Thursday, November 3, 2016

The Sweet Spot

Exciting news!  Well, for me, anyway.  After many weeks of searching I may have finally discovered USNS Leroy Grumman's "sweet spot".  I tested it last night and it looks like a do-able solution. I am SO happy!

Let me explain. The biggest problem I face as an amateur astronomer working aboard a deep-draft vessel is the vibration of all those engines, pumps, motors, elevators and what-not that make the ship a viable organism.  The continual orchestra of mechanical action within the hull is transmitted thru the fabric of the craft so that there is always a background "hum" of vibration, wherever one stands on bridge, deck or lower compartment.You might think that the physical action of the ship (pitch, roll and yaw) in a seaway would be the greatest problem with star-gazing at sea, but I have found over many years of underway astronomy that a moderate roll or pitch can be dealt with when observing with binoculars. The vibration involved with day-to-day (or, in my especial case, night-to-night) operations is the real, ever-present problem with binocular or telescopic observation at sea, let alone any kind of astro-photography!.

'Thing is, the vibration isn't the same throughout the ship; it is transmitted thru the hull in such different ways  that one part of 'Leroy Grumman' might seem almost quiet where another area--only yards away--is filled with a jack-hammer racket of bouncing equipment and tools by the energy being distributed so unevenly through the ship.

So, once I go aboard a new ship I go looking for those areas where a telescope on low-power might actually be focused on a distant galaxy or a binary star without a constant "juddering" of the image seen thru the eyepiece; where a camera tripod might be set-up for photography of the Moon without the image obtained being smeared out of shape by the nearly imperceptible motion of the deck supporting it.It isn't the same location on every ship--even ships belonging to the same class can have very different vibrations, different distributions of motion through the steel of their structures. On each vessel I check aboard in this on-going voyage of mine I prowl the weather decks, feeling the vibration through my boots, touching lockers, motors and other fittings as I explore.  I search for that rare place, somewhere, where I can feel little or even no action in the steel beneath my fingertips.

Once I find a possible sweet spot, I make a note of it in my observing journal and plan to return to that location on a clear night.  Usually, the selected spot has a fatal flaw.  An A/C blower nearby starts and stops at irregular intervals, turning "sweet" to "sour" on further examination.  The location is in a part of the deck from which much of the sky is obscured--a definite down-check--or where it would actually be hazardous to life and limb to loiter there with a telescope.  Sometimes a second or even third visit is required to spot the possible downside to a spot on deck.

It occasionally does happen that I never do locate a sweet spot aboard the ships in which I serve.  I spent a year aboard USNS Big Horn without identifying a decent observing site, and equally elusive was that desired location aboard USNS Supply.  I enjoyed my time and work aboard these ships, but being unable to observe from a reasonably smooth site made things a little less pleasant than they might have been!

That brings us back to today, and what just might be the sweet spot aboard 'Leroy Grumman'.  The potential observing site aboard this ship is located forward, right next to our portside Rescue Boat station.  Initial tests (last night) were encouraging; the site boasts a storage box which I can use to support a small telescope (namely my old, reliable Astroscan Rich-Field Newtonian) that stands tall enough to allow me to stand comfortably whilst observing with it.  The deck around the storage box seems remarkably vibration-free and allows viewing of a fairly large area of the sky.  Unfortunately the box at the starboard Rescue Boat station doesn't share the characteristics of the port one--on THAT side of the deck the vibration problem is as bad as any other part of the ship I have tested to date!

So...tonight is the acid test.  If the weather holds fair as it is now I plan to set-up the Astroscan and photo tripod at this presumptive sweet spot at sunset and spend the evening checking out the heavens.  By midnight I should have a pretty good idea of how well this ship-board "observatory" will allow access to the skies.

Wish me luck!

No comments:

Post a Comment