Astroasis Electronic Focuser – New Version

[PeterC65]

I’ve been considering getting an electronic focuser for EAA for some time but have been put off by their need for permanent installation and consequent disabling of manual focusing. I have several scopes that I use for EAA and didn’t want to buy a focuser for each, and I also use them for visual astronomy where I prefer manual focusing.

I’d considered the first version of the Astroasis Electronic Focuser but it required a separate 12V power supply. The new version does not, so I’ve taken the plunge.

What I like about this focuser compared with the alternatives is:

• It clamps on to the round barrel end of the focusers drive shaft, replacing the coarse adjustment knob. The knob is replaced by a gear which meshes with another in the electronic focusers body, and the clamp is secured via a single Allen head screw, so the focuser is easy to remove and use with multiple scopes.
  Each scope needs to be fitted with a gear in place of the coarse adjustment knob which remains in place, and sometimes the clamp on the electronic focuser body needs to be changed to accommodate different sizes of focuser barrel (three Allen head screws). For focusers that do not have a round barrel there is an adapter which uses the same type of L-bracket used by other electronic focusers to provide a round barrel, allowing the clamp arrangement to be used. So in all cases it is possible to easily remove the electronic focuser body.
• Because of the clamping arrangement, and the short cylindrical form of the focuser body (the new version is even shorter), when fitted directly to the focusers barrel, the Astroasis Electronic Focuser is neat and unobtrusive.
• The geared drive incorporates a manual clutch which disengages the gears, allowing normal manual control of the focuser with the electronic focuser still fitted.

The new version of the focuser can be powered via its USB-C connection, but there is also a separate 12V power connection for very heavy loads. The focuser has an internal heater to warm the mechanism in very cold environments and this benefits from the 12V power supply.

I’ve installed the focuser on my Photoline 72mm refractors and on my Explorer 150PDS and 200PDS. This install on the Photoline 72 was straightforward, not so with the Explorers. The Explorer PDS focuser only has a bearing at the fine adjustment end of the drive shaft so Astroasis provide an adapter kit that fits a bearing at the other end to support the gear replacing the coarse adjustment knob. This is a useful improvement to the original focuser, but unfortunately the ball race bearing supplied was too small to fit the shaft and I had to dismantle the Explorer focusers, put their drive shafts in the pillar drill and spend 10 minutes reducing their diameter a little with some sandpaper. After doing that the installation was straightforward.

Here is the Photoline 72, with and without the Astroasis Electronic Focuser fitted:

And here is the Explorer 200PDS:

I’ve tried the focuser with SharpCap in daylight and it works fine. There is a driver for it that can support up to three instances of the focuser if you ever wanted to use more than one at the same time. The way to setup the focuser is to engage the clutch with the focuser tube fully inward and set this as the zero position. You can then set the maximum position for each scope, and record the focus positions that you use regularly. I’m getting 1260 steps per mm with the Photoline 72 and 2150 steps per mm with the Explorers.

I bought my Astroasis Electronic Focuser from Dark Clear Skies at the IAS show. Paul Stevenson was very helpful in determining which adapters I needed for the various scopes, as this is a complication with this electronic focuser. FLO have stocked the previous version of the focuser and I understand they are planning the stock the new version.