Whitepeak Observatory Tacoma, WA
Recently received one of these: Orion Accufocus electronic focuser and had some time today to get some stats on it's capabilities for anyone interested in one of these type of units. (Such as cg-5 class mount owners with larger OTA's like myself.)
Overview: Unit cost is 50$ plus shipping, which was very fast. Made in China and comes with complete instructions. Operates on one 9V battery (which is included). Handset has extend and retract directional buttons and a knurled plastic shaft with which to set the speed at any point between between maximum and minimum. Designed to mount onto specified Orion scopes-- but it went on my AR-5, using the supplied bracket, just fine regardless, though not exactly as designed. If a person is at all handy, a simple custom L-bracket with four holes would allow this unit to be used with almost any focuser. Black in color, typical Chinese quality finish. Requires removal of one focus knob and attaches to the shaft with a semi-flexible plastic coupling with allen screws (2ea). An allen wrench is included. Gearbox is designed to mount to the screw plate under the focuser utitilizing two of the existing screws. There is NO accomodation made to focus manually while this is attached; it must be used exclusively for all focus adjustment. However, if the two allen screws are loosened on the coupling, normal manual focus is available without further disassembly. Two knurled & slotted thumbscrews are provided to attach motor/gearbox to bracket.
motor/gearbox unit is:
31mm housing inner face to end of shaft coupling
8mm maximum shaft diameter
Here are the operational stats taken from a Meade AR-5 with a 2" to 1-1/4" reducer with a 5mm UO eyepiece:
time to travel 5" of focus travel:
fastest speed: 50 seconds
slowest speed: 200 seconds; 25.4mm 40 seconds; 0.64mm/sec
fastest speed shaft revolution rate: one rev/11 seconds
slowest speed shaft revolution rate: one rev/40 seconds
Dragging an Antares 2" diagonal with 9mm GSO wideview, a 1 lb 11 oz load, fast tavel time decreased to 15sec/rev.
100 switch pulses at lowest speed advanced the focus 5mm total for a per pulse average (stepsize) of 0.05mm.
Current draw: 40 mA measured while on the scope at it's fastest speed. That equates to an estimated 12.5 hours of continuous operation at the fastest speed to deplete it's 9v alkaline battery rated at 500mAh--so in practical terms one battery should last for weeks of observing sessions. Current drain with the unit plugged into the power cord, ready for operation, was below 1 microamp so it is OK to leave it plugged in in an observatory setting without unduely shortening battery life. I mention this because some other electric focus units (specifically some of Meade's) draw over 2mA just by being connected and must be unplugged between sessions.
Conclusions: What can I say? It works as advertised and makes focusing a vibration-free simple pleasure. Optimal focus is certainly much easier for me to attain than by hand focusing; this is particularly noticable at higher powers which, as a fan of the moon and planets, I use a lot. The battery is a very tight fit in it's compartment; removal requires a prying tool. This is the only fault with the unit I can find, however, and it isn't a really significant one IMO. The unit is very compact, has adequate power/torque even with Meade's less than perfectly smooth OEM focuser. The minimum focus step size is right in there with units costing much more giving this unit an excellent cost/benefit ratio, IMO.
back to index page