How To Determine Telescope Tube Length. To determine the absolute minimum size the Newtonian secondary mirror clear aperture can be and remain in the geometric cone of light formed by the primary mirror, let's start.
Telescope tubes come in a variety of lengths, and understanding the basics of how best to determine the length of a tube can help you make the best choice when shopping for a new telescope. Telescopes are typically measured in millimeters (mm) and inches (in), so it is important to understand both systems when looking at a telescope tube.
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The length of a telescope tube will typically be determined by the focal length of the telescope. The focal length is the distance from the primary mirror or lens of the telescope to the point of focus on the eyepiece. This is sometimes referred to as the “back focus” of the telescope. The longer the focal length, the longer the telescope tube length will need to be. For example, a telescope with a focal length of 600mm will require a telescope tube that is at least 600mm long.
Factors Affecting Telescope Tube Length
The length of a telescope tube can also be affected by a variety of other factors. These can include the type of telescope, the size of the primary mirror or lens, the type of mount, and the type of eyepiece used. For example, a refractor telescope will typically require a longer tube than a reflector telescope, and a larger primary mirror will also require a longer tube. Additionally, the type of mount used can affect the length of the tube, as some mounts will require a longer tube to accommodate the movement of the telescope. Finally, the type of eyepiece used can also affect the length of the tube, as some eyepieces will require a longer tube in order to provide adequate focus.
When purchasing a new telescope, it is important to consider all of these factors when determining the length of the telescope tube. Many telescope manufacturers will provide detailed information on the length of the tube required for their particular telescopes, but it is still important to understand the basics of how to determine the correct length for your particular telescope.
The easiest way to determine the correct telescope tube length is to use an online telescope calculator. These calculators will typically ask for information about the telescope, such as the focal length and the size of the primary mirror or lens, as well as the type of eyepiece being used. Once this information is entered, the calculator will then be able to provide the correct tube length for your telescope.
It is also important to consider the type of mount being used when determining the correct telescope tube length. Some mounts will require a longer tube in order to accommodate the movement of the telescope. In these cases, it is important to take into account the type of mount being used when calculating the correct telescope tube length.
In summary, understanding the basics of how to determine telescope tube length can help you make the best choice when shopping for a new telescope. By taking into account the focal length, the size of the primary mirror or lens, the type of eyepiece being used, and the type of mount being used, you can easily determine the correct telescope tube length for your telescope.
Telescope Basics 2 (of 6): Learn to calculate magnification for a telescope/understand focal ratios
Hosted by David Fuller of "Eyes on the Sky," this video discusses the basics of telescope magnification and focal ratio. Each concept is covered, guiding the viewer through how to calculate magnification of a telescope and eyepiece combination, and how to determine the focal ratio of a given telescope. An excellent primer for anyone wanting to understand more about telescopes. #withcaptions
Figure 1. The minimum tube diameter is determined b y MTD = 2 * D2E * Tan (TF / 2) + D + 0.5 where the d istance (D2E) is from the primary mirror face to the end of the. The resulting focal length can be calculated by multiplying the telescope’s focal length by the focal reducer’s multiplier. For example, a telescope with a focal., How To Determine Telescope Tube Length.
