Another macro rig (the "Bratcam")

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AndrewC
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Re: Another macro rig (the "Bratcam")

Post by AndrewC »

Chris S. wrote:... A couple of friends dubbed it the “Bratcam” (just why is a long story).....
C'mon, spill the beans - why ?
rgds, Andrew

"Is that an accurate dictionary ? Charlie Eppes

Chris S.
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Post by Chris S. »

Elf, I apologize for my slow response. Work snuck up on me and diverted me from fun things like photomacrography.
elf wrote: I'll add comments about steppers to http://www.photomacrography.net/forum/v ... php?t=8261
Many thanks for that excellent post. Will ask questions about your approach there.
elf wrote: I'm assuming the goniometers are aluminum. If you glued a thin piece of sheet metal on top of the stack (with holes to allow access to the threaded holes in the goniometer), you would be able to use magnets to position the subject.
Jolly good idea, and I may try it. Though so far, the simple binder clips have been staying put very nicely without assistance. I could also simply add a piece of double-faced tape, but have so far not seen the need. Your idea about using magnets, though, would be neat and elegant.
elf wrote: Are you limited to subjects less than 1" tall or can you replace "N" with other angle pieces to lower the goniometers?
I'm not limited to subjects less than one-inch tall, but do feel constrained by the inability to lower the subject stage further. So I've been looking (since before your suggestion, but in perfect agreement with it) for a smaller right-angle bracket to replace "N," and have several candidates in mind--which, as you point out, would give me more working room above the goniometric stage.

Also toward this end, I've had a spacer made to raise the camera height when needed. It consists of two of Chris Hejnar's 10-inch dovetails mounted by Don Wilson above and below an aluminum block. I added a pair of Really Right Stuff clamps (keyed to be either parallel or at 90 degrees), so I can place it between C & D or between G & H. Also--and this was my primary purpose in creating this spacer--it allows the camera and a macro lens to be used without the bellows, adding to the range of magnifications the Bratcam can easily handle. But, as per your point, it also can be used to raise the bellows up and give more working room above the subject stage.

Best,

--Chris
Last edited by Chris S. on Sat Oct 24, 2009 9:15 am, edited 1 time in total.

Chris S.
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Post by Chris S. »

ChrisR wrote:Possibly the neatest method for stepping a focus mechanism is as used by Saphicon
http://www.saphicon.com/focus-drive-integrated-s.htm
eg on an Olympus :
http://www.tofrainc.net/mounting-focus- ... us-BH2.htm

With a cheapie stepper motor you get 200 steps/rev, which is 1 micrometer per step for common Nikon and Olympus scopes.
1/16th steps from the cheapie driver boards gives steps down to 62 nanometers which is probably enough to keep Rik and Charlie happy for a week or two.
"Yipes!" on the Saphicon, Chris R. I'd been looking at this myself--neat indeed, but ouch, what a painful cost. Will probably go the cheapie route--partly to keep the cost within sane limits, and also because it might be fun. . . .

richard martel
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Post by richard martel »

Chris, Really tight setup you have there. You may be able to get a bit more range (downward) on the Z axis by milling off the bottom section of the angle plate, N , so that it is flush with the bottom of the slide portion of the linear stage??? At least it "appears" in your photo to extend below the slide.

Regards, Richard

Chris S.
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Post by Chris S. »

richard martel wrote:You may be able to get a bit more range (downward) on the Z axis by milling off the bottom section of the angle plate, N , so that it is flush with the bottom of the slide portion of the linear stage??? At least it "appears" in your photo to extend below the slide.
Welcome to the forum, Richard!

I've made some upgrades to the Bratcam in the 11 months since I posted this thread. As you point out, the old L-bracket extended below the subject stage and cost me about 5/8 inch of vertical range. So I replaced N with a smaller right angle plate, a Thorlabs AP90 Precision Right Angle Plate. Yes, I could have milled off the old one, but I saw an AP90 on eBay at a very low price, and so replacing it was a quicker, neater solution.

I also replaced B, the 12-inch Arca Swiss dovetail plate from Chris Hejnar, with a longer one also from Chris Hejnar--he made me a 17.5-inch long, 3/8" thick plate. Why? It gives me full travel more quickly. The old slider was moveable with screws (my baseplate has multiple holes) to get full travel, but I found myself wanting to be able to adjust the rig through its full range without tools.

Items C, D, E, F, and G--which constitute the stepping stage--are in the process of being replaced with a similar assembly based around another Nikon focus block mounted so as to connect to a stepper motor via timing belt. I have a stepper controller on the way, so the Bratcam is about to go electric. I'm not cannibalizing any of these existing parts because the current stepping stage also works very well on a tripod for field use (its much better than any commercial macro focusing slider I'm aware of). The old 12-inch Hejnar plate clamps on my tripod head for rough distancing, and the stage clamps onto the plate to provide fine focus and stepping capability.

Am also conspiring to make a drop-in filter housing to hold a polarizing filter (called an "analyzer" in this use, I've recently been taught) for cross-polarized lighting.

I'll post some pictures when I get further along.

Cheers,

--Chris

richard martel
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Post by richard martel »

Thank you Chris. Glad to be around so many great photographers and tinkerers.

when I get back from vacation, (Maine, NY, UP Michigan) then back home to the Florida Keys ) I'll start on A project similar to yours. Thinking of using a granite surface plate for the foundation...Locating the used parts may take some time. My mechanical skills are pretty good so this will be a fun endeavor.

I just ordered a Cognisys Stacker that I'll play around with. Mainly got it for field work though. I know little to nothing about driving stepper motors so I will be interested in the details of your latest electric drive.

Thanks again, Richard

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