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© Croydon Astronomical Society 2012 Croydon, Surrey, England. Charity Registered in England and Wales No. 251560


Croydon Astronomical Society
est. 1956

This is primarily an amateur astronomer event and is particularly suitable for beginners and the public. The idea is to see as many deepsky objects during the session, the sort of objects we buy and use telescopes for.

We hold this once or twice a year, on this occassion it would have been Saturday 7th April.

The minimum items to bring with you will be a pen and paper so that you can record the Messier numbers of the objects you have seen; this is a record for your own satisfaction.

It will very much help to first read an introduction to this event and deep sky objects in particular.


Guide to the Messier Marathon: choice1, choice2

Messier Marathon Planner: choice1, choice2

Messier Finder Charts: choice1, choice2

A simple Internet search easily brings up many more that may suit you better.

It’s possible to observe all the Messier objects in one night for a few weeks from mid-March to early April (in the autumn there is a lesser but still valuable window of opportunity to see most). The dark nights around the time of the New Moon are best, and is more or less the case this year in 2018 as the Moon will be in its last quarter and won’t rise until later. Our society hopes to hold this event at Kenley at this time but these events are always subject to the weather so please check (back here and in the usual way we notify of openings) closer to the time.

It is not so much a race in time, as in who wins first, but an attempt to see all the objects in the list, in one night. You ‘win’ if you have seen all 110 objects (this is unlikely from the UK) and our objective is to actually have the satisfaction of any that we do see (modern interpretation is that there are only 109 in the list but for consistency across all events the disputed object is included). Many are easy, and the rest tend to increasing difficulty.

Difficulty varies throughout the night. For most of the night, especially during the middle, there is plenty of time to see and most objects are easy. Difficulty is for those that are faint and those close to the southern horizon but the real challenge is to see those objects close to the Sun at sunset and again at dawn, as they won't be set against a dark sky. Again, for or purpose it’s an opportunity just to see those we can.

From Kenley it is possible to see all 110 (109 have been seen throughout a year), but not in one night. The marathon for us therefore defaults to seeing as many as possible (clearly those below the horizon or in too light a sky are not expected to count). As an example 37 of the 110 were casually seen on Friday 11th August 2018. From more southern latitudes as in southern Europe, the USA, middle and far eastern countries it is feasible to see them all in one night.

The most challenging will be those very low in the sky, and these few are in the constellations of Scorpio and Sagittarius, visible only in summer. Usually it will be buildings and trees that will intervene. It can be said that all but two have been seen with the main telescope at Kenley, and the last two escaped at a time when the dome was under repair during summer 2014. It will involve seeing them between gaps in the trees to the south.

Various members of the society have seen most on the list in one night. A moonless night is certainly preferred but not essential, if the most difficult are not affected by moonlight (it is sufficient to have seen the object, not in how well).

What makes the marathon work is that there is a gap in the distribution of objects across the sky, and if the position of the Sun occupies that region, as it does during late March and early April, then all the objects can be seen in darkness or sufficiently so.

Lastly, and again, this is an opportunity to be shown and see deep sky objects through a reasonably sized telescope, with the enjoyment and satisfaction of having done so.


The following are available as downloads:

MessierMarathon_March_Guide (pdf)

MessierMarathon_Object guide_NoImages (pdf)

MessierMarathon_Object guide_WithImages (pdf)

MessierChart_Map (image)

MessierChart_List (image)

MessierMarathon_TickList (pdf)

Messier Marathon - Sat 7th April 2018 (postponed to another night, unfavourable weather)

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