How to Recycle a Solar Filter

I purchased a rather expensive 82 mm solar filter (also IR blocking) in anticipation of the Eclipse on 8/21/17. I'm not traveling to the path of totality, but hope to photograph the phases from home, weather permitting.

 

So what do you do with an 18 stop filter on 8/22 and after? A fun thing occurred to me, not possible otherwise.

 

I photographed a nearby street, with an exposure of 13 minutes at ISO 100, f/5.6. About a dozen cars passed, and several pedestrians, without leaving a trace in the image. This is not a new technique, but made easy with the nearly opaque filter, and a digital camera, which intrinsically has no reciprocity failure, just cumulative thermal noise. Stacking with a black frame should help.

 

My next stop is a public areal, like the Chicago Botanic Garden, which is always loaded with people. That way I can take a before/after shot for comparison, and share it on PNET. Something post-apocalyptic, simulated.

Interesting! Looking forward to your shots.

Great idea. I remember taking a long time exposure at night in Baltimore's inner harbor. It was a coincidence but someone walked through the viewed area wearing white sneakers. They ONLY recorded when the foot was stationary on the ground! The effect is like a set of 30 or so transparent white sneakers in 2 rows. Time can bw messed with & it can mess back with you too!

I used a "normal" 12 stop ND at the last partial solar eclipse and found it more than dark enough. The lens used was only f/5.6 maximum aperture anyway, and I had it stopped between f/16 to f/5.6 as near totality approached, using Live View to focus and find. However there was some light cloud cover for most of the event too.

 

I must admit I've not used the 12 stopper to ghost out busy scenes. There's bound to be at least one gawker that'll stop to stare into the camera lens! One benefit of film was that you could set the shutter to B and split a long exposure into several shorter bursts - thus blanking out any "slow traffic".

 

Aha! (Penny dropping) A bit of black card would serve the same purpose with a DSLR set on T.

Edited August 17, 2017 by rodeo_joe|1

Can anyone recommend stacking software for use with multiple, shorter exposures? I've used "Nebulosity," but it seems like overkill, targeted for deep space objects. Another possibility is "Helicon Focus", which is in my collection.

 

I don't think a black card is black enough for use in daylight, unless you touch the lens. At night, anything opaque will work. I use the lens cap for a separate black frame. A car next door was parked for about 1/3rd of the exposure, then moved. The only parts visible were bright metal trim and wheels. The Botanic Garden usually has old-timers who sit almost motionless for hours on benches. The possibilities are endless.

 

Gawkers and tripod-trippers are a distinct possibility. I had one driver stop and demand to know what I was doing (like checking for California Stops at the intersection). He moved on before registering even a bit. Most other drivers merely slowed to the legal speed limit, which was welcome if not intentional on my part.

Edited August 17, 2017 by Ed_Ingold

I also purchased an iPhone app called "LE Calculator," which translates the daylight exposure to the filtered version. It also serves as a timer (with alarm) for the duration.

It took a bit of fiddling to establish the correct parameters, but this is my best trial run.

 

Using an 18-stop solar filter, I set the exposure at ISO 100, f/5.6, 1/250. This places the brightest part at about 75% in the histogram. I took six exposures at 60 second increments using an intervalometer application in the camera (Time Lapse). Without moving the tripod, I took an establishment photo without the filter, using Aperture Priority. I used a Sony A7Rii camera with a Sony 24-70/2.8 lens at 24 mm.

 

I pointed the camera per PhotoPills at the azimuth and elevation of Monday's eclipse, placing the maximum eclipse in the center and about 1/3rd from the top. The eclipse will peak at 1:19 pm Chicago time. This photo was taken about 4:30 pm. The eclipse will span 62 degrees from start to finish, and the FOV at 24 mm is 72 deg x 56 deg.

 

I loaded the images, including the establishment image, into Photoshop, and used the layer stacking script in the menu. I then adjusted the opacity of the solar images to 20%, leaving the establishment photo as is. The solar disk overlaps at 60 second intervals, so I took the first and last, with a space of 5 minutes. Suggestions regarding stacking and processing are welcome. This is my first attempt.

 

Sell it on Astromart or Ebay or wait for the 2024 eclipse. They are used for sunspots etc.

Why recycle...hold on to it for another 7 years and you'll get another shot as the path of another total solar eclipse travels in a line from Dallas up thru Champaingne IL from what I saw on the news last night.

You didn't get the joke implicit in the title. After the eclipse I have other uses for the filter, a non-destructive form of recycling. In seven years, if not before, I might have a telescope too. I'd like to do some deep space photography before the next eclipse.

Carbondale is also in the path of the the 2024 eclipse.

 

I avoided the expensive filter and got the Celestron mylar one.

Worked fine:

 

Carbondale is "centrally located", but for once that doesn't just mean "equally far from anywhere".