solar photography resorces

[Kirk Keyes]

I've played around with this. Somewhere, I'd seen that the magnitude of the sun is about 13 times brigher than the moon. (Try this link http://en.wikipedia.org/wiki/Apparent_magnitude)

That means the sun is about 500,000 times brighter. That worked out to about a ND 5.0 filter (2^19=524,000, remember that every 0.3 is one stop of exposure - 19*0.3=5.7. I suppose a 6.0 ND would have been closer...).

Using the sunny 16 rule and the moon needing expsure similar to daylight exposure given by sunny 16, you can expose the disk of the sun with 1/film speed at f/16 with a 5.7 ND filter. So I tried this, with a 2.0 and a 3.0 Wratten ND filters. Since I only had 5.0 ND of filtration, I had to stop down about 2 stops (5.7-5.0=0.7, 0.7/0.3=2.3 stops).

My test shots showed this was pretty close - maybe a little more exposure on the sun would have been good. I was shooting near sunrise so it was probably a little dimmer due to the light going through more atmosphere.

Since I was not using telephoto lenses, just a 240 and 150 mm, I did not have to worry about heat on the shutter or film plane. I focused on the landscape as normal, did an exposure of the scene before the sun had risen, and then did multiple exposures for the disk of the sun with the filter. It worked pretty nicely, I just needed to work out my timing interval between multiple exposures to make a nicer looking shot. (This was all on a normal day, not for a solar eclipse or anything.)

The Wratten does transmit some IR, but for normal lens lengths, don't worry about focusing with the sun in the field of view. Just don't use your loupe on the sun to focus it...

As far as hooking large format to a telescope, I built a platform that bolts to the top of my Meade LX-200 8 inch Catadioptic telescope and I've used both my Linhof Technika on it as well as a Fuji 617 camera. I never really got enough exposure time to make a really cool photo, but it shows a lot of promise. It was quite a load on the telescope, but you can get balancing weights to counterbalance with.

Also, look into Barn Door Mounts for doing exposures that are in the 10 minute ranges. They can be built big enough to mount a 4x5 - or even an 8x10 on them. I built one that uses a stepper motor to run the thing so you can do shots without having to touch the mount.

[GPS]

Never ever ! focus direct Sun without a proper Sun filter. Thinking that some focal length is safer than other for focusing without a filter is very dangerous idiocy.

[Jim Jones]

Rather than use a conventional 4x5 camera, consider putting the back from your camera on an improvised tube. For the last solar eclipse in my area, I used 25 feet of drain pipe, the back from a view camera, and a pinhole mounted in a shutter. A fractional diopter close-up lens stopped down to optimum apreture would have provided much better images at little cost.

[Kirk Keyes]

Never ever ! focus direct Sun without a proper Sun filter. Thinking that some focal length is safer than other for focusing without a filter is very dangerous idiocy.

I assume you are talking about my comments. I did say to focus on the landscape, and not the disk of the sun. You don't need to use any filter when doing that.

So how do you focus sunset shots then?

[Zach In Israel]

Baadar solar film can be had for pretty cheap, maybe $20 a sheet. It will let you make a filter to take pictures of the sun. However unless you have a VERY long lens or are doing some form of piggy back optics a 4x5 seems like overkill. Maybe if you got a 8" shmidt-Cass telescope and then pointed the lens of the camera into an eyepiece, this will give you a very long optic.

PLEASE BE VERY CAREFUL WHEN SHOOTING THE SUN
It is all too easy to do real harm to your eyes or your equipment.

[Zach In Israel]

Just to do some math, if you were to make a lens with an effective focal length of 10m (10,000mm) the disk of the sun would still fit on a 4x5 film. On the other hand tracking and focus would be an interesting challenge.

[GPS]

On the other hand, while it is easy to make a F 2000mm pinhole camera, the picture obtained with this instrument doesn't allow sufficient magnification (the loss of sharpness is then evident). Solid solar photography is rather difficult and demands specialized tools.

[Jim Jones]

Just to do some math, if you were to make a lens with an effective focal length of 10m (10,000mm) the disk of the sun would still fit on a 4x5 film. On the other hand tracking and focus would be an interesting challenge.

Tracking is simple. Exposures are short enough that the camera doesn't have to track the sun. With a 25 foot tube, I centered the shadow of the front of the tube on the back of the camera for framing. Focusing should be a minor problem if the camera can be operated as fixed focus with no problems due to temperature changes, gravity, etc.

[Jim Jones]

On the other hand, while it is easy to make a F 2000mm pinhole camera, the picture obtained with this instrument doesn't allow sufficient magnification (the loss of sharpness is then evident). Solid solar photography is rather difficult and demands specialized tools.

Filling 4x5 film with a pinhole image of the sun shows little, if any, more detail than can be seen directly through a suitable solar filter. Significant solar photography is beyond the reach of most amateurs. However, there is satisfaction in accomplishing what we can with what we have. I've heard of people actually using Holga camras!

[GPS]

[QUOTE=Jim Jones;.. Significant solar photography is beyond the reach of most amateurs... [/QUOTE]

Just the opposite! With today's telescopes available to amateurs (Solar MaxScope 90 to name just one of them) amateurs interested in solar photography can achieve excellent results. Amateurs can even build professional quality coronagraphs!