Are you ready for the Partial Solar Eclipse on Oktober 25th, 2022?

World map of the solar eclipse on October 25, 2022.
© Ekkehard Domning

Every now and then, the moon moves in front of the sun and we experience a solar eclipse. In Europe, we will have to wait until August 12th, 2026 for the next total solar eclipse. It will be visible as a total solar eclipse e.g. from Spain, while the sun will remain only partially eclipsed from Germany.

Fortunately, we won't have to wait that long for the next partial solar eclipse: In the midday hours of October 25th this year, the moon will eclipse a third of the sun's disc. Observers in the north-east of the German-speaking region will have somewhat more of it than those in the south-west: on the island of Rügen, as much as 35% of the sun will be covered, in Switzerland only about 15%. At 82%, the greatest occultation will be seen from western Siberia.

In contrast to a total solar eclipse, where everyone waits anxiously for few minutes of totality, a partial solar eclipse is a rather relaxed event - over the course of (this time) about two hours, you can watch the moon move along in front of the sun.

Safe observing

With Astrosolar solar viewers Solar Viewer AstroSolar® Silver/Gold (1pc, 10pc, 25pc, 100pc) Solar Viewer AstroSolar® Silver/Gold (1pc, 10pc, 25pc, 100pc) (various versions available) , you can already see with the naked eye how the moon moves inch by inch across the sun. What is particularly impressive is that the rather low degree of occultation in Germany will otherwise hardly be noticeable: Our eyes compensate the drop in brightness quite good, so anyone who doesn't know that a partial solar eclipse is taking place may miss it. Those who do know, on the other hand, may notice certain differences in the mood of the light!

Using a pair of binoculars – which of course must be equipped with securely fitting solar filters in front of both lenses – will show you even more: Small binoculars with seven to ten times magnification are sufficient to show some the larger sunspots next to the lunar limb. These are cooler regions on the Sun that appear darker only because they shine less brightly than their surroundings - and are much larger than the Earth!

You can easily build a pair of lens filters yourself from AstroSolar® Safety Film OD 5.0 (ECO-size, 20x29, 100x50, 117x117 cm) AstroSolar® Safety Film OD 5.0 (ECO-size, 20x29, 100x50, 117x117 cm) (various versions available) and cardboard, or you can use ready-made ASBF: AstroSolar Binocular Filter OD 5.0 (50mm - 100mm) ASBF: AstroSolar Binocular Filter OD 5.0 (50mm - 100mm) (various versions available) , that are mounted onto the lenses and additionally secured with Velcro.

If possible, use a sufficiently high tripod like the Astro&Nature to observe in a relaxed manner: Through the solar filter you will only see black until you have the sun in the field of view. Therefore, it is not easy to find the sun in the sky! With a tripod, you can observe in a much more relaxed way and also have your hands free to protect your eyes against stray light. Ten times magnification is also about the limit to which you can hold binoculars steady in your hands. Looking at the midday sun, which is still quite high even in October, doesn't make it any easier to hold a pair of binoculars steady while pointing them upwards.

The event becomes even more impressive in a spotting scope or even a telescope: then you can see that the moon's edge in front of the sun's disk is not smooth, but jagged. Here you can see the mountains which rise above the edge of the moon. You only get this view in this clarity during a lunar eclipse.

For the best quality, you should use a ASTF: AstroSolar Telescope Filter OD 5.0 (80mm - 280mm) ASTF: AstroSolar Telescope Filter OD 5.0 (80mm - 280mm) (various versions available) ; owners of lens telescopes can also use a Herschel wedge.

The partial eclipse from June 10th, 2021, shot with an APS-C-camera at a focal length of ca. 1,5m. The irregular limb of the moon is good to see, and this year, we can expect more sun spots than in 2021 – the sun's activity is getting stronger. © A.Kerste

The partial eclipse from January 4th, 2011, shot with an APS-C-Kamera and a Baader Herschel wedge at a lens telescope with a focal length of 600mm. Let us hope that this year only the moon will block the view of the sun, and not clouds as well. © A.Kerste

On the sun, on the other hand, the solar granules become visible at higher magnification in addition to the sunspots: a network of countless gas bubbles over 1000 km in size that rise from the boiling interior of the sun, much like in a pot of boiling water. It becomes even clearer with the Baader 7.5nm Solar Continuum Filter (540nm) Baader 7.5nm Solar Continuum Filter (540nm) (various versions available) in addition to the AstroSolar Filter; it raises the contrast even more.

When can you see it?

With about two hours of time between first and last contact, there is no need to rush – but it is worth taking a look at the sun every now and then. After just a few minutes, you will see how quickly the moon passes in front of the sun.

The table gives the times in CEST for some cities in the German-speaking area:

Quelle: Wikipedia

For your own location, you can get an idea of the eclipse by viewing it in a planetarium app. For iOS and Android, SkyPortal Celestron SkyPortal is a free option, and for computers, Stellarium is also a free software and can be used either as stand-alone software (stellarium.org) or online at stellarium-web.org.

The peak of the eclipse at ca. 12:10, on the left in southwest Germany (Stuttgart, 21%), on the right in the northeast (Rostock, 33%). Simulations created with Guide 8, projectpluto.com.

Photography

Partial Solar Eclipse 2015, at Baader Planetarium

You can also mount a solar filter in front of a telephoto lens; the same safety instructions apply as for observation with the naked eye or through binoculars/telescope. As long as you photograph the entire sun, you can use the same film as for visual observation (i.e. filter factor ND5). The weaker photo film with ND3.8 is only for when you want to photograph details on the sun with long focal lengths (usually with eyepiece projection or a Barlow lens) and a video module.

If you use manual mode, a low ISO and short exposure times, plus a medium aperture (around f/8), then most lenses will produce the sharpest images – at smaller apertures (f/16, f/32) the exposure times only increase unnecessarily and the image sharpness is no longer optimal; at open apertures (f/1.8, f/3.5 or similar) the lens will also not work at the best possible sharpness. A tripod is obligatory with these focal lengths, a remote shutter release (or the self-timer) is highly recommended.

Take a series of exposures and take a few test shots in advance, then you can also see when the lens is sharpest and which exposure times work best – you can then use these values directly during the eclipse.

With a bit of luck, the autofocus will also work; you have the best chance if you can set the focus point manually. From 200-300mm focal length, the sun is imaged large enough to be interesting.

On telescopes with a focal length of 1-2m, the sun fits best on the sensor; but for this you should start preparing early. You can find a lot of information about solar observation at https://astrosolar.com/en/information/

About the author: Alexander Kerste

Alex is a studied biologist and works as a freelancer as an author, consultant and translator. After his studies and the publication of the Kosmos Starchart-Set in 2004, he was a regular freelancer for Astronomie Heute and the yearbook Der Himmel for the Spektrum-Verlag in Heidelberg. He is in charge of the Beginner courses on www.Astronomie.de and is a voluntary active member in the Robert-Mayer-Observatory since 1993. Since then, he has published a number of books on Celestron-Telescopes as well as Digiscoping and Astrophotography. One of his books on Astronomy with binoculars is also freely available at freebook.fernglasastronomie.de. In addition he supervises the Northern lights and star tours from Hurtigrute – these were also published in a travel guide, further articles can also be found on his blog kerste.de.