Our nearest star can provide some of the most outstanding astronomical views
Astronomy is something you usually associate with the dark, so the Sun can be easily overlooked as an astronomical object for observation. However, with the right equipment and a simple safety routine, solar observing can be one of the most visually rewarding observation projects in amateur astronomy.
One of the easiest things to view is the sunspots on the Sun’s visible layer, the photosphere. It’s important to never look directly at the Sun through a telescope directly, as you can damage your eyesight. Likewise, you should never look directly at the Sun with sunglasses or darkened glass as these do not block out the most harmful wavelengths of light.
However, you can safely project the Sun’s image through a telescope. It’s usually a refractor as the intense heat can damage some other types of telescope. With the dust cap on your telescope to stop harmful stray light, place a square of white card behind the telescope eyepiece and adjust the scope until the instrument’s shadow is rounded on the card; only then remove the dust cap and the Sun’s image
should be projected onto the card. If not, adjust the telescope slightly until it appears but remember to never look down the eyepiece directly.
Using solar flters
White light observing is generally the study of the solar photosphere where dark sunspot groups are found and bright patches called “faculae” are seen more clearly near the solar limb. As an alternative to solar projection, you can also equip your telescope with a glass white light flter which will allow you to look directly through your telescope at the photosphere to see sunspots in fne detail. Such flters can be purchased from any reputable astronomy retailer and ft on the objective end of your telescope. If cost is an issue you can make your own, though it’s vital to use certifed solar safety flm and make sure the fnal flter has no holes or gaps in it.
However, it is the solar atmosphere or chromosphere where the real action takes place. This can be seen by using a special solar flter which only allows light through towards the red end of the spectrum known
as a hydrogen/alpha flter. Here you can see solar prominences, flaments, plage and fares.
Solar prominences extend from the solar limb out into the darkness of space and are vast emissions of hydrogen travelling along magnetic feld lines. Sometimes, the feld lines can loop back down into the chromosphere or break, ejecting plasma into space. Prominences can be short- or long-lived features but the really fascinating ones are the short-lived eruptive prominences that can almost grow and twist as you watch them in real time. Dark flaments can also be seen in this wavelength, streaked across the solar disk. These are actually prominences but seen as dark features across the bright solar disk rather than bright features seen against the dark background of space hence another name to differentiate them.
The only down side is that hydrogen/alpha flters can be very expensive to purchase. You can either buy a specialist solar telescope, or a kit to ft your existing telescope. These have both an energy rejection flter that will reduce the heat entering your telescope and a blocking flter for the eyepiece. Coronado and Daystar produce the cheapest hydrogen/alpha telescopes, around the £700–£800 mark.
A refractor can be used for projecting the Sun’s image onto a white card
A hydrogen/alpha flter allows you to enjoy amazing views of solar features in the chromosphere