When purchasing the QUADTCC you must add the proper length backfocus spacer extension according to the chart below in order to achieve the required 80.8mm spacing.
If you have a TEC scope, you will also need to order a Drawtube Endcap (S35RFAA) for the focuser. This only applies to the TEC focusers. This part is integral to the Astro-Physics 3.5" focusers and is not needed as a separate purchase. The S35RFAA screws onto the drawtube's 4.100" x 24 thread (same as Starlight Instrument's 3.5" focuser endcap thread).
||Length of Extension
||Spacing with 3.27" Extension
||Spacing without Extension
|AP 130 GTX
||EXT327-22.1 (formerly A5020)
||EXT327-18.3 (formerly A2680)
||EXT327-17.0 (formerly A5022)
||EXT327-16.0 (formerly A5023)
||EXT327-34.1 (new in May 2021)
If you own more than one scope that can use the QUADTCC, simply substitute the required backfocus spacer extension for each instrument. All other components in your imaging train can remain the same since you will have achieved the correct backfocus spacing.