I have been working in my spare time for the last 6 months developing a better combination tool. I think I am now at the point where I can share this with the community. There have been many hundreds of hours spent on the tool and more than 30 revisions of this tool have been manufactured and tested. I would like to thank CN member Kipper-Feet for his input and help testing multiple revisions of my collimation tools. Note: the results of collimation with this tool have been checked against a well aligned laser (Farpoint), Cheshire (Farpoint), Combo tools (Orion USA, Celestron), and other tools. The tool will meet the focuser axis error requirements and primary axis error requirements for telescopes between F/4 and F/6 (it is recommended that those using coma correctors get an accurate laser for alignment of the secondary mirror).
This tool combines the features of a variable length sight tube, combination tool (crosshairs), Cheshire, and collimation cap. While it has some of the features of each of these tools, it combines all of the best features of each tool. In its current form, the tool is 3D printed with an aluminium 1.25" barrel. Why do you ask does it have an 1.25" barrel? It is intended to be used on telescopes having a 1.25" focuser. It is also intended to be used with a centring adapter like the Glatter Parallizer such that, in 2" focusers, it will well centred and aligned to the focuser axis by the adapter (I have an adapter tool in development that achieves similar centring and alignment) making a 2" version unnecessary. As such, it is intended to be universal for both 1.25" and 2" focusers.
NOTE: There are slight errors visible in the collimation images below due to the photography technique.
The sight tube portion of the tool is extendable.
Long (F/6 Telescope)
Short (F/4 Telescope)
This variable length is achieved through a movable tube that includes the cross hairs. The tube is held in place at any length by friction with the outer body.
The tube can be removed at which point the upper portion becomes a Cheshire/Collimation Cap. The reflective ring in the Cheshire can be manufactured with a 19mm diameter for triangular mirror markers and with a 14mm ring for standard telescope manufacturer's round mirror markers (triangular version below). Because the surface is also printed in light grey and the pupil is small, the tool can also be used as a collimation cap. A flashlight can be used to illuminate the Cheshire ring via the cut-out.
With the sight tube in place, the peephole view is as shown in the image below. With the sight tube portion in place, it is easy to see that the secondary mirror physical outer diameter edge is concentric to the tool inner diameter (concentric to the focuser) and the primary reflection is concentric to the secondary. By changing the overall length of the tool and varying the position of the peep hole to a position slightly below the apex, the tool can be set to be used for telescopes from F/4 to F/6. Additionally, the crosshairs will allow for alignment of the secondary mirror by aligning the crosshairs to the middle of the primary mirror marker using the secondary alignment screws.
With the sight tube portion removed and a flashlight shining in the cut-out, the mirror marker and reflective ring of the Cheshire are clearly visible. Additionally the black dot of the eye's pupil through the tool peep hole is also visible. The primary mirror can be aligned using the inner diameter of the reflective Cheshire ring to centre the mirror marker or by centring the black dot of the peep hole/pupil in the centre circle of the mirror marker.
In summary this Ultimate Combination Tool can be used for all steps in collimation for telescopes with focal ratios from F/4 to F/6:
1) Centre and round the secondary as a sight tube,
2) Align the secondary as a combination tool,
3) Align the primary mirror as a combination tool, Cheshire, or collimation cap.
Thanks for reading.
All the best