On Tuesday October 25, a partial solar eclipse was observed in Finland and at Aalto University's Metsähovi Radio Observatory in Kirkkonummi.
The solar eclipse was be visible from 12:11 to 14:31 and it was at its deepest at 13:21, when the Sun was be 62.7 percent covered. The exact times of the solar eclipse are calculated for Kirkkonummi and western Uusimaa.
Finland's only astronomical radio observatory is located at Metsähovi. Even though it was raining the whole time, Metsähovi's radio telescopes were able able to produce solar maps and record the eclipse even through clouds.
Here is the eclipse at maximum, in the solar radio map done with the 14-meter radio telescope (frequency: 37 GHz).
The largest (and the main) radio telescope in Metsähovi is enclosed by the protective radome.
All maps from the eclipse can be found here, and all old solar radio maps in the archive.
The full data set containing all Metsähovi solar data is reachable via the fairdata.fi-service, offered by the Ministry of Education and Culture.
Eclipse from the beginning to the end
The video of the eclipse is made of images taken with the 14-meter radio telescope.
5.5-meter radio telescope "MCA-1"
The eclipse as ween with the smaller radio telescope at 7 GHz frequency.
The 5.5-meter "MCA-1" is much smaller than the main telescope, and operates on lower frequency. Therefore its resolution is also much lower, and later processing is needed afterwards to bring out details.
MCA doesn't have a protective radome, so it cannot be pointed at the Sun for except when it's cloudy, or only for a short while at a time, or the heat radiation starts to affect the instruments.
The smaller radio telescope, SunAnt, measures the total brightness of the sUn at 11.2 GHz frequency.
SunAnt's resolution doesn't allow imaging &msadh; it is used to monitor the Sun continuously and spot solar flares.
The brightness shows the sunrise at around 5 AM UT time (around 8 AM local time), and the eclipse starts to show around 8:30 UT. Rain causes disturbances throughout the day, but the eclipse is still clearly visible.
"Behind the scenes"
Radio telescope doesn't take pictures like a "normal" telescope. Instead, it measures brightness in one small point in the sky at a time, and images are formed when the radio telescope "scans" over the disk of the Sun, measuring brightness in hundreds of points.
In this picture (click to enlarge) each green dot is one measurement point. The yellow "half moon" on the right is the Sun, partially covered by the blue Moon.
"Main telescope", 14 m
MCA-1, 5.5 m
SunAnt, 1.8 m
The largest (and the main) 14-meter radio telescope in Metsähovi is enclosed by the protective radome. It's used for making 37 GHz solar maps every day.
The 5.5-meter "MCA-1" is much smaller than the main telescope, and the frequency, 7 GHz, is also lower. Therefore it's resolution is also much lower.
1.8-m "SunAnt" observes the Sun at 11.2 GHz. Its resolution is not enough for mapping; instead, it monitors the total brightness of the Sun.
Sun at visible wavelengths
What the sun looked like at Metsähovi in the optical waveband...
Metsähovi Radio Observatory
tel. +358 29 442 4852
Image usage / copyright
All images are freely usable, as long as the source Metsähovi Radio Observatory is acknowledged.
(CC BY 4.0)
Citing this page / Author information
Title: "Solar eclipse with a radio telescope"
Authors: Joni Tammi, Juha Kallunki, Juha Aatrokoski, Derek McKay;
Publisher: Aalto University Metsähovi Radio Observatory, Finland