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 My images could not be published as the details were to small.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

Explaining the Sodium tail of Mercury 16 days before or after perihelion.

The phenomenon behind the visibility of Mercury's sodium tail is a fascinating interplay of orbital mechanics and light. While Mercury reaches its maximum orbital velocity of about 59 km/s at perihelion, its radial velocity—the speed at which it moves directly away from the Sun—is nearly 0 km/s at that exact moment. However, due to its highly eccentric orbit, the planet begins to recede rapidly after passing this point. Approximately sixteen days post-perihelion, this radial velocity reaches an optimal peak of over 10 km/s.

This radial motion is critical because of the "Sodium Trap." The Sun's atmosphere contains sodium that absorbs light at specific wavelengths, particularly the D-lines (around 589 nm), creating a deep "dark gap" or absorption line in the solar spectrum. At perihelion, the sodium in Mercury's exosphere is aligned with this dark gap. Without sufficient photon flux, the atoms lack the radiation pressure needed to be pushed into a visible tail.

The sodium atoms are supplied to the exosphere by several distinct processes:

Thermal Desorption: Extreme daytime temperatures of 430 °C cause sodium to evaporate from the surface.

Solar Wind Sputtering: High-energy particles from the sun strike the surface at an atomic level, knocking individual sodium atoms loose.

Micrometeorite Impacts: Tiny dust particles strike the surface, causing mini-explosions that throw material into space.

Think of a surfer paddling away from a wave. If the surfer stays still relative to the wave's source, the frequency remains the same. But by paddling away at high radial speed, the frequency of the incoming waves of light shifts. This Doppler effect causes a redshift in the solar light reaching Mercury. Sixteen days after perihelion, the shift is large enough (about 0.02 nm) that the sodium atoms move out of the solar absorption shadow and receive approximately 40% more light.

This increased photon flux provides the physical momentum "kick" needed to accelerate the atoms away from the planet, while simultaneously causing them to glow through fluorescence. This specific timing is why observers look for windows sixteen days after perihelion—such as June 3, 2026 or November 26, 2026—to capture the tail at its most brilliant.

Het fenomeen achter de zichtbaarheid van de natriumstaart van Mercurius is een fascinerend samenspel tussen baanmechanica en licht. Hoewel Mercurius zijn maximale baansnelheid van ongeveer 59 km/s bereikt tijdens het perihelium, is de radiale snelheid—de snelheid waarmee hij direct van de zon af beweegt—op dat exacte moment nagenoeg 0 km/s. Vanwege zijn zeer excentrische baan begint de planeet echter snel afstand te nemen zodra hij dit punt passeert. Ongeveer zestien dagen na het perihelium bereikt deze radiale snelheid een optimaal hoogtepunt van meer dan 10 km/s.

Deze radiale beweging is cruciaal vanwege de zogenaamde "natrium-val". De atmosfeer van de zon bevat natrium dat licht absorbeert op specifieke golflengten, met name de D-lijnen (rond 589 nm), wat een diep "donker gat" of een absorptielijn in het zonnespectrum veroorzaakt. Tijdens het perihelium bevindt het natrium in de exosfeer van Mercurius zich precies in dit donkere gat. Zonder voldoende toevoer van fotonen ontbreekt het de atomen aan de stralingsdruk die nodig is om ze weg te duwen en een zichtbare staart te vormen.

De natriumatomen worden aan de exosfeer geleverd door verschillende processen:

Thermische desorptie: Extreme dagtemperaturen van 430 °C zorgen ervoor dat natrium uit het oppervlak verdampt.

Sputtering door zonnewind: Energierijke deeltjes van de zon raken het oppervlak op atomair niveau en slaan individuele natriumatomen los.

Inslagen van micrometeorieten: Minuscule stofdeeltjes raken het oppervlak en veroorzaken mini-explosies die materie de ruimte in slingeren.

