Moon rise / Sun set trivia

[Mark Wagner]

Good Morning TACos!  Today "mid-winter" full moon occurs.

This is an "unusual" moonrise as it nearly coincides with sunset from the bay area.

Sunset 5:33 PM 249 degrees azimuth
Moon rise: 5:34 PM 66 degrees azimuth

Per (imperfect) chatGPT, asking it how often there is a nearly concurrent rise and set, the results went thru a number of interesting comments.  Latitude, is what matters most.

At our latitude, moonrise and sunset are within 10 minutes of each other on a monthly basis.  I was surprised as I've seen different, but then realized it was due to the local horizon.

At our latitude, within two minutes once every few years.  That is why some consider tonight's a really good one!

Exact minute?  Once or twice in a lifetime.  I've not see this.  Chat even mentioned exact second (for bragging rights).  But for that one the answer gets quite specific/complicated.

I have been outdoors for within two minutes.  I'm planning on it again tonight (depending on cloudiness), and thought to give a head-up here if others just feel like getting out and "being there". It helps to pick a place with good horizons.

Also, there is something called the "Harvest Moon effect" chat mentions messing with "moonrise timing in a really neat geometric way."  Anyone familiar with this?

Lastly, February is the only month that technically can't have a blue moon (by one of the definitions).  Huh, why blue?

-- 
Mark

[Dan Smiley]

Hi Mark,

According to my skysafari 6 pro sunset tonight from Mill Valley is at 533 and 50 seconds. Moonrise is at 534 and 47 seconds. So that's within the same minute, or at least 60 seconds. Also April 1 full Moon rises less than a 60 seconds after sunset. assuming skysafari is accurate. I've had trouble with chatgpt. For example I asked it to generate a list of Jupiter Galilean moon shadow transits visible from Mill Valley within two hours after local sunset. The list it made was completely wrong, not sure why but is seemed confident of itself.

[Mark Wagner]

Dan,

I think everyone finds some faults with chatGPT's output. It can ok for some things but frequently seems to need checking.

I use a free android app called Daff Moon for things such as this, it is pretty handy.  All sorts of solar system utility.

To get down to a "the second" match, you need to be in the right location within (I think I recall) a matter of a few feet or tens of.  If chat's chatworthiness can be trusted on it. Maybe its wrong on the frequency of 2 minute or less.... I haven't seen this closeness in a year or so (I tend to watch for them).

Mark

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-- 
Mark