Star trails

[Wayno]

Hello,

I work in the Kimberley in WA. Theres no light for miles, and the stars are bright.

I want to start taking pictures of star trails. Is there anyone out there that can impart some words of wisdom?

My camera is a Canon 550d. I have a sturdy tripod, and a remote control. I have the twins lens kit (18-55mm, and 70-300mm), a Sigma 10-20mm wide angle lens and 50mm f1.8 prime lens.

I’ve been reading about long term exposures (I have downloaded the EV exposure formula) versus the stacking of shorter exposures.

Is there anyone out there who can guide me on photographing techniques, and which exposure method works for the best results?

Also, can anyone recommend an image stacking program?

I look forward to the feedback.

Cheers,

Wayne. :beer_mug:

[ameerat42]

(Wisdom I'll leave out. Here are some words.)

Star trails? And later maybe stars non-trailing, like the Milky Way? I don't know how much you know, so bear with me if it's too-oo simple. First, congratulations on having clear and limpid skies.

1. About star trails.
"The Heavens" appear to wheel about you throughout the dark hours. Depending on your latitude (South for us). part of the night sky towards the south will appear to revolve around the point in the sky called the South Celestial Pole, or SCP. Look at this thread (http://www.ausphotography.net.au/forum/showthread.php?84695-How-to-find-the-South-Celestial-Pole-for-your-StarTrail-images) for a recent illustration. Part of the sky about 90 degrees away from the SCP appears to go fairly straight overhead. This is the region called the Celestial Equator, or CE. Further north (for us) the sky appears to arch to the horizon. The whole lot moves across the sky at approx. 15 degrees per hour.

2. What you want to capture.
Depending on what part the sky you want to get, set your camera up pointing to it, then leave the shutter open for as long as you can. If you have a B setting, use that. (It was easier with film cameras because you didn't have to "force" the shutter to stay open.) Typically, anything over about 1 minute exposure will show some trailing with most lenses. A good longish trail needs about 15-30 mins. exposure time, more or less, depending what part of the sky you're photographing.

With digital images, you can take a series of shorter exposures (say about 30 seconds each) over an hour or so and then use a "stacking program" to merge them into a single, trailed image. (Like Ozzie did in the above thread.)

3. Your gear.
Well, don't expect great results straight off. And, do you have any sort of shutter release? Attach this to the camera first, and start with your widest angle lens. Set the focus to "infinity", select B for the shutter, and set the lens to its widest f-stop (maybe f/3.5???). Point to an interesting part of the sky and start the exposure. Just as a TIP: Don't just press the shutter, but hold a dark card over the lens first and then open the shutter. Remove the card to start the exposure. For an ISO setting, first try 100-200, then maybe up to about 800 max.

4. And briefly on...
Use your longer lenses more to isolate small parts of the sky, like the Southern Cross, and use smaller exposure times, like 15 sec. max., to get crisp non-trailing images.
TIP: generally, use as wide an aperture as you can for stars as they are "point sources" of light. (There's a lot more to it but...) you get more and more of the dimmer stars when you use wider apertures. It is referred to as "deeper" imaging. That is why they call some types of astrophotography "deep sky photography".

All the aforementioned has been dredged up from the past - from before the flood, which destroyed much of my stuff.
Now sit back and wait for some more replies. then go out and let us see what you can get.
Cheers, Am.

[OzzieTraveller]

G'day Wayne

I've just been having a long chat with another AP person about this too
I'll copy the bulk of our stuff into a PM to you

Regards, Phil

[Wayno]

Thanks for the info Am.

I do use a remote control for my shutter release, so all good there.

I did read somewhere that some cameras can be set up for 30" exposures, through the continuous shooting mode. I haven't had any luck with my Canon on that one. Otherwise I assume all I can do is keep hitting the remote control after every shot.

Hopefully I can get some good pics up soon.

[Astroman]

Good points above and good luck with your venture into Astrophotography... Don't forget to set your lens to MF too, and test star focus (it wont always be perfectly on the infinity line) :)

[ameerat42]

...I did read somewhere that some cameras can be set up for 30" exposures...
Hopefully I can get some good pics up soon.

Even better: I just checked and your camera has a Bulb or B shutter setting. Use that instead of the 30sec speed.
And as Astroman said, (use Live View and) zoom in on a bright star to check when it is in sharp focus.

If your good shots come up a bit later than sooner that's OK too.
Am.

[Wayno]

Thanks for the tips. I have a remote cable in the post. Should see some good results soon....:D