Astronomical Photo of the Day
Everyone loves APOD. See this.
What started this?
I saw an analemma of Moon in one of the reddit post but then one fellow redditor said that its fake and gave an explanation which seemed sophisticated and I didn’t bother much. Few days later (as it always is the case), the same image found its way in my facebook newsfeed, so I sort of became determined in answering that.
astropy. I was thinking of using
spiceypy but they felt overkill. For a given epoch and Earth position, I compute the Moon’s position (returned by
astropy.coordinates.get_moon) and transform it local
Then, I plot the
AltAz scatter plot.
Find the code here: github.
At first, I didn’t get any analemma pattern using a time step of one day. I thought I had to use sidereal day. But, that APOD enlightened me to use a time step of
1 day 50 minutes 29 seconds and lo, it works like magic.
I don’t know why this specific time difference works. I would love to find out. But, maybe next time.
It would totally depend on the time and position but as an example:
So, what I saw on reddit and in my newsfeed is indeed fake, or maybe their timestep was only a day. In any case, that’s no analemma.