Sirius rising

I am such a nerd. I spent an entire day looking up coordinates for various cities and calculating the heliacal rising of Sirius to see if there’s a pattern. There is. Here’s what I learned:

The heliacal rising of Sirius varies by latitude (how far north or south you are). Longitude doesn’t affect the results. You still need to enter your longitude when doing the calculation, but if two cities are on the same latitude, they will get the same date regardless of their longitude. I thought elevation was supposed to be a factor, but it didn’t make any difference for any of the numbers I checked.

Anyhow, the long and short of it is that the date depends on latitude. For most of North America, we’re looking at mid-July to mid-August.

If you are farther north, it will be later in the year. If you’re up in someplace like Alaska, it could be as late as the beginning of September.

If you are farther south, it will be earlier in the year. It could be as early as the beginning of June. So it’s a pretty big range.

If you want to calculate the heliacal rising of Sirius / Lokabrenna / Wep Ronpet for yourself, I made a walkthrough here.

Dates may vary a bit from year to year, but it will generally be very close to the same date. (I got the exact same date 3 years in a row.) So if you just want a close estimate, here’s a cheat sheet to look up the most likely date based on your latitude.

45°S = 1st of June
42°S = 4th
40°S = 7th
37°S = 9th
35°S = 12th
33°S = 13th
31°S = 15th
29°S = 17th
26°S = 20th
23°S = 22nd
20°S = 24th
18°S = 26th
15°S = 28th
12°S = 30th

9°S = 3rd of July
7°S = 4th
5°S = 5th
2°S = 8th
1°N = 10th
3°N = 11th
6°N = 13th
9°N = 15th
12°N = 18th
15°N = 20th
17°N = 21st
20°N = 23rd
22°N = 25th
25°N = 27th
28°N = 30th
30°N = 31st

31°N = 2nd of August
34°N = 4th
37°N = 6th
39°N = 8th
41°N = 10th
43°N = 12th
46°N = 15th
49°N = 18th
51°N = 20th
54°N = 24th
58°N = 29th
61°N = 3rd of September

As I said, I got the same date 3 years in a row. I have not looked farther into the future. If the dates start to shift in future years, I will update this page, but I expect it to be fairly accurate for quite a while.

Personally, I don’t feel the need to celebrate holidays on the exact day, so having a close estimate would be good enough for me, but I’ll still do the calculations, because it’s fun!

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