Solar filters for upcoming eclipse this summer

Can't recall exactly who on this forum mentioned it (sorry, whoever you were!) but making a solar filter out of two UV filters & Baader film sandwiched in between isn't too difficult. Just need to test it's got no holes in it before using it visually with your eyeball, and no worries!

To be safe for your eyes (if you are going to look through the viewfinder to frame and focus) then the filter MUST block 99.997% of the Sun's energy both in visible wavelengths as well as in the infrared wavelengths. That's an absolute minimum.

However, most certified solar filters are blocking 99.999% (ND 5.0) which works out to about 16.67 photographic stops. Basically one photon out of every 100,000 can make it through the filter (e.g. that's what the Thousand Oaks solar filters and Baader solar filters are blocking.)

You may remove the filter no sooner than 50 seconds before totality and probably want to make sure it is removed at least 20 seconds before totality.

HOWEVER... DO NOT look through the camera to do a final adjustment to frame and focus once that filter is no longer on the camera. Do your final frame & focus before removing the filter.

If your camera isn't on a tracking mount, then while the filter is still on the camera, compose the sun & moon to about the left third of the image (it will appear to move from left to right). Earth spins at about 15 arc-seconds per second... so in 4 seconds that's 1 arc-minute. In 120 seconds, the sun will basically move the equivalent of it's own diameter. The eclipse will last around 2 minutes and 38 seconds at max ... most people will experience at least 2 to 2.5 minutes. (so that's 150 seconds). But since you want to remove that solar filter about 30 seconds before totality... you should count on it taking more like 180 seconds. That means the Sun will move about 1.5 times it's own width (if your camera is not on a tracking mount). That's why I suggest composing the sun a little to the left... so that as totality is happening it will be just about in the middle ... and will be slightly to the right as totality ends.

If you do have a tracking head (such as a tracking telescope mount or a photo tracker like the Sky Watcher "Star Adventurer" head or the iOptron "SkyTracker Pro" head) then you can just center the sun, set the tracker to the Solar rate, and let it go.... it'll keep the sun in the middle the entire time with no drift.

I drew up a holder for solar film that fits Cokin P size holders if if you have access to a 3D printer. Thread on it here - https://photography-on-the.net …/showthread.php​?t=1481448.

IMAGE LINK: https://flic.kr/p/UDKt​uf

CatchingUp wrote in post #18356306
I am planning to do time lapse shots so if the frame is too tight on the sun I don't want to risk it moving out of the frame during the 2 1/2 minutes. I was thinking about using my 70-200 with 1.4 ext on crop camera with would be...almost 450mm focal length?

I'd bring my 400 but hate to think what the filter would cost for that.

not much I have one similar to the thousand oaks filter for my 100-400mm Canon was around AU$120 = ~ US$90
it fits just inside the lens hood, I used a bit of bluetack to stop any stray light from entering
400mm will still give quite a small image on the frame, I usually use the 2x teleconverter as well to improve things a bit more
you can see it attached to the other end of the lens

Ohhhh and during totality, you wont need any filter at all !!!

Dave

What if you used a auto darkening welding mask over your lens, Or just a welding lens?

davidv wrote in post #18396732
What if you used a auto darkening welding mask over your lens, Or just a welding lens?

No... use only proper "solar" filter material. Once upon a time the glass used for welding was safe. Today they are modern polymers that only block wavelengths emitted by the welder which would be harmful to the eyes... but they don't actually block true full visual spectrum PLUS infra-red spectrum (and the Sun emits nearly as much energy in that non-visible part of the spectrum and it will still blind you even though your eyes can't detect it).

I'm thinking a proper solar filter is both cheaper and easier than buying a white cain and learning to read Braille. You don't even have to buy the filter... you can just get the material (solar film) and make your own filter. Just make sure you use proper solar filter material.

We're getting down to crunch time on the eclipse... I've noticed that on a recent visit to the Thousand Oaks Optical website, they are listing that they have run out of pre-made filters and all orders are now back-orders... AND have now reached a point where they believe new back-orders are unlikely to be fulfilled before the eclipse.

