Telescope Mounts Comparison: A Comprehensive Guide between Equatorial and Alt-Azimuth Models
For those embarking on a stargazing journey or delving into astrophotography, the choice between an equatorial mount (EQ mount) and an alt-azimuth mount (Alt-Az mount) is a crucial one. The decision hinges on your observing goals, particularly whether you prioritise astrophotography or visual observations.
Equatorial mounts, with one axis aligned with the celestial pole, are designed to compensate for Earth's rotation by moving the telescope in sync with the sky’s apparent motion. This feature is invaluable for long-exposure astrophotography, as it keeps the target centred without star trails. Properly powered and polar-aligned EQ mounts provide smooth all-night tracking, ideal for deep-sky imaging. Additionally, they frequently support motorised drives and are designed to handle autoguiding equipment used in high-quality imaging.
However, equatorial mounts present some challenges. Their setup can be complex, requiring careful polar alignment, making them more challenging for beginners. They are also heavier and less portable, which might be a downside for casual observers or those travelling to dark sky locations. Quality EQ mounts often come at a higher cost than comparable Alt-Az mounts.
Alt-Azimuth mounts, on the other hand, allow easy up-down and left-right motions, making them very intuitive and suitable for beginners and casual visual observers. They are typically lighter and more compact, which is great for quick setup and travel. However, since Alt-Az mounts do not track Earth's rotation with a single axis aligned to the celestial pole, the field of view rotates during tracking, causing star trails in long-exposure images. To overcome this, users can add an equatorial wedge that tilts the mount to act more like an EQ mount, but this adds complexity and does not eliminate rotation entirely.
In summary, for serious astrophotography, especially deep-sky imaging requiring long exposures, equatorial mounts are strongly preferred. For visual observing and casual planetary imaging, an alt-azimuth mount offers ease of use and portability with less setup time. A "hybrid" equatorial mount, which can be tilted into an alt-azimuth configuration, also exists.
If you start with an Alt-Az mount for simplicity but want to try astrophotography, you can upgrade with an equatorial wedge to improve tracking, though this remains a compromise compared to using a dedicated EQ mount. Today's eyepieces have much wider fields of view, making the advantages of equatorial mounts less crucial.
In short: - Choose equatorial mounts if you want precision tracking and serious astrophotography. - Choose alt-azimuth mounts if you want simplicity, portability, and ease of visual observing, with some capability for short-exposure imaging. - A hybrid equatorial mount, which can be tilted into an alt-azimuth configuration, also exists. - Alt-azimuth mounts can only track the sky automatically if they have a more complex computerized pointing system. - German equatorial mounts are recommended for larger refractors, Schmidt-Cassegrains, or deep-sky astrophotography. - Dobsonian alt-azimuth mounted telescopes are recommended for beginners. - Computerized alt-azimuth mounts add tracking but are not necessary for smaller aperture telescopes. - Catadioptric telescopes of 8" or larger aperture usually require tracking and/or computerized mount for high magnification. - Today's eyepieces have much wider fields of view, making the advantages of equatorial mounts less crucial. - An altitude-azimuth (alt-az) mount allows an instrument to move along two axes: altitude (up and down) and azimuth (left and right). - An equatorial mount rotates along a single axis called the right ascension (RA) axis. - Cheap German equatorial mounts (GEM) are not suitable for long-exposure deep sky astrophotography under $1,000 USD. - Cheap alt-azimuth mounts may have an outboard design, making aiming frustrating. - Computerized pointing is now available for both equatorial and alt-azimuth designs. - Manual tripod-mounted alt-azimuth mounts are suitable for refractors and smaller reflecting and catadioptric telescopes. - Even with computerized tracking, alt-azimuth mounts are difficult to use for long-exposure astrophotography. - Equatorial mounts are more suitable for tracking objects in the sky over long periods of time for astrophotography. - In very large telescopes (16" or larger apertures), alt-azimuth mounts are often used in conjunction with special tools like field derotators for long-exposure astrophotography.
- For serious deep-sky imaging, particularly long-exposure astrophotography, the use of an equatorial mount (EQ mount) is preferred due to its precision tracking capability.
- Equatorial mounts are designed for celestial pole alignment, allowing them to compensate for Earth's rotation and keep the target centred without star trails, an advantage for visual observations as well.
- On the other hand, an alt-azimuth (Alt-Az) mount is more suitable for simplicity, portability, and ease of visual observing, with less setup time and capabilities for short-exposure imaging.
- A "hybrid" equatorial mount that can be tilted into an alt-azimuth configuration exists and might be a good choice for those starting with an Alt-Az mount but interested in astrophotography.
- Dobsonian alt-azimuth mounted telescopes are recommended for beginners due to their simplicity and affordability, but they might not be ideal for long-exposure astrophotography.
