Dear Chandra, we are also currently getting quotes for a new microscope. I recently worked at Oak ridge with a Zeiss SteREO Discovery.V20 https://www.zeiss.com/microscopy/us/products/stereo-zoom-microscopes/stereo-discovery-v20.html (everything motorized, which is not really needed) and at diamond with a leica M205 C Stereomikroskop. Both are high end machines and I can't say which one is better, the quality was perfect for both. However the Leica at diamond has a very flat base. If you keep the plate on the glass everything is fine. But the frame get's warm and fried my crystals. However all mentioned microscopes are modular and you can also get a base with external light source. So contacting your local dealer or looking at synchrotrons or a microscope facility helps a lot for the right decision.

What we are still looking for is a light source for intrinsic flourescence and trace label flourescence. We just found one vendor http://xtal-concepts.com/index.php/en/xtallight-100.html

We would also build it from parts of an electronic store if we get a good plan. Nowadays with LED's in all colors that can't be too difficult?

I asked now for quotes for a Zeiss

SteREO Discovery.V8    magnification     10x … 80x

SteREO Discovery.V12   magnification     8x … 100x

and the
leica M205 C, because they have sales representatives here in Vienna and I can test the microscopes before buying.

A recent post on the bulletin summarizes well on what to focus:

○ Full Working Distance (FWD) - how much space is there between the front objective lens and the tray - anything less than ~55 mm and you will likely be frustrated when harvesting crystals

○ Magnification - for screening & harvesting anything less than a total magnification of ~80x will leave you wanting more, ideally 120x or more will let you resolve those <10 µm crystals

○ Base Size - how large is the working area of the base - anything less than 250 mm (deep) x 300 mm (wide) can leave your plates dangling off the edge when harvesting from the perimeter columns

○ Light Source - a bright external LED cold light source, with a fiber optic transmitted feed into the microscope base, will give the light you need while preventing your trays from heating and drying out during viewing

Best regards, Georg.

[log in to unmask]">

Hi Chandra

My only comment is be careful of modern microscopes that have a frosted glass screen with LEDs behind it, just below the plate.  For looking at crystals you need directional light.  I've seen some very expensive modern microscopes with illumination that just doesn't work for crystallization.  If I come across that situation I normally make a platform and raise the plate up by a few inches - it can dramatically improve the quality of images.  You can also cut a round hole in e.g. a piece of aluminium foil and use it to make the area of the light source smaller.

On the other hand illumination mustn't be too directional because the drop itself acts as a lens.  If you have a light source that is small and too far from the sample you'll get black regions around the outside of the drop where you can't see crystals.

It's all about the solid angle of the light hitting the sample - I'm sure others can explain better than I can.

Good luck, Patrick

On 7 March 2018 at 02:06, Chandramohan Kattamuri <[log in to unmask]> wrote:

Hi

I'm looking for suggestions on a good microscope for looking at crystals, which includes polarization, light source (fiber optics), crosshairs and camera mount.  What Models and make?

Thanks in advance

Chandra

--

 [log in to unmask]    Douglas Instruments Ltd.
 Douglas House, East Garston, Hungerford, Berkshire, RG17 7HD, UK
 Directors: Peter Baldock, Patrick Shaw Stewart

 http://www.douglas.co.uk
 Tel: 44 (0) 148-864-9090    US toll-free 1-877-225-2034
 Regd. England 2177994, VAT Reg. GB 480 7371 36