Sun June 22 Sol'Ex and JSolex setting

Day 6 of the second* heat wave in Belgium so far this year. So conditions are moderate with temperatures above 25°C this morning and moderate seeing. I added extra protection with Aluminum foil on the camera and parts of mu Sol'Ex Pro version to protect for heating.

I spend time to a sharp apture aswell a good Sx/Sy. 

But more important was the time I spend on editing the images using JSolex. The slit contains some dust and previous images didn't show them. So went back to the basics and changed JSolex settings with some good results. 

* the first heat wave end May is not official as measured in Uccle but was registrated locally at my hometown.

E-Corona woth Sol'Ex

Last year I tried a couple of times to capture the E-Corona of the Sun. This time, the Sun was higher in the sky and a UT noon time about 62°. Most of the time a blue sky with sometimes very dim high clouds. 

Setting:

TS/TLAPO 80/360 with ND filter and ASI290MM camerea

AZ/EQ6 mount

Solex Pro version with tilted continuum filter 

Camera temperature : 46°C

Seeing: moderate to poor

ROI Capture Area 1936x68

Tilt:-0,17°

Sx/Sy: 5,82

Binning 2x2

Exposure time: 1,79ms Gain 116

Frames per second : 550

Total scans : 105

Software: Sharpcap

Editing: Inti, JSOLEX, CS4, DeNoise AI

ImageMath by JSolex; setting by Cedric aswell as by Olivier. Below images are made using setting by Olivier.

Conclusion:

- use of tilted continuum filter makes it easy to find the area of interest (Fe XIV)

- impact of seeing conditions

- almost One hour of scanning, resulting in 105 images

- sky not all the time blue and transparent

- Sx/Sy to high; rate should be x32 in stead of x16

- some signal in the image but still to weak to really make the link with the E-corona

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.

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. 

Workproces astrophotography using ASIair Plus

 

My workprocess when using TAL200K with ASIair for deepsky imaging. 

The difference between f/1.8 and f/3.5

Since a couple of months I own a Sigma 18-35mm f/1.8 lens. I know this lens captures more light but how much more and what about comparing with my Nikon 18-200mm f/3.5-5.6 lens.

I captured the same scene with same settings:

- Nikon D7500

- Exposure time 1.3s

- ISO 800

The difference, which is significantly can be seen in the picture below.

The Sigma lens f/1.8 captures 4 time more light as my Nikon 18-200mm lens on 18mm f/3.5.

So f/numbers do matter :)

Supernova SN2026fvx in NGC4205

 

On March 17, 2026, a remarkable celestial event was recorded with the discovery of supernova SN2026fvx in the galaxy NGC 4205. Located in the constellation Draco at a distance of approximately 57 to 75 million light-years, this supernova initially appeared with a faint magnitude of 19.3. Scientific analysis quickly classified it as a Type Ia supernova, a catastrophic explosion occurring in binary star systems. In such a system, a white dwarf accretes matter from its companion star until it reaches the critical Chandrasekhar limit. At that precise moment, a runaway thermonuclear reaction is triggered, completely tearing the star apart in a brilliant flash of light.

By early April, the supernova’s brightness had increased significantly to magnitude 12.3. Given its high altitude in the sky, it provided a perfect opportunity for observation. This session was particularly meaningful as it marked my first deep sky object since April 2025, requiring a period of re-learning the technical workflows. The process began with polar alignment using SharpCap and an ASI224MC camera, followed by a three-star alignment. The SynScan was then connected with an ASIAIR Plus controller, and the TAL200K f/8.5 telescope, mounted on a Skywatcher AZEQ6 GT, was moved into position. To capture the event, I used a cooled ASI2600MC camera to take 13 300-second exposures, opting to work without guiding or the use of a Bahtinov mask for this session.

The technical journey was not without its challenges, particularly regarding data management. I encountered a frustrating problem getting the data out of the ASIAIR Plus, as Windows 11 did not support the direct PC connection. Several troubleshooting ideas from the ZWO network were attempted without success, and even using a card reader resulted in errors within the fit files. Ultimately, an ordinary USB stick proved to be the solution that worked.

Although some tracking errors occurred during the session, I was able to retain 8 high-quality light frames. These were stacked together with darks, flats, and bias frames using Astro Pixel Processor to create the final image. The resulting view clearly features the supernova, and its observed brightness was further validated by performing photometry within ASTAP software, confirming the magnitude of 12.3 as reported by Rochester Astronomy. It remains a staggering thought that the light captured in this image traveled through the vacuum of space for tens of millions of years before finally reaching my sensor.

