Lowrider wrote:
I don't want to get into the tripod debate but I do have a question about tripod heads. All I currently own is a medium travel tripod and know very little about the various models. I plan on traveling to the top of a mountain in North GA to take pictures of the solar eclipse. It occurs to me that during the eclipse, the sun will continue to set and will move within the viewfinder. Does anyone know of a tripod head that is adjustable incrementally by turning a dial to move the focus small increments at a time? Unlocking and moving and relocking can result in a very difficult adjustment especially when using a telephoto lens.
Thanks for your help.
I don't want to get into the tripod debate but I d... (
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Hmmm. I'm curious to see if someone does come up with a workable product or plan. I'd think though for tracking anything in space you would need a telescope / astronomical mount (head). Remember things like stars and planets, etc. move in arcs not straight lines. On the cheap and with crude adjustment or movements you might try a Video fluid head (the ones with the long handles).
Different types of telescope mounts
To a large extent, a telescope [think telephoto lens] is only as good as its tripod and mounting. A telescope is used to magnify the sky, but unfortunately it also magnifies vibrations. A telescope mount has two primary functions:
Support the telescope firmly so that objects can be viewed and photographed without vibrations
Provide a system for smooth controlled movement to point and guide the instrument
There are two major types of mounts for astronomical telescopes:
Altazimuth and
Equatorial.
AltazimuthAltazimuth (sometimes called alt-az) is the simplest type of mount with two motions, altitude (vertical) and azimuth (horizontal): thus the name Altazimuth. Good Altazimuth mounts have slow-motion knobs for making precise adjustments, aiding smooth tracking across the sky. These type mounts are generally good for terrestrial observing and for scanning the sky at lower power but not for deep sky photography. Some Altazimuth mounts are now computer driven and allow a telescope to track the sky more accurately. This is generally good for visual use but can lose tracking on longer exposure astrophotography.
In addition to a standard Altazimuth, mounted on the top of a tripod, there is also the Dobsonian Mount.
Dobsonian MountThe Dobsonian mount is a newer, modified version of the Altazimuth mount. This mount was invented in the 1970's by John Dobsonian. Dobsonian mounts are mounted on the ground by a heavy platform, and designed to support massively sized Newtonian Reflectors, while keeping a steady image. It is common for Dobsonian telescopes to have very large apertures - anywhere between 6 and 20+ inches!
EquatorialEquatorial mounts are superior to non-computerized Altazimuth mounts for astronomical observing over long periods of time and absolutely necessary for astrophotography. As the earth rotates around its axis, the stationary stars appear to move across the sky. If you are observing them using an Altazimuth mount, they will quickly float out of view in both axes. A telescope on aproperly aligned equatorial mount can be aimed at a celestial object and easily guided either by either manual slow-motion controls or by an electric motor.
There are two relatively simple steps to aligning your equatorial mount:
Position the tripod so that it points along a line with celestial south. The tripod can be placed pointing anywhere in a 360 degree circle, but you want the front of the mount aiming south. Do not confuse this with magnetic south, as they are not aligned! Some mounts are equipped with a device for rotating the telescope, which can be pointed south instead of aligning the tripod itself.
The first joint above the tripod allows adjusting the telescope to be tilted back. This needs to be tilted to the same number of degrees as the viewer's latitude. Once this is done, the telescope should be pointing at the celestial South Pole.
There are two basic types of equatorial mounts:
German Equatorial MountBoth Newtonian Reflectors and Refractor telescopes normally use this type mount. The German Equatorial mount’s distinguishing feature is the large counterweight extending on the opposite side from the telescope. This counterweight is vital, as it provides balance to the telescope.
Fork MountMost Catadioptric and other shorter optical tubes use this style mount, which is generally more convenient to use than the German mount, especially for astrophotography. A computer controls the telescope using an internal, digital equatorial drive to calculate the Altazimuth setting for the mount. This is the style of mount most commonly used in modern research telescopes. This fully automatic operation can make observing extremely fun and easy, while saving the observer considerable time and effort in locating objects. With this type of mount, you will often only need to align the telescope to celestial south, and enter your latitude and longitude, and the computer will do the rest.
Good luck.