DIGITAL SETTING CIRCLE SYSTEM INCLUDING ENCODERS, HARDWARE NGC SKY VECTOR Improved-Now Has 12,000 Objects Improved LUMICON NGC SKY VECTOR with over 12,000 object. Lumicon Sky Vector II Digital Setting Circles with 2 x 4000 step encoders and all mounting hardware for C5/C8. Original instructions and manual. Eratta for the Sky Vector v3.65. Eratta for the Sky Vector v3.65. Eratta for the Sky Vector v3.65.

Digital setting circles Digital setting circles are the electronic equivalent to the right ascension and declination dials found on many telescope mounts. They may be used in conjunction with a star chart to find objects in the night sky, in a manner similar to using latitude and longitude on a map. The digital circles have the advantage of being much more accurate, are easy to read (even in the dark) and will work on almost any telescope. Current models have built-in computers which can retrieve information on thousands of objects, without having to refer to a star chart. When commercially produced digital setting circles for telescopes were first introduced to the amateur market, the name pretty much described what you got: a digital read-out for the right ascension (RA) and declination (dec.) axes.

That was all, and to work correctly they had to be mounted on a perfectly aligned equatorial mounting. They were also fairly expensive. As a result, the market response was not exactly overwhelming. A few years later, US telescope manufacturer Celestron, introduced the first 'smart' digital setting circles.

These compact units (made for Celestron by Tangent Instruments Inc.) had the amazing ability to correctly point the telescope no mater how poorly aligned it was. They had built-in databases to steer you to any object in the NGC or Messier catalogues, and could even identify an object if you were not sure what you were looking.

Times have changed, and while the basic functions of smart digital setting circles are much the same, the enhancement and changes make them worth looking at again. SKY & SPACE were kindly supplied with units from three manufactures: Celestron, Lumicon and Jim's Mobile. The models received covered the least expensive, mid-range and top end of the market. Lumicon Sky Vector I At the least expensive end was the Lumicon Sky Vector I. This unit is aptly described as 'digital setting circle instrument with a small database'. The Sky Vector was shipped directly from Lumicon in a Styrofoam-chip-filled mailing box; the encoders and display were wrapped in 'bubble wrap' and the whole shipment easily survived any torments the postal service might have inflicted on it. The unit we tested was designed to fit onto a Meade Instruments LX-6 fork mount.

Lumicon also supply mounting hardware for many other telescope brands, and this should be specified at the time of ordering. The Sky Vector's manual was very clear and comprehensive. Its 24 pages described all modes of operation, specifications and a printout of the database. The installation sheet was a little on the tricky side; I nearly missed it altogether, as I was expecting to find a sheet with at least a few schematic diagrams to help me along. Instead there was a printed sheet of instructions, which for the mechanically minded are easy enough to follow, but the addition of a few pictures could save a thousand words to the technically less able. The Sky Vector is unique amongst the three units tested, in that it has high-resolution encoders to measure the angular position of both RA and dec.

There are two types of optical encoders currently on the market, one with 2,048 steps per revolution (0. Jungle Book 1967 Sub here. 17 degrees per pulse) and one with 4,000 steps (0.09 degrees per pulse). The Sky Vector was also unique in not having intermediate gearing to rotate the encoder shafts. They mounted directly onto the RA and dec. Shafts of the telescope.