The Astronomical Unit


This page last modified 2012 December 17

A Simple Telrad Dewshield

fitted dewshield

Telrads and Dew

Telrad reflex finders are notorious dew-magnets: the screen is completely open to the sky. The commerically available dew-shield needs to be flipped out of the way in order to make the finder usable and, when flipped, obstructs access to the adjustment thumbscrews (only an issue if you use your Telrad on more than one telescope).

A solution is to make a simple "flatpack" one out of 2mm foam sheet or similar.



  1. Download and save the 2 parts of the pattern:

    Part 1    Part 2

    Print them out full size from your graphics programme. (Do not do this from the browser: it will probably resize them. If you don't have a graphics programme, get The GIMP; it's free and it works.)

  2. Cut out both parts of the pattern.

  3. Butt them together along the inside edge and use adhesive tape to hold them in place.

  4. Place the pattern on the dewshield material, mark around it, and cut out the material. A sharp utility knife or craft knife on a cutting board works best, but you can use scissors.

  5. Cut the Velcro to length according to the pattern.

  6. Stick the hook part to the Telrad:
    telrad LHStelrad RHS

  7. Stick the loop part to the dewshield:
    dewshield flat

  8. Fix the dewshield to the Telrad.

  9. Enjoy a night's observing with a dew-free Telrad

In Use

This dewshield is far longer than many other DIY ones; this makes it very effective at preventing dew, even on the really dew-soggy nights of southern England.

The rearward extension helps with eye-positioning and will also act as a glare shield if there are lights around.

Update: 2012 Dec 17: In some circumstances, I have found that the sticky-back Velcro becomes detached from the dewshield material. You may need to stitch it in place for added security. (I have had no incidences of the Velcro becoming detached from the Telrad body.)