Skip to content



Why a Drying Agent?

If you do not want your expensive optics, optical accessories, eyepieces, CCD cameras or the interior of your telescope tube to suffer from humidity when in their closed containers, then it is recommended to take the same precautionary measures as is common practice in research labs with expensive instruments, placing a small bag or pouch of drying agent into the telescope tube or into the accessory cabinet.

This can help to prevent the extremely annoying build up of condensation in the interior of eyepieces, telescope lenses, mirrors or Schmidt corrector plates – especially if one can prevent fresh humidity getting into the telescope tube later when changing accessories by the use of a prism diagonal or a plain glass filter to keep the telescope tube closed.


  • We offer a 2" filter holder for SC telescopes into which any 2" filter can be inserted (e.g. clear glass, UV/IR cutting filters, nebula filters UHC-S) to prevent moisture from getting into the interior of the tube.
  • Narrowband Solar filters ( LUNT, Daystar H-alpha, SolarSpectrum, etc.) are particularly susceptible to moisture.

Baader Silica gel with coloured indicator:

After some searching, we have discovered a particularly reliable drying agent which is foolproof. in indicating its remaining effectiveness…

  • The beads of drying agent are a bright orange/pink colour when dry, but are white and transparent when saturated.
  • The beads become paler in the transitional phase, so that you can easily estimate the level of saturation.

    To re-use, simply put the beads on a plate, put the plate into an oven and slowly heat it up to a temperature of around 150 degrees Centigrade (do not pre-heat the oven as this can cause the beads to burst). After about five or six hours, the silica gel is once again bright orange/pink and may be used further.

    WARNING: Drying in a Microwave oven is NOT possible.

    This procedure can be repeated indefinitely. Nothing needs to be thrown away, as is unfortunately often the case with normal drying agents.