Very brights object seem to have a blue rim on top and a red one at the bottom.
Have you ever seen the "blue/ green flash" on top of the Sun seconds before it sinks below the ocean horizon? If so you have witnessed a rather rare natural event. It is Atmospheric Dispersion. Still maybe even unknowing you have seen atmospheric dispersion on Jupiter these days.
Have you noticed the blue/ green rim on top of Jupiter and the bright orange/ red on at the bottom? Nothing to do with your telescope, diagonal or eyepiece, it is the amospheric dispersion that you see.
Light is refracted in the atmosphere, specially more so through the thick layers at the horizon and bends blue rays up, and red rays down. It is only a matter of arcseconds, but enough to color the rims of Jupiter and to blur details on it.
Can't we do anything about it? Well yes, Let's bend the rays back on their right place before it reaches the eyepiece. That is exactly what an Atmospheric Dispersion Corrector does. Two rotatable prisms that work together in order to eliminate the atmospheric effect. And it works! Even professional observatories use it.
Effects:
- Blue and red rims are virtually eliminated.
- Details on the planet are no longer blurred by lightrays of another color. More details? Sometimes. At least better defined details.
- As atmospheric refracted light rays are brought together again; they do not interfere which each other. Fluttering red and blue light beams are not given the opportunity to flutter one above the other, but are brought together at the same point. Seeing seems to calm down a bit.
- Overall effect: Planets seem calmer and with better defined details, as well as double stars near the horizon.
If you are interested, more reading and illustrations about it
https://www.astrosystems.nl/atmospheric ... ncorrector
Although this is a sort of explanation / advertisement, it contains tons of more information. More than I can write before you fall asleep.
It is essential that the zero starting position of the levers is set at 0 and parallel with the horizon, as it is an earth/ atmospheric bound effect. Some ADC's have even a bubble to make sure.
Some critical remarks:
- Although meant to be used in a
- Although theoretically meant for larger apertures, I have used it with succes in a 4 inch refractor.
- It need not be as expensive as the ad above indicates: https://agenaastro.com/zwo-1-25-inch-at ... r-adc.html
- Don't think you can suddenly use much higher magnifications. The atmosphere stays the same.
- 12mm Brandon eyepiece.
- ADC ,note the red levers.
- Helical focusser for fine tuning (not essential, just for my pleasure: tuning the last 0,01 mm)
- Baader prism
- 1,4X barlow , works as 2X because placed before the prism and helical focusser.
- 1,25"--> 2" adapter.
The whole train assembled:
