A finderscope is a small telescope mounted on top of the main astronomical telescope. By having a smaller magnification than the main telescope it allows the observer to see more of the sky.
The smaller magnification helps to locate objects in the night sky far easier. Many finderscopes have crosshairs to show exactly where the main telescope is looking.
Shown here is a fully-coated achromatic finderscope by Skywatcher. It features crosshair eyepieces, 8x magnification and a 50mm aperture objective lens and provides a brighter, sharper image than many smaller finderscopes. It comes with a diecast mounting bracket with spring-loaded screws for easy alignment.
The majority of telescopes do come with a finderscope which is satisfactory for most observers, although you may want to upgrade to a better quality one in certain cases.
How To Align A Finderscope
You will find that aligning a finderscope is probably best done during daylight when it is easier to locate objects.
The finderscope is an extremely useful accessory, and when aligned correctly with the telescope can quickly locate objects bringing them into the center of field.
If it is necessary to refocus your finderscope, sight it on an object that is at least 500 metres away.
The majority of finderscopes can be focused using the following guidelines, if not the principle still holds good.
Loosen the finderscope locking ring by unscrewing it back towards the bracket. The front lens can now be turned in and out of focus. When focus is reached lock in position with the locking ring.
First choose a distant object, then point the main telescope towards the object and adjust the telescope so that the object is in the center of your eyepiece.
Next, check the finderscope to see if the object in the main telescope is centered in the cross hairs.
Then adjust the small screws to center the finderscope is on the object. You should now be all set and ready to go. Depending on the type of finder there will usually be two screws for up and down, or three screws that move the target at different angles.
This well respected telescope add-on is ready to attach to your scope using the universal supplied base plate via screw holes or sticky pads.
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