4 replies to this topic

[Guy]

Yo Tuco's ( me ) home made barn door tracker. Also known as a Haig or Scotch mount. This device will cancel out the diurnal motion of the earth for a short time.  Long enough to do some astro-landscapes this summer.  

 

In the northern hemisphere, aim this at the North Star to get the hinge parallel to the Celestial Pole and rotate that dial every 15 seconds to match the elapsed time.  This will get you times a little longer than the 500 Rule.  That is, divide 500 by your focal length and that is how many seconds before star streak will become noticeable in your picture. But go too long and the foreground will streak.  However, it is common in astro-landscapes to focus stack the foreground for DOF if you are typically shooting wide open.   

 

 

 

 

 

 

 

 

[Eagles1181]

I have a friend who made one of those when we were teenagers. He was able to get about 30 minutes before things started to streak. However, his was much rougher looking than this one. Your wood wofk looks very nice. Eagle

[Guy]

I have a friend who made one of those when we were teenagers. He was able to get about 30 minutes before things started to streak. However, his was much rougher looking than this one. Your wood wofk looks very nice. Eagle

 

Thanks.  This one is a tangental version which tracks for a short time; that is, while the sin( angle) = angle in radians for angles less than about 6 degrees if you're after sub 1 sec of arc of accuracy. 

[Eagles1181]

Yea, now you are way over my head. I just remember his was huge (several feet square) and helping him figure out how he was going to fit it in the trunk of the car with his other "essential" camping eqipment.

[Guy]

Yea, now you are way over my head. I just remember his was huge (several feet square) and helping him figure out how he was going to fit it in the trunk of the car with his other "essential" camping eqipment.

 

That's big.  The size is a function of the fastener thread pitch.   The finer the thread pitch and the shorter it gets.  Most people rotate at 1 RPM so a 360 turn equals the thread pitch. But you don't have to turn it at 1 RPM.  You could calibrate the time marks on the dial such that 180 deg turn = 1 minute ( 45 deg = 15 seconds ) of time thereby reducing the thread pitch by 1/2 and cutting the distance from the hinge to the bolt by 1/2 as well.