How to Calculate the Field of View of the Sky-Watcher SK705AZ3 Short Tube Refractor Telescope

The area that you can see through your telescope is known as the true field of view or the actual field of view. The field of view of your telescope is determined by the design of the eyepiece of the telescope. This basic information can help you when calculating the field of view of a telescope.

Difficulty: Easy

Instructions

1. Find out the value of the field of view. Every eyepiece has its own value of the apparent field of view. This value of your eyepiece is supplied from the manufacturer.

2. Verify the value of magnification. The value of magnification can be found by dividing the value of the focal length of your telescope by the focal length of the eyepiece. For example, if your telescope has a focal length of 750 mm and the focal length of your eyepiece is 10 mm, the magnification for your telescope will be 750 / 10 = 75. It is usually denoted as 75X. The focal length for this model is 900mm.

3. Divide the value of the apparent field of view by the value of magnification to get the value of the field of view. For example, if your eyepiece has a value of apparent field of view of 50 degrees and a magnification of 75X, the value of the actual field of view is equal to 50 degrees / 75X = 0.66 degrees.

Tips & Warnings

• In cases when the magnification is not too high and the field of view does not have a very small value, finding the objects you wish to observe through your telescope may become a little difficult. Ideally, the magnification should be 2X per each mm of aperture.
• If you are a beginner, then start with a lower magnification to spot the object you want to observe. Once you have spotted the object, you can use a larger magnification telescope for a magnified image of the object.