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Telescopes and Chromatic Aberrations

This is where the chromatic simulations are made for. See below a set of three different apo-chromatic refractors. Notice that the colours are to dominant due to saturation, this problem has to be solved still. All the telescope designs come from “Telescope Optics” a book written on optical design by Rutten en van Venrooij. The telescopes are all 200mm refractors operating at a focal-length of 2000mm (F/10). The data was exported from ATMOS.

The top rows are chromatic images where the colours of 5 wavelengths (photopic sensitivity) have been mixed according to their wavefront-maps. The bottom rows are exactly the same 5 wavefront-maps but now used in all white-light simulation with a photopic sensitivity response.


An immersion triplet design using BK7, KZFS1 and BAFN10 glass. The colours are far too strong in all these simulations, but they can to be compared too each other. Clearly the defocussed images are rather different. Also the grey-images show the differrent total intensities at 1 wave of defocus. Look at the bright spot at +1 wave of defocus, that is mainly due to red-light in focus and yellow-green out of focus.

Click here to see how they perform on planets

The same triplet design but now with air-spacing between the elements.

Note that the colours are paler than those in the above example. Also the hole at the center of 1 wave of defocus is better visible due to a better color-correction. The grey-scale images are also looking more alike.

Click here to see how they perform on planets

The last glass (BAFN10) was replaced with a TIF2 glass element. Once more the +1 wave focus image has become paler and also the difference in the grey images is smaller.

This design is the best of these three, the TiF2 glass however seems to be very difficult to produce pure enough for the usage in optics.

Click here to see how they perform on planets

The images on the left are made Rafael Barberá from Valencia, Spain showing
Sirius at both sides of focus (>10 waves) through a Helios 102mm f/5 achromatic refractor with a
Philips ToUCam Pro Webcam mounted. The image is averaged over 150 stacked image-frames.

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