The important numbers? 173 minutes. And right in the middle of that, 156 seconds.
Monday the 21st cannot come soon enough for me. The Total Solar Eclipse of 2017 is going to be amazing natural phenomena that most of us have never come close to experiencing. History will record this day.
Of course, we don't go crazy like they used to and thought the world was ending or the sun had burnt out. Amazingly the Mayans seem to have been able to predict eclipses accurately, both solar and lunar, and we still marvel at their precision. Their calendars and the predictions of eclipses seem to have been based on an amazingly complex calculation scheme that has been shown to be accurate to the day all the way back to the earliest eclipses from recorded history. Wow. No computers, heck not even a TI-81 calculator (if you are under 30, ask your older brother or sister.)Â
I have been working for the past few days on trying to create a spreadsheet with formulas that will show the correct exposure in shutter speed based on the ISO, F-stop and the 'Brightness Exponent' (a value assigned for different events that occur during the eclipse.) Add in the fact that exposures before the start of the totality of the eclipse require solar film filters that block the majority of light so that you can look directly at the sun with a telephoto lens and not burn up your eyes or the sensor in the camera. Then at the start of the totality, you remove the filter, make a huge adjustment to the shutter speed on the camera, and for the next 156 seconds, you can look at the sun with no filter. As you can imagine, Tom 'I didn't learn my multiplication tables until I was 14' Benson has some fights with the math parts of this stuff. But after a while, I did manage to get a result out of the equation that I thought made some sense.
 t=f^2/(I x 2^Q)
(Where t= exposure time (seconds), F= F-stop of the camera, I = ISO (sensitivity setting on camera equivalent to using differing film speeds back in the pre-digital time) and Q = Brightness Exponent.)
The scary part of this is the part where you take off the filter. During that 156 seconds, I am going to try to shoot 35 different exposures, from 1/4000th of a second at the start and end, and a six-second exposure right in the center to capture 'earthshine.' And the other 32 shots I will make a 1/3 of an f-stop change in the shutter speed between each. But it will not just be 35 photos. Every 3 seconds or so I will hit the shutter button and take five separate images that span:
Four stops below the metered exposure, two stops below the metered exposure, the metered exposure, two stops above the metered exposure and lastly four stops above the metered exposure.
Fortunately, the camera will do the adjustments for those five exposures itself as I hold down the shutter release. Altogether, in 156 seconds, I hope to have the shutter click 180 times. Oh, did I mention that the sun will move close to 3 degrees across the sky during that 156 seconds? So I have to recenter the sun in the frame a few times to make sure I am catching as much of the prominences and chromosphere as I can.Â
And that is just one camera. I will have a second camera that will be setup on a tripod that will be doing the whole '5 exposure bracket' thing automatically every 8 minutes for the 173 minutes from the start of the partial eclipse to the end. During the totality, with the filter off (yep, had to buy two. And they are not cheap.) I hope my lovely wife Nancie will press the shutter release on that camera every 3 seconds excepting the 6 seconds surrounding the mid point of totality. Then back on with the filter, and restart the 8-minute intervals until the end. Â
One of the first articles I read on photographing a solar eclipse suggested that you make a sound recording that spans the 10 minutes surrounding the totality with you telling yourself what you should do at that time. And then during the eclipse play it over a loud speaker so you can follow all the instructions. I thought it was crazy. Then I realized... in that time frame, there will be over 230 separate steps to perform. ON TWO DIFFERENT CAMERAS!
Did I mention the travel? Oh yeah, we are going to be in Lexington, South Carolina. In the parking lot of a Lutheran church that is about 200 feet off the midpoint line of the eclipse path. I decided a church with a graveyard attached would be ideal because 1: Clear line of sight to the horizon 2: Unlikely to be crowded. 3: And I asked the minister if it was ok. So I have 'official permission' from the property owner if other folks decide to crowd us. Staying in an Airbnb about 11 minutes away. I looked first at locations around Santee, SC. The Super 8 motel wants $450 a night for the 19th through the 21st. THE FLIPPING SUPER 8!!! We are driving down early Sunday, like leave at 5 am, so we can get there through the traffic, scout out our location and a backup location, get some food and decamp to the Airbnb. Then back up at 5 am for weather checks and such. I am going to be working during the a.m., and then during the eclipse, I will be available for client emergencies. These are the sort of boneheaded things you have to do when you wait until the last moment to make plans. More hassles, more money, more chances for failure.
My advice for you, True Believer? Get some approved Eclipse viewing glasses. Do not cheap out on these. And look to make sure they are NASA approved or certified. Amazon had to refund an enormous amount of money to folks who had purchased glasses and filters that the supplier ultimately could not prove the materials providence. (Yeah, guess who had to track down TWO new filters one week before the eclipse. They arrived yesterday. Plus $50 for overnight shipping.) Get your kids, your partner, your parents, put on the glasses to watch the moon slowly eat the sun from the sky. (Even though they were sophisticated enough to calculate the exact day and time it would happen, most of the Mayans believed that is what occurred during the eclipse.)
 And at UTC 18:41 or so (that's 2:41 pm EDT), when the last of the little flares around the edge has stopped (those are called Baily's Beads), take the glasses off and marvel. Darkness. The shadow of the moon will travel across the surface of the earth at 1469 miles per hour. The temperature will drop 10 degrees or so. Animals and birds will silence. Some flowers will start to close like at dusk. And for 156 seconds you will see what is likely the most amazing thing you will ever see.
Until you see my photographs of it, that is. HA!
Oh, and if you think you might want to try to take a few photos yourself here are a few resources I found useful:
Observing and Photographing the 2017 Solar Eclipse
The Solar Eclipse of August 2017: A Photographer's Astronomical Dream
The CLDC is a Treasure Trove of Solar Eclipse Photography Information
Solar Eclipse Map: Shows you times and a visual indication of what will be happening at the location at any given time. Neat Tool!







