Wednesday, May 31, 2017

Southern Stars: Overture

The Sky Tonight (Image: Stellarium)

As I step from wheelhouse to starboard bridge wing the heat and humidity strike me like a mallet; it actually takes an effort of will not to close the door and remain inside.  But I am there to view the stars, not shelter against the equatorial climate of the east African coast.  I shut the door behind me and after a quick glance at the darkening sky to ensure that it remains cloudless begin preparations for the night's star-gazing.

Together my equipment and I will require time to adjust to the conditions to be found off the Somali coastline in May. The 7x50 binoculars are tightly capped and will remain so until their lenses and prisms have the opportunity to warm from air-conditioned coolness to near ambient temperature--to remove their caps any earlier would be to invite their being instantly fogged to uselessness in this humidity. In similar fashion my eyes require time to adapt to the darkness; for the half-hour or so that these acclimatizations take I will be updating my observing plan and journal in the amber illumination of the chart-house.

The Tanker entered this area a few days ago in the course of her assigned duties, and is scheduled to depart soon; tonight might well be my only opportunity to study these skies before we head north and the treasures revealed sink once more to the misty southern horizon.  Clear, calm nights are a rare commodity on the open sea--this night is a rare opportunity not to be cast aside lightly, and I don't plan to do so.

The bridge watch-standers are accustomed to seeing me in the evenings and sometimes the early hours as well; nobody questions my quiet presence in the chart-house as I plan my observing campaign and make notes on laminated star charts with a dry-erase marker under the red lights. The Watch Officer stops by to inquire as to my targets for the night, and one of the Lookouts takes time to report a bright meteor seen late last night. I appreciate the conversation with my Shipmates, and the curiosity they express about the dark skies that we work and play under; they know they are welcome to join me on-deck as their duties allow--I'm always happy to share my Universe!

At last I'm ready to begin. The optics have had plenty of time to warm and my eyes are nearly as well dark-adapted as they can be before heading outside.  Once again the heat and humidity attack as soon as I leave the cool bridge, but this time I have a mission; I step out from under the bridge wing awning and turn my eyes toward the heavens.

Beautiful!  I simply stand and stare, absorbing the vista before me.  In the still air the stars are sharp, fine points from zenith nearly to horizon; even Sirius in the west gleams with uncharacteristically steady blue-white light.  Nearly overhead, mighty Jupiter dominates the constellation of Virgo, while to the east the claws and heart of Scorpius rise. The Milky Way is a down-turned curve of curdled light, masked in places by dusty paths of shadow, stretching from southeastern to southwestern horizons.

It's within that bowl of stars that I plan to begin tonight's explorations...

A word on binocular star-gazing from the deck of a powered ship at sea; it's a real challenge because, by definition, EVERYTHING is moving.  Even in the most gentle seas the hull shifts slightly beneath your boot-soles; there is always some "rock & roll" (technical terms: pitch, roll and yaw) to be dealt with by the observer trying to keep his optics trained on that distant patch of fuzz in the constellation Hercules.

Other factors come into play as well.  The deck and every surface of the ship are vibrating continuously--the diesel motors and generators far below decks ensure that the entire mass of the vessel is in a constant state of oscillation. It can be quite windy up on deck as well; this flow of air is caused by both the actual,"true" wind and by the ship's motion relative to the direction and speed of nature's breath--not surprisingly this is called "relative wind".

The combination of these elements--the ship's motion, vibration, and winds across the deck--can make locating that double star or contemplating that nebula something of a chore.  Usually, after two hours or so of supporting the binoculars while keeping myself as steady as possible on the shifting deck I find myself sore and tired, more than ready for a break or even my welcoming bed.  But the results--especially on a night like this--can make the effort and resulting exhaustion well worth while.

Back to the bridge wing...the Bushnell 7x50 binoculars have had plenty of time to warm-up, and my eyes are nearly fully dark-adapted. Off come the caps and on go my "infinity" glasses--a special prescription I arranged with my optometrist-- and it's time to explore.
Tonight's Playground (Stellarium)

As I rarely get the opportunity to observe this far south I am planning to concentrate on the Three 'C's tonight; that is, Carina, Crux and Centaurus. These constellations are invisible from my home in Virginia but tonight, in the western Indian Ocean four degrees south of the Equator, they light up the sky off our starboard side, inviting inspection and discovery. 

Since Carina has already passed the meridian and is slowly falling toward the south-western horizon, it's to be this Sailor-Astronomer's first port of call tonight.

To be continued.

The Constellation of Argo Navis

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