Spacers

Spacers are tubes to put between the scopes last lens element and the camera. This distance to cover is in many cases 55mm but depends on the telescope, extra elements like filters or reducer.

Very extensive information about the spacers is here.
I bought them at Ganymedes in Amstelveen in The Netherlands.
Spacers and specific set of Celestron spacers.

Spacers in the optical train

My inventory of parts and spacers with their extension sizes:
ZWO ASI2600MC PRO camera with tilt plate 17.5mm ZWO Filter holder: camera side 42M - 48F 21mm
Filters: 0,33mm per mm filter thickness.
Altair quadband type F200QUAD-V2-0074-0622 2mm thick = 0,7mm spacer
Artesky rotator 48 M&F 13.5mm
Spacers:
M48 M&F: 5, 5, 10, 20, 30
M42 M&F 21mm
M42M -> M48F 16.5mm
Adapter ring 48->42 (2x)
T-adapter M48 M 14mm (connects optical train to telescope or reducer)
I'm about to acquire the ZWO Camera Angle Adjuster (CAA) with 16.5mm spacing.

Telescope Celestron EDGE HD 8”
Native 133mm backfocus
With 0,7 reducer 105mm backfocus

The order of the sizes is the order of the optical train:
Camera - filter holder - (filter) - (CAA) - Rotator - Spacers - T-adapter
The rotator is needed to position the CAA in such a way that is doesn't get in the way of other parts.

Native 133mm backfocus:
17.5+21+13.5+30+21+16.5+14‎ = 133.5 no filter
17.5+21+0.7+13.5+30+20+10+3+3+14‎ = 132.7 with filter
With CAA:
17.5+21+16.5+13.5+10+3+21+16.5+14‎ = 133 no filter
17.5+21+0.7+16.5+13.5+30+15+5+14‎ = 133.2 with filter

With 0.7 reducer 105mm backfocus:
17.5+21+13,5+30+10+14‎ = 106 no filter
17.5+21+0.7+13.5+21+16,5+14‎ = 104,2 with filter
With CAA:
17.5+21+16.5+13.5+3+3+16,5+14‎ = 105 no filter
17.5+21+0.7+16.5+13.5+10+5+3+3+14‎ = 104,2 with filter

Parts that I am missing for the fine tuning:
3mm x M48 = €21
15mm x M48 = €23,50

This is the Celestron Spacer Set. I sent it back as the adapter ring from 42 to 48mm is wider than the tube so when screwing it into a 48mm tube with a long thread it won't stop at the required point.
7,5mm x M42 = part of Celestron set
12mm x M42 = part of Celestron set = €59,95
30mm x M42 = part of Celestron set