Mountain Instrument MI-250 German Equatorial Mount

Here's the TMB-152 astrophotography rig all set-up, ready to start drift alignment as soon as it's dark enough.  That's why there's an eyepiece and star diagonal in the little Takahashi FC-60 guidescope, where during an exposure the STV camera head would be there instead.  In this photo, you can see the STV head sitting on the STV control box on the milk crate in the foreground.  This image also shows the original MI-250 counterweight shaft, which is threaded over its whole length.  The design allows fine adjustment of the counterweights, but I eventually bought a new shaft made by Robin Cassidy that accepts the same size counterweights as the G-11, so I don't need two sets of weights of different sizes.  Since the two 15-pound weights that came with the mount (I bought it used from Tony Hallas) were not enough to balance the big refractor and associated gear, you can see a standard 10-pound barbell weight sandwiched in between the two white-coated counterweights.  This worked just fine, but I'm happier now using G-11 style weights on this mount.

This photo also shows a Cassidy saddle plate mounted to the basic mounting plate of the MI-250, but it's sideways because the dovetail locking knobs were not long enough to clear the basic plate on the mount otherwise.  Robin eventually sold me some longer knobs, and now the plate is mounted as it should be, longitudinally.  The rat's nest of wires is typical of astrophotography set ups, with power, declination motor, dew heater (2), autoguider, and hand control wires all over the place, and the vacuum hose for the camera isn't even set up here yet.  It's not as bad as it looks once everything is set up for a shot.

The mount itself is really fine piece of engineering and tracks beautifully during even the longest exposures.  The only complaints I have are that it doesn't have an integral polar alignment scope, and no analog setting circles.  Because of these minor drawbacks, polar alignment can take some time, especially at a new site, and composing the shot can be tedious because of the need to star-hop to the target.  A Telrad finder, out of sight in this photo but held on by the two blue Velcro strips around the main tube, is essential.  The shower cap over the end of the TMB-152 is used to keep the optics clean but still allow fine balancing of the mount, since the metal dust cap is heavy enough to affect the balance.  All in all, it's a great rig, and it's made a lot of nice images for me.