5. Making a solar observation

There are many websites where you can see the latest images and data on solar activity. If you are going to make your own solar observations it is vital that you do not look at any of these websites before starting your observation. This is because looking at these websites will influence your observations and ruining them. Avoid looking at any solar activity websites until you have completed your own observation for that day and then you can compare what you really saw with your own eyes and what others saw. Never change your observations so the fit perfectly what is online. Be honest with your astronomical observations and record only what you saw.

Look carefully at the solar disc (either the projected solar image, or by using a full aperture solar filter over the front of your telescope). It will take a while for you to notice all of the sunspots that are visible, so be patient.

  • Are there any groups (clusters) of sunspots?
  • Are there any single large sunspots?
  • Are there any single small spots?
  • Where are they? Are they near the centre (the Central Meridian) of the solar disc?
  • Are they near the edge (called the limb) of the solar disc?
  • If any large sunspots are near the limb, do any of them look oval (called fore-shortening)?
  • If there are sunspot umbrae, are there any bright lanes of light through them? These are called  light bridges).
  • Are there any bright patches (faculae) near the limb? Are they on their own or (more likely) are they near sunspots?

If there are none, then we record this as a blank solar disc. If there are sunspots, count how many groups there are, then carefully count how many individual sunspots there are too.

If you have not done so already, start an observing book. Use this to record all your astronomical observations. Don’t record your observations on pieces of paper as these can become lost unless you put them in a ring binder or something similar. Over time your book will fill up and you can look back at them later. It also helps you develop as an observer if you make the right start.

In your observing book, write the date like this:  2014 November 5

then on the next line down add the time using the 24-hour format in UT like this: 1245UT

Next write the aperture of your telescope in millimetres and the type, such as: 80mm refractor

If you know the magnifcation of the eyepiece used, write it like this: ×75

A couple of lines down add the seeing conditions (how steady is the solar image?) and then the transparency of the sky (how clear is it? Is it hazy?) Excellent seeing means the image hardly moves, Poor seeing mean the image is moving so much the limb appears to “boil” and the sunspots go in and out of focus. Excellent or good transparency means the sky is clear and blue while poor transparency means you can hardly make out any sunspots on the Sun’s disk. If possible, use the scale on the SPA Active Region and Relative Sunspot Monthly Activity Form as a guide. Alternatively, write down the observing conditions as both these affect your observations.

Next write down the number of sunspot groups you saw. Then write down the number of individual sunspots you saw.

Note down anything unusual or interesting. The more you observe the Sun the more you will notice each time you do it. This will help you develop your skills as an observer.

Make some drawings if you wish. You can use our Solar Disk Drawing Blank template if you wish or you can create your own (just ensure the drawing blanks have a circle diameter of either 10cm or 15cm ideally and mark the N, S, E, W points and don’t forget the date, time of observation, equipment used and your name).

You can either make a drawing of the whole solar disc or draw individual sunspots. Use a fairly soft pencil (HB) to draw the sunspot lighter toned penumbrae and a very soft pencil (2B or 4B) for drawing in the much darker umbrae. You can either shade in the sunspot penumbra or draw the outline, whichever you find easier. The sunspot umbra are best drawn as dots, start small and increase the size of the “dots” so they match the shape and size that you can see in the solar image. If you make a mistake carefully erase with a rubber and try again. Don’t exaggerate your drawings but try to record exactly what you can see. A common mistake is to draw the sunspots far too big especially when you are trying to draw a section or the whole of the Sun’s disk. Add the date and time the drawing was made, the magnification, which way is north, and which way is east on your drawing.

An alternative to drawing sunspots is to draw prominences and filaments while observing in Hydrogen-alpha light. The drawing shown below on the left, was made by using a H-alpha Coronado PST. The prominences are shown in red, the filaments in dark blue. Bright areas of plages are drawn in yellow. The number written on the disk is the sunspot Active Region (AR) number. The image on the right is the Sun in H-alpha taken on the same day but a few hours later. If you line-up the north and east points they both agree well.

You can use the  SPA Active Region and Relative Sunspot Monthly Activity Form to record your counts on the days you observe. This form can then be used to calculate your ‘Mean Daily Frequency’ (average) for the month. We use these in our Activity Graphs so it worth doing. As you make your observations they will build up over time and then you will start to see the change in sunspot activity over time. You will be able to see for yourself the rise and fall of the 11-year sunspot cycle.

Something more advanced to attempt once you have the basics sorted is the classification of sunspots according to the McIntosh Sunspot Classification. If you fancy trying this for yourself then take a look at this guide on the Peter Meadows Solar Observing website. In brief, the McIntosh Sunspot Classification system, is based upon the older and somewhat simpler Zurich Sunspot Classification, and it allows you to record the size and complexity of sunspot groups as they come and go by using a three-letter shorthand ‘code’. The McIntosh system is not an easy one to learn, especially if you try using all three letters to classify sunspots but ultimately worthwhile as it add detail to your observations.  If the McIntosh system is too much to learn from scratch then try the Zurich Sunspot Classification first.

If you wish to take images of the Sun please take a look at our brief guide.

Next: Counting and recording activity for the SPA