Aurora Flatfield Panel 590x590 mm with 220 V Inverter

Aurora Flatfield Panels for even Flats

These flatfield light panels use a thin electroluminescent foil, the Aurora flatfield foil, which emits an even, gentle white light after an external voltage is applied to it. The most important advantages are:

Perfectly even illumination - brighter areas which would deteriorate the flat are excluded.

A broad, continuous spectrum which may be used with emission line filters

As the foil itself emits the light of being backlighted, the design can be significantly lighter and flatter design is possible.

Choosing the right size - practical tip from Teleskop-Service:

The useable diameter of the flatfield panel should be at least 15% larger than the aperture of the telescope. Also, the larger the sensor, the larger the flatfield panel should be. Thus a telescope with 200 mm aperture should be equipped with a flatfield panel of at least 230 mm illuminated diameter.

It is not a problem to use a larger flatfield panel. We recommend to make a mask. Plastic foam has proven to be a a good material. On one hand such a mask guarantees a neat centered seating at the telescope, on the other hand you can use the use the panel with the telescope pointing in any direction, as there is no need to swivel the telescope upwards.

How do I get a good flat field image?

A good flat compensates for edge shading (vignetting), but also for darkening caused by dust on the filter, sensor or corrector. The background becomes even, the contrast can be raised further to make finer details visible in faint nebulae. The following basic settings should be noted:

The ISO or gain setting must be the same as for the lights, i.e. the actual astrophotography.

Telescope, camera and accessories, such as filters, off-axis guider etc., must be the same as for the actual exposure, also the position of the focuser should be unchanged.

The exposure time should be so short that nothing is "burned out", i.e. overexposed. Only in this way can the flat unfold its full effect. We recommend an exposure of 30-50%. The flat should not be burned out, but it should also not have any unexposed areas.

How do I find the right exposure time with the shooting software, for example Maxim DL?

The ADU value (Analog Digital Units) helps here. Every capture program shows this value when you move the mouse over the image. In the center of the image, where the illumination is highest, the ADU value is highest. The longer you expose, the higher this value becomes. If the ADU value is higher than the maximum value of the camera, the image is overexposed. A camera with 16 bits has a max. ADU value of 65536, one with 14 bits has 16384, one with 12 bits only 4096.

The exposure time of the flat should be so short that in the middle of the flat the ADU value is at most 50% of the maximum value of the camera. Then the flat looks well exposed. We recommend to take at least 10 flats per exposure and to process them to a "master flat".

If the flatfield box is too bright, that means it always produces overexposed images, then a white paper, which is fixed in the flatfield box, helps. This will dim the light and allow for slightly longer exposure times.