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.

Drone DJI Neo 2

One of my objectives is to expand my photographic skills and in particular taking pictures from a different angle. How would a sunset or sunrise look like from an angle way above ground level? For this reason I bought a drone or UAS (Unmanned Aircraft System).

I bought a DJI Neo 2 drone; it's a beginners drone in the Open Class A1 and Cx label type C0.
The camera sensor specs :
    * Sensor: 1/2-inch CMOS
    * Effective Pixels: 12 MP
    * Lens: FOV 119.8°,
    * Aperture, 16.5mm equivalent focus 35mm
    * Video Resolution: 4K/60fps (up to 100fps), 2.7K (9:16)
    * Max Video Bitrate: 80 Mbps
    * ISO Range: 100-12800
    * Stabilization: 2-Axis Mechanical Gimbal + RockSteady EIS
    * Storage: 49 GB Internal

The drone is equipped with a LiDar (Light Deteection and Ranging) sensor which measures distance and detects obstacles.

As the drone is equiped with a camera, the drone is regsitrated. For Belgium no certification is needed but for some other countries it's mandatory eg. Spain. I downloaded the 101 page training and completed succesfully my exam. So I'm a certified A1-A3 UAS Pilot :)

Nikon D7500 Shutter Count

 

My Nikon D7500 has currently 42472 clicks. According to Nikon, my camera can reach 150.000 clicks.

The count was made using  https://www.camerashuttercount.com/

Solar Scintillation Monitor SSM3 and SharpCap

After downloadoing the latest version of SharpCap (adjusted for the SSM3 bug) I connected my Solar Scintillation Monitor SSM3 (See https://www.analog-astronomical-device.ch/solar-scintillation-monitor). . Using the tools menu and selecting Solar Scintillation Monitor, the SSM3 can be connected. The result works very good with a good graphic follow up.

Overal seeing below 2 arcs with moments even lower.

The increase is due to upcoming high clouds

For instructions to connect the SSM3 with SharpCap see https://forums.sharpcap.co.uk/viewtopic.php?p=48907#p48907 (New Feature : Support for Solar Scintillation Monitors).

First Light with Skywather Star Adventurer 2i

I expanded my equipment with a transportable travelmount: a Skywatcher Star Adventurer 2i. I will install this mount on my Manfrotto tripod. The purpose is to image wide field using my DSLR at home and when I travel.

After putting all together I did some testing last week; unfortunately not successful. I did a more accurate  polarallignment, but stars were still not tracked. Last thursday I found out that I forgot to set the direction of the tracking. Once done, the SA2i is following up to 70s (I did not test longer). To test accurancy over time, I shot 190x30s pictures of Orion using my Nikon D7500. So far this works really good. 

 

Stacking was done using APP and final editing in CS4.

Lacerta Herschel Wedge - Brewster Angle

TLAPO80/480 with Lacerta Herschel Wedge and ASI290MM

Some information about my new Lacerta Herschel Wedge. According reviews a Herschel wedge or Herschel Prism would provide more details then the use of Solar film.

My objective is to get more details of the photosphere and the more specific on the granulation itself. Another objective is to use the wedge with my Sol'Ex. 

The Herschel Wedge is equipped with a neutral density filter ND3. On the back of the wedge it's noted that the total light reduction with ND3 filter us ND4.07.

This means that the wedge itself has a light reduction of  4.07 - 3 = ND1.07 . For both visual and photografic observation a value of ND1.07 is too low and even dangerous. To compare with my Solar film ND3.8 I would need to install a filter ND2.7 or  ND2.8. on the wedge. But for now I will keep using the ND3filter.

A value of ND1.07 means a transmission of :  T= 10 exp (-ND) = 10 exp (-1.07) = 0.0851 or 8.51%.

Another interesting one is Brewster Angle.The Brewster angle, named after the Scottish physicist Sir David Brewster, is the angle at which the reflected light rays from a non-metallic surface are fully polarized. In other words, the light waves that strike a surface at the Brewster angle are reflected in only one specific direction (polarized light), while the perpendicular light waves are absorbed.

The Brewster angle can be calculated with the following formula:

tan⁡(θB​)=n2/​n1​​

where θB​ is the Brewster angle,

n1​ is the refractive index of the medium from which the light comes (e.g., air),

n2​ is the refractive index of the medium in which the light is reflected (e.g., glass or water).

