogue contains approximately 2,600 near-side objects. Spreadsheet Tab MainLunarCatalogue. The catalogue was developed by the following means.

• Several popular guides were reviewed for showcase item lists. These included Wood's Lunar 100, Rukl's Rukl 50 (in the back of his atlas), the AstroLeague Lunar Club beginner and intermediate observing lists, and the NextStar Lunar Club 50. A consolidated list of approximately 180 showcase lunar objects was developed.
• Named-nearside craters in the USGS Gazetteer of Planetary Nomenclature for the Moon was imported as the base list of craters and lunar features. All Gazetteer named features (mons, palis, mare, etc.) were imported. This included feature size.
• Kapral's and Garfinkle's (of the Geologic Lunar Research Group) 2005 draft GLR Catalogue of Lunar Domes (Draft) was imported. This included data on the height and diameter of domes.
• Named-nearside satellite craters larger than 50km were imported from the USGS Gazetteer.
• A draft Assoc. of Lunar and Planetary Observers (ALPO) Bright Ray database issued in May 2006 was imported.
• Miscellaneous named-nearside satellite craters smaller than 50km were imported from the Gazetter, typically when they were referenced as a showcase item in a guide or in Wood's LPOD articles.
• An index to approximately 460 features discussed in C.A. Wood's LPOD articles between 2004 and June 1, 2006 was prepared. See related Index to LPODs website.

This process yielded approximately 2,600 object entries. Then the catalogue was enhanced with object characteristic coding, described as follows:

• Columns were added for the main guides (Lunar 100, NextStar Lunar Club 50, Rukl 50, Astroleague) and the object numbers or tag for each list was coded.
• Approximately 190 objects representative of various lunar geologic period features were coded from Don Wilhems's 1987 A Geologic History of the Moon, USGS Survey Paper 1348 and Westfall's Atlas were assembled into a "Geologic Period" table column. This allows the user to filter lunar tours by geologic period.
• Cameron's 1974 list of approximately 450 ring-dike craters were annotated into the comments column. Cameron, W. S.; Padgett, J. L. 1974. Possible Lunar Ring Dikes. 1974Moon....9..249C
• Elger's 1895 object notes on bright ray craters were added to the comments field. Elger, Thomas Gwyn. 1895. The moon: a full description and map of its principal physical features. London. G. Philip & Son. (Data file of bright rays from C.A. Wood 2006)
• Cherrington's Gazetter, covering approximately 1,000 objects was reviewed and the heights of crater rims, mare walls, mountains and massifs and the depths of valleys were extracted. Cherrington assembled his data from chart take-offs from 1960s NASA LAC charts. Cherrington's height data is in feet. This was converted to meters. Cherrington, Jr. E.H. 1984 (reprint). Gazetter. In Exploring the Moon Through Binoculars and Small Telescopes. Dover.
• Miscellaneous feature characteristics discussed in LPOD articles, Rukl's Atlas and the author's personnel knowledge, like dark floor craters, dark halo craters, and albedo asterisms were coded into the comments field or added as new objects.
• Where an object record (a table row) is based on an IAU official or USGS assigned name and position, a field was coded assigned as "true." Where an object name is not officially recognized by the IAU or the USGS or the object position is not known with certainty (e.g. it is near an officially-named object), this field is coded "false".

The catalogue is also available as a separate static html document.

Download the spreadsheet

To get the lunar observing spreadheet: click here. 7.5 megabytes

Download the Main lunar catalogue 4.2 megs as static html document. Excel users can import the catalogue into Excel by simply pasting the catalogue url into Excel's "open file" dialogue box.

• Worksheet SetObservingPoint

This worksheet stores the observing point location.

In the blue highlighted cells, enter the terresterial longitude and latitude for your observing point in integer degrees, minutes and seconds. The remaining sheets use this information to compute the Moon's local horizon altitude and azimuth.

• Worksheet TerminatorLocation

This worksheet is used to set the planned observing time and to calculate the position of the lunar terminator at that time.

Enter your UTC to local time offset in the blue highlighted cell B5.

