Part II - Spectroheliograph Sol'Ex

After numerous tests with the first version the idea came up to increase the resolution. The small apo was good, but surely it can be better.

Fortunately a Skywatcher Skymax127 found its way to us, which the owner rejected. This was probably a version built for the Indian market. A few small things have been done differently, like the guiding of the main mirror.

An astrosolar film ND3.8 from Baader was a good start, but the exposure times became too long, so the frame rate in turn reduced the resolution in scan direction. (A narrow strip is directed to the sensor and with tracking turned off the whole sun is scanned as a line).

So the reflective layer had to go down: Using hydrochloric acid with copper sulfate or sodium hydroxide alone to remove the reflective layer.

I chose caustic soda, since hydrochloric acid and copper sulfate are not really environmentally friendly. However, the advantage of the hydrochloric acid combo would be that it doesn't attack the gals. So with the caustic soda, don't marinate the mirror all night. (If you need further explanations just let me know, I'm happy to give hints).



After a few hours the mirror looks like this: only 4% reflection:

The tube was then painted white to minimize the absorption of sunlight on the tube. The nail polish in the background was for the stitching...

E Voila: this is how the whole setup looks like:

Euer Karsten