Sol'Ex observation March 29

Sol'Ex observations done with the following settnig:

- TS/TLAPO80/480, ASI678MM with 2nd Gen slit (but with dust!!!)

- Herschel wedge

- SSD 

- Software: SharpCap, Inti, JSolex, CS4 and DeNoise AI

- Tilt angle 0,15°

- Sx/Sy : 0,88 (H-alpha)

- SSM3 monitor avg 1,5arcs

Relative Prominency number Rpha = 10H + E = 10 * 10 +53 = 153

H-alpha activity - H-alfa number

In the period from August 2024 to March 2026, 52 H-alpha observations were carried out using a Sol’Ex spectroheliograph on a TLAPO60/360 and later a TLAPO80/480. Processing via INTI results in superior resolution, meaning the calculated prominence relative number (Rp = 10H + E) is systematically higher than the VdS reference. This is reflected in a k-value of 0.76 with a strong correlation (R2 = 0.88). Furthermore, the data confirm the time-lag effect of the chromosphere: the H-alpha prominence maximum occurs later than the sunspot maximum in the photosphere. This is logically explained by the fact that prominences are often residual phenomena of active regions that are already decaying underneath. The methodology used follows the standard from "Die Sonne beobachten" by Reinsch and Völker.

Determination of the H-alpha Relative Number for the solar limb (Rp or RHa)
The formula is defined as follows (1)

Rp or RHa = 10 H + E

With:
Rp or RHa: the H-alpha relative number
H (Herde): the number of activity centers on the solar limb
E (Einzelerscheinungen): the number of individual limb phenomena, individual phenomena such as separate prominences or limb flares.

(1) Die Sonne beobachten - Reinsch, Beck, Hilbrecht and Volker

Conclusion:
My observations follow those of VdS and Kanzelhohe.
My observations are systematically higher, which may indicate a difference in equipment resolution, cf. traditional H-alpha versus Sol’Ex.
The k-value is 0.76 with a reliability (R2) of 0.88.
Observations confirm the "time-lag" effect of the H-alpha maximum relative to the sunspot number. This is logically consistent, given that sunspots occur in the photosphere and prominences in the chromosphere.

Sunspot AR4392 March 22

 

Inverted image of H-alpha spectrum of the Sun from last Sunday March 22, 2026. Crop from AR4392.

Picture made using SolEx with ASI678MM on TLAPO80/480.

Coronal Hole and Sol'Ex images March 22

My Sol'Ex was used to capture the HeD3 line and after editing is was possible to bring forward the current coronal hole of the Sun. A comparison was made with SDO/AIA 211A and GOES19 195A. All in all it's not most beautiful picture but still I could capture the coronal hole. For sure I will try this again when a more deligned coronal hole shows up.

The day started with some bad seeing but during noon time seeing became better. I made time to adjust the Sol'Ex and was able to get sharp images in all captured wavelenghts.
Tilt was corrected with some very good results: 0,1° deviation... not bad at all. The most suffer from dust on the slit. Yesterday I did some cleaning, but not enough it seems. 

Sun March 21

The Sun this afternoon, observed with Sol'Ex in H-alpha and CaIIH.

CaIIH1v

Sun in CaIIH

My last So'Ex observation was on January 4th this year. So today it was some trial and error...

Sun today in CaIIH 

Sol'Ex by James R with TS TLAPO80/480 and ASI678MM

SharpCap, Inti, CS4, DeNoise AI

Solar Observation Indices: White Light vs. H-alpha

 

I was inspired by the VVS Solar Working group organised last Sunday, March 8, 2026 on the determination of H-Alpha activity on the Sun using indices. Going through some of my books like "Die Sonne beobachten" from Beck and Völker (see aswell link to my books) and a couple of websites I made following list on potential use of H-alpha indices. I made a reference towards white light observation.

Corona

The corona is the outermost layer of the solar atmosphere, consisting of extremely tenuous and very hot plasma.

- Plasma: H⁺ and e⁻
- Follows magnetic structures
- Temperature anomaly:
        - Magnetic reconnection provides the basic heating

        - Alfvén waves (wave heating) transport energy further out into space
- Radiation spectrum: X-rays (RX), EUV, and white light due to electron scattering
- Density: ~10⁻¹² of the photosphere
- Charged particles escape from the corona and move through our solar system as the solar wind.

We can destiguish different regions:

E Corona (L Corona – Line Corona)
Emission from highly ionized metals (Fe XIV, Ni XII, Ni XIII, Ca XV).
Ionization occurs at t = 2 million K.

K Corona
Thomson scattering by high-energy electrons.
The scattering does not affect the wavelength itself, but the electrons’ velocities cause a Doppler effect, which smears out the wavelengths and thus forms a continuous spectrum (continuum).

F Corona
Caused by dust that scatters photospheric light.
No change to the spectrum shape, and it shows an absorption spectrum; hence the Fraunhofer-line spectrum.

Differential velocity - H-beta - JSolex

 

Differential Velocity of the Sun - JSolex 4.5 release

With the release of JSolex 4.5, it's now possible to calculate the differential velocity of the sun's disk using doppler effect of H-alpha.

I used some of my better Sol'Ex images and the result is very good compared with the theoretical one.

