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- GSO 8-inch TRUE CASSEGRAIN
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Focus knobs for a Synta Refractor (too drool for!)
Focus knobs for a Synta Refractor (too drool for!)
By: Richard Anderson (RAnder3127@aol.com) 9 Jan. 2002
Every so often a "surprise" comes along in the telescope world. Hopefully, the surprise will be a pleasant one. Sometimes, it's not; Like discovering you've ground up the plastic gears on a department store telescope mount two days after buying it. Thankfully, all surprises aren't bad; In fact some produce real joy. Here's an example.
I was reading through one of astro newsgroups when I came across a post telling of a source for higher quality knobs for the focuser pinion shafts on Synta (Chinese) refractors. Most people will know that the focusers aren't too bad on these scopes. They are not of great precision, like a JMI focuser, but they are robust and generally pretty smooth. But one drawback is the focus knobs on them. They are composed of a black plastic, attached to the pinion rod end with a set screw. The knurling on the knob is functional, but the edges are sharp. I've procrastinated in grinding them down for awhile now, but it should be done. The grip you get on them is good, but overall, they impart the typical cheap feel and look you generally find on lesser telescopes.
Enter the knobs from www.focusknobs.com. I read the posting about the product, and went to the website. I couldn't believe it! A set of machined aluminum and anodized focus knobs, complete with stainless steel set-screw and allen wrench to fit my 4.7" Synta's pinion shaft for a whopping $16.95/pair! The website had a photo of them and they looked really good. I figured "Hey; Now I can get rid of the plastic things!"
I emailed the proprietor of the site, Bryan Varney and he speedily emailed me back with the shipping to Toronto and the final cost. So I ordered a pair.
The knobs arrived about five days later, and I have to say they are impressive. Better than the picture made them out to be. The knobs have a light anodized aluminum finish.
The machining is excellent, virtually zero flaws that I could detect. Check out this comparison picture:
Here is how they differ from the plastic knobs. On more than one occasion, I have jammed the tip of my finger between the sharp edge of the plastic knob and the side of the focuser. This is due to the fact that the knob edge is only a fraction of an inch from the body of the focuser and the teeth on the knob assure you of "grabbing" the edge of your finger. Not so with the aluminum knobs. They have a tapered shaft bored to accept the pinion shaft and the knob is held in place with the s/s setscrew.
Although the knurling on the aluminum knob is well cut, the manufacturer has beveled the edge so there is no
finger "grab" tendency. The knob edge is also further from the side of the focuser due to the length
of the tapered shaft. The width of the knurled area on the plastic knob is only ½" wide. The aluminum
knob's knurling is ¾" wide. The focusing action feels better using the aluminum knobs as well, less
effort is required and the feeling of solidity of the scope is enhanced. This is also a much better solution if
you happen to live in an area that experiences cold winters, as using these aluminum knobs with gloves will be
The appearance of the knobs really improves the scope. For the most part, there is still little plastic on the Syntas (knock wood) and getting rid of the plastic knobs is an aesthetic improvement. The knob has a dished face that really sets it off.
In my opinion, these knobs are a bonafide bargain that can improve the functionality and the appearance of your Chinese scope. The mfg. also offers the knobs in solid brass and even 2" wide knobs for the really gung-ho tweaker. SCT replacement knobs are offered as well so you can use them to try to forget about the rabid cost-cutting practices of the SCT manufacturers out there.
(Please note my Synta tube and backplate are homemade so it won't look like the regular tube).
The next thing I intend to do is replace the horrific knobs that come on the G5 and other Chinese mounts for
slow motion control. Those weak plastic things crack so easily!