Stel je een surfer voor die wegpeddelt van een golf. Als de surfer stil blijft liggen ten opzichte van de bron van de golf, blijft de frequentie hetzelfde. Maar door met een hoge radiale snelheid weg te paddelen, verschuift de frequentie van de inkomende "lichtgolven". Dit Doppler-effect veroorzaakt een roodverschuiving in het zonlicht dat Mercurius bereikt. Zestien dagen na het perihelium is deze verschuiving groot genoeg (ongeveer 0,02 nm) zodat de natriumatomen uit de "schaduw" van de zonne-absorptie stappen en ongeveer 40% meer licht ontvangen.

Deze verhoogde fotonenstroom geeft de fysieke "kick" die nodig is om de atomen van de planeet weg te versnellen, terwijl ze tegelijkertijd gaan gloeien door fluorescentie. Deze specifieke timing is de reden waarom waarnemers zoeken naar momenten zestien dagen na het perihelium—zoals op 3 juni of 26 november 2026 —om de staart op zijn helderst vast te leggen.

VVW Halo and Publication

Since end 2025 I'm a member of the whatsApp groep VVW Halo. The associated WhatsApp group is a private community for members of the Weather association VVW. It is used for real-time weather observations, such as reporting storms, lightning, or optical phenomena like halos and rainbows. The reportings are analysed and published in their monthly magazine Halo.

The first quarter results are published last month including my observations and pictures. Looking at the graphs, a halo could be seen in the mentioned period average every 3 days.

My first Meteorite Sikhote-Alin USSR 1947

The Sikhote-Alin meteorite fall remains one of the most spectacular events in modern astronomical history, occurring on the morning of February 12, 1947, in the Primorye region of Russia (USSR). Unlike many meteorite falls that occur over uninhabited oceans or deserts, this event was witnessed by numerous people who saw a fireball brighter than the sun descending over the Sikhote-Alin Mountains. The bolide entered the atmosphere at a high velocity and began to break apart under the immense pressure of the descent. The final explosion was so powerful that it was heard hundreds of kilometers away, leaving a thick smoke trail in the sky that persisted for several hours.

When the meteorite disintegrated, it created a massive debris field known as a strewn field, covering a significant area of the dense forest. The impact was violent enough to produce over a hundred craters, the largest of which measured twenty-six meters in diameter. Because the parent body was a massive iron meteorite, it did not simply burn up; instead, it showered the taiga with tons of iron fragments. Explorers and scientists who reached the site discovered a scene of total devastation, with shattered trees and jagged metal shards embedded in the ground.

Collectors generally distinguish between two types of specimens from this fall. The first type is the individual meteorite, which traveled through the atmosphere long enough to develop a smooth surface known as a fusion crust, often covered in thumbprint-like indentations called regmaglypts. These are prized for their aerodynamic appearance. The second type, which is frequently found at major events like the ATT fair in Essen, consists of shrapnel fragments. These are jagged, twisted pieces of iron that were torn apart by the force of the main explosion or upon impact with the frozen ground.

Owning a piece of Sikhote-Alin is special. The Sikhote-Alin meteorite is classified as an iron meteorite belonging to the meteorite group IIAB and with a coarse octahedrite structure. It is composed of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus and 0.28% sulfur, with trace amounts of germanium and iridium. Minerals present include taenite, plessite, troilite, chromite, kamacite and schreibersite 

When you hold a piece purchased at a specialized fair like the ATT in Essen, you are holding a fragment of a planetary core that formed billions of years ago, only to be violently delivered to Earth in a remote Russian forest less than a century ago. It serves as a tactile connection to the raw power of our solar system and a permanent reminder of the day the sky literally fell in eastern Siberia.

Aurora Flatfield ¨Panel

At the annual ATT Essen I purchased a second hand flatfield panel. The Aurora Flatfield Panel with a diameter of  315 mm and an 12V Inverter works perfect with my ASIair. 

This flatfield shield will serve to make flats.