Sunday 10 March 2013

Observing sunspots with a camcorder and home-made filter

The moment I saw a TV demonstration of how to view the sun safely with a simple, affordable home made filter, I knew I had to have one. Observing the sun has always had its fascination for me. It is our nearest star and we are entering a period of increased sunspot activity. In the past, I had been able to film the sun at high magnification, simply on a camcorder. However this was at sunset when its brilliance was greatly diminished.

The video below shows how I made a filter and used it to record sunspots on a Panasonic HC-V700 camcorder. If you have problems viewing, go to

WARNING: do not look at the sun directly by naked eye or through any type of telescope etc, even when using filters as you can damage your eyes.

The almost magical material is a thin film that cuts out 99.9% of light passing through it. AstroSolar (TM) is made by Baader and it arrived as an A4 sheet by post after ordering on Amazon a couple of days later.

Useful instructions to make a sun filter that could be slipped over the front of a telescope barrel were included. My problem was going to be the fact that camcorders do not have much of a barrel. There was a simple solution.

To make my filter:

  • I first cut out two equally sized squares of stiff cardboad, about 10cm x 10cm.
  • I then drew diagonal pencil lines from opposing corners on each card, to find the centre.
  • My camcorder front lens aperture was about 4cm.
  • I therefore cut out a 4cm diameter disc from the centre of each card, using a circular cutter.
  • The A4 Astro Solar film was sandwiched between two sheets of paper to protect it.
  • Using scissors, I cut out a square of about 6cm x 6cm from the paper-film-paper sandwich.
  • The side of one of the pieces of card was coated with glue from a glue stick (Prittstick).
  • The glue covered card was placed sticky side uppermost on a table.
  • The AstroSolar film square was carefully placed on the glued card, completely covering the 4cm diameter hole.
  • The second piece of card was then placed on top of the first card and film.
  • I now had a Card- Film-Card sandwich with the filter exposed where the card had a hole.
Frustratingly, it was another few days before cloud cover broke and the sun shone through and I could try out the new filter with my camcorder.

To use the filter on the camcorder, I made a roll of Blutack and placed it to create a ring on the cardboard, around the filter aperture. The camcorder face was then pressed gently and accurately onto the Blutack to create a light-tight seal.

Mounting the camcorder onto a tripod, I dashed out of the house and prepared to record the sun. Despite there being a light high altitude haze that might blur any sunspots, I had a go at finding them.

Using the Panasonic HC V700 to zoom in on the sun's disc, I could see two faint islands of sunspots. These corresponded to those numbered 1683 and 1686 on the daily images from the Solar and Heliospheric Observatory


Modern camcorders can have a sufficiently good optical and digital zoom to observe sunspots with an appropriate filter!

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