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Telescope Optics and Eyepiece Cleaning

Telescope Optics – Your telescope is a scientific instrument and should be treated as such. Dirty optics will reduce and scatter light which reduces contrast, objects you view are less crisp.

You should only clean your telescope optics twice a year, remember less is more. To help keep optics clean always replace the telescope cover when not in use and put your eyepieces back in their containers or plastic sandwich bags.

Eye piece cleaning

Never cover your telescope optics or eyepieces if they have dew or condensation on them, instead use a hairdryer on low heat until they are dry then cover them.

You can buy cleaning kits with everything you need at Adorama. They sell telescope optics Cleaning Kits for $9.95 and lens cleaning kits for $4.95 they also have plastic eyepiece holders and dew shields if you need them.

In the Telescope Optical Cleaning Kit you will find….

  • Blower Bulb – Removes coarse dust and dirt particles.
  • Packet of Lens Tissue – Soft and lint-free, used to apply cleaning fluid; won’t scratch.
  • Optics Cleaning Fluid – Safely removes grime and oily residues from telescope optics.
  • Cleaning Cloth – Great for quick cleanings; micro fibers pick up tons of dirt from telescope optics.
  • Cotton Swabs – Ideal for cleaning small lenses and around lens edges.

In the Lens Cleaning Kits you will find….

  • Blower Bulb.
  • Packet of Lens Tissue.
  • Optics Cleaning Fluid.
  • Cotton Swabs.

Please, Never Use household window or mirror cleaners on your telescope optics. Also Never Use towels, dust cloths or paper tissues as they will scratch and damage your telescope optics.

Cleaning Eyepieces – You should only need to clean the eyepiece’s outer surface as this is the surface most likely to be dirty. Never dismantle your eyepieces unless you know what you are doing. The internal surface should not need cleaning unless moisture has penetrated. In this case send it to a specialist for cleaning.

  • First blow off any loose dust using the “Blower Bulb”.
  • Dip the “Cotton Swabs” into the ” Optics Cleaning Fluid” and dab don’t wipe the eyepiece lens.
  • Lay the eyepiece on its side and allow to dry naturally.

Cleaning Refractor Telescope Optics– The refractor’s objective lens (the large mirror at the top of the tube) gets dirty and can be cleaned if you are careful.

  • If possible, lay the telescope on a draining board so that it is vertical or alternatively, turn the telescope on its mounting so that it is aimed slightly downwards.
  • Cover any electronics components so that they cannot get wet.
  • Blow off any loose dust using the blower brush. For refractors, also blow out any loose dust inside the dew cap.
  • Using the telescope optics cleaning fluid and lens tissues wipe the mirror and allow to dry naturally. To see if there are any finger prints or stains, shine a torch into the tube from the eyepiece end.
  • Leave the corrector plate (or objective) in the vertical position to dry. Your telescope optics are now clean.

Cleaning Schmidt-Cassegrain telescope Optics – The corrector plate ( the window like covering at the top end of the telescope) gets dirty and can be cleaned if you are careful. NEVER remove the corrector plate – or the primary mirror unless you know exactly what you are doing.

  • If possible, lay the telescope on a draining board so that it is vertical or alternatively, turn the telescope on its mounting so that it is aimed slightly downwards.
  • Cover any electronics components so that they cannot get wet.
  • Blow off any loose dust using the blower brush from the telescope optics. For refractors, also blow out ant loose dust inside the dew cap.
  • Using the telescope optics cleaning fluid and lens tissues wipe the mirror and allow to dry naturally. To see if there are any finger prints or stains, shine a torch into the tube from the eyepiece end.
  • Leave the corrector plate in the vertical position to dry.
  • If any liquid has got inside the corrector plate, leave the telescope’s front cover off, and allow to dry naturally.
  • Your telescope optics are now clean.
  • If internal stains on a corrector plate or objective lens are evident, then the telescope optics should be cleaned by a specialist, or returned to the manufacturer.

The telescope optical components of commercial Schmidt-Cassegrain are assembled and tested in a specific relationship to each other, at the factory.

Cleaning Reflector Telescopes Optics – You will need to remove the primary mirror (the big one at the bottom of the tube) from the telescope. Most reflectors use a mirror cell, attached to the end of the tube, to support the primary mirror. All good mirror cells have large and obvious screws (or bolts) on the back side, to adjust the tilt of the primary (see alignment below). You DO NOT need to undo these, look instead for screws or bolts at the sides or edges of the mirror cell. In general:

telescope eyepiece

  • It is advisable to remove the primary mirror from its cell before washing, because this will keep liquids out of the cell assembly. However, you can begin cleaning before mirror removal.
  • Place the telescope cell (with mirror) on a clean surface (such as a draining board), with the mirror facing upwards. Then use the blower brush to blow off any loose dust from telescope optics.
  • You will see some restraining device(s) around the edge of the mirror’s upper surface. Typically, these are small padded metal plates which are held in place by screws attaching to the mirror cell. Some mirror cells may use a padded ring, or spring-steel “fingers”. Carefully remove the restraining device(s) from the mirror. A magnetic screwdriver is helpful!
  • Some large Dobsonian mirrors are restrained by a sling or girdle which is hung between two strong supports on the side of the mirror cell. The sling supports the weight of the mirror when the telescope is aimed low in the sky. Be sure to replace the mirror and cell “right way up” when you’re finished.
  • You should now be able to lift the primary mirror out of the mirror cell. Small mirrors may be resting directly on the padded metal surface of the cell. Larger mirrors are supported underneath by an arrangement of balanced metal plates, be careful not to disturb these, because their positioning is important to your mirror’s telescope optical performance. Good mirror cells will feature alignment studs and holes which “automatically” reposition these plates when the mirror is replaced.
  • Blow off any loose dust from the telescope optics using the blower brush.
  • Use the telescope optics cleaning fluid and lens tissue from your cleaning kit wipe the mirror, repeat if very dirty.
  • Leave the corrector plate in the vertical position to dry. Your telescope optics are now clean.
  • Telescope optic Mirrors used near the sea, or sources of industrial pollution, will tarnish within a few years. Tarnish is typically a brown or dirty yellow patina on the mirror. If tarnishing is severe then your mirror needs to be re-aluminized. This is a task for a specialist.

Now that you have cleaned your telescope optics, you will need to realign them. Your telescope’s manual will show how to align your telescope optics or go to the page on Telescopes Problems – Collimating Optics

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