Fitting a digital camera to an AO 580 head

[Scarodactyl]

Hello everyone,
I mentioned in my introduction post that I was hoping to get advice on adapting a digital camera (an older Canon EOS) to my american optics 580 microscope head. Einman suggested I get a dovetail adapter from RAFcamera on eBay, and I gave that a try. I picked up a 43mm dovetail to 42m threaded mount, plus an adjustable length extender an a 42m to canon adapter. The dovetail finally came in today, and I realized that I'd badly mismeasured the diameter (probably something wrong with my digital calipers)--the actual diameter is more like 41.5mm at the top, and it looks like it tapers in a bit as it goes down too. The depth of the AO port also appears to be significantly deeper than the dovetail adapter, so I'm not sure how well one with the appropriate diameter would fit.


Fortunately though I have a drill press and free time on a thursday so I was able to make some adjustments (pictured in progress):

A horrible thing to do to such a beautifully made part, but I wasn't about to ship something that inexpensive back to Russia. Anyway, I got it to the point that it has a nice snug fit, though I will probably do a bit more later to get it perfected. One way or another though it was fit well enough to put on my test camera to get some photos. Here are my test photos, each a stack of 6 photos done in Helicon (subject is a negative crystal filled with petroleum and a methane bubble inside a quartz crystal).
With the canon:

Freehand with my phone through the eyepiece:

Unsurprisingly the area is way smaller through the adapter, since it was meant for a polaroid camera. However, cropping out the appropriate section of the phone photo shows the canon does take a better picture:

That's not entirely fair, though, since I could increase the magnification to get a better shot through the eyepiece.
I have a feeling that adding a reducing lens would be a real pain to do and probably degrade the image significantly. As-is the mismatch in sizes is kind of annoying, but this could still be useful for getting shots of some mineral inclusions.

[MichaelG.]

Here are my test photos, each a stack of 6 photos done in Helicon (subject is a negative crystal filled with petroleum and a methane bubble inside a quartz crystal).

What a fascinating subject you have there !!
Please tell us more.

MichaelG.

[Hobbyst46]

@Scarodactyl
Did you use the drill press like a grinder, to file off or grind the perimeter of the dovetail? if so, how do you center the (now 41.5mm) dovetail inside the 685 A.O. port? will you do it empirically with shims, or is there a side thumb screw as I guess from the photo?

[billbillt]

It looks like this part is made from aluminum.. If he is using a grinding wheel to do this, the wheel will clog up in short order.. you will have to dress the wheel constantly...

BillT

[Scarodactyl]

What a fascinating subject you have there !!
Please tell us more.
MichaelG.

These quartz crystals come out of Pakistan, but are very similar to those found in Herkimer, NY. They formed in cavities in a limestone, apparently crystallizing in the center of the pockets so they are complete all around with no wall contacts. These limestones are formed of marine sediments and one of their major impurities is oil from algae. For whatever reason these pockets of oil get trapped in cavities within the quartz while it is crystallizing--as the temperature goes down the methane gas exsolves from the petroleum so you get a two-phase inclusion. Some of them also include bits of native carbon too. The petroleum is also quite fluorescent which makes for fun photos. I should probably test that out too to see how the canon sensor handles it vs the phone.

@Scarodactyl
Did you use the drill press like a grinder, to file off or grind the perimeter of the dovetail? if so, how do you center the (now 41.5mm) dovetail inside the 685 A.O. port? will you do it empirically with shims, or is there a side thumb screw as I guess from the photo?

Yes, I used a few different dremel grinding bits to file down the perimeter (basically using it like a router) with a bit of sandpaper and a file to finish, just taking it slow and occasionally measuring to be sure that it was still essentially circular. The paint job helped quite a bit with that, since I could eyeball the exposed aluminum to be sure that it maintained a constant thickness and made a straight line. Clogging didn't seem to be a big issue for whatever reason.
The dovetail is held in with a set screw, but mostly it is just a very snug fit so it can only move up or down, with essentially no lateral movement or tilting, so it is fairly self-centered. It's not completely ideal, and I think I can improve the fit a little bit, but it seems to be functional. I'm still waiting on the adjustable 42m extender to get it perfectly parfocal but it's not far off with the fixed one I have in place now. It doesn't matter that much anyway since I am doing focus stacking anyway so I have to go through a range of focus settings anyway.

[MichaelG.]

What a fascinating subject you have there !!
Please tell us more.
MichaelG.

These quartz crystals come out of Pakistan, but are very similar to those found in Herkimer, NY. They formed in cavities in a limestone, apparently crystallizing in the center of the pockets so they are complete all around with no wall contacts. These limestones are formed of marine sediments and one of their major impurities is oil from algae. For whatever reason these pockets of oil get trapped in cavities within the quartz while it is crystallizing--as the temperature goes down the methane gas exsolves from the petroleum so you get a two-phase inclusion. Some of them also include bits of native carbon too. The petroleum is also quite fluorescent which makes for fun photos. I should probably test that out too to see how the canon sensor handles it vs the phone.

Absolutely astonishing ... Thank you.
I am frequently amazed by the complexity of of our planet, and; only this morning, I read this on the National Geographic news feed: https://news.nationalgeographic.com/201 ... ience-spd/
... That story has a strange symmetry with yours !!

MichaelG.