The following set-up description is an update of the former configuration of my Esprit 100ED. In the meantime numerous details have been modified. Beneath the request for a better Focuser the weight should be less as possible without performance restrictions.
The Telescope
The Scope is basically the same as before, but some update have been applied:
- Replacement of the original Skywatcher Focuser by a Feather Touch 3035.
- New focus drive.
- Replacement of guide scope by off axis guider.
- Replacement of the electronic box, which was part of the guider by a smaller one
- All alloy parts are now anodised black.
The Focuser
Finally I replaced the good-but-not-perfect Skywatcher Focuser by a Feather Touch 3035. On of the best decisions I ever made in the context of astro gear. It is really a nice piece. Solid as a rock, backlash free, really rotatable and simply speaking: it is so good that you forget it! The photo shows it in my workshop already with the focus motor. Is is a NEMA14 motor with a 1:19 planetary gear (14HS13-0804S-PG19). It drives the shaft via a toothed belt directly. For the case that I come into the situation to use this telescope visual, I milled a guider bracket. In case somebody wants to build that thing the drawing is available. If you need a FreeCAD model then contact me.
Off Axis Guiding
I replaced the guiding scope with an off axis guider after my first tests showed excellent results. By this the numer of parts and weight reduces, which matches to my plans. I designed an off axis guider realising M68ix1 thread at the scope side and compatibility to Baader S72 at the camera side. The company Baader kindly supported with information regarding the S72 dovetail ring. So it was easy to design an OAG for my needs wich interface the Esprit at the entry and the Baader UFC at the exit. The drawings for the main body and for the tower with 1.25″ thread are linked. If you need FreeCAD models, please contact me.
The Image Train
Matching the proper distance of the focal plane to Flattener or reducer is of great importance for best photographic results. Usually for a given Flattener or reducer it depends on the telescope. So the task is usually to find the optimum back focus distance. Here I didn’t have to investigate to much into optimizing, because I knew the distance from the former scope set-up. So the main task here is to reproduce the known distance as good as possible and check it under the night skys.
In my experience the Esprit seems to behave with the riccardi even better than with the original flatenner. Hence the workhorse at the Esprit probably will be the ASI6200MC with the Riccardi.
The Image Train with Riccardi Flattener/Reducer
Adapter
The back focus distance for the Riccardi Flattener/Reducer is is 77,85 mm from the M75x1 thread. In order to bring the Riccardi to M68 I designed an adapter where the Riccardi is screwed into. The Riccardi itself partly vanishes in the Focuser tube and partly in the adapter tube. The adapter is screwed into the M75x1 of the Feather Touch. The picture shows the transparent adapter in pale green with the blue Riccardi and a read adapter ring with M63x1 thread at each side. The drawing is available here.
Set-Up
The photo shows the final image train with imaging cam and guiding cam. The distance had settled after some test runs. They are given in the table below.
| Pos. | Element | optical path / mm | connector at telescope side |
| 1 | ASI 6200 | 17,50 | M54x0,75 |
| 2 | Baader UFC M54 adapter | 2,00 | S72 |
| 3 | Baader UFC base | 13,00 | S72 |
| 1/3 of 3 mm UHC-S filter thickness | -1,00 | ||
| 4 | Baader UFC extension | 15,00 | S72 |
| 5 | DIY OAG S72/M68 | 23,00 | M68i x 1 |
| 6 | M63-M63 | 3,00 | M63a x 1 |
| 7 | adapter M75 auf M63 | 4,70 | M75ax1 |
| 8 | |||
| sum | 77,20 | ||
| Riccardi needs | 77,85 |