The top sights to observe or image this month

DON’T MISS: Venus, Saturn and Mars join the Moon for a morning meeting

BEST TIME TO SEE: All month
RECOMMENDED EQUIPMENT: Naked eye

The morning sky is getting interesting this month as a trio of planets jostle for position. The group consists of Venus, Mars and Saturn, which all appear rather low when they are observed from the UK. Dimmer Mars and Saturn take advantage of the fact that they appear close to the bright planet Venus which, currently shining at mag. –4.4, is considerably easier to see despite its low pre-sunrise altitude.

At the start of March, Mars rises approximately 90 minutes before the Sun, popping up above the southeast horizon while 5˚ south of Venus. Mars will be shining at mag. +1.3 on this date, and easy to recognise because of its orange hue.

On 8 March, the gap will have closed between Venus and Mars, the separation being 4.3˚ on this date. Mars will be a fraction brighter too, at mag. +1.2.

By 13 March, the gap will have dropped to a fraction less than 4˚. It’s about this time that mag. +0.9 Saturn may be glimpsed, rising 30 minutes after Mars. Venus remains close to Mars over the next few mornings, only starting to separate from the Red Planet around 18 March. Mars, Venus and Saturn will be contained within a circle 12˚ across on this date.

By 23 March, the containing circle will have reduced in size to 8.5˚, the three planets now quite tightly packed together. It’s fascinating to watch the pattern formed by the trio change shape over the remainder of the month. On the morning of 24 March, they form a squat isosceles triangle, with Venus as the upper vertex. Mars will have brightened to mag. +1.1 on this date. All three planets are above the horizon 60 minutes before the Sun, but will need at least 20 minutes longer to reach a visible altitude.

An altitude-challenged waning crescent Moon joins the group on 28 March. Located 5˚ below Mars, the 18%-lit waning crescent rises around 40 minutes before the Sun above the southeast horizon. a re contained within an area 6˚ from Venus with mag. +1.1 Mars now 3.3˚ from Saturn.

As March transitions into April, Venus leaves Mars and Saturn, the dimmer pair reducing their separation to just 19 arcseconds on 5 April. On that date, it will be possible to catch all three planets rising around the same time, By 31 March, all three planets across. Venus appears east of the group on this date, shining at mag. –4.2 and the easiest to see by far. Meanwhile, Saturn remains at mag. +0.9, just 3˚ approximately 80 minutes before the Sun above the east-southeast horizon.

Tracking Comet 19P/Borrelly

BEST TIME TO SEE: 1–4 March and 20–31 March, avoiding the Moon
RECOMMENDED EQUIPMENT: Small/medium scope

Comet 19P/Borrelly was at its brightest last month, the comet reaching perihelion on 1 February. At its peak it was expected to reach mag. +8.9, making it a binocular target. As we head into March, the comet may just remain within binocular range, but it is dimming. On 1 March, Borrelly shines with a predicted integrated magnitude of mag. +9.5, about 15˚ to the west of the Pleiades open cluster, in the middle of Aries, the Ram. It’s currently tracking northeast, passing 4˚ to the south of the mag. +3.6 triple star system 41 Arietis on the night of 3/4 March. By 12 March, Borrelly’s magnitude will have reduced to mag. +10.0. At 00:00 UT on the 12th, the comet is about 8˚ to the west-northwest of the Pleiades.

On the nights of 13/14 and 14/15 March, it passes close to the mag. +4.5 TYC 1796-1306-1 in Aries, an orange coloured star. If Borrelly is showing the greenish hue associated with comets, this should make a nice colour contrast, despite the large difference in brightness between the two.

Closest approach to the Pleiades occurs on the night of 15/16 March, the comet expected to be around mag. +10.1 at this time as it passes 7˚ to the northwest of the cluster. On the 21/22 March, Borrelly will lie about one-third of a degree north of mag. +3.8 Omicron (ο) Persei.

Its northeast track takes it up towards NGC 1499, the California Nebula. It lies a couple of degrees to the south of the nebula on the 26/27 March, moving within one degree of its eastern edge on the 28/29 March, when Borrelly is expected to have faded to around 11th magnitude.

Porrima’s occultation

BEST TIME TO SEE: 19 March from 04:30 UT
RECOMMENDED EQUIPMENT: Small/medium scope

The Moon will occult the mag. +2.7 binary star Porrima (Gamma (γ) Virginis) on the morning of 19 March. This will be an interesting and challenging occultation to observe because the sky will appear quite bright as sunrise approaches.

The best strategy will be to locate Porrima early, say from 04:30 UT. The Moon’s phase will be full at the time of the occultation, so use some optical assistance to see the star, such as binoculars or a telescope finder. At 04:30 UT, Porrima lies 0.6˚ from the Moon’s limb.

As the occultation approaches, it’ll get harder to see the star, but a telescope should still show it even though the sky is becoming blue. Occultation disappearance occurs around 05:52 UT as seen from the centre of the UK, with reappearance occurring around 06:24 UT after sunrise. As the occultation chord – the apparent path of the star behind the Moon – is close to the Moon’s northern limb, times will vary by a number of minutes depending on location. If you do have clear skies, this is a fascinating event to observe, forcing you to do battle with the Moon’s glare and the bright morning twilight just before the Sun rises.