March Sky

I generally comment on the night sky in these posts, but the major astronomical event in March is the total solar eclipse on 20 March, so I am going to focus on that.

There are two types of solar eclipse – total eclipses and all the rest. It is a remarkable coincidence that the apparent diameters of the sun and moon are so similar that when they are lined up precisely in a total eclipse, the bright photosphere that is all we see of the sun most of the time is completely obscured, allowing the pink chromosphere that surrounds it, including prominences arching from it, and the wispy corona beyond, to be seen for a brief couple of minutes. It is an awe inspiring sight – once seen, never forgotten.

The March eclipse is for us in the UK the nearest chance to see a total eclipse since the 1999 event. The area where totality can be seen is a curving band that runs between Iceland and Scotland, crossing the Faroes, then Svalbard, and finally ending up at the north pole! As I understand it all accommodation on the Faroes was booked up long ago, but cruise ship companies are still advertising available space as part of an eclipse and northern lights offering over this period, so it is not too late to book a space. However, even if you can get yourself to the right place, you will be at the mercy of the weather for those vital minutes. For this reason, another option is a range of commercial eclipse watching flights above the clouds.

In the UK itself, we will only see a partial eclipse, which is still dramatic, but will have none of the special features I mentioned above. What you can see is the black disc of the moon gradually obscuring most of the sun’s disc, up to a maximum of about 88% in Bath (the exact figure varies across the UK), and then moving away again. The eclipse starts for us at about 8.23 am, reaches the 88% maximum at about 9.28am, and finishes at about 10.38am. The 2 hour period of the partial eclipse that we can see at least increases the chances of the weather being cooperative at least for some of the time!

The standard health warnings about observing the sun apply. The sun’s disc is extremely bright, and looking at it directly, even when partially obscured in eclipse, will damage your eyes, perhaps permanently, and looking at it through normal binoculars or a telescope will certainly do so.

There are 3 safe ways in which you can observe this partial eclipse:

– an internet search will reveal several sources of special solar eclipse observing glasses for a few pounds each. If you get them directly from a reputable source and they are undamaged they should be fine. You don’t need any magnification to get a good view of the gradual obscuring of the sun’s disc.

-another method is to use an ordinary pair of binoculars or telescope to project the sun’s image onto a piece of card. This is slightly awkward to do unless you have done it before, and of course you must avoid the risk of anyone looking directly through the instrument. You will also find that the eyepiece end can get very hot. A much simpler variant that will give you some sense of the eclipse is to use another piece of card with a pin hole in it in place of the binoculars or telescope – in effect making a pinhole camera.

– some astronomers will have specially adapted telescopes with special filters that can be used to observe the sun safely. But don’t be fooled if you have a telescope in the attic that claims to have a solar filter as an optional attachment. Many such devices sold in the past are dangerous, and should never be used to look at the sun.