As I have prepared for the eclipse over the last several months, I have periodically studied a variety of solar images in order to help me create my own. It turns out that there are two satellites that continuously orbit the sun taking images in a variety of different wavelengths of light from UV to visible to IR. The goal of these scientific missions, which are staffed by scientists all around the world and operated by NASA and the European Space Agency, is to better understand the inner workings of the sun. Believe it or not, in an age when mathematics can predict the occurrence of a total eclipse to within half a second along the path of totality (half a second!), there are still unanswered questions when it comes to our nearest star. Using this data, scientists have learned a lot about this little yellow star, as well as things like the solar wind, which is responsible for the aurorae that occur over the far northern and southern latitudes on Earth.
I hadn’t checked the images from these satellites for a while, so I decided to get an update in my hotel room this morning before hitting the road. I was very happy to see that several sunspots are present on the sun right now! I know what you’re saying, what’s the big deal? Sunspots and the eclipse have nothing to do with each other. True. After all, the relative positions of the sun, the moon, and the earth are not affected by sunspots, so why are sunspots helpful for photographing the eclipse? Well, there are two reasons.
First, believe it or not, it is not so easy to focus a camera on the plain yellow orb of the sun. That was surprising to me. It should be easy to focus on something as bright as the sun, right? Not really, even on the edges of the sun. Remember, you have to work this gear in the full glare of the sun when it is difficult to see LCDs and viewfinders. But the presence of a sunspot provides some contrast and texture, both of which are really helpful to determine when something is in focus. What a shame it would be to go to all this effort and walk away with blurry images! With the arrival of these sunspots, which should be on right half of the sun come Monday, focus will be much more reliable. Yay!
The second reason is even more subtle. Sunspots tend to be located along the equator of the sun. Why is this important to know? Well, during totality, the corona, or the atmosphere of the sun, will be visible with the naked eye and my cameras. Only during a total eclipse can we see the beautiful corona. The corona is the grand prize for all those who witness totality! For reasons I won’t go into here, the corona will predominantly emanate from the along the equator of the sun during this eclipse. Knowing where the equator is in my field of view will help me frame my images so I don’t accidentally crop the corona. Bonus! Thanks to the sunspots, I should be able to get the sun in focus, and orient the camera for a pleasing composition. If the clouds cooperate that is. Remember, clouds own eclipses!
I’ve attached the latest satellite image here for you to see for yourself. The sunspots are located in the middle of the image at 9:00. Also, check out the website here for more information. It’s actually pretty cool, so I encourage you to check it out. Over the course of the next several days, you’ll see the spots slowly move from the left to the right of the image. You can also review the historical images from the last couple of days to see how much the spots have already moved. If you really get in to this kind of thing, google “SOHO” and “SDO HMI” for more cool sun science stuff. Enjoy!