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Hello from Huntsville, Alabama

 
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Bob Topp



Joined: 21 Jan 2011
Posts: 9
Location: Huntsville, AL

PostPosted: Sat Jan 22, 2011 1:09 pm    Post subject: Hello from Huntsville, Alabama Reply with quote

First- what an impressive site! Thanks to David Walker, micscape (UK), for directing me here in an email. I have been shooting digital for ten years, and, like some of the hobbyists here, find myself stuck for stuff to shoot in the wintertime. I embarked on microscopy after playing with some reversed lenses for macros. Fortunately for me, I did only a enough reading to convince myself I should be able to image directly from a a commercial objective to my D200 and 300 sensors. That is, if I had read all there was to read, I'd have become discouraged at the cost of entry. As it was, I just went out and bought some 1" tubing from Thorlabs and a 4x 0.1 DIN objective from Edmunds to play with. I was afraid that the 160 mm lens would not be able to image all of the roughly 16x24 mm sensor, since it is intended to image an 18mm circle for a standard eyepiece. However, the lens arrived today, and I quickly shot it handheld through the tubing with reasonable results. I'll post something once my T-mount comes in and I figure out how to adapt the 1" tubing to it. In the meantime, thanks for all the great stuff posted here.

Regards, Bob Topp
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2011- I am building my first tube microscope from a commercial 4x 160mm DIN objective.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18923
Location: Richland, Washington State, USA

PostPosted: Sat Jan 22, 2011 3:37 pm    Post subject: Reply with quote

Bob, welcome aboard!

Most of the recent postings about microscope objectives have been made by people pushing the envelope of high magnification, high resolution, and high image quality. That takes money and sometimes unusual setups. Stay away from the high end stuff and the price of admission goes way down.

I can think of a couple of things to watch out for in the setup that you've described.

One thing is that stray reflections from the sides of a tube can cut your contrast quite badly. When you get everything assembled, be sure to look down the tube with the camera removed and see where flocking and/or masking may be required.

The other thing is to check for color fringing (chromatic aberration) in your images. If that's one of Edmund's commercial objectives, you'll probably be OK. Many older objectives that appear in the used market were designed to have quite a bit of CA in the objective, intending that to be canceled by opposite CA in a "compensating eyepiece". Those objectives don't work very well by themselves.

Looking forward to seeing your images...

--Rik
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Bob Topp



Joined: 21 Jan 2011
Posts: 9
Location: Huntsville, AL

PostPosted: Sat Jan 22, 2011 7:26 pm    Post subject: Reply with quote

Thank you for the observations. I hope I've chosen wisely on tubing- it's from the Thorlabs SM1 series, flat black anodized aluminum for optics labs. Doing some handheld tests, I have gotten a bit of flare, but I think it was from the angle/power of my flash. The lens is an achromat, but not a plan or semi-plan. I haven't seen any color fringing yet, but on a couple of shots with a white background, I could have sworn I had seen interference rings!

Due to my construction method, I think stability will be a major task to tackle. The long tube could vibrate quite a lot I think. My primary concern right now is the very shallow depth of field I'm seeing- to be expected since I shortened the design working depth and chose a non-plan lens. I plan to try stacking shots, but I will be driving the stage, not the camera/lens combo. After reading some of the comments about stacking, I'm going to have a challenge translating perfectly in and out without my subject moving obliquely relative to the axis of the lens. Once I have a stage assembled, I will try the Helicon software- I'm interested to see how much variation it can tolerate.

Regards, Bob
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2011- I am building my first tube microscope from a commercial 4x 160mm DIN objective.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18923
Location: Richland, Washington State, USA

PostPosted: Sat Jan 22, 2011 9:02 pm    Post subject: Reply with quote

That tubing looks pretty good, but check anyway.

About stability, the usual advice with Nikon cameras is to shoot with flash in a darkened room, mirror lockup and 2nd curtain sync with a couple of seconds exposure time. That gives mechanical vibration some time to die out after the shutter movement. It's still a good idea to specifically stabilize the objective -- you don't want that thing vibrating undamped on the end of 5 inch tube.

Unless your setup is something completely different from what I'm imagining, you won't have much trouble with the subject sliding across the field. If things are a lot out of line, you'll notice and adjust to bring it closer. If things are a little out of line, any of the standard software packages will just correct for it as part of normal alignment.

--Rik
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