Here another DIY project, this time, a lightweight guidescope built by 3D printing.
Note: 3D modeling knowledge is needed.
The steps are quite simple:
1.Choose and buy a simple achromatic lens from Aliexpress. There are several options. I found a D:43mm F:130mm (f/3) that fit my needs, for 18€.
I recommend to paint the border of the lens in black to improve contrast.
2. Design the tube taking into account to respect the focal distance:
3. 3D print it, better in black. Anyway I suggest to paint it in matt black, outside and inside too, to increase contrast.
4. Insert the lens into the housing. The piece that I’m touching in the image is a second piece that fits into the tube and presses the lens. It acts as a dewshield also.
I recommend to glue the lens to the tube also to avoid it to move in case that the dewshiel/holder loosses.
Don’t design the threads (for camera fitting, for example), is better to make it later. Actually 3D printers don’t have enough accuracy to do a M4 thread, for example.
I used 2 screws to avoid misalignment of the camera.
Add ribs to increase stiffness. Make it wide enough to act as a housing for the thread (more thread lenght = more reliability)
You can design an attachment to the corresponding dovetail/plate of your telescope.
Mine has two knobs on the left side, so I made a housing for one of them to act as a rotation point and this let me to rotate the guidescope up and down in case that I have to search a better guide star.
And that’s it, mine weights 235g (lens and guide camera included). Very lightweight, and has no differential flexure at all. I built it with ABS, that is a polymer very rigid and has the paint has good adherence to it.
With this configuration I guide at aprox 9.5″/pix, being able to guide with 7th magnitude stars. Not a high resoltion guiding, but as told, you can choose any other lens to fit with your imaging resolution.