Glossary | Telescope accessories | Capacity | Right ascension axis diameter
The diameter of the right ascension axis is fundamental to the load-bearing capability of a mount.
According to a rule of thumb, when using a refractor, sufficient stability is achieved for astrophotography if the diameter of the axis is around one third of the diameter of the lens. When using a Newtonian telescope, the axis diameter should be one fifth of the mirror diameter.
Source: Handbook of Astronomy, published by Oculum