Re: The Sun today. Last night's occultations.

George Reynolds


I don't understand the reference to railroad tracks. What does that have to do with observing the stars?


On Mon, Apr 26, 2021 at 8:59, jimcoble2000 via
<jimcoble2000@...> wrote:
Things are ramping up as there are three sunspots connected by a bright hot region (in H Alpha). The Ha view shows several large filaments (overhead views of prominence) on the face of the sun. There is a large loop prominence and a single tower type. Nothing huge in the profile view but things are definitely coming to life.

Last night's twin occultation of the almost full moon.

There was a nice occultation of 65 Virgo (6th magnitude) by the moon. The phase of the moon was not quite full so I was curious as to how close the star would get to the terminator. This would show how much of the moon was not illuminated. It got a lot closer than I imagined before it disappeared. The moon is very close to completely full so the star got very close to the terminator. Not much hidden there. Usually we assume that full moon illuminates the entire visible face but actually full moon only lasts a very short time, hours at most. The terminator never stops moving so even on a "full moon night" something is always dark somewhere. The occultation gave a chance to accurately judge how much was till hidden (not much BTW). Less than I would have though as I said above.

At 2142 there was a second 6th magnitude star occulted to the same effect.

How precise are the predictions based on location? Well pretty good. Only a few miles can make a difference as Kent and I found out years ago while trying to observe a grazing pass. We could not see the graze from our location but only a few miles away another observer could see the graze. At 1/4 million miles distance to the moon you would not think a couple of Earth miles would make a difference but it does.

So the night turned out to be salvageable astronomically speaking. God the moon looks huge compared to the star. Sort of like the Star Wars death star approaching. I love occultations as they give you a sense of things in motion. Thank God they aren't normally observed on rail road tracks as it takes a bit of concentration and it could be fatal to occultation observers.

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