Barn Door for astrophotography

The Barn Door Works!
After initial bad luck n effort, last night I managed to get over 20-30seconds! With a 90-300mm (@1.6x thats about 480mm)

With $1 !
It's such a elegant idea.
Simple.
1.Take 2 plywood boards of12x18inch.
Join the 2 boards with a hinge( see image).
2. Make a hole EXACTLY 11.4INCH AWAY FROM THE HINGE-PIVOT.
3. Fix a 1/4-(tripod plate screw size) NUT thru the hole. Seal it with super glue.
4. Pass a 3" long 1/4 bolt through the nut.
4.5 Acc to mathematics the 1/4 screw will move 1° in 4 complete turns. Earth rotates 1° in about 4mins!!
So u have to turn the bolt at 1 rotation per Minute. Which is thr speed of the seconds hand in a clock.

5. To make the turning smooth use a metal piece like a Ruppee coin at the point where the Bolt pushes the board.
6. To make the rotating each n precise, stick a long plastic handle.
Make a clock face for you reference.
7 To make it Even more smooth PULL the plastic handle with a RUBBER BAND. This will be needed for Telephoto lens.

Picture s come here.