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Binning
Binning is a technique where groups of pixels are added together, with the result being a brighter
image. The CMOS sensor in the Atik Horizon only supports binning in software. This is where the
pixel values are added together after image acquisition, as opposed to hardware binning where
pixels are combined on the sensor.
Gain and Offset
Your Atik Horizon allows you to change the gain and offset settings for the camera. In very simple
terms, this is analogous to the volume control on a radio. The greater the gain, the easier it is to
detect faint signals, however less detail might be seen in the brighter ones.
The full well depth (ie maximum signal) of the Atik Horizon is around 20,000e-, which we map to a
pixel value of 65,535. By increasing the gain, we reduce the full well depth, which has the effect of
making the images appear brighter. Using a gain of x2, the full well depth is around 10,000e-. This
10,000e- now gives a pixel value of 65,535, which makes the image appear twice as bright. The
read noise, or how ‘grainy’ the background looks, will also increase. However, this increases a little
less than two times.
The useful range for gain is up to x30. Here, the image is 30 times as bright, but the full well depth
is only ~650e-. This means bright stars will saturate very quickly. Although it may look bad due to
the small full well depth, the read noise will only be about 1/3 of what it was at x1 gain. These kind
of settings are very useful for very dim objects or narrow band imaging if you don’t mind the bright
objects saturating.
Gain Presets
We provide three gain presets, and the option to use your own custom settings. The presets are:
Low - Best for normal imaging. It is the best setting for detail in brighter objects and when individual
images have high dynamic range.
Medium - A compromise of low and high. It’s very useful if your mount is unguided and you need to
take a lot of shorter exposures.
High - Best for sensitivity on dim objects, but sacrifices detail in some of the brighter parts. It’s good
for imaging with narrow band filters.
Custom - You can also experiment with using your own gain and offsets. As mentioned, we find gain
settings up to x30 are useful, depending on the situation, but above this the full well depth becomes
incredibly low.
Offset for Advanced Settings
The offset is a voltage added to all pixels. It’s used to ensure the digitised pixel values remain above
zero while maximising dynamic range. It can set between 0 and 511, with the default setting as the
Low preset values.
In Artemis Capture and Infinity, these are set in the Exposure window. In third party software, they
can be set through the ASCOM set-up dialog.
