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Altair ADC Atmospheric Dispersion Corrector


Quick Overview

Altair ADC Atmospheric Dispersion Corrector - designed to mitigate the effects of atmospheric refraction of light when imaging or observing objects, particularly at low altitude.
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As many observers and imagers are aware, the Earth's atmosphere acts as a giant lens itself, which causes a slight spectral spread of light coming into telescopes, which is particularly pronounced, the lower the altitude of the target object in the sky. This is particularly noticeable when observing or imaging objects at high power.
The Altair ADC Atmospheric Dispersion Corrector is a very useful device which fits between the telescope and camera (or eyepiece) and allows for the correction of this spectral spread.

This is accomplished by offsetting two narrow prisms inside the device against one another - pulling in the stray wavelengths of light and producing much cleaner and sharper images as a result. Scroll through our selection of images to see the results of a before and after screenshot of the Altair ADC being used with one of their cameras on the Moon. Note the colour "fringing" around features in the upper image - this is the effect the ADC is designed to correct. Compare this to the image below this with the ADC correctly adjusted and you'll see that this fringing has disappeared. The correct use of the ACD will make quite a bit of difference when trying to tease out fine detail on the Moon and brighter planets - particularly those that are currently low down in the southern part of the Ecliptic, for those of us in the northern hemisphere.

Altair's description and insturctions for the ADC are as follows:

"The ADC corrects for atmospheric dispersion (rainbow effect) producing sharper images of object closer to the horizon.

Particularly useful on Mars, Saturn, Jupiter and the moon at about 20-40 degrees altitude.

The prisms are high quality K9 glass with broadband multicoatings and a maximum deviation angle of 2.5°.

The rear side has 1.25" pushfit adapter with 3x thumbscrews and internal compression ring to protect your Altair or other CMOS cameras and eyepieces. The pushfit adapter can be unscrewed to reveal a T-Thread for direct camera connection. The nosepiece is threaded for filters.

The unit has a rotating lockable scale, so you can record your optimum settings.

Instructions and tips for using the Altair ADC: We have included and "before and after adjustment" image in the product images which is worth viewing. Firstly, examine the image of the target object in the video preview window. You should see a subtle "rainbow effect" on objects below an altitude of 40 degrees above the horizon. This effect is increased the closer you get to the horizon until it's very obvious. To see the "rainbow effect" more clearly it is recommended to increase the saturation control of your camera (this feature is found under the "Colour Adjustment" menu in AltairCapture and other image capture software and it will not affect the final image provided you are imaging in RAW mode recording .SER files which is the best setting for solar system imaging). Because adjustment of the prisms offsets the image slightly, it helps to zoom in (mouse wheel in AltairCapture) to see it more clearly while starting at lower powers then moving to higher powers - look along the border of high contrast features on the moon and the edge of planets to see the effect more clearly. Move the levers together or apart, to change the divergence angle of the prisms relative to each other. By changing the angle of deviation, you will get a feel for the optimum position by viewing the target object in preview mode. Once you are satisfied with the image, and the "rainbow" effect is cancelled out, your prisms are set. The prism levers overlap so that most of the time you won't need to rotate the ADC itself, however you may need to rotate it a little to accommodate the overlap, which is as large as it can be without causing the body of the ADC to flex too much. Be patient. It takes a little time to get the feel of an ADC, possibly a session or two, however the results are well worth it and they are far higher quality than attempting to align the colour channels in post processing software because you are starting with a better image. We recommend putting the barlow lens in front of the ADC in most situations as the prisms will perform better at higher focal ratios used in solar system imaging."


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