Monday, August 27, 2012

Digital Setting Circles

After more than a year observing with the 15-inch by star hopping, I just acquired a set of Sky Commander digital setting circles for it. These consist of encoders that record movement along the altitude and azimuth axises and send electronic signals to a small computer unit that contains a database of some 16,000 stars and deep sky objects. The computer calculates which directions and how far to move the telescope and when the display indicates it's aimed at the right spot, the object will appear in the eyepiece. That assumes of course, the computer is set up and initialized properly and the encoders are installed correctly. I had to make mounting hardware to install the encoders because the altitude bearings are hollow arcs and the pivot bolt supplied is 3/8", not 1/2". I found some bronze bearing sleeves that will compensate for this and I made a new lock nut mounting plate for the ground board with a 3/8 all metal lock nut.
After some trial and error, I made a stalk for the computer which attaches to threaded inserts in the rocker side. It also has a stud for the altitude encoder arm and a hole through which I can drop the cables to the encoders to keep them out of the way. I also made a detachable bracket for the altitude encoder so it can too can be removed for transportation.
 
During the past week for three nights I had a chance to put the Sky Commanders through their paces. In half an hour I learned how to operate the computer and on the first night I had no problem setting it up. When I initialized and tried it out for the first time, it got every object in the field or just outside of it at 142 and 227X, even though I did a hasty alignment. The following two nights it performed better because I took more time on the alignment, and I learned how to resynchronize the computer when pointing accuracy fell off due to the telescope not being on level ground and possibly the telescope not being perfectly orthogonal. The computer copes better with both than my JMI digital setting circles however, and the LCD display is easy on the eyes.
 
I built the stalk so I can keep the computer in sight while at the eyepiece, but without the glow from the display in my eyes when I am peering into the eyepiece. The computer is secured in place with Velcro, and having it on the stalk also keeps it from affecting the telescope's balance. While the JMI's are good, the Sky Commander is better. If I had to choose between the two, for the price the Sky Commanders are a better deal. One nice thing about them is there is no need to point the tube perfectly vertical when aligning it, and there are more stars to choose from to align it on too. There's more deep sky objects and more memory space for user defined objects, and the unit can hold information on up to 30,000 objects. With a set of these digital setting circles, one can take command of the skies for a mere $500.00 and change. Now I can spend more time looking at objects rather than hunting for them, and do more observing when the moon is up.  I am going to attend the 2012 Deep South Regional Stargaze if at all possible so I can observe more fall and winter galaxies.