PRO-AM Collaboration for Systematic Solar Observations

 

PRO-AM Group | JASON2025

Systematic observations of the solar chromosphere and photosphere began 117 years ago at the Meudon Observatory with the spectroheliograph developed by Deslandres. Since then, an exceptional collection of more than 90,000 monochromatic images in Ca II K and Hα has been built up, covering over 11 solar cycles. This unique dataset is made available to the international scientific community through the BASS2000 database.

In 2023, this long observational tradition received new momentum with the launch of a “PRO-AM” collaboration between professional and amateur astronomers. This initiative makes use of the Solar Explorer (Sol’Ex), a compact, high-quality spectroheliograph designed by Christian Buil. The aim of the collaboration is to record solar images on a daily basis, and whenever possible several times per day. Thanks to dozens of observing stations distributed across different geographical locations, the impact of local weather conditions is significantly reduced.

Meanwhile, the range of available spectroheliographs has been further expanded. In addition to the original Sol’Ex, Sol’Ex Pro, Sol’Ex V2, Sol’Ex by James R, Sol’Ex original, and the SHG700 are now available, enabling amateurs with diverse technical backgrounds and resources to participate in the project.

In 2025, a total of 59 amateur astronomers were actively involved in the PRO-AM collaboration. The majority of them, 39 participants, were based in France, while the others were spread across nine additional countries. Together, they were responsible for no fewer than 4,548 observations in various spectral lines, including Hα, Hα 2cb, Ca II H (H3), Ca H1v, Ca II K (K3), and Ca K1v.

Thanks to the strong commitment of the amateur community, there was only a single day in 2025 without an Hα observation, namely 22 December. For Ca II H and Ca II K observations, however, the number of days without data remains significantly higher, highlighting the importance of further expanding the observing network.

Within this international collaboration, I am currently still the only Belgian amateur actively submitting images to the Meudon Observatory. In total, I submitted 82 observations in 2025, placing me seventh among the most active amateur contributors. For the specific Ca II H and Ca II K lines, I rank fourth and fifth respectively. This clearly demonstrates not only the value of individual dedication, but also the crucial role amateur astronomers play in achieving long-term, continuous solar monitoring.

Sun May 2025 Sphere Synoptic - Inti Partner and Naming _YYYY-MM-DDTHH-MM-SS

I installed the new verion 1.2 of Inti Partner which has a tab Synoptic. It's possible to create a mp4 or GIF file made from solex images over multiple days. The end result is a simulation of the sun's rotation. I had some issues with the error "Date Error" but this is now fixed:

1) only use PNG/fits/ files

2) make sure the Log file is available at the same or upper map

or 

1) if you don't have the Log file, change the naming of the file to following format:

_YYYY-MM-DDTHH-MM-SS_  

2) be aware to change timing to UT time

I used files from May 2025: May 30, 19, 14, 11 and May 2nd. The synoptic maps identified 21 active regions from AR 4070 till AR4103

AR 4070 lat=-12.0° lonCarr=10.0°
AR 4072 lat=-19.0° lonCarr=325.0°
AR 4076 lat=5.0° lonCarr=305.0°
AR 4079 lat=8.0° lonCarr=244.0°
AR 4081 lat=7.0° lonCarr=213.0°
AR 4082 lat=-9.0° lonCarr=188.0°
AR 4084 lat=-21.0° lonCarr=129.0°
AR 4085 lat=3.0° lonCarr=139.0°
AR 4086 lat=7.0° lonCarr=207.0°
AR 4087 lat=15.0° lonCarr=57.0°
AR 4089 lat=17.0° lonCarr=28.0°
AR 4090 lat=-13.0° lonCarr=20.0°
AR 4091 lat=-13.0° lonCarr=33.0°
AR 4092 lat=-13.0° lonCarr=337.0°
AR 4094 lat=20.0° lonCarr=332.0°
AR 4096 lat=6.0° lonCarr=306.0°
AR 4099 lat=-13.0° lonCarr=255.0°
AR 4100 lat=8.0° lonCarr=243.0°
AR 4101 lat=3.0° lonCarr=259.0°
AR 4102 lat=-22.0° lonCarr=297.0°
AR 4103 lat=-17.0° lonCarr=287.0°

Sun January 4th

A 5cm layer of snow and a perfect blue sky. Sol'Ex time :)
My SSM3 Seeing monitor registrated very good seeing with levels below 1 arcs with sometimes below 0,5arcs. I still have issues with my allignment of the spectral lines which are curved. Maybe I need to adjust the slit? 

Setting: TLAPO80/480 with Sol'Ex by James R and ASI678MM

2nd Gen slit and Herschel Wedge

Tilt <0,5° and Sx/Sy 1,15

SSM3 seeing Monitor via SharpCap

Software: SharpCap, Inti, JSol'Ex, CS4, DeNoise AI

Sun January 2nd

My first observation of the Sun this year.
Moderate conditions and settings of Sol'Ex not perfect, mainly the north side of the Sun.

Setting

Sol'Ex by James R, TLAPO80/480 with ASI678MM

Tilt < 0,1° Sx/Sy 1,04

2nd Gen slit and Herschel Wedge

Software: SharpCap, Inti, JSolex 4.4.2 and CS4

Sun on December 28

The Sun on December 28, 2025. Interesting is the Magnesium Mg I B2 line with a small prominence.

Setting: Sol'Ex by James R, with 2nd Gen slit and Herschel Wedge

Software: SharpCap, Inti, JSol'Ex, CS4, DeNoise AI

Tilt < 0,2° Sx/Sy 1,1