Milky Way via Canon and Barn Door

[2020BC]

Here's a picture taken with a Canon 350D mounted on a home-made barn door tracker.

This is a single 2 minute exposure at f3.5 and a focal length of 18mm. Lens was the Kit lens (EFS 18-55mm).

For a much larger view Click Here (http://www.zodiaclight.com/images/BarnDoorMWayCore2MinsF35ISO800-17Jun06IMG1900Web1280.jpg) .

[2020BC]

Here's a picture of the barn door.

It's a stool bought for $10 from "The Reject Shop" with some boards, bolts and hinge, etc. from Bunnings. The most expensive bit is a camera ball-joint.

[xelasnave]

Great work. I love wide fields of the Milky Way and yours is a cracker, on a barn door no less. That has to inspire others to have a go. Congratulations on a fine effort.
alex

[danielsun]

Brilliant stuff there Bill!!!! Well made and a great shot!!:thumbsup:
Question: How did you track it? Do you have a motor drive which connects on it or something?

[RAJAH235]

That particular design is strictly a 'hand cranked' model Daniel. Give it 1/4 turn every 15 secs.... Nice pic btw Bill. :D L.
ps. There are quite a few designs out there. Here's (http://i2.photobucket.com/albums/y7/RAJAH235/IMG0004.jpg) my (http://i2.photobucket.com/albums/y7/RAJAH235/IMG0002.jpg) take (http://i2.photobucket.com/albums/y7/RAJAH235/IMG0001.jpg) on them.

[2020BC]

Yep, strictly hand-driven. Yes, I'll get around to putting a motor on it, maybe, one day...:whistle:.

One thing I did experiment with was an innovation of my own. It worked very well and let me image at focal length of 200mm. Instead of using a watch/timer I attached a video camera with long (200mm) telephoto lens for guiding. Used it to guide an SLR with wide-angle lens (50mm) but also used it for imaging video directly at long focal length (200mm). That worked a treat.

Here's a closeup shot of Eta Carina (D=200mm) created last year on the barn door using RGB filter and stacking B&W video. My Mintron 13V1C video camera has two outputs. One video port was used to capture data while the other video port was fed to a TV for guiding. A red box drawn around a bright star let me keep a guide star centred. Just turned the handle fast enough to keep the star in the box...

I've only done long-focal length (200mm) video imaging on a Barn Door a few times when I was just getting started in astro. If I spent more time on it (barn door video) today I'm sure I could produce a much better result. So many things to try, so little time....:zzz:

[danielsun]

Thanks RAJAH :thumbsup: I've heard a bit about barn doors but wasnt sure about manual driving them till now:)
Yours looks like a deluxe premium set up:thumbsup:
Can you tell me what size threaded rod and pitch is needed for this manual design?

[RB]

That's so cool Bill.

Well done.

[2020BC]

I made the barn door last year so the bits of paper I did my calculations on are well, they're around here somewhere :rolleyes: .

No drama, it's easy to start from scratch. Go to Bunnings and get a long bolt. The long bolts are usually displayed prominently in the aisles nearest the "nuts and bolts". The long bolts come in different diameters and are about 2 feet long, so you'll have to cut yours to size with a hacksaw. I cut mine to about 18 cm which left heaps of room for movement plus attaching a handle, etc.. I put a rounded cap nut on the upper end of the bolt on which the moving board rests. This rounded nut limits area of surface contact and really cuts down on friction as the bolt turns. I used two plates from the bottom of lounge-chair legs to hold the bolt to the bottom board. These plates come with a threaded hole in the middle of them which holds the bolt in place. By holding the bolt in the bottom board the bolt as it turns is able to apply force and lift the upper board. If you look in the picture you'll see one of these plates screwed onto the bottom side of the lower board.

Getting the tape measure onto the bolt it's about 5/16" diameter and, just checked, appears to have a thread of about 60 turns per 84mm. Working out the distance for 60 turns is the key to your calculations.

60 turns will be 60 minutes which is 15 degrees sidereal movement.

Using X= Y / tan (15degrees) yields distance X from hinge to bolt hole of around 313 mm. (i.e. Y=84mm)

Just used the tape-measure on my tracker and that's about right.

Hope this helps. If in doubt, use the formula and work it out on paper before drilling. Besides if you put the hole in the wrong spot you could always drill another.:whistle:

p.s. Note that the hinged board is tilted to 37 degrees (Canberra's Latitude) and the door hinge MUST be arranged as shown otherwise the tracker will be turning in the opposite direction to the movement of the sky...

p.p.s. I chose to hinge the lower board (see the two small hinges attaching it onto the stool's seat) and used a protruding bolt to set the latitude (tilt) just in case I move or travel and I can adjust latitude accordingly.

p.p.p.s. I use a bungy strap to secure the lower board these days to prevent the weight of the cameras from tipping the boards backwards.

[xelasnave]

thats pretty tricky guiding ..fantastic idea
alex

[Octane]

Bill,

I was in the introductory meeting at CAS on Thursday night, and saw you demonstrate that little beauty. I was the guy with the black hair tied back, nodding along in your introduction to astrophotography talk. :)

I would like to build one of those, seeing as I usually take five hours setting up my LX90 before I take a single test focus exposure!

Cheers!

Regards,
Humayun

[RAJAH235]

I used a 1/4" 20 tpi, threaded rod for mine but the measurements vary with the size chosen. The distance from centre of hinge to centre of hole is 290 mm or 11 & 7/16th inches. I also used 2 X brass hinges as these have absolutely no play in them.
An easy formula for finding the hole position is > D (distance from hinge) = 228.6 divided by, tpi of your threaded rod. eg; 228.6 / 32 (tpi rod) = 7.14"
This is from "Handbook For Star Trackers" by Jim BALLARD. (1988).
HTH..:D L.

[2020BC]

I know how that goes. Tonight I've spent 5 hours getting everything ready for the "perfect" shot on M17 (Swan). No sooner had I got everything just right when that classic nor' easter wafts a blanket of cloud over everything. :doh:

The Met Bureau is predicting buckets of rain for all of next week.

Maybe next weekend...

I've just got to get an observatory....

[Lester]

Hi Bill,

10 out of 10 for effert. Observatory will help remove some of the frustrations.

[tornado33]

Yes a great effort, getting excellent results from gear you made yourself.
Scott

[danielsun]

Thanks Bill and RAJAH for your detailed descriptions.:thumbsup:
I take it that (being used for widefield shots) you just have to roughly polar align the point were the two boards meet(where they are hinged together)?
Is that so?

[2020BC]

Yes, the edge where the two boards meet points at the SCP. If you use wide angle lenses the alignment doesn't have to be precise.