Filters on filters!

Stu · September 1, 2023

I’ve been using my Canon 15x50IS binos for some quick solar sessions recently, using 58mm screw in filters which work well and are very secure.

My one ‘complaint’ is some CA that shows up around the solar limb, not entirely sure where it comes from but it may be atmospheric as I’ve been observing when the sun is relatively low in the sky.

Anyhoo, I had a sudden thought that, in the absence of continuum filters, UHC and OIII filters do a decent job. I was pleased to find that the solar filters maintain a 58mm thread on the outside, so my step down rings fit into these and the two filters screw into the front.

The result is no CA, and a bluish coloured Sun, not unpleasant at all. I was seeing some worthwhile detail in them, not dissimilar to the images on SoaceWeather although only the main spots showed up, not all the smaller ones around the main ARs. I could see AR3413, 3415, 3416, 3417 and 3418, plus a couple of patches of faculae. The faculae was actually more obvious without the narrowband filters I think, but the spots were sharper.