Budget Solar Imaging - Continuum Subtraction?

[Macavity]

No Solar images from me... but a question to the more experienced producers of them...

I came across an interesting article yesterday: http://www.astrosurf.../us/sun/sun.htm

Basically, the guy is trying to extract (white light) CaK image information by SUBTRACTING (wide-band) "adjacent" continuum solar image data from "on spectral line" CaK image? As a sometime Particle Physicist, well used to "background subtraction" stuff, this rang my "interested" bell.

The original article was limited to CaK imaging. Filters were limited to 100 Angstrom width. The author achieved some success with CaK and speculated that H-alpha solar imaging might be possible? Now we have narrow-band H-alpha filters... Could one dig out e.g. modest images of Prominences, via some cunning combination of H-alpha filters and continuum subtraction? Anyone tried such things?

Chris / Macavity

[markt]

Interesting stuff, may have to give this a go at some time...

[nytecam]

This is a familiar and interesting experiment but as quoted in the article the H-apha line >x10 narrower that the K line and the captured H-alpha image was unsuccessful in detecting chromosperic events - the bandwidth was too great and swamped by the continuum. I still think it worth experimenting with the cautionary note that some newbies to this field confuse DSO 12um and 7um H-alpha filters as OK for direct solar observations with very dangerous consequences. Be warned I cheat with Coronado H-a and CaK scopes but due to age the latter is invisible but my cam can

Just remembered - using an occulting disk to block the sun's disk a great than sub angstrom H-alpha filter [don't know bandpass] will show proms but scope must accurately track the sun. Also a high dispersion spectroscope will show limb proms by open the slit slightly - so there are other ways to see proms

[Macavity]

Thanks, Nytecam.

A "fair 'nuff" warning re. unprotected Solar observation! I suspect H-alpha is beyond this technique. I had a gut feeling that (prematurely) selling my Coronado H-Alpha was not a *great* idea. (LOL) But maybe one day in the future? In the interim, I may mess with a Baader CaK filter. Heck, even Solar Continuum (Green!) filters are "double stacked", these days...

The GENERAL idea of continuum / background subtraction (in other astronomy, too)

seems interesting... But, as is the way of things, results are never guaranteed?

[michael.h.f.wilkinson]

One of the problems with subtraction is photon noise, which equals the square root of the number of photons in the signal. If the desired signal is much lower than the photon noise, you are in trouble.