# What does D and F mean on a telescope?

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The aperture of the objective lens of this simple telescope is D. The focal length of the objective lens if F. The focal length of the eyepiece is f.

## What does the f number mean on a telescope?

Scope Focal Ratio (f/number): A lens or mirror’s focal length divided by its aperture. For instance, a telescope with an 80-mm-wide lens and a 400-mm focal length has a focal ratio of f/5. Eyepiece Focal Length: Eyepiece focal lengths are nearly always printed on the eyepiece itself and are labeled in millimeters.

## What is a good aperture for a telescope?

As a rule of thumb, your telescope should have at least 2.8 inches (70 mm) aperture — and preferably more. Dobsonian telescopes, which are reflectors with a simple mount, provide lots of aperture at relatively low cost. A larger aperture lets you see fainter objects and finer detail than a smaller one can.

## Is 700mm focal length good?

And a 700mm focal length telescope, properly mounted and with a good eyepiece, can provide visually interesting views of Mars. You should be able to just make out the ice cap, and perhaps even some slight shading of the planet surface, though that is less likely.

## What is the best focal length for telescope?

A good all round first telescope should have a focal length of around 1000mm to 1200mm. All refracting telescopes use a glass lens as their primary focusing unit.

## What does D mean in telescopes?

The Moon seen through a telescope at high magnification. … The aperture of the objective lens of this simple telescope is D. The focal length of the objective lens if F. The focal length of the eyepiece is f.

## How do you find the f number?

The F-number of a lens is the ratio of its focal length divided by the diameter of the aperture.

## What does f 10 telescope mean?

A telescope’s “f/number” is its “focal ratio”. A scope with a focal LENGTH of 1000mm and an aperture (diameter) of 100mm has a focal ratio of 10, and is designated “f/10” (divide aperture into focal length).

## What magnification telescope do I need to see planets?

Experienced planetary observers use 20x to 30x per inch of aperture to see the most planetary detail. Double-star observers go higher, up to 50x per inch (which corresponds to a ½-mm exit pupil). Beyond this, telescope magnification power and eye limitations degrade the view.

## How good is a 70mm telescope?

With a 70mm telescope, you will easily be able to see every planet in the Solar System. You will also be able to take a great look at the Moon and clearly distinguish most of its recognizable features and craters. Mars will look great. … The magnitude limit of a 70mm telescope is about 11.9.

## Is 400mm good for a telescope?

With 400mm you could watch objects like: Andromeda galaxy core. Orion nebula, other large emission or reflective nebulae (e.g. Pleiades) large star clusters.

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## What telescope is best for viewing galaxies?

Best telescopes for viewing galaxies

• Orion SpaceProbe 130ST.
• Solomark 114AZ.
• Orion SkyView Pro 8.

## Is 76 mm aperture good telescope?

✔Large aperture. 76mm aperture provides more lights and clearer images, even beginners can get clear images. The bigger the aperture, the bigger the field of vision, and the clearer the image. Imagine that the moon at night is as clear and bright as the scenery during the day.

## What can you see with a 100mm telescope?

What Can You Expect From 100mm Telescopes? (With Photos)

• The maximum magnitude of a 100mm telescope is 13.6. For reference, the Moon has a magnitude of -12.74 and Mars has a magnitude of -2.6. …
• The Moon. The Moon looks amazing in these telescopes. …
• Mars. …
• Venus. …
• Jupiter. …
• Saturn and Neptune. …
• Pluto and Dwarf Planets. …
• Mercury.

## How much magnification do you need to see Jupiter?

Generally a magnification of 30-50x the aperture of your telescope (in inches) works well on nights of average seeing. So if you have a 4-inch telescope, try 120x to 200x. If you have razor sharp optics and steady sky, you can get away with even more magnification.

## How strong of a telescope do I need to see Saturn?

The rings of Saturn should be visible in even the smallest telescope at 25x [magnified by 25 times]. A good 3-inch scope at 50x [magnified by 50 times] can show them as a separate structure detached on all sides from the ball of the planet. Want to see Saturn’s rings?

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