When imaging the sun using “lucky” imaging techniques with a high frame rate camera like the Altair Hypercam, it’s best to keep the exposure duration of the camera as short as possible – ideally under 10 milliseconds is ideal, though less than 5ms is even better.
This “freezes” air motion to show granulation and other small details. Being designed for visual or imaging use, the internal polariser module (controlled by rotating the turret top) has a wider brightness range than normal Hershel wedges allowing fast frame rates and short exposure duration.
When set for fast frame rates, the image can appear very bright visually through an eyepiece – like looking at a light bulb. This is uncomfortable, but not dangerous due to the protective ND filter inside the unit allowing a fraction of the sun’s light through.
Therefore, an additional 1.25″ neutral density filter is provided, which transmits 75% of light, blocking 25% for initial focusing and setup with an eyepiece.
When you first set up the Wedge and align it with the sun for visual use, you should first add the provided 1.25″ Neutral Density filter to the eyepiece, then rotate the turret-top until the image is quite dim. Once you are satisfied with the balance of contrast and sharpness, lock the polariser locking thumbscrew, and you are ready to observe.
If using the wedge for imaging only, you can just insert the camera and turn the turret-top until you are satisfied with the exposure duration and gain settings.