ND1000000 Solar Filter: Do You Need One Yet?
As an astrophotographer, I have collected many different types of filters over the years. Some are designed for use with a telescope, but most of mine fit my camera because this is what I use for much of my astrophotography.
One thing that soon becomes apparent is that not all filters do the same job.
Some filters are designed to allow particular wavelengths of light through and can be extremely useful when photographing objects such as nebulae. Others reduce the amount of light reaching the camera. When photographing the bright Moon, for example, a neutral-density or variable neutral-density filter can sometimes be useful, allowing the photographer to control the amount of light entering the camera.
At the extreme end of neutral-density filtration we find something rather different: the ND1000000 solar filter.
What Is an ND1000000 Solar Filter?
An ND1000000 filter is an extremely strong neutral-density filter intended for solar photography. Rather than merely reducing glare from a bright terrestrial scene, it cuts the incoming light enormously so that the Sun can be photographed.
These filters can be particularly useful for photographing a solar eclipse, but they can also be used by people who regularly photograph the Sun and record features on its visible surface.
ND1000000 corresponds to a reduction of the incoming light by a factor of one million — about 20 stops photographically.
That gives some idea of just how bright the Sun really is.
This Is Specialist Equipment
This isn’t a filter that the average beginner needs simply because they have bought a camera or telescope.
If your interests are the Moon, planets, star fields or deep-sky astrophotography, an ND1000000 filter may spend most of its life sitting unused in your equipment case.
But if you decide that you want to photograph the Sun or a solar eclipse, it becomes a very different proposition.
That is when a specialist solar filter becomes an important piece of equipment.
Solar Photography and Eye Safety Are Not the Same Thing
Important: A filter sold for solar photography should not automatically be assumed to be safe for looking directly at the Sun.
ISO 12312-2 relates to filters and viewers intended for direct observation of the Sun, such as suitable eclipse glasses and handheld solar viewers. Cameras, telescopes and binoculars require solar filters specifically designed for those optical systems.
Never look through an unfiltered camera, telescope or binoculars at the Sun. Optical equipment concentrates sunlight and can cause serious and potentially permanent eye injury.
Eclipse glasses should not simply be placed behind a telescope or camera eyepiece.
For that reason, I would never choose a solar filter purely because the words ND1000000 appear in the description.
Buy a filter specifically made for the intended solar-photography application, from a reputable manufacturer or astronomical supplier, and follow its instructions.
Buy From a Reputable Source
This is one area of astronomy where I don’t believe saving a few pounds is worthwhile.
There are plenty of inexpensive photographic accessories where buying a cheaper alternative may be perfectly reasonable. A solar filter isn’t something on which I would personally take that chance.
The filter is being placed between an extraordinarily powerful light source and expensive photographic equipment — and potentially your eyesight if the equipment is used incorrectly.
Check exactly what the manufacturer says the filter is designed for. Inspect it before use and do not use damaged solar-filter material.
Dark-looking glass by itself is not evidence that something is a safe solar filter.
Make Sure It Fits Your Lens
There is another practical consideration that is easily overlooked: size.
Camera lenses have different filter-thread diameters. A wide-field lens might require one size while a longer telephoto lens requires another.
Look on the lens itself for its filter-thread diameter before buying.
Do not try to improvise by balancing an unsuitable filter over the front of a lens. With solar photography, the filter needs to be appropriate for the equipment and securely fitted according to its manufacturer’s instructions.
If you use several lenses, check whether suitable manufacturer-approved adapters or step rings can be used with your particular solar filter rather than assuming that one filter will automatically be suitable for everything.
Do You Need One Yet?
- Beginner astronomer: Probably not.
- Beginning night-sky astrophotographer: Probably not.
- Solar or eclipse photographer: A suitable dedicated solar-photography filter becomes relevant.
That’s really the point of these Equipment Reviews. Astronomy has an enormous number of accessories, and seeing something for sale doesn’t necessarily mean you need to add it to your collection.
Buy equipment when it solves a problem or allows you to do something you actually want to do.
Final Thoughts
Photographing the Sun can be extremely rewarding. A solar eclipse in particular can provide photographs quite unlike anything else we take in astronomy.
But solar photography is one area where safety has to come before getting the photograph.
If you decide that solar photography is something you want to pursue, research the filter required for your particular camera, lens or telescope, buy from a reputable source, follow the manufacturer’s instructions and never improvise.
An ND1000000 solar filter may not be something every budding astronomer needs.
But when you reach the stage where you genuinely want to photograph the Sun, the correct solar filter is one piece of equipment on which you shouldn’t cut corners.