At the Brewster angle, the resulting reflection of light for a particular polarization direction is minimal, which can be useful in various optical applications such as my use of the Sol'Ex.

Air typically has a refractive index of approximately 1 (as an approximation), while the refractive index of glass (like in the Lacerta Herschel wedge) is typically between 1.4 and 1.6, depending on the type of glass.

Let's assume a refractive index of 1 for air and a refractive index of 1.5 for glass for simplicity. So, in this example, the Brewster angle for air and glass is approximately 56.31. According the website the Brewster Angle is 56.6°.

Above picture is taken with TLAPO80/480 f/6, ASI290MM and Herschel Wedge. Editing using new beta release of IMPPG and CS4 after stacking with AstroSurface Urania V1.

Scan time for Sol'Ex

The scanning of the solar disk using a Sol'Ex can be calculated using following formula

T = 8.79 * P / (f * v * Cos (delta))

• T = exposure time in s
• P = pixelsize in micron; include binning
• f = focal point of telescope in mm
• v = scanning time of telescoop, typical 4, 8, 16
• delta = declination of the sun

It looks like that the outcome of the exposure time compared with the scanning time is rather exponential.

Effective focal length and best sampling factor

My Helios collegue, Walter, asked me about the effective focal length of my set up when imaging Saturn (august 22, 2023).

So here it is:

I uploaded my picture of  Saturn in WinJupos. Using the measurement - adjustment tab it's possible to obtain the diameter of the planetary disk in pixels (Di). The apparent diameter of the planet in arc seconds  (Dp) is provided by ephemerides tab. 

Sampling S = Dp/Di = 19/128.8 = 0.1475 arc seconds per pixel

The image sampling is equal to :

S = 206 P / F  (P = pixelsize of the camera and F = effective focal length in mm)

So F = 206 P / S = 206 3.75 / 0.1475 = 5237 or F/D = 5237/200 = 26.18 

Conclusion :

My set up with barlow x2, ADC and ASI224MC (3.75 micron) on TAL200K f/8.5 has an effective focal length of f/26.18. This means that my magnification is 26.18/8.5 = 3.05

Based on this f/26.18 and a Dawes resolution power (RP=1.02 wavelenght/diameter telescope) of 0.5838 it possible to measure the sampling factor k (k = RP / S).

k = RP / S = 0.5838 / 0.1475 = 3.95. 

Conclusion :

The Nyquist-Shannon theorem requires a k>2 but in practice a sampling factor of  3 to 3.5 is recommended according to Christian Viladrich - Solar Astronomy page 300 - Planetary Astronomy page 80). Increasing the sampling factor k beyond this would not bring a significant gain. Wirh my set up of 3.95 I will investigate how to reduce this to a value of 3 to 3.5. 

For information: the formule on page 81 of Planetary Astronomy should read F =206 Tp Di/Dp and not using factor 260.

Capturing Cosmic Rays with DSLR Nikon D7500

I read an article (cosmic rays) on facebook on capturing of cosmic rays using a DLSR. I was wondering if I could reproduce this at home using my Nikon D7500 with CMOS sensor. I set up my Nikon  (see settings) and found some "strikes" in my images which I believe could be linked to cosmic rays and even Muons.

Muons are part of the secundary cosmic rays still having huge energy up to 4GeV. We can expect 1 muon count/cm2/min at sea level. Having a APS-C sony sensor and planning for 10min exposure, this would mean about 30 hits. When analyzing my pictures I see a lot of dots of which some are hot spots. I counted about 40 counts on two images without the hotspots.

The double rings on the image are identified as hotspots. 

To compare, the energy of photons are 4x10exp-19 Joule (3.5eV), muons have an energy (when reaching Earth) of 6.4x10exp-10 Joule (4GeV) or 1.600.000.000 higher. 

Setting:

- Nikon D7500, without lens, but with cap and installed in a carton box

- Camera and thus sensor, horizontal positioned

- Lights: 12x600s, ISO3200

- Software : N.I.N.A. , APP, CS4

Some literature :
- Catching Cosmic Rays with DSLR.

- Capturing Cosmic Ray with a DSLR Camera

First light with ASIair plus - M81 Bode's Galaxy

A couple of weeks ago I bought a second hand ASIair Plus. The idea is to have two set ups for my telescopes: one telescope equiped with PC (N.I.N.A.), the other with ASIair Plus.
Having two skywatcher mounts and all camera's from ZWO, the purchase of an ASIair Plus is a good alternative in stead of an extra PC.

