Observer’s Challenge – Mini Messier Marathon – Open Clusters

2020 March 18

Observer’s Challenge – Mini Messier Marathon – Open Clusters

Callum Potter

March New Moon is the traditional time for the Messier Marathon challenge – to observe all the Messier objects in one night.

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

Cover photo M103 by David Davies