Introduction

At OASI workshops on solar eclipse photography, I've shown pictures of eclipses and some of the equipment used to produce them. I've also shown some less successful efforts that wouldn't normally see the light of day - hopefully they illustrate what can go wrong and how to achieve best practice. I thought that it was worth putting my thoughts and experiences into print for the benefit of others. Some of the points below may appear obvious - yet they can strike at the most inopportune moment during an eclipse! I will not own up in print as to which of the following recommendations I've failed to observe...

MOST IMPORTANT: if observing an eclipse, it is not compulsory to photograph or video the event - only to experience it!

Basics

Weather

How much/what you see is largely dependent on the weather. Exposure tables in books for totality generally relate to a clear sky - if it is misty or cloudy your personal experience is the only guide...

In clear skies it can be (very) warm. Many modern cameras are black and will absorb heat and get hot. Take some shade for your equipment - covering it with a white T-shirt is better than nothing.

Vibration

Vibration is the single biggest cause of poor eclipse pictures (after the weather!) It is essential to use a cable release to avoid camera shake. A finger on the fire button moves the camera, even when it's mounted on a tripod. Handheld shots are possible only with fast lenses and short exposures. Tips to minimise camera shake:

Hand held rule: Maximum exposure ~ 1/focal length (in mm) in seconds.
Use a tripod - the stronger the better for long/heavy lenses.
Don't take pictures too quickly - to determine how quick "quick" is, do some tests in advance on something other than an eclipse e.g. the Moon in a dark sky or another high contrast target such as a photographic test target or good black/white printed material.
Maximum untrailed exposure ~500/focal length (in mm) in seconds. If you need a longer exposure time an equatorially mounted camera will be necessary.

Lenses

Short lenses can be safely left set to infinity, but do tape the focusing barrel in place as it can easily be knocked in the excitement of the event. However, long lenses e.g. 500 mm and upwards, do not have an infinity setting as temperature changes alter their effective length, and theyh must therefore be focused on a distant object, ideally the Sun or Moon. If you intend to record 2^nd contact with a long lens, you need a solar filter to look through to set the focus of the lens beforehand.

Smart (=expensive) autofocus cameras need to point the autofocus sensors at an object e.g. the Moon, to let you take a picture at all. Simpler autofocus cameras default to infinity if they can't find anything in the field of view.

Tripods

When observing an eclipse, don't have tripod legs or column fully extended - they will not provide a firm mount for the camera! Instead, you can add a heavy weight to the central column to increase stability.

Check beforehand that the tripod head can tilt to the altitude of the Sun on the day. Large heavy lenses on top of a tripod make the tilt head top heavy, so the locks must be twisted tight to avoid toppling (when pointing at high altitudes). This makes it difficult to adjust the pointing as the Sun moves across the sky. Give some consideration to counterbalancing or displacing the lens so that its centre of gravity is on/close to the tilt axis.

You do not need an overly sturdy tripod if the focal length of the lens is "short". Determine by experiment whether your tripod is adequate for your camera and lens. (I have used a table-top tripod, but only with a 17 mm ultra wide angle lens!)

Using The Camera

Know your equipment, how it works, what it can do and that it is working properly. Do not put yourself in a position where you need to find "p77 - Mirror Lock-up" in the instruction manual during the eclipse! Some specific tips:

Remember that it gets dark (like twilight) during totality - so be able to find your camera controls in low light or use a (red) torch. Many modern cameras have liquid crystal displays, but they cannot be read easily in the dark! On some cameras the shutter speed indicator in the viewfinder is a light next to some black numbers, but these numbers don't stand out against the dark sky of an eclipse. Use new batteries - modern cameras will not work with dead batteries!
Don't bother to take more than a couple of shots of partial phase before totality (to confirm that the camera operates). The partial phases are much less interesting than totality. (Take shots of partial phases after totality and turn them upside down - nobody will notice...!)
Don't change lenses during totality. Even if you can do this smoothly at home, you will find that it takes ten times as long during totality and won't go as smoothly.
Be aware when third contact is about to occur - you risk permanent eye damage if you are looking through optical aid when the Sun reappears...
Do remove the lens cap to take pictures during totality!
Do remove the solar filter to take pictures during totality!

The Corona

There is no "correct" exposure for the corona. It is bright near the Sun and it becomes fainter further out. Try to use the "chevron sequence" i.e. stepping up one stop between exposures to the maximum exposure, then stepping one stop down back to the original exposure. This is particularly effective if your camera is one with a big exposure knob, marked "1000, 500, 250" etc., that is easy to handle in the dark. You do not even need to be looking through the camera to do this.

The corona can be very asymmetric, with long equatorial streamers. Therefore, if you use a long lens e.g. 500 mm or longer, orientate the camera beforehand so that the long axis of the frame is parallel to the Sun's equator.

Preparation

If you have anything more than simple photographic equipment, write down in advance what you are going to do and what equipment is needed - you don't want to discover on eclipse morning that you have left a vital piece of equipment behind! Also note in advance what exposure times you are going to use for the (few) partial shots, 2^nd/3^rd contact, the corona etc. This must be with reference to the other settings that you will be using.

Finally

DON'T USE FLASH during totality! You may need surgery to recover your camera if you do...

Good luck for your eclipse viewing!

You can see some of my photographs in OASI's compilation of reports of the 11 August 1999 total eclipse.

Nigel Evans