Solar Observing

With the Solar Eclipse in Northern Australia less than a week away, it is time to talk about Solar Observing. I have been busy making more filters and investigating activities about the Sun. Here in Melbourne, we will have a partial eclipse of around 50% of the Sun being blocked by the moon. Just to get you thinking…What do you think life would be like if the Sun was only 50% of it’s brightness all the time? Let me know your thoughts.

Firstly, the warnings which should never be taken lightly. It is so tempting to look straight at the Sun, but many people do not realise, especially students, how dangerous it is and how quickly irreparable damage can be done. It is even more tempting when you are trying to align a telescope at the Sun.

  • NEVER look at the Sun without an approved filter.

Sunglasses, welding masks, and other suggested alternatives to Solar film should not be used. Even if you do have an appropriate filter, you should never prolong your viewing time.

  • ALWAYS use a solar filter on the telescope or use Eclipse glasses.

The solar filter should be fitted onto the mirror end of the telescope. If light from the Sun is allowed to enter the telescope, the mirrors and lenses are likely to heat up enough that they will shatter, let alone damaging the eye of anyone observing through the telescope.

  • ALWAYS check the filter and glasses before use with a strong torch to ensure there are no scratches or holes in the filter.

If there are scratches, dispose of the filter immediately.

  • ALWAYS remove the finderscope from the brackets attached to the telescope.

If the finderscope is left on the telescope, it is also looking at the Sun and you may inadvertantly burn a hole in your shoulder or the person standing behind you. The round brackets that hold the finderscope can also be used to align the telescope with the Sun!

There are a number of ways you can safely look at the eclipse without directly looking at the sun if you are unable to obtain a Solar filter or glasses;

Pinhole camera with viewing times on the sheet from Paul Floyd

Strainer (this effect can also be seen on the ground from the shadows from the leaves of the trees)

Telescope Projection 

The ASA Factsheet on the 2012 Solar eclipse also talks about these methods.

Aligning the telescope during the day.

It is much more difficult to align the telescope during the day as we can’t see the stars to align the telescope. Not only that, but often the Sun is not listed as an object due to safety reasons.

Here is my method for aligning the telescope and tracking the Sun;

  • Remove the finderscope, but leave the brackets, we will use these to determine the correct direction.
  • Place the solar filter on the end of the telescope.
  • Now set your telescope up into it’s usual home position – facing North and level in Australia using an AltAz mount.
  • Perform the usual alignment process – one or two star – with stars in the sky at the time – use Stellarium with the atmosphere turned off so you can see which stars are in the Northern sky at the time. I suggest Betelgeuse and Spica – but you won’t be able to centre the stars in the telescope, so just hit ENTER.
  • Now head to a star that is in the vacinity of the Sun, we used Zuben Elgenubi, or on the day of the Eclipse you can track the moon.
  • The alignment is probably out, so to ensure the best tracking, manually move the telescope around until you are in the right direction, it should be the right altitude you will just need to alter the azimuth position, you can use the shadows of the findersope brackets for this. The smaller the shadow, the better alignment. When you are pretty close, you can use the handset to do the finer adjustments.
  • The last thing to do is to focus the image.
  • For the 12″ telescope we recommend using the focal reducer and the 40mm eyepiece as the image too large otherwise.

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