Comparing MgI B2 and CaIIH line and magnetic canopy

When observing the sun through the MgI B2 line, we are looking at the absolute base of the solar atmosphere—specifically within the transition zone from the high photosphere to the low chromosphere (the temperature minimum) at an altitude of approximately 600 to 700 kilometers above the visible solar surface. At this specific height, the gas pressure is still relatively high, causing the churning gas to powerfully push the magnetic fields aside and tightly compress them along the edges of the giant supergranulation cells. As a result, a MgI B2  image reveals supergranulation as a sharp, thin, and geometric 'spiderweb' of bright magnetic lines, interspersed with relatively quiet, dark cell centers where the normal, smaller granulation of the photosphere still faintly shimmers through. This yields a pure and undistorted view that lays bare the exact roots and foundation of solar magnetism.

Comparing MgI B2  with CaII H.

When we compare these images with observations in the CaII H line, we ascend several floors up into the active chromosphere, reaching an altitude of 1,000 to 1,800 kilometers. Because the gas pressure drops exponentially at this great height, the crushing force that compressed the magnetic fields below completely vanishes. Consequently, the sharp, thin lines from the magnesium image transform into broad, fluffy, and cloud-like structures in the calcium image; the magnetic fields flare out in a funnel-like shape, forming the so-called magnetic canopy that partially drapes over the dark cell centers.

Furthermore, the entire texture of the sun changes completely: the crisp, geometric appearance of the magnesium line gives way to a chaotic and 'hairy' landscape in the calcium line, filled with fibrils (magnetic gas streams shooting upward like blades of grass) and bright flashes from acoustic shock waves. Finally, due to intense heating higher up in the chromosphere, active regions around sunspots light up as gigantic, brilliant magnetic clouds (plages) in the calcium line, whereas those very same regions remain highly compact and sharply bounded in the lower magnesium line.

Concretely, we see the emergence of supergranulation in Mg I B2, which then further develops and expands in CaII H. I  dived into my archives and reprocessed my images from December 28, 2025. The results clearly showcase the sharp, crisp definition of the supergranulation in MgI B2 versus the fluffy, chaotic magnetic field boundaries in CaII H. According to solar physics papers, the phenomena we observe in MgI B2 can only be explained if we assume they occur in an NLTE (Non-Local Thermodynamic Equilibrium) environment. This stands in contrast to LTE (Local Thermodynamic Equilibrium), which is typically much easier to calculate and model.

Setup & Processing Details:

Equipment: SOLEX by James R with a 2nd Gen Slit, mounted on an AZ-EQ6, using an ASI678MM camera.

Capture & Initial Processing: Captured in SharpCap and processed via Inti.

MgI B2 Image: Created from a stack of 3 exposures using AstroSurface, with final editing done in IMPPG and Photoshop CS4.

CaII H Image: A single-exposure capture, processed and enhanced using Photoshop CS4 and Topaz DeNoise AI.

Reversed images

Sodium tail of Mercury

Not a good sky at all but good enough to do a test to catch the sodium tail of Mercury.

Set up:

- AZEQ6 Mount

- Sigma 18-35 f/1.8 lens

- Sodium Filter

- ASI2600MC

Software : SharpCap 4

Stacking : AstroSurface and editing CS4

So, weather was not good with poor transparency resulting in no tail at all. Next time focal point will be increased aswell.

Sol'Ex Pro fine adjustments

The Sol'Ex Pro version has an adjustment ring for the collimator block. It works better then version 1 but still it's difficult to get a sharp image. Christian Buil provided an exact number for the distance of the collimator block: 88,5mm. This setting is explained in below.  Be aware this distance is for H-Alpha. I asked the question about CaII H/K line and this was Christian's response:

Regarding a question I was asked: the 88.5 mm value I recommend is optimal for H-alpha and, more generally, for the visible spectrum. For the Ca II H & K lines, it is preferable to aim for 88.8 mm. This corresponds to about 0.3 turn of the adjustment ring when switching from H-alpha to Ca II directly on the telescope, without having to disassemble the instrument.


So te difference between H-alpha and CaII H/K is according to Christian 0,3mm. 

I''m using the distance of the opening in the collimator block to adjust for H-alpha and CaII H/K.

As a base this is about 6,24mm and will be 6,54mm for CaII H/K

Sun with SolarMaxIII Double Stack and 678MM

The Sun this afternoon with SolarMaxIII Double Stacked and first time using my ASI678MM. I used a reducer x0,5 and made flats using SharpCap. Also the seeing monitor of SharpCap was used to capture only the 2% best images. Exposure time 0,294ms and 2000 frames. AstroSurface completed stacking and keeping 1000 frames for editing.

The sun was very active with a relative H-alpha number of 184.

Sun with Coronado SolarMaxIII DS

It is already the sixth consecutive day with clear skies and temperatures are climbing above 30°C. Therefore, I absolutely wanted to observe the sun, but given my surgery, this was not possible. Today went better and I asked the kids to set up the telescope with my Coronado SolarMaxIII DS BF15. The sun is still quite active with several sunspots and prominences. According to my observation, the Rp or relative H-alpha prominence number was 131.

Pictures made with my IPhone 16 - no editing.

Comet C/2025 R3 PANSTARRS published in Magazine Heelal

My observation of Comet C/2025 R3 PANSTARRS is published in magazine Heelal of June 2026.

"Perhaps the observer who was the last to record PANSTARRS from our region was Pascal Hilkens. On Sunday morning, April 19, he set his alarm for 04:30 AM local time “to then go by bicycle to the hinterland in search of a dark sky. At a distance of 5 km from Nieuwpoort-aan-Zee, I found a nice location with a full view of the east. There were still some light domes and the horizon had some high cloud cover. From 5:25 AM to 5:55 AM, I took several photos with my Nikon D7500 with a Nikkor 18-200 mm lens, but visually I could not observe the comet.”

Very cool to have my observation published. My images could not be published as the details were to small. 

Solex Image and fall of Solex

This morning I made two images of the Sun using my Sol'Ex by James R. Unfortunately I walked into the Sol'Ex which fell on the ground with some damage. Luckely my camera and the optics are fine. Only damage to 6 3D parts.

Setting: Sol'Ex, ASI678MM with Herschel Wedge

Software: SharpCap, Inti, CS4