How to connect the DSI to a Meade LX200 Telescope

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How to connect the DSI to a Meade LX200 Telescope

with the microfocuser and a Meade f/3.3 CCD focal reducer/field flattener
by Mike Luckow

The parts are intended to be connected in the following order:

Visual back " MF " SC Adapter " FR " T-adapter " DSI

  • MF: The microfocuser.
  • SC Adapter: The SC Accessory Adapter that comes wrapped up separately with the LX200 scope, NOT the 2�? " 1.25�? adapter that came installed in the microfocuser. It’s the one marked “L�? on page 5 of the LX200GPS Instruction Manual. The front end of this adapter is 2�? in diameter and smooth, and the back end is threaded, just like a 2�? visual back. The front end goes into the microfocuser, and the back end screws on to the focal reducer.
  • FR: The Meade f/3.3 CCD focal reducer/field flattener, which comes with a T-adapter.
  • T-adapter: Consists of three parts: a T-adapter ring, a 30 mm T-thread spacer, and a 15 mm T-thread spacer. Only one of the T-thread spacers should be used; the other should be removed. For telescopes with a focal ratio of f/10, the 30 mm T-thread spacer is used to produce f/3.3, and the 15 mm T-thread spacer is used to produce f/5.
  • DSI: Has a 1.25�? nosepiece that can be unscrewed. Under the nosepiece is a very fragile infrared filter glued to a circular piece of glass.


  1. Leave the microfocuser connected to the visual back.
  2. Set up the T-adapter so it has only the T-thread spacer that produces the desired focal ratio. To get f/3.3 with an f/10 scope, use only the longer (30 mm) spacer.
  3. Screw the focal reducer and the T-adapter together. They should be tight enough that the T-thread spacer does not spin freely in the T-adapter ring.
  4. Carefully unscrew the 1.25�? nosepiece from the DSI, being careful not to drop or touch the infrared filter glass inside. Screw the T-adapter into the DSI where the nosepiece was, being careful to keep the infrared filter in the proper position, aligned over the hole. Do not screw the T-adapter on too tightly or it may break the infrared filter glass.
  5. Next, screw the threaded end of the SC Adapter into the focal reducer.
  6. Remove the 2�? " 1.25�? adapter that came in the microfocuser, and insert the smooth end of the SC Adapter (which is now connected to the focal reducer, T-adapter, and DSI) into the microfocuser, with the connector jack on the DSI pointing towards the right side of the telescope. Tighten it securely.
  7. Connect the DSI to a computer using the USB 2.0 cable.

You’re all set! Good luck!

This isn’t the only way to connect a DSI to an LX200. There are many different ways, and they all apparently produce different results. However, this (I’ve been told) is the “recommended�? configuration to minimize vignetting and increase chances of getting good photos.

If you have any comments or corrections, please let me know at: mluckow at comcast dot net (I need to write my email address in this form here to prevent spam software from finding me).

Many thanks to Mike Sabina, Chris Taylor, Kurt Massey, Chuck Reese, Pete at, and others in the Yahoo DSI groups for providing help and information.

Mike Luckow © 2005
Boulder, Colorado
Meade 12�? LX200GPS-UHTC, Peterson Equipped

Published on Sky Insight with the author's permission.