The remainder of the spreadsheet is driven by the observing date year, Month, Day and integer UTC hour in blue highlighted cells B19 throug B22. In the hours field only enter an integer. Note that the time entered in the hours field is UTC, not local time.

Using this observing time data, the current position of the lunar terminator and the Moon's altitude and azimuth in the observing point's local horizon system is computed. An estimated geocentric distance to the Moon is computed. The distance computed is not the observing point distance.

Cells B19 through B22 is the primary means by which recalculation of the spreadsheet is forced. To force recalculation, simply change the hours value.

Recalculation takes about 10-15 seconds on a 1.7 Ghz IBM personal computer.

The position of lunar terminator (the solar colongitude) is determined using a table lookup algorithm by Meeus reproduced at pages 120-122 of Rukl's (2ed) Atlas. That table method returns the colongitude of the terminator through 2030, but does not return the solar colatitude. (A reverse lookup algorithm - "When will a particular object be on the lunar terminator?" - was not implemented. A brute force filtering solution to reverse lookup across one year is provided in worksheet "PlanAnnualOpportunities".

Because Meeus's lookup algorithm only gives solar colongitude but not the colatitude, this spreadsheet is not suitable for high-precision planning for observing objects in libration areas on the lunar limb.

• Worksheet MainLunarCatalogue

This worksheet contains the main catalogue of 34 characteristics about approximately 2,600 near-side lunar objects, displayed in Excel data filter mode.

The catalogue is sorted by descending lunar latitude and descending lunar longitude. Longitudes are negative of West lunar longitudes and positive for East lunar longitudes.

At first, the display order may be disorienting.

Once you have determined the current longitude of the lunar terminator, filter the catalogue using the Excel Data Filter drop-down on the column for lunar longitude in decimal format. That column, worksheet column E, is labeled "Long_dec". A typical filter query, that filters of objects within two degrees of a rising terminator in the first quarter located at 20 degrees East lunar longitude, is:

Long_dec is greater than or equal to 20 AND Long_dec is less than or equal to 22

A similar filter for objects on the west side of the Moon at 20 degrees West lunar longitude would be:

Long_dec is greater than or equal to -20 AND Long_dec is less than or equal to -18

Once the Main Lunar Catalogue worksheet is filtered, objects along the terminator are listed from north to south latitude.

To select and display only desired targets for a particular night, place an "x" or other marker in the column labeled "Selected", column A of worksheet MainLunarCatalogue. Then filter for non-blank entries in that column.

Using the full power of Excel's drill-down data filter feature, a variety of interesting lunar tours can be developed, e.g. - by geologic period, by crater size, by feature type, by bright ray crater, by dark halo crater, by dark-floor craters, by fractured floor craters, etc.

The display is reset using the standard Excel menu option "Data | Filter | Show All".

Worksheet Articles-on-Objects

This worksheet is used to store article references tied to a lunar object and position.

As currently published, this worksheet contains in index to approximately 460 C.A. Wood LPOD articles. Once you have determined the lunar longitude of the terminator, like the main catalogue, this catalogue of articles can be filtered by lunar longitude. This provides a convenient an easy way to identify interesting targets on a particular night and to access (via hyperlinks) to Dr. Woods lively expert narratives on those objects in LPOD articles.

The article catalogue is also useful for lunar star parties, where internet access is available. The public can view the object through a telescope and then read more and see more detailed astrophotographs of that lunar object at the LPOD website.

This author is not affiliated with the LPOD site.

• Worksheet PlanAnnualOpportunities

This spreadsheet is used to determine when a feature will next be favorably positioned for viewing during the next twelve months.

The spreadsheet automatically takes a beginning current observing date and time from the worksheet "TerminatorLocation" (Cells B19 to B22). Using this date and time and the following four (4) hours on every following day for the next year, the spreadsheet computes the Moon's altitude, azimuth and size in arcsecs. This calcluation covers approximately 1400 table rows (4 * 365 days in a year).

The Plan Annual Opportunities worksheet can then be filtered by a range of lunar longitudes using the decimal lunar longitude in worksheet "PlanAnnualOpportunities", column G. The procedure is the same as described for under "MainLunarCatalogue" above.

