Cleaning SCT Optics

Ways to Prevent from Cleaning your Optics

Don’t let your optics get dirty!Keep them covered when not in use.Use a Series 6 Skylight filter on the eyepiece end of the telescope to prevent contaminates from entering the tube.A Skylight filter also increases lunar and planetary contrast.

TO CLEAN OR NOT TO CLEAN

Make Sure Your Optics Need Cleaning

Specks of dust or pieces of lint do not impair the visual or photographic performance of your telescope.Excess cleaning can cause small scratches which scatter light, this is very harmful to optical performance.Telescopes, used nightly, generally need to be cleaned only every six months to a year.

When Cleaning is Needed

Keep children and pets away.Clean off dust and dirt by using compressed air.Never apply cleaning solution directly to optical surfaces.Never rub or apply pressure when cleaning optics.

Cleaning Solution and Materials

½ cup distilled water – DO NOT USE TAP WATER1 cap full of 70% Isopropyl Rubbing Alcohol1 – 2 drops of dish soapCotton Swabs – useful for Stubborn particles and for cleaning eyepieces.Cotton Balls – general cleaningAcetone – useful in cleaning sticky materials such as tree sap from the corrector. DO NOT USE ACETONE ON MIRROR OR SECONDARY.

Cleaning Stroke

What tools do I need to perform a collimation?

Two or three eyepieces that offer a range of magnification from about 200x to 600x. An Allen wrench or screwdriver appropriate to the screws that you will use to set collimation. A flashlight in case you need to look closely at the collimation screws. Patience!

Collimation Guidelines

Always put the eyepiece directly into the visual back of the telescope. Never use a diagonal. You want the straightest possible light path for collimation. Make one adjustment at a time.Always (repeat: always!) re-center the star after every adjustment. Be patient!

Setting up for Collimation

To start collimation, point your telescope at a moderately bright star.Place an eyepiece that gives you about 200x in the visual back, and center the star in the field of view. Defocus the image slightly. You need a slightly out-of-focus star image to work with during collimation. The image at right shows what you don't want: an almost solid doughnut of light.

What does collimation look like?

The image at right shows what a mis- collimated scope will look like. The diffraction rings are not concentric -- they

are pinched or bunched up in one direction. The image at right shows the proper amount of defocus you are looking for. These diffraction rings are concentric, and show the ideal state: a perfectly collimated telescope. Air turbulence will no doubt result in

diffraction rings that move and shimmer

QUESTIONS?