Messier Marathon Night Results

"Mission Accomplished!" to use a cliched phrase. "Goal Reached" might be a little better, or maybe "Dumbness Overcome."

This was one of my first attempts to use my DSLR in quite a while, and I managed to make a lot of mistakes early on:

• Forgetting to return to ISO 1600 from the composing setting of 6400
• Forgetting to set the shutter control to bulb
• Forgetting to increase the number of frames on the DSLR controller from the dark frame to light frame counts

And so on. The evening began with starts and restarts, but once it got going it went well. The time I lost meant I wouldn't go after the dimmer planetary nebula I had included on my object list in the last post, but that was okay.

All the hardware worked perfectly, although some went untested. The dry air and the gusty to breezy conditions meant the dew preventers weren't needed. It was only around 2 A.M. that frost began to appear, and my scopes stayed clean until the end a little before 3 A.M. The DSLR power supply worked perfectly and the 35Ah battery was barely tested running that and the mount. I used my laptop for PHD with its power supplied by it's own battery augmented with a Duracell 600 battery pack. The Duracell ran down pretty far in the five or so hours, so this might not be a good option for multi-night imaging. For more power conservation I need to find a way to turn off the laptop's display, not simply dim it.

The evening tally was six Arp galaxies and one planetary. In terms of Messier objects it was 9 1/2. Let's see some marathon images:

Leo Triplet (clockwise from NGC 3526 at top, M65, and M66) Together these are Arp 317. M66 is Arp 16.

M49 (right of center, Arp 134)

M60 (left of center, Arp 116) and M59 (right of center)

M87 (Arp 152)

M90 (Arp 76) and M89 at bottom edge

M97 (Owl Nebula) and M108 at bottom edge

All the images are based on 10 three minute exposures with a Canon T2i (at ISO 1600) riding on a TV 102 operating at f/7--except the image of M90, which was 5 three minute exposures at ISO 6400 (see list of mistakes above). These were calibrated with 20 dark frames collected throughout the night as the temperature fell from around 30°to 20°F. They obviously haven't been flatted. I reprocessed them to include synthetic flattening, and now they look a lot nicer!



An inspection of single light frames shows that they surpass visual observations, so why not bring back the idea of an Imaging Messier Marathon? Three minutes at ISO 1600 is about the same as 45 seconds at ISO 6400. 3/4 minute times 110 objects is only 82 minutes; out of a six hour marathon night that leaves four and a half hours for acquisition and composing images. Definitely doable.

That aside, the evening bumped my Arp list count to 26 and my planetary list count to 23. Both lists are about 1/4 done!

Onward to warmer weather!

Imaging Messier Marathon list PDF

Here's a PDF I created that is adapted from Don Machholz's Go-To list in his Observing Guide to the Messier Marathon. I have added the multi-object image opportunities for those using a medium-size sensor and 700mm focal length imaging system. Have a suggested change or find an error? Leave a comment and let me know. Here's what a portion of it looks like:

A portion of the IMM list PDF.

Imaging Messier Marathon: Combining Targets in One Frame

So many objects, so little time. If only there were fewer objects!

Well, in a way there are. Some of the Ms are close enough together that one shot can encompass two or more objects, thus saving us time. Let's see what we can find in the way of grouped Messiers.

I'm going to list the Messier objects in the order given by Don Machholz in his book The Observing Guide to the Messier Marathon--A Handbook and Atlas. This book is available from Amazon, Barnes and Noble and other sellers. Frugal? Look to used book stores. I paid $25 for my copy at Half Price Books.

Here are some combined fields for two different focal lengths. If I missed some, please let me know so  that I can add to the list.

These lists depend your go-to running with at least get-it-in-the-finder accuracy. In the lists I'm leaving out all the single-target fields. I'll add a master list of all 110 objects soon.

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700 mm Focal Length Combined Fields

Eleven fields saved, five go-to ra/dec actions, four camera orientation checks.

