„For WILL and SHALL best fitteth Tamburlaine”
(Temur ~ iron)
2025-03-22, Fe II 501.845nm, a somewhat artistic rendition of the data
Abstract
I recorded full disc solar images, in the spectral line of ionized iron, Fe II at 5018.45A. Due to the bandwidth, He I at 5015.7A was also recorded. I used the Sol’Ex spectroheliograph, mounted on a 62/400 ED refractor, stepped down to 42-46mm, by using 2″ narrow band filters as full aperture energy rejection filters, with an ASI 678MM monochrome camera. I reconstructed and further processed the recordings with JSol’Ex and its ImageMath module, and showed the presence of prominences and filaments. Creating aesthetic, but still faithful to the data renditions was among the goals.
A hobby is a hobby
I decided, with some little help from professional literature[1][2], to go into a particular iron line. Not the Fe (c) (at 495.7 nm, given as Fe I), which is rather well observed[3], and looks like many other metal lines, but the one at 501.845 nm, a line of ionized iron, of Fe II. What’s particularly interesting and somewhat unexpected for me, the amateur playing around with my Sol’Ex instrument, running all kinds of ImageMath scripts in JSol’Ex, is that, in Fe II at 501.845 nm:
- The active regions are dark, just like in He I D3, and unlike in many metals, like Ca in the G band at 430nm
- Faint proms are visible, and with math applied, filaments are also showing up
- Some brighter-than-its-medium areas are also visible, flares maybe
- Unlike with both the Mg and Na of the Fraunhofer lines, this line is relatively easy to extract and reconstruct with much less instrument/recording/processing artefacts, like the dreaded „polar caps”. Present, but much less.
Having explored many exotic lines, like
- the „high hydrogens” from epsilon (raw and „prime”) to „theta” if there is such a thing,
- the blue Helium at 447.15, and
- recently the UV Magnesium,
I needed a new challenge, and this iron line showed up on my radar.
