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Respected Contributor
Posts: 1,921
Registered: ‎02-17-2016

Re: solar eclipse

I think I have demonstrated that I have shot the sun, both with and without a filter - but I only went filterless in those few moments at sunset - when I had to work *fast*.

 

Everone agrees that you need to track, but you do not need a tracker which are generally more useful for long exposures.

VIP
Posts: 8,030
Registered: ‎12-07-2012

Re: solar eclipse

A lot of Canon stuff. Along with, a lot of other stuff.
Esteemed Contributor
Posts: 3,048
Registered: ‎06-11-2013

Re: solar eclipse

[ Edited ]

I realized I should probably comment on some of this.  I recently gave a presentation at an astronomy conference on the topic of photographing the solar eclipse.  "The" expert on the topic is a guy named Fred Espenak.  Fred is a retired NASA physicicist who still does their eclipse predictions (even in retirement).  If you've seen those maps that plot the path of totality across the country... those are all his work.  He's the guy responsible for this eclipse prediction (so if he's right, you have him to thank and if he's wrong you have him to blame.  But he's VERY GOOD at this.)

 

Anyway, I happened to set next to him at a lunch and discussed some of the aspects of eclipse photography in a bit more detail than was offerred at the presentation.  I've done lots of solar observing (I own quite a number of solar filters, a herschel wedge, and a dedicated hydrogen alpha solar telescope).  I've photographed partial eclipses... but never a total solar eclipse.

 

I never talk about the sun without bringing up the topic of safety.

 

SAFETY:

 

The sun pumps out nearly as much energy in the infrared spectrum as it does in the visible spectrum.  That's why you feel warm when you stand in sunlight.  If there were no infrared, you wouldn't feel the heat (it'd be a bit like using LED lighting).

 

MOST welding glass is NOT SAFE for use with your eyes.  Welding glass used to be smoked glass.  Today it's mostly modern polymers that are designed to eliminate the spectrum harmful to the welders eyes (mostly in the visible spectrum and mostly toward the UV end) but not so much in the IR.  

 

You ONLY want to use a filter that is known to be intended for and safe to use with the Sun.  As I tend to joke when I give these presentations "Do NOT stare DIRECTLY into the Sun with last-remainging functional eyeball."  

 

Incidentally there are no pain receptors in your eye... as you torch your retinas, you wont feel it.  The retina doesn't stop working instantly... it takes about 24-48 hours for the effects to set in.  So you may do something unsafe, think you are ok because you aren't blind at the end of the eclipse... then wake up a day ... may be two days ... later and realize you don't see so well.  

 

Spend the money for a proper solar filter before the eclipse... or spend the money for a white cane after the eclipse.  Your choice.  ;-)

 

On the topic of partial phases... 

 

Ernie is right... it is NOT SAFE to look at ANY PARTIAL PHASE without eye protection... even 99% eclipsed isn't safe.  Only when the ecipse is 100% (totality) is it safe to remove all eye protection.

 

Why?  I illustrate this on the white board when I give my presentations... don't think of the sun as being 1 point of light deliverying energy to just 1 point of on your retina.  Instead... think of it as lots of points of light being emitted and focused to lots of points of light on your retina.  When the eclipse is ... say 50%... what that means is that 50% of the sun is covered.  But the light emitted from teh 50% which is still visible is just as bright as it ever was.  This light is now being focused onto a smaller area of your retina.  So if you consider a single cell at the back of your eyeball... that single cell is getting just as much light intensity as it would get even if there were no eclipse.  Covering part of the sun just means fewer cells are exposed to light.  But those cells which ARE exposed to light will be damaged just as quickly as would occur if there were no eclipse.

 

Hopefully that covers the safety topic.  I don't advise using welding glass.  The heat build-up in your camera may be considerable because most welding glass doesn't block infrared and the heat buildup is happening the infrared part of the spectrum.

 

 

FILTERS:

 

Most solar filters are ND 5.0 which means they block 16.66 photographic stops of light.  A proper solar filter blocks both visible and infrared.   That works out to mean that the filter blocks 99.999% of all the energy... or in different terms, 1 photon out of every 100,000 will make it through the filter.  

 

We refer to these as "white light" filters not because the sun will appear "white" per se (although it could) but becuase the entire spectrum is allowed to pass through the filter... but only a very tiny amount of light at each wavelength.  

 

Usually these filters do not block all wavelengths evenly.  The Thousand Oaks filters are designed to block the blue and green wavelengths a little more than the reds... this causes an orange-bias so that the Sun has a somewhat familiar "red/orange" color to it (the sun actually is "white" in human vision but human vision is less sensitive to reds... in truth it's a slightly yellow star.  The spectral classification for our star is G2 on the HR diagram.)

 

Baader film usually blocks the reds a bit more and these often result in a sun that looks white with a slight blue tint.

 

I happen to own a special device called a Herschel white-light wedge and based on it's designed it actually delivers true color. When I use that device on my scope the sun actually appears "white" with no color cast whatsoever.  (it's not a simple filter... it's used like a mirror on a 45º angle and in which only .001% of the light is reflected and the rest of the energy is passed through to a heat sink (which does get hot).  The caveat for this device is that it goes on the back of the scope, there is no energy rejection filter on the front of the scope, and they generally shouldn't be used on any scope that has an objective aperture greater than 100mm / 4in diameter ... to avoid heat build-up in the scope that can damage the scope.

 

BTW... the heat build-up problem is real.

