On March 31st, the inner planet Mercury reaches greatest western elongation and on this date is positioned 28 degrees from the Sun in the morning sky. This is an excellent opportunity for observers located at southern hemisphere and tropical latitudes; the planet is visible for an extended period of up to 6 weeks from about the middle of March. Unfortunately for those located further north, the angle of the ecliptic is unfavourable and consequently the planet is not suitably placed for observation.
Observing Mercury
A clear and ideally unobstructed view of the eastern horizon is recommended when searching for Mercury. On March 16th, from latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury will appear 11 degrees above the eastern horizon 30 minutes before sunrise. Although placed in the morning twilight, at magnitude 1.4 the planet should be a relatively easy naked eye target.
For this apparition, a good time period to look for Mercury is between March 21st and April 15th, when the planet will be at least 17 degrees above the eastern horizon, 30 minutes before sunrise. Its magnitude will also increase from 0.7 to -0.1 and therefore spotting Mercury should be very easy now, weather permitting of course! The peak altitude occurs on March 31st, the date of greatest elongation west, when Mercury is just over 20 degrees high with a magnitude of 0.2.
Once past greatest elongation west, Mercury continues to brighten as it begins to draw towards the Sun. For this apparition, the planet does not reach maximum brightness (mag -1.0) until the very end of the visibility period, more than 4 weeks after greatest elongation west!
The diagram below shows the March and April morning apparition of Mercury from latitude of 35S. The view will be similar for observers at latitudes near 35S.
Mercury data table from March 15 to April 30, 2013
Date | Right Ascension | Declination | Mag. | Size | Illum. (%) | Distance from Earth (AU) |
---|---|---|---|---|---|---|
Mar 15, 2013 | 22h 27m 55s | -07d 39m 51s | 1.6 | 10.1" | 17 | 0.663 |
Mar 16, 2013 | 22h 27m 22s | -07d 58m 56s | 1.4 | 10.0" | 19 | 0.674 |
Mar 17, 2013 | 22h 27m 13s | -08d 15m 40s | 1.2 | 09.8" | 22 | 0.685 |
Mar 18, 2013 | 22h 27m 27s | -08d 30m 03s | 1.1 | 09.7" | 24 | 0.696 |
Mar 19, 2013 | 22h 28m 03s | -08d 42m 02s | 0.9 | 09.5" | 26 | 0.709 |
Mar 20, 2013 | 22h 29m 00s | -08d 51m 39s | 0.8 | 09.3" | 28 | 0.721 |
Mar 21, 2013 | 22h 30m 18s | -08d 58m 55s | 0.7 | 09.2" | 31 | 0.734 |
Mar 22, 2013 | 22h 31m 54s | -09d 03m 53s | 0.6 | 09.0" | 33 | 0.748 |
Mar 23, 2013 | 22h 33m 48s | -09d 06m 35s | 0.6 | 08.8" | 35 | 0.762 |
Mar 24, 2013 | 22h 35m 59s | -09d 07m 06s | 0.5 | 08.7" | 37 | 0.776 |
