Telescope Components for Visual Astronomy: An Overview of Their Roles
Telescope enthusiasts often find themselves navigating a vast array of equipment, from mounts to eyepieces. In this article, we'll delve into the world of telescope mounts and some essential accessories.
Telescope Mounts
When it comes to telescope mounts, there are two main types: equatorial mounts (GEM) and altitude-azimuth (alt-az) mounts. The primary difference lies in their axes of movement and tracking capabilities.
Equatorial Mount (GEM)
Equatorial mounts have one axis aligned parallel to Earth's rotational axis, allowing the telescope to follow the rotation of the sky with a single motion (right ascension axis). This alignment enables precise tracking of celestial objects as Earth rotates, which is essential for long-exposure astrophotography and reduces manual adjustments during observation. However, they are usually more complex to set up, bulkier, heavier, more expensive, and may require more maintenance.
Altitude-Azimuth Mount (alt-az)
Altitude-azimuth mounts move in two perpendicular axes—altitude (up/down) and azimuth (left/right). They offer intuitive, simple movement for casual visual observations but cannot track stars with a single-axis motion. To follow celestial objects, it requires simultaneous adjustment on both axes, which complicates long-exposure photography. Despite this, they are lighter, more portable, and are more comfortable for viewing angles due to vertical and horizontal movement.
A hybrid mount like the WarpAstron WD-20 combines the two modes, allowing operation both ways: equatorial mode for precise tracking and astrophotography, and alt-azimuth mode for comfortable visual observation.
| Mount Type | Advantages | Disadvantages | |-----------------------|----------------------------------------------------------------------------|----------------------------------------------------------------------------| | Equatorial Mount | - Accurate tracking of stars with a single motorized axis | - Usually more complex to set up (alignment needed) | | | - Ideal for long-exposure astrophotography | - Typically bulkier and heavier | | | - Keeps objects centered longer without much manual adjustment | - More expensive and may require more maintenance | | Altitude-Azimuth Mount | - Simpler and more intuitive to use for beginners | - Cannot track celestial objects with a single axis | | | - More comfortable viewing angles due to vertical and horizontal movement | - Less suitable for astrophotography without computer control or field derotators | | | - Usually lighter and more portable | - Requires simultaneous dual-axis motion for tracking |
Accessories
Finderscopes
Finderscopes are targeting tools used to point the telescope at a target. Common types include magnifying finderscopes (RACI & Straight-through), which offer a wider field of view and higher visibility in light-polluted areas. An alternative to these is the red dot finder (RDF), a low-cost, easy-to-use targeting tool that uses a simple alignment process.
Eyepieces
The eyepiece is the part of the telescope system that provides magnification. It is common to have multiple eyepieces in a starter package. Eyepieces are standardized and can be shared between telescopes. The higher the number on the eyepiece, the lower the magnification it provides.
Focusers
The focuser is a moveable device that is used to focus the image that we see on the eyepiece. Beginner packages usually have a single-speed focuser, while more expensive packages may have a dual-speed focuser for precise focusing.
Diagonals
Refractors, SCTs, and MCTs typically have diagonals, which bend the light to a more convenient viewing position. Common sizes for diagonals are 1.25 inches and 2 inches, which determine the diameter of the eyepiece that the diagonal can accept. A 90-degree diagonal, or star diagonal, is optimized for astronomy, while a 45-degree diagonal is optimized for daytime use as a spotting scope.
GoTo Mounts
A GoTo mount is a motorized telescope mount that tracks a target as the Earth rotates. The setup and alignment of a GoTo mount vary by brand and model, so refer to the user's manual for the alignment procedure.
- Telescope enthusiasts can choose between equatorial mounts (GEM) and altitude-azimuth (alt-az) mounts, each offering different advantages and disadvantages in terms of tracking capabilities, complexity, portability, and cost.
- Equatorial mounts, like the WarpAstron WD-20, have a single motorized axis aligned with Earth's rotational axis for precise tracking of celestial objects, making them ideal for long-exposure astrophotography.
- On the other hand, altitude-azimuth mounts move in two perpendicular axes, allowing for more intuitive and comfortable movement during visual observations, but they may require simultaneous adjustment on both axes to track celestial objects.
- Accessories such as finderscopes, eyepieces, and focusers are essential additions to any telescope setup, with finderscopes like magnifying finderscopes (RACI & Straight-through) offering a wider field of view and higher visibility in light-polluted areas.
- Beginners may find diagonals, which bend the light to a more convenient viewing position, particularly useful, with common sizes being 1.25 inches and 2 inches. A 90-degree diagonal, or star diagonal, is optimized for astronomy, while a 45-degree diagonal is optimized for daytime use as a spotting scope.
