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Glossary | Telescope accessories | Capacity | Type

Describes the type of accessory in more detail.

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Aluminium dew shield cap

Protects the front surface of the telescope from condensation.

Amici prism

A prism at 45° or 90°, which produces an upright and right-sided image for refractor, SC, and Mak telescopes.

Barlow lens

Extends the focal length and thus increases the magnification of a telescope. Is seated between the telescope and eyepiece or camera.

Binocular viewer

This accessory makes observation with both eyes possible.

Broadband filter

Nebula filters that allow a very wide range of the spectrum through, but block stray light and certain wavelengths associated with artificial (neon) light. They are also used for photography at dark sky sites.

Colour filters

Colour filters are used for observing planets. Surface details, bands of clouds and other phenomena become more easily visible.


A weight used for balancing the declination or ascension axes.

Diagonal mirror

A deflecting mirror connected to a focuser, which deflects the image upwards by 90°. This makes observing more comfortable.

EQ platform for Dobsonian telescopes

Motorised tracking especially for Dobsonian telescopes.

Erecting lens

An erecting lens corrects the image for nature observing and extends the focal length by a small amount.

Filter wheel

A filter wheel provides space for several filters, which can be easily selected via a rotary function. This eliminates the need for time consuming filter changes.

Focal reducer

Reduces the focal length of the telescope.

Grey filter

Also known as a neutral density filter. For reducing the glare from bright light sources such as the Moon, Jupiter and Venus.

Interferential filter

Filters light through thin layers and allows it to pass only at certain wavelengths.

Laser pointers

Adjusting lasers serve to collimate a Newtonian telescope.

Moon filter

A moon filter reduces the bright light of the moon and protects against glare.

OIII filter

A nebula filter for larger telescopes and as a supplement to the UHC filter. OIII filters are suitable for planetary nebulae and supernova remnants.

Polarising filter

Linear polarising filters reduce the light and let it through in one direction only, for example vertically. Double polarising filters can be rotated against one other. As a result, the filter can be infinitely adjusted from light to dark.

Solar prism

The Herschel wedge deflects 96% of the sunlight away from the light path and allows only 4% of the light to pass through. Additionally, an ND3 grey filter, a UV/IR blocking filter and a solar continuum filter are also required for observing.

T Adapter

An adapter with an integrated T2 thread. This is a standard thread for which there are many appropriate accessories.

UHC Filter

A nebula filter is mainly suitable for visual observing and for smaller telescopes. It increases the visibility of hydrogen bands and planetary nebulae.

USB filter wheel

A filter wheel that can be connected to a PC via USB and controlled electronically.

Vibration damper

Stable support pads for the tripod. Ideal for vibrating surfaces such as a patio with a timber floor.