Talk:Analemma

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Lunar analemma

Isn't there also a lunar analemma? If so, why isn't it mentioned in the text of the current version of this article? 173.88.246.138 (talk) 07:27, 28 November 2021 (UTC)[reply]

Technically yes, but it changes every month and is pretty much never used that I am aware of. --Lasunncty (talk) 07:54, 29 November 2021 (UTC)[reply]

The calculated analemma image from Germany is rendered backwards.

The "fat" side of the the actual analemma happens in November when the sun is heading south. The image presented here shows the "fat" side with the sun moving north. This image should not be on the page for the analemma. Any image on this page should show that the "fat" side of the analemma happens when the sun is moving south, roughly from July through November. Steven L Allen (talk) 23:36, 1 May 2022 (UTC)[reply]

I think the issue is that the straight line drawn is not the meridian, but instead connects the two solstices and the crossover point. Without this line it would be fine. --Lasunncty (talk) 10:32, 6 May 2022 (UTC)[reply]

The line from one solstice to another does not pass through the crossover point, so even that is misleading. The straight line must be removed to avoid severe confusion, but even so it is unclear why this image is deemed to be useful by comparison to the actual photos which have been taken of the analemma starting with Dennis di Cicco in 1978/1979. Steven L Allen (talk) 07:54, 14 May 2022 (UTC)[reply]

Yes, I would support either removing the image or replacing it with another one. It contributes no information that is not already elsewhere in the article. -- Lasunncty (talk) 22:20, 16 May 2022 (UTC)[reply]

Shape of analemma is a straight line on an object whose orbit is circular

In the section "Description", in the third paragraph, it is stated that: "For an object with a circular orbit but significant axial tilt, the analemma would be a figure of eight with northern and southern lobes equal in size. " I think that the shape in this case would be a straight line in the north-south direction. According to Kepler's laws, a circular orbit results constant velocity. Constant velocity means that the Sun would not "run forward" or "fall behind" the mean solar time. — Preceding unsigned comment added by 2001:1aa1:4:10d8:3171:7a61:64fc:c4d5 (talk) 12:21, 17 December 2024 (UTC)[reply]

The tilt makes a difference. With no eccentricity, you still get a '8', with reflectional symmetry in both east-west and north-south; the crossing on the equator. It's not hard to simulate, and I have done so.

Consider the case with tilt 90°. At solstice, the phase of the day flips by 12 hours; this means the analemma crosses the pole, which it cannot do if it is a straight line. —Tamfang (talk) 02:44, 18 December 2024 (UTC)[reply]

You are right. In my way of thinking the Sun does in fact "run forward" or "fall behind" mean solar time, but not because of varying velocity on the orbit. 193.91.67.20 (talk) 08:57, 18 December 2024 (UTC)[reply]