Wednesday, January 14, 2009

Binocular astronomy session from Central Park

Session name: 20090109.2123

Location: Top of the Lawn, Central Park
Site Classification: Urban
Dark Sky Scale, Bortle: Class 8, City Sky
Seeing Scale, Antoniadi: --
Transparency: --
NELM: ~mag 4.7
Weather: Clear sky, cold evening, light pollution beams from specific sources along the southern skyline radiated sharply up into the sky. Mostly calm air with some light breezes (Beaufort 2)
Moon: 14d10h waxing gibbous, near Full.
Equipment: Tak Pack, 22x60 Binoculars
Observing Party: Peter
Passersby: 14
Objects observed: M41, NGC1981, M42 & Trapezium, Mel25/Hyades, M45/Pleiades, epsilon CMa*, NGC2362/tau CMa Cluster, H3945/ADS5951 (same fov as 2362), NGC2354*, M93, M47, Sigma1171 in M47, M46*, Saturn & Titan, Moon.
* attempted but not seen.

Clear sky and a waxing, gibbous Moon seen on my way home from work, enticed a quick session beneath the stars. Later in the the evening, I looked out the window to see the Winter Hexagon and the brighter stars of Canis Major and most of Orion.

Arrived later than usual at TotL with the Tak Pack and laid out the optics beneath the tripod to acclimate to the cold air. While waiting snapped some photos of the southern skyline and constellations with a Canon G10. About an hour after arriving, I began an observing session with binoculars.

Canis Major (CMa) rose above the treeline to my east, sitting like an obedient dog looking up to Orion (Ori). I count 10 stars of the not-so-bright constellation excluding the head,nu^2 appearing faintest. Within the Sword of the bright constellation Orion, I can see the fuzzy patch of theta and two stars of iota. A glance to bright Taurus in the west, high in the sky, clearly reveals Hyades (Melotte25) and Pleiades (M45).

Back in CMa, M41 in the Tak bins is faint for an otherwise bright open cluster because it suffers from being low in the NYC sky. I count 24+ stars in an estimated area of 30', uneven distribution with a denser concentration to ESE.

A few different groups of passersby visited at this time, including the police. Each was able to observe M41, with relative ease. I described how an open cluster signifies a group of stars that are "born"from the same gas and dust cloud, sharing the same proper motion in space. Over time - a very long time - the stars under the influence of the Milky Way's gravity will be pulled like taffy and the cluster extends across greater distances. I point to Pleiades, Hyades and the Big Dipper as specimens of the same ilk. I often describe open clusters like leaves that fall from a tree into a river. At first they all move down stream together but over time they separate and go their own way.

M47 is a more impressive open cluster to show to the public since its brightness, size, shape are easily discerned and the additional feature of a double Sigma 1171 is a bonus. In the binoculars, I can easily count 15 for the first level of bright stars and the double star. (I see a schnauzer shape in these stars. I may have said terrier in the past but it is a mustached dog.) There are more that are fainter that probably increases that number. Nearby open cluster M46 is not seen because its surface brightness is too low to be observed through the bins or even the 4" Tak refractor. My best view of M46 has been with the 10" to see the cluster and planetary NGC2438.

Afterward the Tak bins were turned to one of my favorite fields of view through the Tak bins: Orion's Sword. This 2° span frames the bright nebula M42 and the Trapezium between NGC1981 and iota Ori very beautifully. With steady air and mount, the Tak bins resolve the Trapezium, theta^1 Ori, where the western star of the "Mickey Mouse triple" resolves to two stars bringing the count to four. A nearby trail of three stars in an E-W direction constitute theta^2 Ori.

The Mexican Jumping Star, a.k.a. tau CMa Cluster, NGC2362, is an open cluster that surrounds magnitude 4.4 tau CMa. 4 stars persist in a clockwise arc from 4 to 11 o'clock. Dark adapting in the eyepiece yields many more stars that flicker at the edge of resolution. This cluster seems to be star rich, its treasures slightly beyond the reach of these bins in the city sky.

Debbie, Ben, and Pooch stopped by. We turned the bins on to Saturn, situated above the trees and south of the Leo's rear end. I was able to see Saturn with flat, stubby wings extended and Titan to its west. Debbie and Ben had a difficult time seeing more than the disk of Saturn, but Ben clearly spotted Titan. Despite not being the ideal instrument to observe Saturn,the view improves as Saturn climbs higher in the sky.

Last object observed was the Moon, high in the sky in Gemini - a neck breaker for tripod mounted bins. Before packing up for the session and looked on the bright orb if only for a moment. I was flabbergasted by the site and couldn't constrain myself form uttering how spectacular she looked. The terminator produced a rugged and attractive western lunar limb. My attention was drawn to craters Pythagoras and Carpenter to the north, then looked south along the limb to a dark patch of Oceanus Procellarum where it mixes with Sinus Roris. I wonder if libration is favoring this region.

15 minutes prior to curfew a pair of midnight shift police stop by. They ask about the skies and what's of interest. One asks whether I've see the northern lights followed by a story of her friend's reaction to observing them: it was a religious experience.

Oh! I can appreciate that because that's how I describe every night in Central Park beneath stars and mingling with the constellations and regular passersby.

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