Secondary Mirror Size Calculator

Secondary Mirror Size Calculator

What size of secondary mirror do I need?

To determine the appropriate size of a secondary mirror for a telescope, you generally want to aim for a specific percentage of the primary mirror’s diameter. This percentage is often referred to as the “obstruction ratio” or “central obstruction.”

The common guideline for the central obstruction is to keep it between 20% and 30% of the primary mirror’s diameter. However, the optimal range can vary depending on various factors, such as the telescope design and the intended use of the telescope.

Here’s a simple calculation to determine the size of the secondary mirror based on the desired central obstruction percentage:

1. Measure the diameter of your primary mirror (let’s say it’s “D” inches).
2. Decide on the desired central obstruction percentage (let’s say it’s “O” percent).
3. Calculate the size of the secondary mirror (let’s call it “d”) using the formula: d = (O/100) * D.

For example, if you have a telescope with a 10-inch primary mirror and you want a central obstruction of 25%, you can calculate the secondary mirror size as follows: d = (25/100) * 10 = 2.5 inches.

Keep in mind that this is a basic guideline, and there may be other considerations specific to your telescope design or personal preferences. It’s always recommended to consult the manufacturer’s recommendations or seek advice from experienced astronomers or telescope experts for your specific telescope model.

What is the size of the secondary mirror on a telescope?

The size of the secondary mirror on a telescope can vary depending on various factors, including the design of the telescope, the manufacturer’s specifications, and the intended use of the telescope.

In general, the size of the secondary mirror is determined by the diameter of the primary mirror and the desired central obstruction percentage. The central obstruction is typically expressed as a percentage of the primary mirror’s diameter.

As a rough guideline, the size of the secondary mirror is often chosen to be within the range of 20% to 30% of the primary mirror’s diameter. However, this can vary depending on the specific telescope design and other considerations.

It’s important to note that different telescope manufacturers may have their own recommended sizes for the secondary mirror based on their specific optical designs and performance goals. Therefore, it’s best to consult the manufacturer’s specifications or documentation for the specific telescope model you are interested in to determine the size of the secondary mirror.

How do you calculate the offset of a secondary mirror?

To calculate the offset of a secondary mirror in a telescope, you need to consider the optical design and parameters of the telescope. The offset refers to the distance between the secondary mirror and the primary mirror’s center of curvature.

Here’s a general approach to calculate the offset:

1. Determine the focal length (F) of the telescope. This information is typically provided by the telescope manufacturer or can be measured directly if you have the necessary equipment.
2. Calculate the primary mirror’s radius of curvature (R) using the formula: R = 2 * F. The radius of curvature represents the distance from the mirror’s surface to its center of curvature.
3. Determine the desired offset ratio (OR) as a fraction or percentage of the primary mirror’s radius of curvature. The offset ratio is the distance you want to offset the secondary mirror from the primary mirror’s center of curvature.
4. Calculate the offset distance (O) using the formula: O = OR * R. This equation gives you the specific distance to offset the secondary mirror.

For example, let’s say you have a telescope with a focal length of 1000 mm, and you want to offset the secondary mirror by 25% of the primary mirror’s radius of curvature:

1. F = 1000 mm
2. R = 2 * F = 2 * 1000 mm = 2000 mm
3. OR = 0.25 (25%)
4. O = OR * R = 0.25 * 2000 mm = 500 mm

In this example, the offset distance would be 500 mm.

It’s important to note that the specific offset requirements can vary depending on the telescope design and purpose. It’s advisable to consult the telescope manufacturer’s specifications or documentation for accurate information regarding the offset of the secondary mirror for a particular telescope model.

What is the distance between primary and secondary mirror?

The distance between the primary and secondary mirror in a telescope is known as the “secondary mirror separation” or “secondary mirror distance.” This distance is a critical parameter in the optical design of a telescope and plays a role in determining the focal length and overall performance.

The specific distance between the primary and secondary mirror can vary depending on the telescope design and manufacturer specifications. It is typically determined based on the desired focal length and other optical considerations.

In many telescopes, especially those with a Newtonian or Cassegrain design, the secondary mirror is positioned at a specific distance from the primary mirror to achieve the desired focal length. The distance is carefully calculated to optimize the optical performance and ensure proper image formation.

To determine the exact distance between the primary and secondary mirror for a specific telescope, it is best to refer to the telescope manufacturer’s specifications, documentation, or consult the telescope design engineer. They will provide the recommended or required secondary mirror separation distance for the particular telescope model you are interested in.