Convertible mount

There are two different types of mounts for a fork mounted scope. Alt-az, which mounts the telescope on a level surface. A polar mount holds the telescope so that it is aligned with the Earth's rotation. That way, the mount only has to track in one axis to remain centered on a star, planet or other object.

There are advantages and disadvantages to each type. With an Alt-az  mount, the telescope has to adjust both the altitude and azimuth in order to track an object in the sky. This is not a real problem with my telescope because it's computer does all of the work. Long exposures are not possible because the object will rotate in the field of view. Objects directly overhead are a problem because the telescope is pointing straight up in the forks and the telescope can't easily move the telescope in the proper direction. It is much more stable than a polar mount because the telescope is setting upright and all of the weight is directly over the center of mass of the mount.

With polar mounts, the base of the scope is tilted upward (at 50 degrees in my case) which means the scope is hanging off the mount. It is very stressful for the bearing in the base of the telescope. It has the same problem with objects overhead as with an alt-az mount, but it is objects near the north celestial pole (very near Polaris, the north star) because that is when the telescope is pointing "straight up" in the forks. Long exposures are possible because only one motor is tracking. The mount is less stable because the center of gravity is not above the pier or post, but north of it.

Either method will work for me for most observing. My problem is when tracking the ISS and it passes overhead or nearly so (if using an alt-az mount) or passes near the north celestial pole (if using a polar mount).

My telescope mount is unusual. It started life as a mount for a 12 ft diameter satellite dish. I cut away a lot of unnecessary stuff and just kept the core. I had a steel plate welded to the top of it and a second steel plate that bolts to the bottom of my telescope. Four 3/4" bolts hold the two plates together. I used the altitude adjustment bolt to adjust for latitude and turned the mount on the post to adjust for azimuth when using it as a polar mount. This has worked out very well for me.

It occurred to me that it wouldn't be hard for me to adapt my mount so that I could easily switch from alt-az to polar or back again.

The top photo is in alt-az mode. A bolt with a nut above and below the  mount adjusts it to be level. Once I set it, I can forget it. I drilled a small hole to pass a bolt through to keep the mount from tilting.

The bottom photo shows it in polar mode. I just tilt it up enough to insert the altitude bolt and add the nut on the bottom. The top nut remains in the same place so the mount needs only minor adjustment to get it "just right". I am going to work on an easier way to allow it to change to and from one mode to the other, but as of now I'm pretty happy with it. If the ISS will pass overhead or nearly so, I will use the mount in polar mode. It it will pass near the north celestial pole I'll use the mount in alt-az mode. Sat Tracker will work with either type of mount.