Tips for Stereo Zoom Scopes

Stereo zoom microscopes have features and tradeoffs that can be puzzling, so here are some tips to get you started. The tips are ordered so you should be all set if you try them one after another.

Zoom out

The scopes can change magnification smoothly using the zoom knob on the side, and it's easiest to find a subject, tweak settings, and get in focus if you begin zoomed all the way out.

High eyepoint

The eyepieces that come with the scopes have a little eyeglasses symbol on the side, and that's to indicate that they're "high eyepoint". In contrast to a classic microscope, you position your eyes a bit away from the eyepiece- I measured ~20mm for my phone to get a good field of view. The purpose is to let you keep glasses on (hence the symbol), but the downside is that if you put your eyes right up to the glass then you actually can't see! Move your head closer and further until you see the image and you'll be fine.

Eye spacing

The eyepieces can be moved closer together or farther apart to match the distance between your eyes. This is the equivalent of pupillary distance in a glasses prescription, but here you don't need to measure it first. Try looking through the microscope and changing the spacing until the two circles of vision merge into one. It can be closer together than you expect.

Diopter adjustment

At the base of each eyepiece is a ribbed ring that rotates. These are for changing the relative focus of the eyepieces separately, so you can make them match your glasses prescription/correction. Start by rotating both of them fully clockwise. Get the subject in focus with one eye, and then rotate the ring on the other eye until it comes into focus. Then, if someone else wants to look through the scope, let them know. Can be really confusing to use a scope right after someone who's tweaked it to have a huge correction difference.

Working distance

The default 0.5X Barlow lens gives the scope a working distance of ~9"/230mm, which is quite a bit further away than most people expect. If try to look at a subject that's closer, it'll be impossible to focus. The 0.3X is even farther, ~12.5"/320mm, and the 2X is much much closer at ~2"/50mm. So, tip here is to keep in mind that if you're having trouble focusing, try moving back from the subject (or forward, be smart about it).

Focus and zoom

As you zoom in and out the focal distance will change a bit, and you'll need to move the scope (or subject) back and forth a bit. The fun corollary that I use a lot is that if the subject's a little out of focus, you can often zoom in or out slightly to fix it, instead of moving the scope. Also great for looking at different depths in complex subjects like aquariums.