Moon - third and last quarters.

Most of us out of convenience tend to observer the Moon up to full; that is, through first and second quarters. After full the Moon is not well placed for observations until well into the early hours.

Now that summer solstice has passed we commence the period leading towards harvest and hunter’s moons. It will be seen from the table that between July 6 to July 21 the Moon’s declination increases from –26° to +26°; at the same time the daily interval between rising times diminishes on average to around 4 minutes between the 9^th and 14^th July. (If the Moon were to sustain the same declination for 24 hours it would rise later on the following day by approximately 52 minutes.)

This provides us with the opportunity to observe the rising waning Moon close to the same time every evening/night right up to July 18. Should the late night sky of the 18^th be clear, then at 23h 27m UT (half-past midnight BST) the “old” crescent Moon will rise just 26° east from true north.

Diagram 1 shows the azimuths for the Moon in relation to the eastern horizon for 23h 00m UT each day from 6 July to 17.

Moonrise, setting, declination and phase

Phases of the Moon July 2009

Full moon:                 09h 21m  07 July
Last quarter:             09h 53m  15 July

New moon:               02h 34m  22 July
First quarter:             22h 00m  28 July

There will be an interesting configuration in the early hours of July 19 involving the Moon, Venus, Mars and the bright red star Aldebaran (the eye of the Bull). (Fig. 2).

Dia. 1. The positions for the Moon at 23h 00m UT from July 6 to July 17, 2009.

Dia. 2.  The sky at 01h 00m UT on the morning of July 19, 2009.

 

JV 02/07/09