Obsluga wyciagu GSO.pdf

Making your GSO-based crayford focuser as smooth as it can get

by Pollux Chung

If you are still using those Chinese-made telescopes you probably know their built-in rack-n-pinion

focusers are driving you nuts. I sometimes call these things "toy from hell."

It's been a while we have been seeing some crayford focusers upgrade from GSO (Guang Sheng Optical)

in Taiwan. These focusers aren't in the same league as Feather Touch or Moonlite. However, they still

offer really good performance without breaking your bank.

Problem with the GSO crayfords is that sometimes they do feel rough.

Good news is there're ways to fix this little fella to make your scoping experience even more enjoyable.

This tutorial here covers the dual-speed GSO-based crayford . It may not be 100% working for other

crayfords like those made by Long Perng since the structure (ways to break them apart and put together)

of their focuser is slightly different. Scopes that use Long Perng mechanics are Astro-Tech (66 & 80mm

refractors), Stellarvue (Nighthawk Next Generation & SV102ED), Skywatcher (Equinox Series). You

will have to let me know. Once I get enough request I will make another guide for that type of focusers.

Before you start doing the work, you need a few things:

1) A wrench

2) Allen Keys

3) Medium thick grease (Lithium or Graphite)

4) A little bit of car polish wax, no really necessary but it's good to have

5) Of course, a bit of patience ;-)

STEP 1

Here's a typical GSO-made dual-speed crayford.

Make sure you are not mixing up with its tension and locking thumb screws.

First, loosen up the TENSION thumb screw, or even take it off if you wish.

STEP 2

Take the focus knob (at left) first, you need an allen key to do the job.

STEP 3

Then pull the shaft out from the other side. After the shaft is pulled from the focuser the draw tube will

come out very easily.

STEP 4

The flat surface of the draw tube is where the focus shaft is touching. Generally this surface is flat and

smooth enough (way better than Synta's crayford for sure)

Many people who own a scope with Synta's crayford have to use a grinding stone to flatten and smoothen

the "flat" curvy suface of its drawtube.

Good news is, no grinding stone is needed for GSO crayfords since it's flat surface is flat enough for

doing a decent job.

You still can make it smoother by using some car polish wax (cutting wax is recommended). Apply a bit

of wax and wipe it off once it's dried. You should then feel it's very slippery. Yes, this is what you will

want.

STEP 5

Now look at the inside of the focuser's main body, The 4 wheels (circled in red) are holding the draw tube

in place. Apply a small amount of grease on all of them.

STEP 6

Now here comes the exciting part - The dual-speed knob!

Again, use allen key to remove the fine focus knob first....

.... then the big knob

STEP 7

Here's the internal guts of the dual-speed knob. You see three steel balls sit inside the brass bracket.

Here's the other side of the knob. The steel nut (which the red arrow is pointing) is very important, don't

mess with it yet. This is one of the major reasons why some GSO crayfords are so rough or tight.

STEP 8

Look at the ball bearing side again. With all the GSO crayford I have broken apart and looked at they

generally don't have enough lubricant for the ball bearing to move around, this is the second reason why

the focuser feels rough, so.........

......put some grease here!!!!!! Don't put too much. Then roll the brass bracket to make sure the grease is

evenly applied.

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