Summer Solstice
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Summer Solstice

Summer Solstice

Summer Solstice

This is a section of yesterday’s plotting sheet. While not Summer Solstice exactly, there are some interesting things going on that pertain specifically to the Solstice.

1. The dotted circle in the center is the sun at local noon. It is drawn at the sun’s proper declination at Local Apparent Noon (LAN) for yesterday. N23 24.3 . At Solstice, the sun’s declination is N23 26.5.

2. My noon position is shown as 23 25N.

3. LAN, ie when the sun is at it’s highest point in the sky at my longitude and therefore due south, is 23 28.1N

4. The highlighted dotted line is the Tropic of Cancer. It is the furthest North the sun will travel before heading South.

By some happy coincidence, I was very very close to the Tropic of Cancer at very nearly Summer Solstice at Local Apparent Noon. The sun was directly overhead (the observed altitude of the sun was 89 55.2) at LAN and I went from looking at it due North to due South in seconds as it passed through zenith requiring a 180 degree shift in viewpoints.

The above also means that as of yesterday, the sun will now always be South of me. For the last six months or so, it has been North. South for us Great White Northeners is normal. Looking North at noon for the sun has left me scratching my head on more than one occasion when austral waves and backwards winds have scrambled my sense of direction.

Incidentally, there is a mistake on this sheet. I didn’t catch it until I enlarged the photograph. I’m sure there are at least a few reading this now who have picked it up. For those that haven’t, I’ve drawn in the Tropic at the wrong latitude. It should be at N23 26.5 . For some unfathomable reason, I’ve drawn it in at N23 23.5. Most likely, I muddled the sun’s declination and the Tropic in haste.

While teaching this stuff, I’ve always maintained that your DR errors will be greater than your plotting errors which will be greater than your sextant errors. Case in point …

Follow my tracks in real-time:
https://bit.ly/svseaburban

 

1 Comment
  • BT
    Posted at 10:41h, 02 July Reply

    Bert, you are amazing! Following you progress and posts with great admiration for you courage and wishing / willing you success. You are on the downhill run now. All the best from an Aussie follower BT ( 2 degrees of separation from your Uncle Joe).

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