Interesting Software: ImageJ, FIJI and AstroImageJ

I'm still reading about Stellar Astrophysics and more specific on the radiative transfer equation linked to limb darkening and in view of analysing images on exoplanets.

Some literature make reference to some interesting software called ImageJ (or FIJI is Just ImageJ). According to the website the software is able to display, edit, analyze, process, save and print 8-bit, 16-bit and 32-bit images. It can read many image formats including TIFF, GIF, JPEG, BMP, DICOM, FITS and "raw". It supports "stacks", a series of images that share a single window. It is multithreaded, so time-consuming operations such as image file reading can be performed in parallel with other operations.

It can calculate area and pixel value statistics of user-defined selections. It can measure distances and angles. It can create density histograms and line profile plots. It supports standard image processing functions such as contrast manipulation, sharpening, smoothing, edge detection and median filtering.

This is the link to the website for more information.

ImageJ is open source software with many plugin possibilities for astronomy. There is even a package called AstroImageJ - see this link.

Succesvolle Zonnekijkdag 2022

Op zondag 3 juli werd naar jaarlijkse gewoonte de zonnekijkdag georganiseerd. Sterrenvereeniging Helios Averbode was paraat aan Het Moment van de abdij van Averbode. Het werd een succesvolle editie, niet alleen door het weer maar ook door de vele bezoekers. Meer dan 130 geïnteresseerde bezoekers kregen de mogelijkheid om vragen te stellen aan de 10 aanwezige Helios leden en om de zon te observeren middels 6 opgestelde telescopen.

Lees het volledige verslag via deze link.

Meridian Line of the Milan "Duomo" Cathedral

On my way to Bologna and Firenze I stayed for three days in Milan. I visited the Duomo of Milan which is one of the biggest Cathedrals of the world. The Cathedral hosts the Duomo Sundial which was built in 1786 by the astronomers of Brera. The Sundial or Meridian Line measures theoretical 61,53m (horizontaly 55,07m and due to be blocked by the northern church's wall the meridian line ends vertical by 2,5m height). 

The sun light, is entering through a 25,2mm pinhole located at 23,8188m height in the church's ceiling. Due to the construction of the roof, the sun light only enteres the pinhole a 15min before and after it's heighest point in the sky.

Some interesting math about this Duomo Meridian line can be found via this website.

Other interesting data about the Duome Meridian line is available aswell via :

- https://www.divinamilano.it/la-meridiana-del-duomo-di-milano/

- https://eratostene.vialattea.net/meridianeaforo/milano/milanoduomo-2.html

Meridian Line of Basilica San Petronia in Bologna

When visiting Bologna I entered the Basilica San Petronia and remembered a presentation by Patrick from Helios on the famous meridian line.

One of the largest meridian line is located in this Basilica San Petronia in Bologna (Italy). It was constructed by (Gian Dominica) Cassini and the meridian line measures 66,8m. The sun light, is entering through a 27,07mm pinhole located at 27,07m height in the church's wall.

The meridian line was constructed to continue checking the dates of the Gregorian calendar, but Cassini also used it to verify Kepler’s second law by observing if the apparent diameter of the Sun decreased in the same way as its apparent speed. Cassini could thus observe the diameter variations of the Sun image which were projected on the floor of the church with the incredible precision and derive from them the variations of the Earth to Sun distance. He verified also that the Sun diameter (and hence its distance) did not decrease in the same way as its speed decreased: the Sun velocity variations during the year proved that the Earth was faster when it was closer to the Sun and slower when it was further away. That was the first observational confirmation of Kepler’s second law proving that celestial bodies were not uniformly moving along circular orbits as astronomers had believed and tried to describe for over twenty centuries. Moreover, Cassini’s measurements preceded of more than three decades the publication of Isaac Newton's Philosophiæ naturalis Principia Mathematica, which would have given a physical framework, the law of universal gravitation, to Kepler’s empirical relations, experimentally proved by Cassini with his meridian.

Even today Cassini's observations are used for scientifical studies eg.  analysis of Solar Diameter Measurements Made at the Basilica of San Petronio during and after the Maunder Minimum (The Astrophysical Journal, 912:122 (6pp), 2021 May 10)

ISS July 17, 2022 (Tyrol Austria)

The International Space Station above Tyrol (Bichlbach Austria) on July 17, 2022 (UT21h26).

Setting: Nikon D7500 18mm f/3.5 ISO6400 with exposure time of 13s).

Milky Way @Bichlbach (Austria)

Picture taken of the Milky Way in Bichlbach (Austria - Tyrol) at the border with Germany. A clear sky with no Moon and the picture was taken between the mountain with a light cone from the town itself aswell as the mountaintop Zugspitze.

Setting : Nikon D7500 18mm f/3.5 ISO6400 and exposure time of 13s.

Visiting Virgo (EGO) Cascina

Today I (together with my Family) visited the Virgo center (European Gravitational Observatory) at Cascina near Pisa in Italy. The road for the last 2km were terible and my car was almost damaged!

The tour started with only 5 of us and later on 2 more Polish people joined. The presentation at the seminar room was clear and to the point. Next we visited the main building office and getting more in depth technical information about the mirrors (these look like glass but do reflect the infrared laser light), the vacuumsystem, the michelson interfermeter, the pendulum system (7 pieces),…

Thereafter we could get into the tube system (which is 3km in total and another 3km for the other one which is 90' oriented). In side the main building we could see the laser, the laserrecuperation system, the beamsplitter, the mirror to resend the laserbeam up to 100times back and forth before getting back into the splitter and to the detector.

The Virgo detector is currently upgraded and to be commissioned and should be ready next spring. Currently Virgo detected more the 80 gravitational waves and typical one per week. With the upgrade expectations are to record gravitational waves on a daily base.

Thx to the Virgo team to share the information and showing us the location in detail.