Dear Members,

Gordon Ewen has offered to give a demonstration of his new MLAstro spectroheliograph (SHG) this Saturday at 08:45.

For those of you who were present at last week's monthly meeting this is a demonstration of what the SHG can do.

For those of you that weren’t at the meeting the SHG allows the Sun to be viewed at numerous wavelengths associated with the many elements present there, which can give a significantly different picture of the Sun.

The forecast is looking O.K. early morning, so fingers crossed!     

So, if you are If you’re interested, please log on.

The Zoom link is:

https://us06web.zoom.us/j/83632647053?pwd=aFXVXKaOOtAtgXLbgTujhnqfzrbuUy.1

The Spectroheliograph isn’t a new invention—it’s one of the oldest methods of observing the Sun in narrow bands. George Ellery Hale and Henri-Alexandre Deslandres independently developed it in the 1890s, and Robert R. McMath improved it in 1932 to capture motion pictures. Thanks to recent advancements in software and hardware pioneered by Christian Buil, Valerie Desnoux, and others, the Spectroheliograph has now entered the digital era. Image acquisition and reconstruction are done digitally with the help of specialised software.

Here’s how it works: A slit is used to capture a small slice of sunlight. This light passes through a collimator, which turns it into parallel rays. These rays then hit a diffraction grating, which spreads the light into a spectrum. A lens refocuses the spread beam onto a camera sensor. By adjusting the tilt of the grating, you can choose which part of the spectrum is focused on the sensor, allowing you to observe the Sun in different wavelengths (such as H-alpha, Sodium D, Helium D3, or Ca K).