Str Trails - Find "Center"?

If the weather approves this weekend I will try to do some Star Trails

What star should I be looking for to see where the "center" of the spin is?


/Jocce

http://digital-photography-school.com …tar-and-why-youd-want-to/

TeamSpeed wrote in post #18256669
http://digital-photography-school.com …tar-and-why-youd-want-to/

Thak you! Very helpful!


/Jocce

I think a more pleasing shot is to have that circumpolar star off center. If centered it looks like a target.

Hopefully you get clear skies. Sometimes it's interesting to photograph the section of sky at declination 0 (these are stars located direction above the Earth's equator) because with a wide angle lens, the stars trails on either side will appear to curve in opposite directions (so you get an interesting geometric pattern that isn't just a circle).

Since this is northern hemisphere 'winter', in the evening hours you'll find the Big Dipper asterism located to the "right" (northeast) of the pole. The handle will be hanging down toward the horizon. The bowl will be on top. The two end stars on the bowl can be traced to make an imaginary line that points to Polaris (the pole star). It's not exact, but it's close. Each season it will slowly migrate 1/4 of the way around the pole (if you check it at the same time each night.)

BTW, the pole star isn't technically at the pole. It's about 2/3rds of a degree away from the pole. But since it's within 1º that's pretty close (it's technically getting closer due to the precession of the Earth and by the end of the century it will only be 1/2º from the pole... but that's the closest it gets and it appear to start getting farther away again). Anyway... while 2/3rds of a degree doesn't seem like much, the moon is only about 1/2º from edge to edge. That means if you could move the moon's location in the sky, you could fit it between the Polaris and the true north celestial pole... and still have a bit of room to spare.

Getting the precise location of the pole is important when aligning a tracking head (for photos where you don't want star trails), but if using a stationary tripod (non-tracking) to capture star trails, it doesn't really matter where you point the camera.

Interesting and clear explanation.