Choosing the best finderscope for your telescope will make finding and centering celestial objects easier, and some finder scopes can also be used for terrestrial viewing or guiding during astrophotography sessions. Here is short list of the most common telescope finders:
Red Dot Finder or Reflex Finder: This simple and easy to use finder offers a zero magnification view of the sky that is right-side up and left-to-right correct. When you look through a red dot finder that has been aligned with your telescope, you will see a red dot (hence the name!). To use a red dot finder, simply move your telescope while looking through the finder until the red dot is centered on your intended target, then look through the eyepiece. Some red dot finders project shapes other than a red dot, like a bull's eye or a crosshair. Other models let you choose from a collection of illuminated reticles or dots.
Optical Finder Scopes: An optical finderscope is basically a small telescope or monocular that has an integrated eyepiece with low magnification. A 7X or 10X magnification finder is most common, but other finders offer 8X or 9X or even have interchangeable eyepieces. Common finderscope apertures are 30 mm (for small telescopes), 50 mm, or 60 mm. Remember the rule of astronomy optics...the larger the aperture, the more light it gathers to reveal fainter objects.
There are two basic optical finderscope body styles: Right Angle Finders and Straight-Through Finders. A right angle finder scope has an eyepiece that faces up. Most people agree that this makes it easier to look through, especially when the telescope is pointing high overhead. Many right angle finders are "image erect" or "image correct" as well, which means the image you see will be right side up and/or left-to-right correct. If you will be using your telescope during the day as a big spotting scope, having an image erect right angle finder is recommended. A straight-through finder puts the eyepiece at the back facing out. Many astronomers use a straight-through finder because it offers the brightest images, and, when doing astronomy, it is not important to have right-side up images.
Solar Finders: If you will be viewing the Sun through your properly filtered telescope, you will need to make sure the finder you use is absolutely safe. The best way to insure that is to trade out your regular finder with a solar finder explicitly made for solar use. Most solar finders are not designed to be looked through. Instead, they project an image of the sun on a screen that is aligned to your telescope's eyepiece. When the Sun is centered in the screen, it will be centered in the eyepiece.
Want to know more about choosing and using finder scopes? Read the High Point article entitled Types of Finder Scopes for Astronomy.
If you need help choosing a finder scope for your telescope, feel free to contact one of our non-commissioned product advisors by phone or email. We are here to help and want your experience in astronomy to be the best it can be!