Anyone involved in astrophotography will inevitably come across the term " flatfield" at some point. When an image is taken through a telescope, image errors occur as a result of the varying intensity of the lighting on the sensor. In order for the image processing software to correct this error, images of an evenly illuminated area are required, which are taken under the same conditions as the actual images. The Aurora Flatfield light sheet creates such an area.
The advantages of Aurora Flatfield light sheets:
- Completely uniform illumination of the lens aperture
- Full spectrum, therefore also suitable for use in combination with line filters
- Power supply available for 12V or mains voltage
The Aurora flat field foils are supplied ready-mounted in a plastic frame: The frame is made of unbreakable plastic, has rounded corners and is fitted with edge protection: Your Aurora foil is thus perfectly protected during transport to the observation site, and the milky front plate ensures even more uniform brightness distribution.
The diameters of the foils are chosen to cover typical instrument sizes:
- Diameter 100 mm for instruments with an aperture of up to 4"
- Diameter 160 mm for instruments up to 6" aperture
- Diameter 220 mm for instruments up to 8" aperture
- Diameter 315 mm for instruments up to 12" aperture
- Diameter 420 mm for instruments with openings up to 16"
- Diameter 590 mm
- Diameter 750 mm
Selecting the right size:
- To obtain high-quality flat field data, the free aperture of your instrument must be completely covered. The diameter of the dew shield or similar is not decisive! For example: For a 6" (15 cm) refractor, the 160 mm Aurora is sufficient, regardless of the diameter of the dew shield!
- If you are using a Newton, RC, ODK or similar, the Aurora light sheet must be larger than the free diameter of the optics! As a rule of thumb for a Newton: Free mirror diameter + diagonal of your camera's sensor. Here is another example: For an 8" Newton, a 220 Aurora is sufficient if you are using a camera with a very small chip (<14 mm diagonal). If you are using a typical DSLR with an APS-C sensor, you will need to choose a 315 mm Aurora.
It is no problem to use a large Aurora for smaller instruments: for example, if you have a 315 mm Aurora, you can also use it without any restrictions for a 4" refractor or your camera lenses.
The brightness of the foils is ideal for images with filters, but must be reduced for images in white light or with only an L filter. The brightness of the Aurora Flatfield light foils can be adjusted within limits by reducing the input voltage (only when using 12V inverters). In addition, the brightness can be easily and inexpensively adjusted by placing one or two layers of white paper in the frame between the film and the instrument! For use with very bright instruments or large cameras with slow shutters, you will find grey film filters in the appropriate sizes under "Recommended accessories". These films allow a very strong reduction of the brightness. For use with bright astrographs, we recommend ordering these films directly!
Power supply: There is a corresponding inverter for each size of Aurora Flatfield light sheets. A normal power supply cannot be used because the light sheets are operated with high voltage. However, there is no danger due to the low current. Please only use the sheets with the recommended inverter: They will also work with larger inverters, but their service life will be greatly reduced.
Scope of delivery: Aurora Flatfield light sheets are delivered as a complete, ready-to-use set. This consists of the light sheet in the frame, the matching inverter, all necessary cables and printed operating instructions.
