I imaged two helium suns, at 5875.6Å the good old He I D3, together with another He I at 7065.2Å. In the D3, the signal is both stronger and of shorter wavelength, and also not at the very extreme of what the device can do, so there are more details.
He I at 7065.2Å
He I D3
I imaged the Sun in the neutral Helium line at 7065.2 Angstrom (706.52 nm), on 2025-07-20. The weather was unfavorable with passing clouds and varying seeing, so between 0911 and 1033 UT, a bit after local noon, I recorded and finally kept 19 scans.
I ran a few searches on the internet. Just like with the solar disk in Fe II 5018.45Å, with prominences and all, this may well be the first amateur spectroheliogram of the Sun in this wavelength, and probably the first ever to be processed to reveal these details.
It was a challenge to find this line, but among others, the flash spectrum came to my help.
I used a 80/540 refractor, an in-cone band pass 642 IR filter as the energy rejection filter, and the ML Astro SHG700, with the cooled 678MM camera. Image processing with JSolEx, my own scripts.
More data is needed to confirm this, but at a first glance, this line at 7065, just like the He I D3, appears to reflect features from the corona.
because google is no longer our friend when it comes to finding stuff
Solar spectrum, with tellurics https://hs5000.vo.aip.de/
SOLAR-ISS: A new reference spectrum based on SOLAR/SOLSPEC observations https://www.aanda.org/articles/aa/pdf/2018/03/aa31316-17.pdf
GOES X-Ray Flux https://www.swpc.noaa.gov/products/goes-x-ray-flux
Infrared Helium Sun: https://iopscience.iop.org/article/10.1088/1674-4527/ad37f4/pdf
Databases: https://data.nas.nasa.gov/helio/portals/solarflares/datasources.html
Flares and stuff: https://www.lmsal.com/isolsearch
Flare prediction forecast https://www.solarmonitor.org/forecast.php
Liege https://fermi.jhuapl.edu/liege/s08_0085.html
On 2025-06-16, at around 0936Z there was a bright flare visible in both Na D1 and Na D2, but also in He I D3 as a bright flash. 27 scans were recorded between 0856Z and 0940Z, with the last couple having the flare. The presented disk image is a composition of stacks, one stack of the disk without the flare, and another stack that shows the flare (motion blurred over a few minutes). Curious dopplers are also present in the raw, as sample frames from the raw scan show.
A stack of 40 scans obtained with ML Astro’s SHG 700 spectroheliograph.
A stack of 16 scans obtained with ML Astro’s SHG 700 spectroheliograph.
