Field flattener lenses in binoculars improve edge sharpness and lower the distortion. Field flattener lenses counteract the Petzval field curvature of an optical system. In other words, the function of a field flattener lens is to counter the field-angle dependence of the focal length of a system.

How do you use a field flattener?

Using a field flattener is a no-brainer: just screw it at the back of your telescope or insert it in the telescope using a nosepiece. That's it.

Is a field flattener necessary?

To use a telescope for photography an optical device is needed to convert your telescope from a visual instrument to a photographic camera lens. This optical device is a field flattener (or reducer/flattener). Without a field flattener stars that are not in the center will appear distorted. Spacing is critical.

Do field Flatteners reduce focal length?

The former will leave the focal length of the telescope essentially unchanged whilst the latter will reduce the effective focal length by 0.8x, 0.7x or 0.6x, as well as flattening the field – these will both widen the field of view and reduce the focal ratio so shorter total exposures will be required.

Do I need a field flattener with a crop sensor?

Typically a telescope will require about a 3 inch focuser to handle a full frame sensor and usually (a few don't) need a thing called a field flattener to enable the stars to be pinpoints in the corners of the image.

About Field-Flatteners, Coma Correctors and Reducers | DSLR Astrophotography

29 related questions found

Is a field flattener the same as a coma corrector?

Often in the form of an accessory, like a coma corrector that when added to a newtonian corrects it's coma, or a field flattener that when added to an SCT or to a refractor corrects it's field curvature. Some times, the corrections are built-in the scope.

How do you calculate back focus?

To calculate the backfocus of your setup, add up the backfocus of all the separate components. For example, if we take an Atik 460EX camera, this has a backfocus of 13mm. If we then add in an EFW2 filter wheel, this has a backfocus of 22mm.

What is a focal length reducer?

A telecompressor or focal reducer is an optical element used to reduce focal length, increase lens speed, and in some instances improve optical transfer function (OTF) performance. ... The effects and uses of the telecompressor are largely opposite to those of the teleconverter or Barlow lens.

What is a Coma Corrector?

A coma corrector corrects edge of field distortion in short-focus newtonians. This distortion causes stars at the very edge of your field to look like little comas (",") instead of sharp points. This effect, is particularly pronounced at the lowest magnifications; not so much so at higher powers.

Is a focal reducer worth it?

Yes, they're worth it, though less if you also have a 2" visual back, diagonals and eyepieces.

What does a telescope focal reducer do?

Focal reducers are primarily used in astrophotography to compress the light cone exiting the telescope down to a size closer to that of the sensor within your camera. This also results in a brighter image which reduces the exposure time.

What is field flattening?

A field-flattening lens is a thin plano-concave negative lens, which is placed close to the image plane of an optical system to flatten the curvature of its image surface by minimizing the Petzval aberration [7]. ... By being close to the image plane it minimally affects the other aberrations.

What is a flattener?

A bull flattener is a yield-rate environment in which long-term rates are decreasing more quickly than short-term rates. In the short term, a bull flattener is a bullish sign that is usually followed by higher stock prices and economic prosperity.

What is a flattener definition?

flattener (plural flatteners) Anything that flattens. (finance) A trade whose terms are based on the assumption that the rate of return will decrease.

What does an F 6.3 focal reducer do?

An f/6.3 reducer is designed to reduce the focal ratio of an f/10 SCT to f/6.3. ... If the focal reducer is to be used for visual observation, the visual back is threaded onto the eyepiece side of the reducer, and then a star diagonal and eyepiece are installed as usual.

What does a focal extender do?

A Focal Extender does exactly what the name implies; it extends the effective focal length of the lens that it is used in conjunction with, thus producing higher magnifications for imaging and visual applications.

What is Backfocus telescope?

Back focus is the distance from the end of your eyepiece drawtube to the focal plane of your telescope. ... Refractors usually have large back focus distances; their long drawtubes can travel well inside focus, too.

How does a Barlow affect Backfocus?

A Barlow can affect backfocus but figuring out exactly how it affects optimal back focus is difficult because the Barlow diverges the light cone which moves the focal plane reward. The optimal back focus depends on the location of the mirrors.

Does a coma corrector change focal length?

This coma corrector, inserted into the focuser in front of the camera, corrects the image and doesn't reduce the focal length of the telescope. ... This coma corrector, to work best, requires you to place the camera sensor at a precise distance from the back of the flattener thread.

Do I need a coma corrector for astrophotography?

Coma correctors work for both visual observing and photography. Since your telescope is f/7.9, you don't need to worry about coma.

How do you fix a coma in a telescope?

Fixing aberrations

Field curvature can be corrected by the use of an external field flattener, available in two designs, one that flattens only and a second type that also reduces the apparent focal length. These are very popular with refractor users. Coma can be removed by the use of a coma corrector.