What is a star TRACKER?

Olympus E300 · Oct 12, 2010

This may be a wierd question since I know almost NOTHING about this sort of thing but here we go anyway. I've been getting more & more interested in shooting pictures of the moon and stars. I know...Why? Just a phase perhaps. Anyway, as we all know, the earth revolves (from what I've read, about 1 degree per minute) and therefore, subjects such as the moon are forever moving out of the viewfinder and in turn, out of focus. I've heard of these "tracker" devices which your camera mounts to and move in synch to the earth's rotation. My questions are as follow :

1. What is the actual terminology for this type of hardware? I've been unable to produce any tangable Google searches thus far.

2. Can one of these units be had for a decent, blue collar, working man's price?

3. Can anyone recommend a place where a guy like me might be able to buy one of these from (US or Canada)?

4. I've read about people making their own "tracker" using an old clock. Is it worth the effort?

Thanks!!
- Daniel

Bitter Jeweler · Oct 12, 2010

Google

KmH · Oct 12, 2010

To counteract the Earth's rotattion and keep a star in the viewfinder, requires either an equitorial mount (having a single motor because it only moves in 1 axis), or an alt-azimuth mount that has 2 motors that moves the mount in 2 axis at the same time, which requires computer controls.

The mount must be accurately orientated to be parallel to the Earth's rotation axis. Variations in the accuracy of that alignment cause the star to drift in the viewfinder. A good mount usually has controls that can correct that drift as it happens.

The stars move at a different rate than does the Moon and the planets, so a good mount will have 3 speeds.

Since the Earth rotates through 360° in 24 hrs, 5th grade math reveals:

24 hrs x 60 minutes/hr = 1440 minutes per 24 hrs.
360° / 1440 minutes (1 day) = 36 minutes per degree, well short of 60 minutes/°.

You might consider looking for a used AstroTrac TT320X Tracking Mount. http://www.optcorp.com/product.aspx?pid=12026

A lot of people into astrophotography use an equitorially mounted astrononical telescope as a lens. Visit http://www.astropix.com/BGDA/BGDA.HTM for a book for begining DSLR astrophotographers.

Olympus E300 · Oct 12, 2010

KmH said:
...5th grade math reveals:

:blushing: ...Tee hee...

Thanks for the help.

- Daniel

Overread · Oct 12, 2010

If you're getting keen on this might be worth giving astrostu a pm. He does a lot of this kind of photography - he is also part of the mentor scheme:

http://www.thephotoforum.com/forum/beyond-basics/125099-official-mentors-bio-list.html#post1267786

Patrice · Oct 12, 2010

Be careful of astrophotography. Get hooked and say goodbye to every dollar you ever hope to earn!

The device you are alluding to is a 'barn door tracker'. In it's simplest form it is simply a camera mounted unto two pieces of plywood hinged together and a thumb screw to change the angle of the hinge in incremental amounts. The idea is to align the camera to the rotation axis of the earth and then change the angle of the hinge incrementally to offset the rotation of the earth. Google will lead you to lots of sites explaining how they work and how to build one with some plywood and a few pieces from the hardware store.

Don't scoff at the simplicity of the device, it really works. Invest a couple of hundred dollars to add a clock drive and some gears. But it's not a necessity in order to get started. You don't even need expensive camera gear. Point a 50 mm lens at the milky way for 10 to 20 minutes while keeping the camera aligned with your barn door tracker and be prepared to be amazed at the imagery.

Check out the CloudyNights astronomy site. They have a good beginner section as well as a section on astrophotography.

KKJUN · Oct 13, 2010

if you seriously consider doing this sort of thing, get some sort of stacking programm like this. i tried an 8 minute exposure on my E-520 once, and the (predictable) result was a HORRIBLY noisy picture. Also, a remote might be a good idea`?

Derrel · Oct 13, 2010

A Star Trekker lives in his aging parents' basement. A Star Trekker had a girlfriend once, long ago, but he never actually *HAD* her. A Star Trekker goes to a convention once a year, in a far away city, usually someplace exotic like Cleveland,Ohio or Ames, Iowa, and pines for the girl he used to have, and hopes he'll see her there at the convention, dressed as a hot Klingon babe. A Star Trekker almost always has a pocket protector and a scientific calculator with him--at all times. A Star Trekker...oh wait, you wrote Star TRACKER....nevermind...

Olympus E300 · Oct 13, 2010

Derrel said:
A Star Trekker lives in his aging parents' basement. A Star Trekker had a girlfriend once, long ago, but he never actually *HAD* her. A Star Trekker goes to a convention once a year, in a far away city, usually someplace exotic like Cleveland,Ohio or Ames, Iowa, and pines for the girl he used to have, and hopes he'll see her there at the convention, dressed as a hot Klingon babe. A Star Trekker almost always has a pocket protector and a scientific calculator with him--at all times. A Star Trekker...oh wait, you wrote Star TRACKER....nevermind...