The Moon moves across the face of the Sun on 10 June 2021, leading to a solar eclipse as seen from Earth. Along a narrow path running through Canada, Greenland and into Russia the Moon’s disc appears to fit within the disc of the Sun to produce an annular eclipse; the ‘ring of fire’.
Away from this path an ever-decreasing magnitude of partial solar eclipse will be seen until, when far enough away from the path, the Moon will appear to miss the Sun altogether, giving no eclipse experience whatsoever.
For more solar astrophotography, read our complete guide on how to photograph the Sun.
From the UK we do get to see some of this event as a partial solar eclipse, and those who live in the northwest will get the best seats.
Photographing the partial eclipse is an interesting project. During a total eclipse of the Sun, the time around totality allows you to take images through an unfiltered camera/lens/telescope setup, but where a partial solar eclipse is concerned, as is the case on 10 June, a certified solar filter must be used at all times.
Photographing an eclipse using solar projection
A screen is held up to catch the bright light emitted from the eyepiece and with a bit of careful focusing, a detailed Sun image can be projected onto the screen.
This image can be safely watched or captured, but there are provisos.
Projection has associated dangers. It’s a technique only suitable for refractors below 5-inches (127mm) in diameter.
People use reflectors to project the Sun’s image, but there is a potential for damage to be caused to instruments.
Enclosed optical tubes such as those found in SCTs are unsuitable for projection due to internal heating.
If you do go down the projection route, never leave the setup unattended and keep everyone’s eyes away from the eyepiece!
Photographing in white light, hydrogen-alpha, calcium-K
A full or offset aperture white light filter allows you to view and photograph a dimmed version of the Sun safely during the eclipse.
Such telescope filters are normally bought as a sheet or roll and, after a bit of DIY, cover the front aperture of your telescope. Once you’ve capped or removed all finders, you’re good to go.
You can also use hydrogen-alpha (Ha) or calcium-K (CaK) solar filters. These are ideal for grabbing a less conventional image.
Using an Ha filter, you can check for solar prominences and it will allow you to view a ‘fur-like’ edge to the Sun’s chromosphere known as the spicule layer.
Furthermore, a magnified view of the section of limb where the Moon first makes contact or leaves the Sun’s disc will allow you to catch the edge of the Moon as it crosses this strip.
Photograph the 10 June eclipse: step-by-step
You Will Need
- High frame-rate camera
- Telescope with certified solar filter
- Equatorial mount
- Decide on the setup you want to use to image the eclipse: white light solar film, projection, a Herschel wedge (a special prism arrangement that allows heat to be directed away from the eyepiece), and speciality solar filters such as hydrogen-alpha (Ha) and calcium-K (CaK).
- Research how to use these methods properly before the eclipse.
- Select a camera. A DSLR works fine for white light, but it’s less effective with Ha or CaK wavelengths. DSLR still images will be affected by prevailing seeing, the effects worsening with increased image scale.
- A mono high frame rate camera gives crisp results, but captures need to be short to avoid blurring from lunar motion.
- Get to know the view orientation to catch the beginning of the eclipse (first contact) at high image scale. Equatorial telescope mounts are easiest for this, but it also can be worked out for altaz mounted equipment.
- The free software Tilting Sun shows how different mounts will affect the view of the Sun.
- For equatorial mounts, moving a telescope south in declination means the last edge of the Sun visible is the southern limb. Slewing east in RA, the last edge visible is the eastern limb.
- The position-angle measures the number of degrees from north (0°) travelling east (90°), south being 180°, west 270°. First contact occurs at 290º.
- If using an equatorial mount, set it up on nights before the eclipse to ensure accurate polar alignment.
- Practise photographing the Sun in the run-up to 10 June.
- Using control software, ensure your high frame rate camera’s exposure level isn’t saturated, but 80-90% peak. Aim for a rate of over 60 frames per second.
- Set up early on 10 June, say from 09:00 BST (08:00 UT).
- If using hydrogen-alpha equipment, remember first contact will occur a bit earlier than for white light due to prominences/spicules along the Moon’s path.
- Keep capture sequences short, say 10-30”. For the time of first contact see timeanddate.com.
If you do manage to photograph the 10 June solar eclipse, we’d love to see your image! It could even end up in the next issue of BBC Sky at Night Magazine. Find out how to send us your images.
Pete Lawrence is an expert astro imager and a presenter on The Sky at Night. This guide originally appeared in the June 2021 issue of BBC Sky at Night Magazine.