Takahashi Wide Mount T-Thread Spacer 38.5mm for Starlight Xpress & SBIG

Product Overview

The TCD0385 is a fixed-length spacer that sits between a Takahashi reducer's M54 output and a T-threaded camera. It carries male 54 mm (0.75 pitch) threads on the reducer side and 42 mm male T-threads on the camera side, and it takes up 38.5 mm of back focus — the figure the part number encodes. Takahashi describes it as approximately 2 in long and 2.5 in in diameter.

Takahashi lists it for Starlight Xpress and SBIG cameras, whose wide mount plates are what the "wide mount" in the name refers to.

Who It's For

This is a good match if you are connecting a Starlight Xpress or SBIG camera to a Takahashi reducer with an M54 × 0.75 output and the spacing chain calls for 38.5 mm in that segment.

Key Features & Design

• 38.5 mm of back focus consumed: a fixed, known quantity in the spacing chain rather than something to shim.
• Male M54 × 0.75 on the reducer side: the thread Takahashi uses on the reducer output.
• 42 mm male T-thread on the camera side: the standard T-thread interface a camera adapter or wide mount plate lands on.
• Approximately 2 in long, 2.5 in in diameter: Takahashi's own figures, both stated as approximate.
• Mechanical only: no optical elements — it sets distance, nothing else.

Recommended Uses

Deep-sky imaging with a Starlight Xpress or SBIG camera behind a Takahashi reducer, where the reducer's published metal-back figure has to be met and 38.5 mm of it belongs to this segment of the train.

Compatibility and Accessory Notes

Takahashi names the cameras — Starlight Xpress and SBIG — but does not publish a list of the reducers this pairs with beyond the M54 × 0.75 thread it lands on. Tell us which Takahashi reducer and which camera you are joining and we will check the full chain against the reducer's metal-back figure before you order.

The 38.5 mm figure is the useful one when you are adding up a train: it is what this piece spends, not what is left over. The rest of the reducer's published metal back has to be found in your camera's own sensor depth, filter wheel and any adapter plate between them.

Good to Know Before You Order

The length figures are approximate: Takahashi publishes the 38.5 mm back-focus contribution exactly, and gives the physical length and diameter only as "approximately" 2 in and 2.5 in. The 38.5 mm is the number to build the spacing chain on.

Physical length and optical contribution are different numbers here: the threads recess into the mating parts, which is why a roughly 51 mm part contributes 38.5 mm.

Mechanical only: there are no optics inside, so it changes distance and nothing about focal length, focal ratio or field correction.

It is a fixed length: there is no adjustment. If your chain needs a different figure, that is a different part, and we can work out which one with you.

Frequently Asked Questions

Is it difficult to set up?

No — it threads onto the reducer and the camera adapter threads onto it. The work is in the arithmetic beforehand, confirming that 38.5 mm is the figure your chain needs in this segment.

What does "takes up 38.5 mm of back focus" mean?

Your reducer has a published metal-back distance from its rear face to the sensor. This spacer accounts for 38.5 mm of that distance; the remainder has to come from the camera and anything else between them.

Which cameras is it for?

Takahashi lists Starlight Xpress and SBIG. The camera-side interface is a 42 mm male T-thread, so what matters in practice is whether your camera's adapter accepts that.

Which reducers does it fit?

Takahashi publishes the thread — male M54 × 0.75 — rather than a reducer list. Send us your reducer model and we will confirm it.

Does it have any optics in it?

No. It is a mechanical spacer.

How do I know my whole train adds up?

Send us the reducer, this spacer, your camera and anything in between, and we will total it against the reducer's published metal back.

Bottom Line

A fixed 38.5 mm Takahashi spacer taking a reducer's male M54 × 0.75 output to a 42 mm T-thread camera side, for Starlight Xpress and SBIG cameras. Its whole job is one known number in the spacing chain, and we are happy to check that chain with you.