Ray's Thought for the Day - Star Drift

The following spell was submitted by Lomo and translated by the LDR into standard English and presented in this venue by me, Ray.

We have noticed during our evenings of celestial observation that celestial bodies, other than the Pole star, tend to zip along at a frenetic pace with the pace increasing dramatically in direct proportion to the magnification employed in observation. Because we have been too lazy to date to hook up the electric tracking gizmo on the telescope we have had to do much knob fiddling to keep an object in view. However, after a little practice this knob fiddling becomes rather efficient because the requisite fiddling on both nobs is predictable. Knowing this, one can leave the telescope, go into the human and proto human habitat area, retrieve a Dolmen or two, return to the telescope, fiddle with the knobs directionally and have the object in view again in two shakes of a lamb's tail. Nevertheless that electric gizmo would obviate the need for all the fiddling entirely, so someone needs to hook it up one of these early evenings.

Now some of us in these parts are prone to take things personally and be aggravated by almost anything, even the predictable motion of a celestial body that is going about its own business. A good example is Red, who has been known to holler imprecations at the telescope during his telescope viewing turns. An example, "The dern thangs skitterin' along so dern expeditiously thet ah caint keep up, with it. Gaul dern it, there it went. Caint one er tother of ye useless varmints slow the dang thing down, fer me?"

Yes, we do need to hook up the electric gizmo for the benefit of the easily aggravated.

But the expeditious progress of celesital bodies across the telescopery* field of view (fov) aroused our curiosity, for indeed they (the celestial bodies) do, zip along. So we decided to do some research and found several interesting discussions of this phenomena on the internet, that great boon to the curious. The first of these, entitled "Actual Field of View" by Paul Markov provided us with a formula for determining how long it takes for a star located on the Celestial Horizon to zip across the fov of any telscopery apparatus. It is called the drift method and the spell is: Actual fov (deg) = time in seconds/ 240 seconds. What you do is time the stars progress across the fov with a stopwatch and divide that time by 240.

But then we couldn't figure out why you divided by 240, and Mr. Markov wasn't forthcoming on that subtopic so we had to continue our search. Which led us to the Lake County Astronmical Society and the spell "FOV Star-Hopping" which explained the 240, for us.

A star on or near the celestial equator moves westward at the rate of 15 degrees every hour, or 1 degree every 4 minutes.

Hark! Four minutes equals 240 seconds so that's where Mr. Markov got the 240.

Now we need to do this with every possible variation of the telescopery so we'll know, yes we'll know, the fov of all, of it.
_____

*telescopery - This term indicates the character of a telescope which is a constant value plus whatever attachments the telescope has attached to it, which is ephemeral.
For, example, star diagonals, eyepieces, barlows, focal reducers, etc. all change up the telescope and turn it (the telescope)into telescopery. The above allows one to determine FOV of any telescopery.

The Arkdruid