Here's a few photo's of my barn door mount. Still not completely finished ,it still needs a clockface setting up so I can turn the screw 1/4 turn every 15 seconds and the screw cutting down to the correct length.

Also it needs a riser of some sort designing so I can place the ball head camera mount higher up.

The screw I decided on was a 1/4"UNC 20tpi thread and this made the hinge to middle of screw radius 11.43" .To get this as perfect as I could, I made the screw and tilting mechanism on a slliding plate so just by undoing a few bolts I can achieve that perfect 11.43".

The whole screw pivots top and bottom so to avoid tangent error. I can vouch that it is very smooth both up and down and no binding of the threads have accured in practice.

The finder is from my TAL 100r and has the crosshairs so polar aligning shouldn't be to bad as the whole lot is mounted on the TAL EQ mount.
Plus I have the wixey to get the latitude spot on. Going to invest in a few small bubble levels as well.

The only negative I can say is that the piano hinge has a little play in it. Will this effect the final image I can't say as yet.
Remember this is only Mark 1 version I have plans for a bearing and shaft hinge for the Mark 2 version.

If it works Ok my next step is to add a 1 RPM motor and bracket to it.

Hope you enjoy the photo's and comment and advice really welcome.

well done mate, bit of a engineer in you i see

Nice One DOC ... looks the BIZ

The ball bearing hinges that they use for fire doors might be better... Intrested to see you results from this as i need a poor mans astrotrac myself... although the obs mods give me a nice wide clear field of view for piggy backed images.

Billy...

Cheers Rob but I wouldn't call myself an engineer. Maybe a Jack of all trades and a master of none.

Peter good idea about those hinges. I was told piano hinges are the way to go but I think there's to much play.

It's definetly a cheap mans astrotrac have onlly spent maybe £10 so far.

Doc, you have got a lot further than me, my design is still on paper but following a similar design to yours, even to using 1/4" UNC thread which I have in stainless steel.
If you are interested my motor drive was to be a solid rubber drive wheel onto a metal disk, the rubber drive to have a slight taper, by a simple screw device its position can be altered on the disk to give variations in speed, as I understand this is needed to cater for the use of lenses of varying focal length. Thought this may give you some idea for a drive unit. Lovely job so far, looking forward to an update.

John.

LOL!!

That looks excellent, I have been contemplating making one of these myself following an article some time ago in one of the magazines. To my amusement, they called it a 'Scotch mount' in the article

Very good Mick. Look forward to the results. Might be worth getting some form or QR plate adapter to make fitting the camera easier. I invested in a few Manfrotto 323 adapters for that reason... I got fed up with all the different fittings, from the camera tripod, to the monopod, the satcatcher and piggy back.

Thats a good idea John.

Like most things this at the moment another unfinished project. I seem to have a knack of doing this, starting something and not finishing it.

Scotch=whisky=Haig=inventor...

Arthur

i think i cant make such even in a thousand years.
great build

Please excuse my ignorance, but what does it do?

John

The taper will allow you to fine tune the drive rate but once you have it sorted it shouldn't need changing for the focal length of the lens...

The focal length has no effect onthe rate that the "stars" move across the sky only on how visible any tracking errors are...

Adjust it out with a longer focal length lens fitted and you'll be ready for anything...

Peter...

guide stars and stop star trailing when you take long exposures with a DSLR

Here is a link to the commercial version costing over £400

Astrophotography DSLR CCD Webcam and AstroTrac Home

I see, thanks for that.

By the way Mick, it looks jolly well made.

John

Thanks John.

Looks good I agree, but have not used it yet.

Lovely piece of work.
I hope to build a Barn Door for my camera since I do not have a telescope. Where did you source the hexagonal bolt which connects to the main screw? Also, the brackets on the upper pivot - did you make these yourself?

Cheers,
Austin

I never got round to use this, the hexagonal nut is just a bog standard extention nut you can buy at any B&Q. The brackets I found in work lying in the workshop so borrowed them.

It was dead easy to make the only important measurement is the one from your screw to the hinge this must be pretty exact, I overcome this by slotting the part the brackets sit on so this can be moved to get the required exact measurement.

I was going to fit a 1 rpm motor onto the screw so it would move the required pitch which would equate to the motion of the Earth but never got round to it.

It now has a broom handle extention in the middle and top of this is a camera ball and socket arrangement and the camera looks well cool sitting on top of this.

Thanks for that. One more question concerning the finder scope. Can you recommend an inexpensive one?
Cheers,
Austin

Just keep looking here on our for sale boards, any cheap one will do.

you dont have to use a real finder scope.
at a pinch, any tube will do (with crosshairs maybe) or even a drinking straw!

You should see our house Mick.........