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robsch

Customizable Helical Crayford Focuser for Newtownian Telescope

by robsch Dec 4, 2016
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Nice design, I was wondering though, what diameter tube this is made for. Thanks.

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Hi,I like your design,but there is a problem,I want to change to 2",so I opend customizer app to change some infomation,but there shows" We're sorry, but something went wrong" failed many times,but another design of yours is no problem,something wrong with the file?

Ok, there's definitely something wrong with the customizer app. Others are complaining, too, but some see better results with different browsers. However, you can create a 2" version on your own without the customizer app: download openscad and the required libraries (see description). All customizer parameters are at the top of the source file, where you can change them manually. If you simply want a 2" version, it's sufficient to change drawTubeMaxOuterDiameter. Don't hesitate to ask if anything is unclear.

It works,I download a Openscad,this problem solved,thanks

I want to try printing this one, but on my telescope, the location of the 3 screws is different. On yours, you've got one screw on the longest side and the other two screws 60 degrees off of that. On my scope, one screw would go on the shortest side and 60 degress off that. Would it be possible to get a version with the holes rotated around 90 degrees from their current positions? I'm downloading Fusion 360 and can try to make the attempt myself (Solidworks just isn't in my budget), but didn't know if that might be an easy change.

Hi, in fact it is quite simple to change the orientation. I added a variable in the Open SCAD source file and made it available for the customizer. Simply click on "Open in Customizer" and change telescope-adapter/Tube Screw Orientation to 90 degrees. This will give you a new model with the correct positions for your telescope. Depending on your printer, you may want to change some other variables there, too. If you actually print the focuser for your telescope, please share a photo!

Thanks much! I'll try to print it next week. I've got to order the bearings and modify the scope a bit. The existing scope (Astromaster 130) has a reuleaux triangle shaped focuser (instead of circular) and a plastic housing to match it

I've also got a question as to how well the adapter bolts onto the OTA? The screws don't point to the center axis of the cylinder (well with the screws rotated 90 degrees one of them does). Since the screws are not perpendicular to the tangent of the OTA, the bolts won't sit flush against the tube.

You're right, the screws are not perpendicular to the OTA. This is not ideal, but sufficient. Actually, the original focuser that came with the telescope had the same orientation and position of the screws, and the manufacturer didn't mind either. But obviously this becomes more problematic with smaller OTA diameters.

Well, I took the existing focuser off this weekend to get the measurements for the screws and found that they are not an equilateral triangle. So they aren't ever going to line up...

Too bad! If you get the correct measurements, you could still try to change the model in OpenSCAD. Maybe the existing focuser is shaped in a way that makes it easier to measure the distances of the screws than on the OTA.