The Plan Annual Opportunities worksheet also can be filtered on the Moon alitude column, labeled "MoonAlt" - column "M", to filter out any less-than-zero Moon altitudes.

Once filtered by a lunar longitude range, the dates and hours that the Moon is (1) above the horizon, and (2) the terminator is over the object, are displayed along with the arcsecond size of the Moon. Using this information, it is possible to calendar future favorable opportunities to view or photograh an object.

A "Selected" column (worksheet column A) is provided to mark and filter only those dates and times that you are interested in. Standard Excel print options can be used to prepare a hardcopy list.

In typical use, an early evening observing time is set in worksheet "TerminatorLocation". This generally returns rising terminator positions.

To retrieve setting terminator times, that typically occur in the early morning hours, change your observing time in worksheet "TerminatorLocation" to an early morning hour. To pick up both favorable rising and setting times, generally worksheet "PlanAnnualOpportunities" has to be checked twice - once for an early evening observing time and a second time for an early morning time.

When filtering worksheet "PlanAnnualOpportunities", you trigger a recalculation of the entire spreadsheet. It is important to pause and to allow the spreadsheet to fully recalculate before proceeding.

The display is reset using the standard Excel menu option "Data | Filter | Show All".

• Worksheet PlanAnnualGraphical

Once worksheet "PlanAnnualOpportunities" is filtered, the worksheet "PlanAnnualGraphical" displays a chart of the Moon's altitude and its size for all indicated dates. This supplemental graphical information can be used to hone in on the most favorable observing date for a feature in the next 12 months - the date on which the Moon is closest, lunar objects have their greatest angular size, and the Moon is at its highest local altitude.

• Worksheet PlanDateGraphical

This worksheet is a supplemental graphical chart that displays the filtered altitudes of the Moon from worksheet "PlanAnnualOpportunities" for one year.

• Worksheet ObservingLog

This worksheet contains a simple generic table for recording observations.

• Worksheet TelescopeResolvingLimit

This worksheet uses a rule-of-thumb to calculate the smallest visually observable lunar object using various telescopes.

• Worksheet Utility - Misc Calculators

This worksheet stores miscellaneous lunar calculator-utilities. Currently, this worksheet contains only one calculator - an aid to finding the height of lunar objects based on their shadows.

• Worksheet Nomenclature_with_Geology

This worksheet contains handy reference tables and requests no user input. Latin nomenclature in IAU-USGS lunar object types provided in plain English. A table of lunar geologic periods along with representative objects is provided.

• Worksheet Bibliography

List worksheet contains a list of recommended books and lists.

• Worksheet ExportHTMLObjects

This worksheet provides a means for generating rows of objects from worksheet "MainLunarCatalogue" in HTML table format. Table rows are pasted from this worksheet into an HTML template, discussed below under worksheet "ExportHTMLTemplate".

It is assumed that the user of worksheet has a basic working knowledge of how to author a simply html document and html table coding.

A sample web table demonstrates the intended output - quick preparation of web distributed target lists.

Do not enter data in the "Selected" column A of this worksheet. Select objects by placing a mark in the "Selected" column of worksheet "MainLunarCatalogue". Then filter this worksheet "ExportHTMLObjects" on the "Selected" column.

Paste the selected rows into the HTML template. Also paste the row marked "Header" from worksheet "ExportHTMLObjects" as the first table row in the template.

• Worksheet ExportArticles

It is assumed that the user of worksheet has a basic working knowledge of how to author a simply html document and html table coding.

This worksheet is used to generate table rows from the "Articles-on-Objects" worksheet. It is intended to be used in the same manner as worksheet "ExportHTMLObjects" in order to generate web distributed article lists.

This worksheet was used to generate tables in the sample Index to LPODs website. See that website for an example of its use.

• Worksheet ExportHTMLTemplate

This worksheet stores text for preparing an HTML table using the proceeding worksheets.

