March brings the Spring equinox, hope for improved weather, and the possibility of a marathon road trip through the sky via the Messier list of astronomical objects. Note: it’s not supposed to be a “messy” list.
The odd background for this very old list (~1774), published by French astronomer Charles Messier (assisted by Pierre Méchain), is that it started as a “nuisance” list of objects which could be mistaken for comets. Messier was a comet hunter who used a 4” (100mm) aperture refractor and has 13 comets to his credit. The comet hunting was done from Paris, France visually, of course, since photography had not yet been invented. Accordingly, the objects of the list are mainly those which the human eye can see easily through a small telescope, and largely omits the deep red hydrogen-alpha clouds which are so obvious on modern photos of the sky.
Visual Challenge of the Messier Marathon
Because the Messier catalog objects are easy to see visually even with modest amateur telescopes, an annual activity for astronomy clubs is to put out a “Messier Marathon” challenge in mid-to-late March, during which there is a window of time when all 110 Messier objects can be seen in a single night. However, success in the marathon depends on ideal conditions:
- Clear skies all night
- Reasonably dark skies
- Northern latitudes (~20-40 degrees North)
- At or near new Moon phase
- A good supply of hot coffee
In addition, if the objects are not viewed in the proper order, not all of them can be seen since some will be setting soon after sunset, and others will be rising just ahead of the Sun. A viewing order with these constraints in mind was published by Don Machholz (an American comet hunter) and others and is also available as a succinct Messier Sequence List (PDF) online at the website of the Rio Rancho Astronomical Society (New Mexico). The viewing sequence path through the sky can be seen below against a sky chart assembled from Stellarium plots.
Because many Messier objects are clustered together, an expanded view of a couple of crowded areas is shown in the following additional charts. Click on images to see larger views.
This year (2022), the Moon phase is not optimal, occurring at the end of March, so this year is not the best time to try this, but any clear night is fine for “practice” and encourages familiarization with the night sky. It goes without saying that completing a Messier Marathon is quite an accomplishment and is satisfying for those with a competitive nature. And of course, more kudos to you if you can do it without a computerized go-to telescope!
The Photographic Challenge
Photographically, completing the Messier Marathon in a single night is virtually impossible, though teams of amateurs have attempted it with automated telescope mounts. The challenge is that the objects encompass the gamut of deep space objects and vary greatly in size and brightness. In addition, on average, only a few minutes of exposure can be allocated per target, though in certain parts of the marathon path, several objects can be captured in a single field of view with the right camera and telescope size.
An additional compromise may be necessary to find the right exposure to use given the time constraint, especially for the targets close to sunset and sunrise. Choice of the telescope size and camera sensor is very important. Too small a field of view could require the effort of assembling a mosaic of a large target, but too short a focal length could make it difficult to see the small targets. On the upside, with a good combination of telescope and camera, there are several targets that can be captured in a single camera view with the proper framing.
One goal might be to use the same size of telescope Messier used (4”/100mm objective). You may want to use a Barlow lens or 2x teleconverter for increased magnification on small targets at the time expense of reconfiguring and refocusing your telescope, but to start, pick a fixed telescope setup, shoot at prime focus, and use your normal camera to see what you can capture.
Use short (30 seconds or so) exposures and shoot multiple exposures for deeper depth if necessary and avoid using an autoguider which will slow your progress through the Messier list.
Since the Messier objects are visual objects (our eyes have higher sensitivity in the dark in green wavelengths), an off-the-shelf DSLR (or mirrorless) camera should work fine. Only a few of the Messier objects glow by the deep red light of Hydrogen-alpha (e.g. M42 and M8), and these objects are bright and also glow with Hydrogen Beta and Oxygen III components, both in the blue-green end of the spectrum. To capture both the smaller targets and wide-field targets, a high-megapixel, full frame camera (I use a Nikon D850 or modified Canon RP) is preferable.
Clearly, planning is key to success in photographing the Messier objects.I suggest using Stellarium (free) or similar desktop planetarium software to preplan your shots. Stellarium has the ability to overlay a camera frame based on your input focal length and camera size so that you can previsualize each shot and temper your expectations as well as help you compile your shooting sequence as you move along the marathon route. Stellarium also has the convenient capability of displaying only the Messier list objects against the sky, as well as providing assistance in locating targets by simply typing in the Messier object designation.
Easing into the Messier List
Without a doubt, a great deal of pre-planning is necessary for a true Messier marathon! But there’s no need to dive into the deep end of the pool and stress over doing this in a single-night marathon. We can ease into it by making it a year-long project of photographing the Messier list. With experience, a photographic marathon might be carried out over several successive nights. No matter how you do it, the project can serve as a good incentive to get us out under the night skies all year long.
For detailed information on the Messier objects, including size and magnitude, see the convenient, sortable table on Wikipedia.