Observer’s Challenge – Mini Messier Marathon – Open Clusters

2023 March 18

Observer’s Challenge – Mini Messier Marathon – Open Clusters

Callum Potter

M16 The Eagle Nebula taken by Graham Winstanley — M16 The Eagle Nebula data by Telescope Live, processing by Graham Winstanley

March New Moon is the traditional time for the Messier Marathon challenge – to observe all the Messier objects in one night. This year 2023, New Moon will occur on Tuesday, March 21, 2023. This date suggests a primary weekend on March 18/19, and a secondary one on the weekend of March 25/26.

Of course there are many practical problems with a full Messier Marathon – not least that not all the Messier objects are visible from the UK, and as you head north in the country many become un-observable.

And as there are 110 objects in the Messier catalogue, it is also quite hard to get round them all. One of the best internet resources to help with a full Messier Marathon are these pages provided by SEDS.

For this ‘mini-marathon’ we’re just going to look for Messier’s open clusters – these should be easier to find and observe, and with more time available a chance for imagers or those using electronically assisted viewing to capture them too. There is still the big challenge of the objects with a southerly declination, so those objects in Scorpius and Sagittarius will be particularly difficult – even those in the south of the UK will still need a good southern horizon.

The list below of the 27 Messier open clusters is organised in a search order recommended by Don Machholz, whose book The Messier Marathon Observer’s Guide is excellent for anyone taking up the pursuit.

We will need a good clear night from dusk to dawn, though it might be possible to have a snooze or break half way through.

If you manage to observe or image these objects in one night, or even if you just manage a few – please post your observing report or images on your Members Page.

Good luck, happy Messier hunting!

No.	Messier	Constellation	RA	Dec	Visual Mag.	Size (arc-min)
1	M52	Cas	23 24.2	+61 35	7.3	13
2	M103	Cas	01 33.2	+60 42	7.4	6
3	M34	Per	02 42.0	+42 47	5.5	35
4	M45	Tau	03 47.0	+24 07	1.6	110
5	M35	Gem	06 08.9	+24 20	5.3	28
6	M37	Aur	05 52.4	+32 33	6.2	24
7	M36	Aur	05 36.1	+34 08	6.3	12
8	M38	Aur	05 28.4	+35 50	7.4	21
9	M41	CMa	06 46.0	-20 44	4.6	38
10	M93	Pup	07 44.6	-23 52	6	22
11	M47	Pup	07 36.6	-14 30	5.2	30
12	M46	Pup	07 41.8	-14 49	6	27
13	M50	Mon	07 03.2	-08 20	6.3	16
14	M48	Hya	08 13.8	-05 48	5.5	54
15	M44	Cnc	08 40.1	+19 59	3.7	95
16	M67	Cnc	08 50.4	+11 49	6.1	30
17	M29	Cyg	20 23.9	+38 32	7.1	7
18	M39	Cyg	21 32.2	+48 26	4.6	32
19	M6	Sco	17 40.1	-32 13	5.3	25
20	M7	Sco	17 53.9	-34 49	4.1	80
21	M11	Sct	18 51.1	-06 16	6.3	14
22	M26	Sct	18 45.2	-09 24	8	15
23	M16	Ser	18 18.8	-13 47	6.4	7
24	M18	Sgr	18 19.9	-17 08	7.5	9
25	M25	Sgr	18 31.6	-19 15	6.5	40
26	M23	Sgr	17 56.8	-19 01	6.9	27
27	M21	Sgr	18 04.6	-22 30	6.5	13

Best of Luck. Any results are welcome within the Member Galleries, sent to the Deep Sky Section or on the Forum.

The British Astronomical Association supports amateur astronomers around the UK and the rest of the world. Find out more about the BAA or join us.