Go-To target is indicated by bold. Tight fits may require camera rotation

M31+32+110:  Check Camera Orientation

M42+43

M95+96: Target RA 10:45:16, DEC +11:45:54

M65+66

M81+82: Target RA 9:55:39, DEC +69:23:38

M97+108: Target RA11:13:11, DEC +55:20:23 Check Camera Orientation

M84+86

M59+60

M17+18: Target RA 18:20:15, DEC -16:38:38 Check Camera Orientation

M21+20:: Target RA 18:03:23, DEC -23:07:31 Check Camera Orientation

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432 mm Focal Length Combined Fields

Fourteen fields saved, four go-to ra/dec actions, five camera orientation checks.

Go-To target is indicated by bold. Tight fits may require camera rotation

M31+32+110

M42+43

M95+96+105 Check Camera Orientation

M65+66

M81+82

M97+108: Target RA11:13:11, DEC +55:20:23

M84+86+87: Target RA 12:27:51, DEC +12:38:53 Check Camera Orientation

M58+59+60: Target RA 12:40:25, DEC +11:42:19 Check Camera Orientation

M17+18: Target RA 18:20:15, DEC -16:38:38 Check Camera Orientation

M21+20 Check Camera Orientation

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Your choice of imaging focal length(s) may well differ from mine. Focal lengths longer than 700 mm will find that some of the combinations flagged for an orientation check will not work. If your focal length is between 400 and 700mm you're safe if you follow the recommendations for 700mm.

Imaging Messier Marathon: Imaging Focal Length

Last time I mentioned planning for an imaging Messier marathon (IMM), where the goal was to produce images that recreate the impression a visual observer would have looking through a 6" or 8" telescope. This time I'll look at the choice of a telescope for this task.

Focal Length:

Under ideal circumstances imagers try to choose an imagin focal length that best matches the target object. In the IMM that's not really possible without spending a lot of time on swapping gear around. We need to use one telescope. Since this is quick and dirty imagaing with little concern about "going deep," any reasonable focal ratio from f/5 to f/10 will do, with faster scopes being preferred.

More important in my judgement is the ability to frame the larger of the Ms in single shots. If smaller objects end up looking small, that's fine, for that simulates the eyepiece view.

Since I'm planning this for myself, my calculations will be based the relatively common KAF-8300 sensor (18x13.5mm) that is in my CCD camera. DSLR imagers with APS-C sensors will have somewhat larger fields of view.

You can follow along with what I'm doing if you have a good planetarium program. I recommend Sky Tools 3, a package that is very good for planning. Also helpful is this list of Messier objects sorted by size.

Let's get started by examining some of the Messier objects.

The Ms range from the enormous M31 (about 3°x1°) to the tiny M57 (105"x78"). 400-500mm is about right for the entirety of M31, while M57 probably looks best at 2000mm or longer. This is what M57 looks like at 400 and 700mm FL:

M57 @ 400 mm FL,  5.4um pixel size, enlarged 4X

M57 @ 700mm, 5.4 um pixel size, enlarged 4X

The first image is very pixelated, while the second is smoother. Surrounding stars are better seen in the 700mm image. (We don't care about the central star, since that isn't available to visual observers except using  very large telescopes.)

The second largest Messier object is M45 (M44 is almost as big). Here's what it looks like at 700mm:

M45 @ 700mm, 5.4 um pixels. Red box is FOV in KAF-8300

It fits very nicely. At 800 or 900mm we could still get most of the cluster in, but it would seem a little cramped. (Here we don't care about the nebulosity because it's essentially invisible to the eye of a beginner. We just want to capture the stars with enough dark space around them to make it look like a cluster.) 

We could continue, but there's a balance to be set, and it's a very subjective balance at that. Longer focal lengths favor the more abundant smaller objects, while longer focal lengths favor relatively few objects. Short er focal lengths give us a chance to capture several Ms in single frames, which helps us do the IMM. Longer focal lengths will eat up more time with getting targets centered in the camera's field of view.

 From the above I would suggest any focal length between 600 and 1000mm should serve well. 

The ultimate choice depends on the telescopes you have available to you. In my case only one scope fits: My TV102, which has a FL of 700mm with its flattener attached.

Next time I'll look at which Ms can be combined on single frames given a 700mm FL and KAF-8300 sensor.