They do still have glasses, cards, and solar film (sheet stock and roll stock) which means you could make your own filters. You can't just get pre-mounted filters from them.

Making your own filter is fairly simple... find a cardboard tube large enough to fit over your lens, remove the end, cut it to a reasonable depth (perhaps 2" or so) and wrap the solar film over the end and secure it in place. Don't try to make the solar film "drum head" tight... it's ok if it has wrinkles (they won't show up in your images) and I've noticed some films will shrink slightly (tightening themselves).

Now that one of the most significant providers of the solar filters are running low, last minute buyers (and there will be a lot of them) will put increased demand on other suppliers... causing them to run out even faster. I'm guessing that in the next week or two it'll be extremely hard to find a filter anywhere (this is basically what happened for the 2012 Transit of Venus -- everybody was out of solar filters.)

Solar view "glasses" and cards seem to be easy to find still.

Amazon has these and other sizes in stock:

https://www.amazon.com …tailpages00?ie=​UTF8&psc=1

I just ordered one today and it will be here Wednesday.

Tim

this is what i got from my local camera store. and attached is my test shot. ISO 400 F8 1/125 sec shot at 17:54 CDT
http://www.rockbrookca​mera.com …65-89mm-solar-filter.html

^ Seems really soft. Are you sure you had the focus locked in?

DavidWatts wrote in post #18405502
^ Seems really soft. Are you sure you had the focus locked in?

Agree... the focus is a bit soft. Use live-view to zoom in (10x zoom level) an a section near the edge of the Sun's disk and gently refine the focus (turn off auto-focus). Once you are happy with it, you might want to secure the focus ring (you can tape it in place, some people use a wide rubber band) so that it doesn't move during the eclipse.

The exposure is a bit bright and you're getting some reflections (the glow in the space beyond the edge of the sun is reflection - normally the space would be completely black). If you back off the exposure a little then it will likely help with that.

Here's a sample test-shot I did a few weeks ago while testing some gear in prep for the eclipse. I've cropped this in a bit (the actual shot is much wider and for totality I'll want it wider to capture more of the corona.)

I live with in eclipse path. I used an 8x8 sheet of Thousands Oaks solar film to make two filters. One for my EF 70-200 f/4 IS II lens w/ 67mm filter size & sigma 150-600 C w/ 95mm filter. Bought a UV filters each the next size up, plus step-up rings. Cut patterns on thin card stock and used that to cut the correct size in the solar film to fit inside each step-up ring. So basically the solar film is between UV filter & step up ring.

Cost was less than $55 total for all materials. Took maybe 2 hours yesterday to very carefully size & cut to fit & not crease or damage the solar film. Tried the filters yesterday on the sun, both worked really well. Very cost effective & anyone can do this project.

I'll be using these lenses on my crop bodies, & a 1.4 extender on the 70-200 to get the extra reach.

What exposure do you use for the corona during totality? I have all the filtering I need for the sun (done plenty of sunspots, etc), but the corona has been a "bucket list" target for a while.

I have a solar filter for my 6" telescope for while the eclipse is still partial, and then I'll be switching to my 150-600 for totality. Also have 13 stops of ND (Big Stopper + another 3-stop ND) filters that I'm considering using with a 2nd body, but haven't decided for sure yet.

Everything I have read or seen from the experts on youtube and elsewhere all agree that no ND filter will stop the invisible ultraviolet light, and invisible white light, which mean you could damage your sensor and more importantly your vision if you look through the viewfinder.

I will be using a solar filter from Thousand Oaks on my two cameras, but I will only be using live view mode during the partial eclipse, and then removing filter for totality. Solar filters are anywhere from 16 to 18 stops, and also block the harmful light.

This will be my first time trying to capture an eclipse so I am definitely not an expert. Maybe others with more experience will chime in.

For the corona no filter is used, and you have to bracket your shots to capture the most detail. Mr Eclipse website lists a formula.
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