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Special Operations

1. The percent of the Moon’s surface illumi-

nated is a more refined, quantitative description of the

Moon’s appearance than is the phase. Considering the

Moon as a circular disk, at New Moon the percent

illuminated is 0; at First and Last Quarters it is 50%;

and at Full Moon it is 100%. During the crescent

phases the percent illuminated is between 0 and 50%

and during gibbous phases it is between 50% and


2. For practical purposes, phases of the Moon

and the percent of the Moon illuminated are

independent of the location on the Earth from where

the Moon is observed. That is, all the phases occur at

the same time regardless of the observer’s position.

3. For more detailed information, refer to the

United States Naval Observatory site referenced


d. Access to Astronomical Data for Determina-

tion of Moon Rise, Moon Set, and Percentage of

Lunar Disk Illuminated

1. Astronomical data for the determination of

Moon rise and set and Moon phase may be obtained

from the United States Naval Observatory using an

interactive query available at:

2. Click on “Data Services,” and then on

“Complete Sun and Moon Data for One Day.”

3. You can obtain the times of sunrise, sunset,

moonrise, moonset, transits of the Sun and Moon, and

the beginning and end of civil twilight, along with

information on the Moon’s phase by specifying the

date and location in one of the two forms on this web

page and clicking on the “Get data” button at the end

of the form. Form “A” is used for cities or towns in the

U.S. or its territories. Form “B” for all other locations.

An example of the data available from this site is

shown in TBL 10−2−2.

4. Additionally, a yearly table may be

constructed for a particular location by using the

“Table of Sunrise/Sunset, Moonrise/Moonset, or

Twilight Times for an Entire Year” selection.

TBL 10−2−2

Sample of Astronomical Data Available 

from the Naval Observatory

The following information is provided for

New Orleans, Orleans Parish, Louisiana 

(longitude W90.1, latitude N30.0)


29 May 2007

Central Daylight Time


Begin civil twilight

5:34 a.m.


6:01 a.m.

Sun transit

12:58 p.m.


7:55 p.m.

End civil twilight

8:22 p.m.



5:10 p.m. on preceding day


4:07 a.m.


6:06 p.m.

Moon transit

11:26 p.m.


4:41 a.m. on following day

Phase of the Moon on 29 May:  waxing gibbous with

95% of the Moon’s visible disk illuminated.

Full Moon on 31 May 2007 at 8:04 p.m. Central

Daylight Time.

10−2−3. Landing Zone Safety

a. This information is provided for use by

helicopter emergency medical services (HEMS)

pilots, program managers, medical personnel, law

enforcement, fire, and rescue personnel to further

their understanding of the safety issues concerning

Landing Zones (LZs). It is recommended that HEMS

operators establish working relationships with the

ground responder organizations they may come in

contact with in their flight operations and share this

information in order to establish a common frame of

reference for LZ selection, operations, and safety.