DAS Activities

DAS Public Nights

Public Nights
Tuesday and Thursday at
DU's Historic Chamberlin Observatory
Current start time is 8:30 pm.

Costs to the public are:
$4.00 adults, $3.00 children

To book, please click:

Public Night Reservations



Messier Marathon


For a 1-sheet checklist of Messier objects in suggested observing sequence, click HERE (PDF)


M33 – The Triangulum Galaxy, an early evening object. © D.M. Dodge

2019 is a tricky year for completing the Messier Marathon on the Dark Sky Weekend. On March 9th, the Moon will be 3 days past new and thus will interfere slightly with the observation of early evening objects like M-74 and M33.

March – April is the only time during the year when observers at perfect dark sites at our latitude can hope to accomplish the feat of observing all of the 110 objects in the modern version of Charles Messier’s famous catalog of non-comets. For a lot of reasons, however, it’s probably better to have a goal of trying to observe as many as you can, not the entire list (see hints below).

Because of the importance of starting to observe as soon as possible after sun-down, it’s absolutely imperative that participants arrive at the site early (5:00 pm or so). Late arrivers will not only imperil their own chances of seeing the early objects, but may also make it difficult for other observers. Arriving before dark is also a good idea because the site is often packed on Marathon nights. The 14 powered concrete observing pads usually fill up way before dark.

We will have Marathon forms at the site, which provide a check list of objects in one of the preferred orders for observing. And there will be a signup sheet for those wanting to make a competition out of it.

For those who’ve tried a Marathon, the feat seems impossible to achieve without a lot of luck. But you’ll also need perseverance and stamina too.

One reason why luck is required is our fickle and usually unpredictable March and April weather, requiring some flexibility. Several years ago, Saturday looked like the pick of the two marathon nights. In fact, Friday turned out to be the best, which was a shame because only two observers were at the dark site to enjoy it. On Saturday, the warming hut was jammed with folks waiting for the wind to die down. Instead, it kept increasing in intensity, until even boat anchor mounts couldn’t hold a steady image.

This year, six windscreens (pdf) will be available at the Dark Site if the prevailing southerly winds start blowing.

Marathon Challenges

Because of evening and early morning challenges, absolutely perfect observing conditions are required to complete a Marathon at latitude 40 degrees north. (Lower latitudes down to 20 degrees north are better.) And we have found over the years that it’s simply not possible to complete a 110-object marathon at our dark site, although several people have seen 109.

The toughest object in the evening is M74, the low surface-brightness face-on Sc galaxy in Pisces, which is dropping into the “Denver nebula” in the West as darkness falls. Early evening objects like M74 and M33 will be tough during a late March Marathon. The lack of a large Moon in 2018 will make them a bit easier. However, they will be extremely difficult or impossible during the Alternate Messier Marathon on April14th, although the Moon will be only one day past new.

The early morning challenge is the globular cluster M30 in Capricorn, which rises just before the Sun. But the hills to the southeast of our dark site are just high enough to block it until the Sun is starting to turn the sky to a neon blue, which makes the cluster impossible to see in early March. April Marathoners may have a better chance, but will miss M74 in the evening.

Observing Equipment

What’s the best telescope to use? Probably one with a reasonable aperture (at least 4-5 inches), with which you’re familiar. Very large-aperture high focal length scopes can actually make the marathon more difficult because the field-of-view is smaller. Dobs are great for marathons because they are easy to move, have a wide field of view, and are easy to use between declination +30 and -30, where most of the Messier objects are situated.

‘Go-to’marathons are becoming more and more acceptable, with some clubs setting up special categories for them. If you know the sky well, a go-to marathon is really not much easier than a ‘star-hopping’ one, even the trip through the Virgo galaxy cluster, (where it’s essential to verify which galaxy is which). But one clear advantage is that you’ll have more time to enjoy the view, and the different perspective and ability to compare objects that the Marathon provides. Still, there’s nothing that can match the feeling of accomplishment gained from doing any observing program the old-fashioned way.

Let’s all hope for clear skies and light winds this year!

Hints for Happy Messier Marathoning

  • Practice difficult or unfamiliar areas of the sky a week or so before, using the telescope and observing aids you intend to use for the Marathon.
  • Arrive at the dark site well before sundown.
  • Use a checklist that presents the objects in the approximate order you will be viewing them.
  • Please don’t use the Marathon as a way to do or complete the Astronomical League Messier Observing Program. The AL club program requires detailed descriptive comments and there’s not much time for that during a marathon. It also requires star-hopping.
  • Do take the time to scribble some brief notable things about some of the objects. You’ll appreciate having these later, especially when you’re trying to remember if you really discriminated between easy-to-confuse objects like M86 and M84.
  • Aim to observe as many objects as possible, not ALL of the objects.
  • View easier objects first! Don’t spend 30 minutes trying to see M74 while the other objects in the West are sinking out of sight. Observe M77, 31, 110, 32, and maybe M33 first.
  • If you miss the M31 companion galaxy M110, you will probably be able to see it in the morning.
  • Try not to panic when you start going through the Virgo/Coma Galaxy Clusters. These are all bright galaxies (except maybe for M90) and you should have plenty of time because there’s a break in objects to observe when you’re done.
  • When you’re out of objects to view, try to get off your feet and get something to eat and drink. You’ll be busy from 7:10 pm to 11 pm, but a short break in the middle of that period and a longer break (even a nap in your car) sometime between 11 pm and 1:00 am is a good idea. (If you’re “go-to-ing’ you’ll be breaking earlier than that.)
  • Keep reviewing your checklist to make sure you’ve not forgotten an object. Common ones to overlook are M83 and M68.
  • Don’t despair if you can’t see M30 in the morning. As mentioned above, it’s probably not possible to see it in March and it will even be difficult to see in April from the DAS Dark Site, though it’s rising over 80 minutes before the Sun, because of the fact that the site is located in a shallow valley.
  • Remember that all 110 objects were not seen in one night by any observer until 1985. Seeing more than 90 is a great achievement!

– Darrell Dodge, DAS