barn door tracking mount

[silv]

Hey,

I have most pieces together I need for a barn door single arm with a curved rod - following this article here: http://www.petesastrophotography.com (under Mounts/Barn Door Mount on the left hand side).

(even got a drill and a heck saw... wow!)

2 questions:

1. polar alignment - in the southern hemisphere....
a) if I place my compass so that it faces due south - and absolutely parallel to the hinges - is that "enough" alignment?
b) is it necessary that I angle my mount according to my latitude? flat on some really even surface is not an option?
c) if the only possibility is "drift align" - then okay. Tedious- but if that's what it takes I will study that on the web and practice.

2. rotating the rod:
does anyone know of a detailed picture (maybe ?in a building plan) on how to actually move the rod 1 rpm?
I mean like a picture that shows the nuts and bolts and gears and whathaveyou - how they look when they are finally fitted together?

Manually rotating it would be my top most goal, first. To SEE how it all works together... and understand more...
Ultimately, I'd be looking at a motor to decrease the chance of blur due to touching the mount. So a detailed photo of those connections on a curved rod tracking mount would be awesome, too. For the next step.

Please, I have never touched a tool apart from a screw driver - so don't drown me in rocket science :sadeyes:

:help::thanx:

[leon]

Hi Silv, although this is not a barn door tracker the idea is similar i built this curved bolt clock drive some time ago using this formula, which can be applied to and diameter of threaded rod and thread pitch arrangement, one must however use a 1 rev/minute motor, which i had made for me some time ago as well.
Anyway this may give you some ideas.

Leon. :thumbsup:


Formula for building a Camera Clock Drive, using a one revolution per/minute motor and a curved threaded rod with a pitch of 24 to the inch.


Formula

Radius = 1436.5 x ( n / 2 pie t ) where n = 1 and t = 24

Radius = 1436.5 x ( 1 / 2 22 / 7 x 24 )

Radius = 1436.5 x ( 1 / 6.285714 x 24 )

Radius = 1436.5 x ( 1 / 150.85713 )

Radius = 1436.5 x ( 0.0066287 )

Radius = 9.52212 inches, (241.86184 mm)


Motor revolution must be (one) 1 per / minute

Threaded rod pitch in this case is 24, other diameter and pitch can be used

This formula works very well and is accurate to a least 30 minutes plus, of time exposure

[MrB]

Hi Silv.

I think I can answer a few questions for you.
1.
a) For your location, no. Auckland has a magnetic deviation from "True" south of 19 degrees, 26 mins EAST of magnetic south, you will need to compensate. I used this site: http://magnetic-declination.com/
b) Yes, must match your latitude as close as you can get it (protractor and a plumb-bob should be sufficient for widefield.
c) Drift align may be overkill, depends on what FL(Focal length) you will be shooting. I suspect your curved rod may introduce more errors than your alignment will.

2.
Google Image search is sometimes a much better way to find site's.
I found these that may help you:
http://www.garyseronik.com/?q=node/52
http://homepages.nildram.co.uk/~sbuniak/BarnDoor/Barn-door%20basic%20principles.htm
http://slscope.co.uk/astro_projects/barn_door/practical/motor_driven_barn_door.html
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4787727/Main/4785285
Using this search:
http://www.google.com.au/search?hl=en&noj=1&q=curved%20rod%20barn%20door%20trac ker&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=2XKWT7T6OqyYiAe56PnxCQ&biw=1247&bih=678&sei=3nKWT5z9HemKmQWJmMHYDg

Have Fun! :D

[ZeroID]

Hi Silv, just a bit of clarification here, the curved rod does not rotate. The nut on the rod turns. A barn door tracker can be built with a straight rod that does turn although it won't be quite as accurate in tracking over any long length but the earth only turns 15 degrees per hour so not a real problem. For widefeild it is more than adequate though and a lot easier to build.

Your location tells me you are 18 km from me. Whereabouts in Auckland are you ? Might be able to assist, I have a reasonably full home workshop downstairs. Haven't built a barn door but looks like a fun thing to do :thumbsup:.

Cheers
Brent

[silv]

hi guys,

thanks heaps for your help!
the google images search was particularly helpful!

You would probably laugh - as do I - if you saw the finished thing and then the outside setup (with no less than a plastic binder and a door stopper as the base to come close to my 36 latitude... :lol:)
Tested it just now for the first time. one of the shots with 18mm focussed on an object at 45 degrees above the horizon (Orion'sbelt) turned out sharp at 36 secs. I have older shots at 25 secs, same angle with trailing. So there's a little gain, already.
I'm looking forward to testing and tweaking it again, tomorrow night.

Especially with 200mm! I must see the Orion Nebula with a longer exposure than the 2secs I gave it on the tripod!
So, until May 8th - when the moon rise is more convenient for one last glimpse on Orion, I and my mount will be ready! :D

Brent, that sounds awesome! Thank you for your offer!
I had to get used to using tools and thinking like a tool using person ;) on my own, though.
I'd like to build another one. Possibly using plastic cutting boards instead of wood. Hopefully with a motor if I can find a stepper motor in Auckland, that is. (So far no luck) Not for that last glimpse on Orion next week - but soon-ish. We could make 2. Could be handy for you, too, e.g. when holidaying in Fiji. What say you?

[leon]

Silv, if you need a 1 RPM motor, you will have to have one built with the appropriate gearing to bring it to I RPM, when I was looking for that type of thing nothing was available off the shelf, so to speak.

Anyway good luck with your project.

Leon