Using the spreadsheet to prospectively plan for favorable targets during the next lunar cycle

• Determine the starting and ending dates for the next lunar cycle.
• Set the observing date-time to the start of the next lunar cycle and the hour you usually observe. See Cells B19 through B22 in worksheet "TerminatorLocation". For example, in June 2006, the next lunar cycle begins on June 25 and ends on July 24. Due to extended summer hours, observing usually starts at 4:00 UTC for my observing point.
• In worksheet "PlanAnnualOpportunities", filter column M ("MoonAlt") for Moon local horizon altitudes greater than zero degrees and filter column E (observing Hour) for a starting and near ending observing session hour. In the working example, that was 4:00 UTC and 6:00 UTC.
• Worksheet "PlanAnnualOpportunities" now displays the range that the lunar terminator will cross during your observing session for each night. Note these ranges and then use the catalogue worksheet "MainLunarCatalogue" or an authoritative atlas like Rukl's Atlas of the Moon to plan for interesting targets along the terminator during the next cycle.
• In worksheet "MainLunarCatalogue", type the dates of favorable appearance for an object as a reverse text string in the column "Selected".
• Worksheet "ExportHTMLObjects" can then be used to prepare a monthly plan for next lunar cycle. A sample rising half-month plan for the lunar cycle beginning June 26, 2006 is provided. The sample half-month plan is suggestive only. It is based on a narrow 2 degree filter per night and emphasizes unusual intermediate difficulty targets. By using a broader lunar longitude filter and selecting items marked as "showcase" in the Main Lunar catalogue, general pleasure touring plans can also be created.
• To sort the table rows prior to pasting in the HTML template, open a new instance of Microsoft Excel. Paste the rows into a blank worksheet and sort them by descending date. Then paste the date sorted rows into the HTML document template.

Finding the current or future positions of the lunar terminator using online sources

Although a current and future terminator position utility is included in the spreadsheet, the following online resources also display the approximate current position of the lunar terminator:

• Akkana Peck's Hitchhiker's Guide to the Moon displays a current terminator position estimate.
• M. Otlersdorf's Moon Physical Ephemeris. (Web applet).
• NASA/JPL's Horizons System This Horizon's ephemeris generator is difficult to use, but the terminator position can be retrieved.

Sources of algorithms used for lunar and solar ephemeris

• Lunar colongitude: Rukl2004: Rukl, A. 2004 (2ed). Tables for Calculation of Colongitude. Atlas of the Moon. Sky Publishing. (After Meeus 1963). Accuracy: Under evaluation.
• Ecliptic latitude and longitude of Moon (J2000); horizontal parallax of Moon; X,Y,Z equatorial coordinates; lunar distance: Simpson, David G. (NASA Goddard Space Flight Center) 1999. An Alternative Lunar Ephemeris Model for On-Board Flight Software Use. Proceedings of the 1999 NASA Goddard Flight Mechanics Symposium. Link (accessed 6/2006, after 1999 Astronomical Almanac; six polynominal coefficient equations). Accuracy: Against the JPL/NASA ephemeris << http://ssd.jpl.nasa.gov/horizons.cgi >>, this alogrithm returns positions within ~approx. 10 arcminutes of the the JPL webapplet
• Solar right ascension, declination; angular size; equatorial rectangular coordinates; horizontal parallax; distance: Cox, Arthur (ed). 2000. Solar Coordinates and Related Quantities. Section. 27.4.1 in Allen's Astrophysical Quantities (4th ed.). Springer. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000asqu.book.....C. Accuracy: Against the JPL/NASA ephemeris << http://ssd.jpl.nasa.gov/horizons.cgi >>, this alogrithm returns positions within 1 arcminute or 60" of the the JPL webapplet.
• Ecliptic to equatorial coordinate conversion: Duffet-Smith1988: Duffet-Smith, P. 1988 (3ed). Practical Astronomy with Your Calculator. Cambridge Press. 1988QB62.5.D83..… http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1988QB62.5.D83.....
• Lunar sun angle across features: Shaw, J. Scott. 200_. Height of lunar mountains. http://www.physast.uga.edu/~jss/1120L/LunarMount.html (Simple low-precision sun angle estimate)
• Also of interest: Roncoli, Ralph B. (JPL) 9/23/2005. Lunar Constants and Models Document. JPL Technical Document D-32296. http://ssd.jpl.nasa.gov/?lunar_doc

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