CSGNetwork.com Free Information

Lunar Perigee and Apogee Calculator

This calculator requires the use of Javascript enabled and capable browsers. This calculator is designed to display the date, time, and distance of lunar perigees and apogees for a given year. This technology was written for NASA by us in the late 70s, has been converted into many programming languages and into JavaScript in the mid 90s. Enter the year in the box below and press "Calculate"; by default the data is in the current year. This is a complex calculation and depending on the speed of your computer, it may take a while for the results to appear in the text boxes. You may cut and paste data from the text boxes to transfer same to other documents. There is a kilometer and mile conversion tool at the bottom of this calculator.

All dates and times are Universal time (UTC); to convert to local time add or subtract the difference between your time zone and UTC, remembering to include any additional offset due to summer time for dates when it is in effect. Our Time Converters menu page has numerous useful tools on it that can help. For each perigee and apogee the distance in kilometers between the centers of the Earth and Moon is given. Perigee and apogee distances are usually accurate to within a few kilometers compared to values calculated with the definitive ELP 2000-82 theory of the lunar orbit; the maximum error over the years 1977 through 2022 is 12 km (about 7.5 miles) in perigee distance and 6 km (about 3.3 miles) at apogee.

The closest perigee and most distant apogee of the year are marked with "++" if closer in time to full Moon or "--" if closer to new Moon. Other close-to-maximum apogees and perigees are flagged with a single character, again indicating the nearer phase. Following the flags is the interval between the moment of ellipse perigee or apogee and the closest new or full phase; extrema cluster on the shorter intervals, with a smaller bias toward months surrounding the Earth's perihelion in early January. "F" indicates the perigee or apogee is closer to full Moon, and "N" that new Moon is closer. The sign indicates whether the perigee or apogee is before ("-") or after ("+") the indicated phase, followed by the interval in days and hours. Scan for plus signs to find "photo opportunities" where the Moon is full close to apogee and perigee. The moon phase table gives the time of all new and full Moons in the indicated year, as well as the last phase of the preceding year and the first phase of the next year.

Lunar Perigee and Apogee Calculator
Perigee and Apogee Required Data Entry


Perigees and Apogees

New and Full Moons

Data within the text boxes of this document is in the public domain, provided by both NASA and the USNO. The public domain data (but not this program or the proprietary scripts within it, off of the CSGNetwork.Com site) may be freely used without CSGNetwork.Com copyright infringements. Usage of the raw data or the massaged and displayed data has no restrictions. Licensing is available for the program and scripts.

Click anywhere out of the field for calculation.
Kilometers  Miles 
Version 6.0.4

Leave us a question or comment on Facebook
Search or Browse Our Site
Free Information Calculators and Converters

International Copyright Violation
Registered® Trademark™ and Copyright© 1973 - CSG, Computer Support Group, Inc. and CSGNetwork.Com All Rights Reserved

Home | Advertising | Calculators and Converters | Contact Us | Javascript | Sitemap | Glossary | Top Free Apps