 

For anyone who doubts this, I offer exhibit A:

 

https://youtu.be/ObNzrwPDGGU?t=6m8s

 

I am the person holding the finder scope and speaking in this local-access show.  But this finder-scope was on a larger telescope that was pointed at the sun.  The main-telescope had a safe-solar filter.  But what the owner of the scope did not know is that one of his friends had removed the cap from the front of his finder scope (thinking they needed to use the finder scope to help find the sun (very bad idea)) but hadn't gotten around to removing the back-cap.  The owner pointed the scope at the sun and within moments he smelled burning plastic.

 

If you watch the video, you'll see a hole melted clear through the back cap.

 

Additional the cross-hairs inside the finder scope are metal wires... both of which snapped from the heat.

 

So if you want to point your camera directly at the sun at mid-day without filter out both visible and infra-red (that's where all the heat is) energy, that's up to you... but my camera will have safe solar filters on the lens at all times other than the short period of totality.  

 

 

 

TIPS (from Fred Espenak's talk):

 

I took good notes when Fred was giving his talk on Solar Eclipse Photography and I'll share this with you.  These tips assume you are viewing from a location which will experience totality.

 

15 mins prior to totality (filter on)
- Swap your battery & memory card
- Begin looking west for the approaching shadow
 
5 mins before totality (filter on)
- double-check focus 
- look for planets (Venus will be 34º West of Sun (to the right of the Sun as you look at the sky)
- look west for approaching shadow
 
1 min before totality (filter on)
- check focus
- check framing (pointing)
- begin looking for "shadow bands"  (Search YouTube for examples... they look like wavey shadow lines on the ground but mostly easily seen on anything "white" -- sort of like the shadows you might see on the bottom of a swimming pool when there are waves in the water.)
 
10 seconds before totality (or 30, 40, or 50 seconds before totality but not early than 50 seconds)  
- time to remove the filter... you'll want the filter off the AND give the tripod time to let vibrations settle prior to the 10 second point
- An ND 5.0 solar filter would have been blocking 16.66 stops of light so this will change your exposure.
- DO NOT LOOK THROUGH THE CAMERA (at least not with your last remaining functional eyeball) until totality begins
 
During Totality
- Hopefully your computer is running your camera and not you. 
- If your computer can't drive your camera, use an intervalometer and enable auto-bracketing if your camera can do this.  You'll want about 9-12 stops worth of exposure range on the Corona.
- Save space for 3rd contact "diamond ring" effect
- DO NOT try to change memory card, battery, or lens
- DO LOOK at the ellipse yourself (don't waste totality with your head in the camera).
 
10 seconds after C3
- put filter back on lenses
- Watch for moon shadow receding to the East
 
5 mins after eclipse
- lock memory card
- label memory card and store in a safe place
- start planning for 2024
 
 
Other general etiquette rules:
- Do not approach other eclipse photographer's closer than 6' unless they invite you.
 
Eclipses-Interuptis
- Do not stand between someone's camera or telescope... and the Sun
- Do not interrupt someone who is busy adjusting his/her gear
- Do not Disrupt others with questions during totality
- Do not ask for the time or how much time is left during totality
- No music
 
Fred puts a tarp on the ground... puts stakes at each corner and puts up yellow "Caution" tape to prevent people from getting too close to the camera gear during the eclipse.  He may invite others in prior to totality... but closes off the area a few minutes before totality.  

 

 

I do own a solar filter that is threaded onto the front of my lens... but I also own Thousand Oaks filters that cap over the lens.  I prefer the "caps" because in that window of time between 50 seconds and 10 seconds prior to totality.  You will want your camera set to manual focus and you'll need to be able to remove the filter without accidentally altering the focus.  I find I can get the cap type filter removed more quickly and without adjusting focus.

 

Using some gaffers tape to prefern the focus ring from turning (once you've refined focus) might not be a bad idea.  I always have gaffers tape in my bag.

 

 

 

Tim Campbell
5D III, 5D IV, 60Da
Respected Contributor
Posts: 1,921
Registered: ‎02-17-2016

Re: solar eclipse

Those of us who don't have totality will need to filter the whole time.

VIP
Posts: 8,030
Registered: ‎12-07-2012

Re: solar eclipse

So very true.

A lot of Canon stuff. Along with, a lot of other stuff.
Frequent Contributor
Posts: 33
Registered: ‎12-02-2016

Re: solar eclipse

What factor do I look for for a proper solar filter 77mm
New Contributor
Posts: 1
Registered: ‎08-03-2017

Re: solar eclipse

Thank you very much for posting this information! It is a great summary.

Super Contributor
Posts: 187
Registered: ‎01-31-2017

Re: solar eclipse


TCampbell wrote:

Spend the money for a proper solar filter before the eclipse... or spend the money for a white cane after the eclipse.  Your choice.  ;-) 

 

 


I hope and pray that I am wrong, but I fear that some will indeed end up severely damaging their vision or going blind entirely. Here in San Diego, we will not be along the path for a total eclipse. But there have been reports of people here on social media, particularly young people, planning "eclipse parties." I guarantee you some will lose their eyesight. 

Esteemed Contributor
Posts: 3,641
Registered: ‎06-25-2014

Re: solar eclipse


kvbarkley wrote:

Those of us who don't have totality will need to filter the whole time.


During a partial eclipse, every beam of sunlight projects an image of the eclipse on any flat surface it hits. A few years ago the best pictures I got were of the eclipse projected on the leaves of maple trees in my yard.

Bob
Boston, Massachusetts USA
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