Star trail photography in *southern* hemisphere - where to point?

I will be in the islands of French Polynesia soon and would like to have a go at star trail

astro photography. Here in the northern hemisphere it's easy enough to point our lenses

toward Polaris and expect a beautiful arc of star trails to rotate around it. But what

guidelines should I follow to achieve the same while in Tahiti? I found this star trail photo

taken in <a href="http://www.astrophotography.com.au/

ast_gal_Dec03AuroraLMCSMC.html">Australia</a> -- is there a constellation I can look

for to know which way to point? Thanks.

As far as I know, the <a href=http://www.astro.wisc.edu/~dolan/constellations/constellations/Crux.html>

Southern Cross</a> is what you are looking for.

You'd be looking for Octans - but it is most conspicuous for its absence, as it is very dim. There is a "trick" similar to <i>five times the distance between the two end stars of the dipper take you to Polaris</i>, which uses the Southern Cross. Shouldn't be too hard to google. <a href="http://www.pinetreeweb.com/bp-beyond-southern-cross.jpg">This should help</a>

Thanks guys. Nikos that diagram is worth a thousand words, I appreciate it. I burned a

lot of time looking for this answer with google before posting yesterday and didn't find

anything as useful as your responses. Grazie.

Ok, now that we have that out of the way, let me go on the record with a resounding "I hate you!" ;-)<p>

While you're there, bring some binoculars and have a roam for what are probably THE most amazing sky treasures - available only to southerners! (Except Andromeda, the northern consolation). <p>

Large and Small Magellanic Clouds - (actually galaxies)<br>

Eta Carina nebula (largest globular cluster)<br>

Coal Sack (most prominent dark nebula)<br>

and... and ...<p>

Oh well, have a great one!

I you really want to see this stuff like never before then drive into the Australian desert at night. When you are about 1-2 hours away from any township, the light pollution in this area is 0 and you see so much more.

Bear in mind, Tahiti is quite close to the equator at only 17 degrees south. Your celestial pole is going to be very low on the horizon so you might suffer from not ideal seeing (particularly if it's humid). <p>

On the bright (sic) side, you'll easily include foreground interest in the shot. Just aim the camera south with a wide lens, level the horizon at the bottom of the frame, and you'll catch the pole.<p>

Another nice setup is to aim for the celestial equator: you'll get straight star trails along the equator, with one side arching north, and the other side arching south.<p>

<img src="http://photos.photosig.com/photos/80/55/1455580-361c93d83fd7aa47.jpg" width="600" height="570"><br>From 45 degrees North

Scott, that might be impressive but it might be hard to drive to the Australian desert from

where I'll be in Tahiti. Maybe next time. Actually for something better than the Australian

desert, I recommend the Atacama desert in Bolivia. At an elevation of 5000 meters with

no electricity for hundreds of miles, I could see layers of stars overlapping each other.

The photo I present here was taken with a 50mm lens, Fuji NPH 400.

<p>

Nikos, you are amazing. I can see you really know your stuff! I was going to take some

star trail photos as a bonus while I'm going through the French Polynesian islands. I

appreciate the fresh and intriguing ideas you've presented here. Compliments to you, and

your celestial equator photo is beautiful. I'll try to do the same (do I simply point north

from Tahiti?) If you have any favorite how-to sites, please share with me some urls! I

don't have that much experience with astro photography, and have never tried it with

either my Canon 10D/20D, so could use some pointers. For how many minutes was your

above exposure? Thanks.<div></div>

PS Nikos on the wide end I have a 17-40L/4.0 and a 28/1.8 prime. Is it better to use a

zoom at higher ISO? Or the prime wide open? I'm a bit unsure about how to gauge the

exposure that I'll need. (Perhaps you can direct me to an instructional page?) I don't have

any fancy equipment, but I do have a sturdy carbon fiber tripod, and a wonderful <a

href="http://www.luminous-landscape.com/reviews/tc-80n3.shtml">Canon TC-80N3

</a> timer remote control that I think will be perfect for the job. I'd better figure out the

technique soon as I'm leaving in three days! ;-) Other lenses I'll carry: 28-135 USM, 50/

1.4, possibly 100-300. Will probably leave 85/1.8 at home. Using a Canon 20D. I also

have neutral grad filters, if they're of any use. (Perhaps if there's something in the

foreground/horizon for which the brightness should be reduced?) What's a recommended

exposure length and focal length? Thanks again

<a href="http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM">Jerry Lodriguss</a> has a good site covering also star trails. I'm not terribly familiar with doing star trails with a digital camera entails. I read of a good technique to reduce sky glow involving stacking several short exposures. Battery drain and noise are the two "digital" issues you need to work out.<p

Other than that, I stop down my lens one stop from full open. With your crop factor, I would prefer as wide as I can get.<p>

Finally, the celestial equator is nothing other than the projection of the earth's equator into the sky. In other words, if you were standing on the terrestial equator, the projection would run exactly east-west straight above you (zenith). Tahiti is 17 degrees south, so the celestial equator will be a slightly curved line whose highest point in the sky is 17 degrees down in altitude from the zenith (or 73 degrees above the horizon) when you are facing north. It will largely run east-west. <p>

Show us what you bring back!