Difference between type 3 and 4 Barn Door

[Mick J]

Looking forward to seeing this project progress,  key things seem to be the thread size/pitch/rpm and the distance hinge/pivot to drive point.

What I am not sure of is camera position, near the hinge, middle of the moving surface or is it just a matter of placing the camera to keep some sort of balance (lens position considered) - keep weight above mount.

I can see the camera moves a greater distance away from the hinge, but takes the same time to do so, I have seen designs for all positions, any advantage/observations. 

Edit: was wondering why some of the url's not working, then looked at the dates of original posts - seven years ago, 2015. 

Edited June 13, 2020 by Mick J

[Mick J]

Just slowly reading my way through a type 4 construction documented on the Pentax forums from 2015, good descriptions and pictures/drawings.  UNC 1/4 20 threaded rod used, I would like to adjust for M6  1mm pitch,  that will be 25.4 threads/inch instead of 20. 

 

[Chriske]

Busy designing my own type4 version.
It'll be a printed version(no slim line..!), I'll be using ball bearings instead of hinges.
I'll also replace the point of friction(between the two moving parts) by short linear bearing. Maybe I might use Teflon instead.
And last but not least, the driving threaded rod will be self made. Cutting my own thread assures me I have it absolutely regular. Almost all commercially made threaded rods are not.(construction of threaded rods is not what you would call a high precision process...🙄).

Point is I'm planning to use that tracker also with long telephoto lenses. So I need it to be very accurate.
 

 

Edited June 15, 2020 by Chriske

[Gina]

Is this for imaging Chris?

[Chriske]

Yep, but before I get into imaging, I need to build that thing first.
But most of all start asking questions 'how to' do that imaging correctly. From what I've seen so far here on the forum, there's a long way to go...😳
But I might find a person here on the forum who can tell me a thing or two about it all...😁

In the past, when dinosaurs were still roaming here, I've taken pictures of the night sky using 103aE, 103aF, 103aO  developer HC110, or MWP2. I also used TriX, Technical-Pan(Hypered).....aaah those were the days....!!
In those days I took pictures of the Moon with a 6x6 camera and made prints 3'x3'(yep foot). In those days you could buy paper on roll 1.27x10m. I still have a few of these roll as matter of fact. There out of date of course.

[Mick J]

Also have an eye on Stephen Tonkin's page  from 1997, uses 6mm metric rod and may save me some head scratching.  Would like to see a spreadsheet that generates dimensions, change drive speed/thread size etc, any one seen/have one?

Edited June 15, 2020 by Mick J

[Gina]

I've done film terrestrial photography but not astro.  Did all my developing and printing too - both monochrome and colour.