Lacerta Dual Speed Upgrade for Skywatcher Crayford Focusers

92,95 €

The 1:10 micro focuser units have proven very useful in daily use. Especially for astro photography, they allow very smooth focusing. TS herewith offers a micro transmission to retrofit existing focusers. Retrofitting can happen with the focuser mounted to the telescope.

The 1:10 fits, for instance, to the following telescopes:

-- All Skywatcher Crayford focusers with four base screws in a distance of 33 x 22 mm
-- Skywatcher: ED Refractors, Newtonians, Dobsonians, Black Line telescopes
-- Vixen: ED 80 and ED 100
-- Orion USA: ED Refractors, Newtonians, Dobsonians

Why get a Dual Speed Upgrade?

Micro transmission, mounted

Present upgrade versions, like the William model, are often fixed to the focuser with only one screw. No fine adjustments are possible. A tilt of only 1/10mm can lead to non-uniform travel - many focusers with micro transmission suffer this problem.

This micro transmission has a pressure plate (see picture above) allowing fine adjustment. Even the gear axis can be aligned.

Why is a precise alignment essential?

Simple Crayford focusers have two screws: one for friction, one for locking the current position. The friction control screw can bend a simple non-adjustable pressure plate easily and smooth run isn't possible any more.

When the distance between axis and tube can be fine adjusted and the pressure plate is solid enough, a higher pressure can be applied without making the travel unround.

Maximum load capability of the Crayford focuser:

With the micro transmission, not only the travel itself becomes more precise. The overall stability is increased, too. Loads of more than 3 kg are held in position without any problems.

Is motorizing the focuser furthermore possible?

Yes. The new base plate is not thicker than the existing one.

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Micro Transmission - installation manual

Tools needed:
Hex allen key 1.5mm / 2mm / 3mm / Philips screwdriver

Step 1: remove the original screws

Step 2: remove original pressure plate and shaft

Step 3 through 5: remove teflon bearing and keep it for later use.

Step 6: Place teflon bearing inside the micro focuser

Step 7 - 8: Remove one knob of the original shaft

Step 9 - 10: push the shaft into the micro tansmission and fix lightly.

Step 11: Fix micro transmission with mounted original shaft to the Crayford focuser.

Step 12: Check the micro transmission's knob and fix lightly.

Step 13: Fine adjustment

13.a (Left allen key) Lower the pressure on the pressure plate until the drawtube can move freely. If necessary, turn the drawtube until the shaft lies on the full surface. Now, increase the pressure onto the pressure plate until the drawtube does not slide independently in and out.
Control 1: Check whether the Craford focuser runs smoothly or not. If yes, increase the pressure onto the shaft until the focuser has the desired resistance.

13.b (Right allen key) If the focuser still does not run smoothly. The planet wheel has to be adjusted also.

Step 14: Loosen the planet wheel housing with a minimal turn of the right allen key.

Like focusing, move the drawtube in and out while tightening both screws succesively. The planet wheel housing allows a small amount of play so their shaft can take its correct position alone.

If the micro focuser still doesn't run smoothly, the Crayford shaft or the original casting is bended. Loosen the left allen screw again (decreasing pressure onto the Crayford shaft) and vary the tension of the four small Philips screws setting the pressure plate (Step 11). Then, repeat step 13 + 14.

Now the micro focuser is ready for use!

Further adjustment opportunities:

In some cases, play of the focus wheel may occur. The reason is a loosened set screw inside the knob. It is located beneath the rubber armour as shown on the photo:

With friendly permission by Lajos Szantho