I installed the ASIair Plus on my TAL200K f/8.5 telescope. The main camera and guiding camera was connected using USB A 3.0 cables. After powering, connection was made with my mini Ipad. In order to make connection, the wifi should be swithed to ASIair signal. Then open the ASIair app. There are numerous youtube video's how to start using the ASIair Plus. Below some learnings using the ASIair Plus with a skywactcher EQ8-R mount.

- polar allignment and 3-star allignment was done without connection of the mount to the ASIair plus.

- allignment was done using the maincamera which was connected to ASIair Plus (experiment with the exposure time)

- once allignment completed, I connect the synscan of the mount via a USB B cable to USB A 2.0 port of the ASIair Plus.

- polar allignment was redone; take first a picture and plate solve before running the PA - polar allignment.

- to find an object, just select the target and through imaging and plate solving, the object is set in FOV.

- same with guiding, connect the camera and calibration starts automatically; guiding is done using multistar guiding. 

- autorun set up was used to make the pictures.

- afterwards bias, darks and flats were made using the autorun. Pictures are saved under the folders on the e-MMC 

- I used a 32Gb micro SD card to copy the images and to transfer them to my PC. 

- I disconnect the USB A2.0 - USB B cable between ASIair Plus and syncscan when I finishing my imaging session and to park the telescope. Keeping the cable on and choosing the park function in ASIair Plus did not gave the proper coordinates

- so far, no experience with meridian flip, live stacking and planning function. Also no experience with autofocus.

- connection inside the house was lost a couple of times but the session kept running. 

Conclusion:

Connection with camera's went well, guiding was done properly, finding the object through plate solving was fantastic (first time experience). I made 24 pictures (24x300s) on day 1 and 20 more on day two. Transfer via micro SD card was easy. 

Result:

M81, Bode's Galaxy

TAL200K f/8.5, ASI2600MC, ASI224MC on 50x240 guiding scope with EQ8-R

Lights: 40x300s, darks, bias and flats

Software: ASIair plus, APP, CS4, DeNoise AI

Balancing a telescope & mount using a clamp meter

Balancing your scope and mount is very important. Typically I do this by hand moving the scope from one side to the other side,  trying to find the tipping point. A couple of weeks ago, Walter, my astronomy collegue, send me a video from Cuiv, The Lazy Geek - see the video 

In this video a clamp meter is used (with Ampere DC features) to measure the current (Ampere) when moving the scope up or down. When the current is the same for both directions, the scope would be balanced.  If not, adjust the weight and measure the current again... and again. 

So... does it work?  To test it, I borrowed from Walter a clamp meter. It's a Chauvin Arnoux F205AC/DC. The test was done with my AZ-EQ6 with TAL200K f/8.5 including all camera's.

Results: the clamp meter is able to measure the current when the mount moves. There is a difference in current when the mount move up or down. The deviation is about 0,1-0,2A when the scope is out of balance. The deviation is reduced to 0,03-0,05A for a balanced mount.

Conclusion: it's possible to balance your mount & scope using a clamp meter. There is an error of about 0,03 - 0,05A even when the scope is balanced. For that reason I stay with my current workprocess balancing my scope by hand, finding the tipping point.

First light with TS Guiding Scope 50x180

In May this year I bought a second hand TS Guiding scope 50x180 @ ATT Essen for my TAL200K f/8.5 replacing the ZWO mini guide scope 30x120. Yesterday I did some testing with following set up:

TAL200K f/8.5 with ASI2600MC

Guide Scope 50x180 with ASI290MM

Setting: binning 2x2 for ASI2600MC; 180s exposure time

Imaging Software : N.I.N.A and PHD2

Picture edited using CS4.

Results : 

Guide scope gives good field of view and sharp stars which makes it easy to select stars. No issue with calibration and guiding assistance used for guiding settings; adjustment time 1,5-3s and set to 1,5s.

ASI2600MC set to 2x2 binning; start are bright and circular. 

I did have some issues with guiding itself and not sure what the rootcause was. I made 11 pictures of which 4 without "startrails".

Learnings:

N.I.N.A. image settings to be changed to FITS in stead if TIFF. It would be good to have more PHD2 profiles as I have multiple guide scopes. Next I will be testing "multiple stars" guiding.