Sky-watcher Heritage Focus Mod Adapter V2
This is my 3rd version of an adapter to fix the crappy focuser on the Heritage series of Skywatcher Telescopes. This one uses the existing threads of the helical focuser instead of V2 which used a press fit, and in my case, epoxy. V3 screws right on and then the helical focuser screws onto it. I've added knurling to help tighten right down and remove if necessary. I used PLA for this version although PETG might be preferable. I may print a new one in PETG in the future.
The clips to shorten the truss tubes consistently can be found in my previous make. These should definitely be printed in PETG. There are a few lengths, but V3 ideally only needs the 14mm version.
The original press fit version can be found here:
https://www.printables.com/model/1379834-skywatcher-heritage-focuser-mod-adapter
Parts needed for either version (V2 or V3):
https://a.aliexpress.com/_Ez1Ui1G
Original Description Below:
I was inspired by what was made on Dobsonian Power, but didn't like the compromise of the added length to the focuser, plus I couldn't find the adapters he used, nor wanted to buy so many different parts.
My first attempt used a 39mm-90mm, M52-M42 focuser, but it was just a little too tight to get a solid print between it and the existing focuser tube. Plus it was too long for what was needed to focus (it didn't come right down to the end of the tube, wasting space and extended way longer than was needed to focus any eyepiece I use.
Italics below is now deprecated information relevant to version 2. I continue speaking about V3 further down.
Version 2 uses a M58-M42 focuser that is a shorter 25mm-50mm that has room for a nice solid print and the eyepiece holder is right up against the end of the existing focuser tube at it's shortest length. It fits around the existing focuser tube and uses this https://a.aliexpress.com/_Ez1Ui1G helicoid focuser that fits around the tube to minimize the amount of distance added to the end of the new focuser. It still adds approximately 30mm of length which will need to be absorbed by not extending the truss tubes fully.
The info below is now deprecated information relevant to version 2.
It fits quite tightly and needs to be massaged into place, but it holds itself on quite nicely without anything else but I epoxied it on anyway. It fits so tightly that it is basically self-aligned to what the existing focuser is collimated to already.
Once on, the original focuser can still be used by removing the helicoid focuser from the 3D printed adapter, which was one of my goals so that I didn't destroy the existing system should I want to revert to it for some reason. I definitely don't want to do that, although I had to last week as I was using it in -30C and the helical focuser froze right up, so I removed it and went back to the original...which eventually frosted up and wouldn't move as well.
The V3 can also be removed by just threading it off, which was part of what drove me to make a 3rd version as it's easier to add and remove.
Here is the eyepiece holder I use:
I've also modified a set of clips for the truss tubes I found to stop them from extending the last 30mm so that the collimation stays consistent every time when not extending them fully. I've attached those as well. I did base them on someone else's design directly from their website, but I have no idea how to attribute it to them properly.
PS, they're only printed in clear PETG (V2) because the black ran out during my testing and my printer glooped the remainder when the bed adhesion failed, new printer that I haven't fully calibrated yet. It's basically entirely hidden by the focuser anyway. I'll redo the clips at some point in a less ugly colour, lol.
EDIT: I ordered a new eyepiece holder from AliExpress that is significantly shorter than the original one I used and was able to reduced the difference between the original focuser minimum and the new minimum distance to 21mm. So I've included a new file for a shorter, 21mm truss shortening clip to match.
RE-EDIT: I forgot to allow for the 7mm depth of the original eyepiece holder, so it's actually a slight 14mm from where the original focuser top sat, to where it now sits with my focuser design, which is pretty much a close as anyone is going to get without cutting the tube I think. I've now added a 14mm clip file as well, although it's getting to the point where a clip might not even be needed anymore.
Clear Skies!