I've already achieved the theoretical resolution of a 30 cm solar telescope many times, but now, before I switch to H-alpha I wanted to take another step forward in resolution.
I took a UV filtered solar image, and I reached a higher resolution than ever before (and probably higher than any amateur solar photo before - I cannot be sure, but it would be exciting to check).
This result was possible to be reached by the Soleye 300 Violet mirror and the Newtonian arrangement (only mirror system).
The Violet mirror showed its superpower.About the UV technique:
Curiously, the complete method remains experimental for the time being, because the filter I used is actually unsuitable for solar photography, but I have successfully verified a simple idea in this way.
If an ideal optical system works at a shorter wavelength, it has a higher optical resolution, since the size of the Airy disk is proportional to the wavelength. In other words, using a green filter instead of a red filter, or using a blue filter instead of a green filter will usually result in a higher theoretical resolution.
However, this is not the experience, but the opposite, due to seeing, object faintness and other limitations of the optics. The only possible exception is the Sun.
There is enough UV radiation coming from the Sun even through the atmosphere to have a good signal to noise ratio. The contrast of the photosphere is huge in blue or in the UV spectra. All you need is a good telescope with good performance in the UV. It can only be a fully mirrored system, e.g. Newtonian, and it is advantageous to collect more light in UV. And the Soleye 300 Violet mirror is just such a device.
The verification of the idea was successful, the planned increase in resolution was achieved.
The photo was taken in a band around 350 nm (Baader Venus-U) with an effective CWL at 360 nm, so the resolution is exactly 1.5X higher than with Baader Solar Continuum (540nm) or other green filters. It requires approximately a 45 cm telescope to get this resolution with a green filter.
Of course, it's not 1.5X, but "only" 10 % higher resolution than my previous (broadband 393 nm) shots, but that's a big step forward. Unfortunately, since there is currently no UV filter on the market that does not use absorption glass but clear glass, this remains an experiment. The absorption filter glass took 60-100 seconds to heat up enough to affect this highly sophisticated imaging, so after every 4-5 minute cooling period I had 1 minute to catch good resolution.
- Soleye300 with Violet mirror
- 0,15 ms/0 gain - 4000/600 frames
Comments