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Autofocus Installation: Getting perfect focus for an astrophoto is one of the toughest things about astrophotography. Until now, all of my images have been manually focused. Granted, programs like DSLR Focus make this job easier, but there is still lots of room for error - making lots of room for improvement.

I've been shopping around for about a year for a cheap and easy way to add autofocus to my setup. There were several do-it-yourself projects out there, but I never had the time to dedicate to building my own stepper motor mount and controller. In Dec 2008, I noticed that several people were using the Orion AccuFocus motor on their scopes. Shoestring Astronomy has a focus motor USB controller, the FCUSB, for sale for around $70. I asked Hap Griffin if that's what he used to control his Orion 80ED's AccuFocus motor and he reported back that the setup works well.

So, here are the parts I bought for the new autofocus setup for my Celestron 80ED.

• Orion AccuFocus - I bought the one for the Crayford focuser, but both work for the C80ED
• Shoestring Astronomy FCUSB focus motor controller
• Shoestring Astronomy FCCBL-01 AccuFocus cable

The directions provided with the AccuFocus are good, but they're made for mounting the AccuFocus to an Orion telescope. The process is similar, but there are a few differences. Below you can see the AccuFocus motor with the Crayford (silver) and rack-and-pinion (black) shaft couplers. I started the whole process by removing the Crayford coupler & installing the rack-and-pinion coupler.





I spent over an hour trying to get the knob off of the telescope's focuser. Most refractors have a set screw on either the side or end of the knob holding it in place. After no luck online, I figured out that the knobs are threaded on to the focuser shaft. It took a very hard twist, but after it popped loose, the knob threaded off easily.



I looked at the three AccuFocus brackets and figured out which one would fit the C80ED's focuser. I removed two screws on one side of the focuser and attached the bracket. I didn't tighten the screws all the way (yet) to allow for alignment later.



I aligned the AccuFocus motor and tightened all screws. The focuser shaft does not have a flat side, but the two set screws on the coupler seem to hold it well. Here's the AccuFocus installed on my C80ED.







With the stock C80ED focuser grease (glue), the motor moves the focus very slowly even at full speed. I'll strip the grease and use something better soon.

With the Shoestring Astronomy FCCBL-01 cable, the FCUSB will plug into the AccuFocus directly. From there, you can use just about any focusing program to control the focus motor. I plan on trying DSLR Focus on the PC & Shoestring Focus on the Mac.

I'll post autofocused images here as soon as I can get the new setup out!