Barn Door Tracker Mark I

[Marky1973]

Well, I said I would give it a go and I did.

Fancied starting to play around with imaging along with visual observing on my Dob. I'm not in a position to do things "properly" at the moment, so spent a few quid getting some bits and pieces for a basic Barn Door Tracker. It worked out a little more expensive than it should as I needed to get a tripod and ball head for the job, but most of this is put together from bits and pieces.

I used two off-cuts of garden decking as they are quite thick and solid, but not too heavy. And, luckily, as I went with a simple straight bolt with a done nut on the end, the ridges in the decking worked as an ideal guide for the rod as it raises the top block.

I used M8 rod with 20 ridges per inch, spaced at 11.44 inches from the centre of the hinge pin. T-nuts to hold the quick release plate underneath to connect to the tripod, and I needed to use a 3/8" to 1/4" converter to secure the ball head as I soon found out that standard diameters do not equal standard threads when it comes to tripods! The length of bolt should give me enough for about 25 minutes in total although, in practice, the exposures are likely to be less but more numerous.

Got a chrome fruit bowl from Asda for £2 which has two wooden discs as a base, so just took one of those to use for the dial under the tracker. I put it underneath as a few guides I read preferred that approach as you a "touching" the secured base, rather than the "moveable" top board.

Since the photos were taken I have added the 30 degree/5 second gradations on the disc and added a red led above the disc to act as a marker when turning. I also need to add some rubber bands to hooks on either side of the boards to add stability. Some extra weight may help nearer the ball head as well as there was some wobble if care is not taken when adusting the disc.

So tonight I took it out into the back garden, did a very rough polar alignment, sighting Polaris along the hinge bolt - the clouds didn't help this either - then focussed the camera on a bright star using the viewfinder. I just shoved it on the tracker and started snapping.

Actually the battery in my camera didn't last long, but I did get some shots that suggest the tracker is working. Despite the fact that the alignment was very basic and I didn't spend any time focussing (just used the viewfinder - will take the laptop next time for Live View in the EOS software), the pictures came out without any star-trailing. The stars were little balls unfortunately as the focussing wasn't accurate, but there did not seem to be any blurring/trailing. I did various shots between 30 seconds and 1 minute, moving the disc 30 degrees every 5 seconds, and the results were the same. I've not posted them here as they are only in RAW format and not very exciting, but it gives me hope for trying again another night and taking more photos to stack.

So definitely a fun project to play around with if, like me, you fancy trying your hand at astrophotography, but are not ready to splash out on loads of expensive kit!

And bear in mind, when I was at secondary school, my woodwork teacher once wrote in my school report nothing but, "Mark is very good at coming up with ideas,"  - so anyone should be able to have a go.

Next may be an adaptation for a motor, but will plan to get used to the Mark I for now!

[JemC]

Nice, I like it

Look forward to seeing the first images from this as I am in the process of putting one together at the moment, just need to get hold of a tripod and ball head, not sure on the difference it will make but I put m10 rod in mine.

Regards

[Marky1973]

Thanks Jem!

Not sure if diameter is a problem, but the thread may be more of an issue. I just counted the threads in one inch of rod and used this calculator to confirm rod distance from hinge.

http://blarg.co.uk/astronomy/barn-door-tracker-calculator

Not sure when I will get any "proper" images as there is so much cloud around, and I find focussing tricky, but will use the laptop next time to improve accuracy.

Also limited to widefield at the moment as I only have the stock 18-55MM lens on my 1100D. I might need to modify it before it can support a bigger lens as well.

But it was fun to make and looking forward to playing around with it.

Good luck with your build! Let us know how you get on.

[Viewmaster]

Also limited to widefield at the moment as I only have the stock 18-55MM lens on my 1100D. I might need to modify it before it can support a bigger lens as well.

The longer the FL of the lens the more accurate everything has to be.  Hinges, flexing, motor accuracy etc.

But one can track for 15 minutes with a  200-500mm lens but the barn door needs to be a type 3 and

 well constructed with accurate motor control.

The most accurate barn doors  can track to within 1 second of arc over 1 hour.....

........as Michael Caine may have said, "Not a lot o' people know that."

[Knight of Clear Skies]

Nice work. For focussing, have you tried liveview and zoom on the camera? It's easy with that lens if a planet is visible, harder to do on a bright star. Turning up the ISO while focussing may help.

[Marky1973]

Hi Viewmaster. Aware that the Mark I will have limited long term accuracy, but happy to play around and cut my teeth on imaging at a basic level....but I know I will want to tinker soon....have enough bits left over from this one for a couple more trackers!

[Marky1973]

Thanks Knight, have used Live View in the EOS software with my laptop in the past but didn't have time last night. Will take it out next time when I have more time to get it right!

[StuartJPP]

I took the easy (but way more expensive) option and bought a 2nd-hand AstroTrac...

Will be good to see some results from this, weather permitting.

[happy-kat]

I like the groove of the decking as I plan eventually to make one and using a straight rod design. I have some marine ply.

I have been following member Ags barn door ventures too.