Telescope solar filter
Observing the Sun requires a combination of special filters and great care: what you need to know for safe observations.
Astronomy is not only a night-time activity. Our closest star, our Sun, offers a lot of interesting details.
It’s absolutely vital that you equip your telescope with a solar filter if you want to observe the Sun. In the past, solar filters were attached to the eyepiece, but this practice is dangerous and we strongly advise against it.
We only use solar filters that are attached to the objective lens, which filter out the majority of the sunlight before it enters the telescope.
Basically there are foil or glass solar filters.
Our glass solar filters are already mounted in an aluminium frame. This makes it very quick and easy to attach them to the telescope tube.
You simply select the appropriate diameter, depending on the size of your telescope. It’s best to measure the outer diameter of the tube, then you know which diameter solar filter is right for your telescope.
We also stock Baader solar filter foils in various sizes. These are not usually mounted in a frame and so are much cheaper than the ready-mounted glass filters. You can cut the foil to suit your telescope and build a frame for the filter yourself. It is very important that you fix the filter foil securely to the tube opening. It must never be possible for it to be detached by a gust of wind.
Most filters are referred to as optical filters because they have a particularly strong filter effect. Only 1/100,000 of the light reaches the eye. Such filters bear the optical density designation ND5.
ND3.8 photography filters are also available. This are available, for example, from Baader. Such filters are considerably brighter and are not suitable for visual observation. Steer well clear of these unless you need them for a specific task.
Objective lens solar filters make it easy to observe sunspots and flares on the Sun’s surface. Sunspots are formed, develop into whole groups, wander over the Sun's surface and disappear again. Individual spots can even grow to the size of our Earth. The frequency of sunspots and their development have long been documented by amateur astronomers. Even amateur astronomers can take on valuable observation tasks here.
The Sun definitely provides plenty of fascinating observing possibilities.