Meant to be a direct replacement of the stock focus knob, this replacement knob is 3d-printed in black plastic and features a few key improvements:
To be clear, this isn't the only option out there -- flexible cable extensions can be found online, but I wasn't a fan: the stock knob is just as cumbersome at the end of the flexible cable, which also introduces a bit of backlash to the focus chain in my experience. But I think this is an excellent alternative, and a few kind field testers have agreed:
1. The knob is considerably larger, with an outer diameter of 1.45" (ETX-125) or 1.08" (ETX-90). The increased circumference means more precise focusing, while being easier to "find" with your hand while observing uninterrupted;
2. The ridged surface provides excellent traction, making it easy to use a single finger and/or a very light touch to generate travel; and
3. The plastic construction means it doesn't get nearly as cold to the touch on long winter nights.
"After installation, I immediately noticed the knob was much more accessible than the smaller stock knob. I was able to easily reach down while looking in the eyepiece and find the knob. It really gave me much more control on the fine adjustment that’s needed in viewing and astrophotography... I could use my thumb to slowly move it. It was much easier to brace my hand on the mount and slowly move the knob with my thumb. This helped minimize the vibrations during focusing... Overall I would say this is and excellent replacement for the stock knob and makes focusing the [ETX] much less tedious and much more enjoyable."
"Nice work, classy black plastic... The present size and “gear” teeth do make focusing at high elevation a whole lot easier than trying to squeeze a couple fingers in there."
If you're interested in purchasing, the cost is $15 USD shipped free within the CONUS. The package includes one knob, a stainless steel setscrew, and an allen key. Feel free to PM me for details, or if you have any questions.
Thanks and credit to the members of the ETXAstro forum, Cloudynights, and Thingiverse user RobertCL. Adapted from original design and re-distributed under Creative Commons license, CC BY-SA 3.0.
Thanks for reading!
- Location Pasadena, CA