Telescope Reviews: Help with M56

I too frequently view M56 from a light-polluted suburban location where on less transparent nights, Lyra's signature parallelogram of four stars SE of Vega are obscured. It's one of my favorite summer objects in both my scopes (four-inch refractor, 12-inch reflector). HERE'S SOME ESSENTIAL INFORMATION FOR FINDING M56 BEYOND WHAT A STAR CHART OR ASTROPHOTO WILL TELL YOU:

1) APPEARANCE: M56 appears a small misty haze of light not distinctly brighter than the dense Milky Way starfield surrounding it, unlike brighter globular clusters which visually jump out much more readily through the eyepiece. Though it is at a similar distance from us (apx 30,000 light years) as globular cluster M3, M3 is far brighter-appearing and far more easily resolvable into distinct individual stars with 8" or more aperture. That's because the location of M56 forces us to view it much more closely parallel from us to the plane of the Milky Way, such that lots of intervening gas and dust obscures and dims our view of it. NEVERTHELESS, to my viewing tastes the view of the small, faint, but rich mist of M56 embedded within the dense surrounding Milky Way starfield is one of the most subtly beautiful sights in the entire summer sky, well worth the effort in finding it. I note that craytab above mentioned M13 in Hercules (the easiest, brightest globular cluster to find)...I would suggest you also find and visit the other bright globular cluster in Hercules, M92, which is a bit closer and a bit more intrinsically brighter than M56, but roughly similar-enough to give you a sense of how much the view of M56 is impacted by being located much closer to the galactic plane from our P.O.V. than is M92.

2) STARHOPPING (beyond what the finder chart by itself will inform you): It's obvious from any decent star chart that M56 is located almost directly on a line just slightly over halfway between Sulafat (Southeastern-most star in Lyra's distinctive parallelogram of four stars southeast of Vega) and Alberio (just slightly closer to Alberio along this line). Wouldn't that be nice if all four were naked-eye visible? But of course they aren't from your location, but you report you nevertheless CAN find M57. Well, M57 is halfway between Sulafat and Sheliak (the two stars in Lyra's parallelogram furthest away from Vega), and fortunately, Sheliak, Sulafat, and Alberio lie almost directly along a straight line relative to one another. Globular Cluster M56 is about 2/3 of the way along a line from M57 to Alberio (closer to Alberio).

3) You're looking for a FAINT, SUBTLE SMALL PATCH OF MIST which (depending on your aperture) will be likely be visible on nights of better transparency, despite the light pollution, and likely won't be visible on nights of poorer transparency. FIND IT FIRST ON ONE OF YOUR BETTER NIGHTS, and it will become progressively easier to find on your mediocre and more marginal nights. YOUR OPTIMAL CHOICE OF EYEPIECE will be a balancing act between as wide a field as possible (lower power is better) vs a small enough exit pupil to give you a dark enough background/enough contrast to make M56 visible against the rich surrounding starfield (middle to higher power is better). YMMV depending on what's available to you and the aperture of your telescope, but for my NP-101 generally 10mm or 13mm works best and for my 12" 17mm or 21mm works best (I confess that since I have a quiver of Ethos eyepieces, I have a considerable advantage), but it's quite doable in more humble 50 deg AFOV plossls, though it may require a bit more work for success).

WELL WORTH THE EFFORT IMHO (I just viewed it again last night in my NP-101). BTW: if you can at least faintly see Sulafat in Lyra, your probability of success is much greater than if you can't.

Edited by FirstSight (06/14/12 12:10 PM)