Mar 25, 2013 | 22h 38m 26s | -09d 05m 29s | 0.4 | 08.5" | 39 | 0.790 |
Mar 26, 2013 | 22h 41m 07s | -09d 01m 48s | 0.4 | 08.4" | 41 | 0.804 |
Mar 27, 2013 | 22h 44m 02s | -08d 56m 06s | 0.4 | 08.2" | 43 | 0.818 |
Mar 28, 2013 | 22h 47m 09s | -08d 48m 27s | 0.3 | 08.1" | 44 | 0.833 |
Mar 29, 2013 | 22h 50m 29s | -08d 38m 55s | 0.3 | 07.9" | 46 | 0.847 |
Mar 30, 2013 | 22h 53m 59s | -08d 27m 33s | 0.3 | 07.8" | 48 | 0.862 |
Mar 31, 2013 | 22h 57m 41s | -08d 14m 25s | 0.2 | 07.7" | 49 | 0.877 |
Apr 01, 2013 | 23h 01m 31s | -07d 59m 33s | 0.2 | 07.5" | 51 | 0.891 |
Apr 02, 2013 | 23h 05m 31s | -07d 43m 01s | 0.2 | 07.4" | 52 | 0.906 |
Apr 03, 2013 | 23h 09m 40s | -07d 24m 52s | 0.2 | 07.3" | 54 | 0.920 |
Apr 04, 2013 | 23h 13m 57s | -07d 05m 09s | 0.1 | 07.2" | 55 | 0.935 |
Apr 05, 2013 | 23h 18m 21s | -06d 43m 54s | 0.1 | 07.1" | 57 | 0.950 |
Apr 06, 2013 | 23h 22m 52s | -06d 21m 10s | 0.1 | 07.0" | 58 | 0.964 |
Apr 07, 2013 | 23h 27m 31s | -05d 56m 60s | 0.1 | 06.9" | 59 | 0.978 |
Apr 08, 2013 | 23h 32m 16s | -05d 31m 25s | 0.1 | 06.8" | 61 | 0.993 |
Apr 09, 2013 | 23h 37m 07s | -05d 04m 28s | 0.0 | 06.7" | 62 | 1.007 |
Apr 10, 2013 | 23h 42m 05s | -04d 36m 11s | 0.0 | 06.6" | 63 | 1.021 |
Apr 11, 2013 | 23h 47m 08s | -04d 06m 37s | 0.0 | 06.5" | 65 | 1.035 |
Apr 12, 2013 | 23h 52m 17s | -03d 35m 47s | 0.0 | 06.4" | 66 | 1.049 |
Apr 13, 2013 | 23h 57m 32s | -03d 03m 43s | -0.1 | 06.3" | 67 | 1.063 |
Apr 14, 2013 | 00h 02m 52s | -02d 30m 28s | -0.1 | 06.2" | 68 | 1.077 |
Apr 15, 2013 | 00h 08m 17s | -01d 56m 02s | -0.1 | 06.2" | 70 | 1.091 |
Apr 16, 2013 | 00h 13m 48s | -01d 20m 28s | -0.2 | 06.1" | 71 | 1.104 |
Apr 17, 2013 | 00h 19m 25s | 00d 43m 48s | -0.2 | 06.0" | 72 | 1.118 |
Apr 18, 2013 | 00h 25m 07s | 00d 06m 04s | -0.2 | 05.9" | 73 | 1.131 |
Apr 19, 2013 | 00h 30m 54s | 00d 32m 44s | -0.3 | 05.9" | 75 | 1.144 |
Apr 20, 2013 | 00h 36m 47s | 01d 12m 31s | -0.3 | 05.8" | 76 | 1.157 |
Apr 21, 2013 | 00h 42m 46s | 01d 53m 17s | -0.3 | 05.8" | 77 | 1.170 |
Apr 22, 2013 | 00h 48m 51s | 02d 35m 00s | -0.4 | 05.7" | 79 | 1.182 |
Apr 23, 2013 | 00h 55m 01s | 03d 17m 37s | -0.4 | 05.6" | 80 | 1.195 |
Apr 24, 2013 | 01h 01m 18s | 04d 01m 06s | -0.5 | 05.6" | 81 | 1.207 |
Apr 25, 2013 | 01h 07m 41s | 04d 45m 25s | -0.5 | 05.5" | 83 | 1.218 |
Apr 26, 2013 | 01h 14m 11s | 05d 30m 30s | -0.6 | 05.5" | 84 | 1.230 |
Apr 27, 2013 | 01h 20m 48s | 06d 16m 19s | -0.7 | 05.4" | 85 | 1.241 |
Apr 28, 2013 | 01h 27m 32s | 07d 02m 48s | -0.7 | 05.4" | 87 | 1.251 |
Apr 29, 2013 | 01h 34m 23s | 07d 49m 54s | -0.8 | 05.3" | 88 | 1.262 |
Apr 30, 2013 | 01h 41m 22s | 08d 37m 32s | -0.9 | 05.3" | 89 | 1.271 |