Omegon Field Flattener 2"

Omegon Field Flattener Lens - perfectly flat planes for great astrophotography

Images obtained with many telescopes, whether refracting or reflecting, suffer from spherical aberration. The image looks slightly domed and the stars at the edges do not shine or show up as sharply as those in the center. A kind of out-of-focus discs appears. However, Omegon's Field Flattener Lens is capable of magically creating flat images with pinpoint stars all the way to the outer edges of the field of view.

Entrega entre 8 y 10 días laborables
Entrega entre 8 y 10 días laborables

easy problem to solve

Spherical aberration is an image distortion that goes undetected in visual observation and small-chip photography. It is noticeable when taking snapshots with large chip or full frame cameras. There is always the option to crop the photos and leave out the edges, but for that it is not worth spending so much money on a good camera. With this lens the problem is over, in a more elegant way.

Flatness throughout the visual field

The field of view is completely flat and the focal length of the equipment is maintained.

Suitable for telescopes from f4 to f8

You can use the Omegon field flattener with any refractor with a focal ratio between f4 and f8.

M48 thread for better aperture illumination

The Omegon field flattener has an M48 thread on both sides - giving you complete aperture illumination. A T2 thread plus M42 would limit the incoming light beam and so not provide sufficient aperture illumination for telescopes with 2" focusers. But using only the M48 thread, you make use of the entire light entering the telescope.

Use additional accessories - 109mm of back focus

This field flattener has a very generous 109mm of back focus. This means that you need a spacing of 109mm between the lens plane and the camera chip. This is an advantage, as it means you can use other accessories in between - such as a filter wheel, a flip-mirror or an off-axis guider. Using the correct Omegon extension rings will let you set the optimum spacing - whether you use accessories in between or not. Please also note the adapter recommendations in our Expert's Advice.

The advantages in a nutshell:

field flattener for refractors

suitable for telescopes from f4 to f8

M48 thread for complete aperture illumination at 2"

room for accessories between - 109mm of back focus

excellent multi-coating on lenses

Our expert comment:

The field flattener fits all modern ED refractors

Please note the following:

- The shorter the focal length, the longer the spacing that must be used to compensate for field curvature.

- The longer the focal length, the shorter this spacing must be due to the lower field curvature.

The telescope's focal length is important for determining the correct spacing:

- focal length <450mm: 128mm

- focal length 450-490mm: 123mm

- focal length 500-550mm: 118mm

- focal length 560-590mm: 116mm

- focal length 600-690mm: 113mm

- focal length 700-800mm: 111mm

- focal lengths above 800mm: 108mm

Delivery includes an extender combination for spacings of up to 53mm. You will need the flange focal distance of your camera and the thickness of its T2 ring to calculate the correct additional extender length for your telescope.


Your telescope has a 480mm focal length and needs a chip spacing of 123mm behind the flattener. You are using an EOS DSLR with a flange focal distance of 44mm and a T2 ring that is 9mm thick. In this case, the chip distance= 53mm (extender provided) + 44mm + 9mm = 106mmmm Hence the spacing still needs to be increased by 17mm.

Extenders to compensate for the residual difference can be found here: astroshop.eu/telescope-accessories/adaptors/15_37

It is OK if the extender is not correct to the millimetre, as a residual deviation of +/-4mm is still acceptable.

The back focus of more than 10cm allows the use of an off-axis guider. A well matched and inexpensive version can be found at: astroshop.eu/other-astro-photo-accessories/omegon-off-axis-guider/p,33139



Connection (to the telescope)  M48
Connector (at camera end)  M48
Appropriate for...  Refractors f/4 to f/8


Type Flatteners, Correctors, Reducers 
Type of build Flattener

Product Details
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