In this article, we will be discussing what a finderscope is, the different types, the best ones, and how to align a finderscope with the main telescope lens.
What is a Finderscope?
A finderscope is an aiming device used in astronomy, typically a small auxiliary telescope mounted on the main astronomical telescope along the same line of sight. The finderscope usually has a smaller magnification than the main telescope, providing a much larger field of view, useful for manually aiming (also called “slewing”) a telescope and locating a desired astronomical object. Some finderscopes have crosshairs to aid in accurately pointing the telescope system at a target.
Orientation Of Scope
Most finderscopes have one of three viewing orientations:
|Type||Eyepiece mount||Image Orientation|
|Standard||Straight through||Upside down and reversed (i.e. rotated 180 degrees)|
|Right-angle||90 degrees||Backwards (mirror-image)|
|RACI (Right-Angle Correct-Image)||90 degrees||Correct|
Those scopes are all mini telescopes that are attached to the telescope. There are also gadgets called Reflex Sights, which do not magnify, but often have a ‘red dot finder’ or equivalent to show where the field of view is currently located. These are super popular.
There is no best scope for someone to use as it depends on the telescope setup, how the configuration is being controlled, and what the observer is trying to do. If the observer is fully automating their setup, their finderscope will vary to a greater degree than an casual observer. The key is to find a scope that is not too heavy and can suit the needs of your observing.
What we recommend doing is to utilize the finderscope that comes with the telescope or buy a basic one in the beginning. What we then suggest is progressing to more advanced finders as your setup evolves. Moreover, it is recommended to perform alignment with an object in the distance that is easily recognizable. At some locations in Oregon, we use a telephone tower in the distance to align both scopes during dusk before it gets dark.