Solar eclipse March 2015 as seen by Chilbolton Observatory instruments

Posted: April 14, 2015 by tchannon in Analysis, Measurement

As I promised here is the result from the thermal radiation instruments where as expected little was seen through light cloud.


Figure 1. CNR1 radiometer. (two pairs, looking up/down, short/long wavelength)

There is a minor effect during the eclipse. I live close by where the sun could be made out through light cloud. Around 12 hrs the cloud cleared abruptly. Video taken at Chilbolton shows similarly sudden sunshine.

Two factors in figure 1 need comment.

Albedo is a strange result, is the ratio of direct and ground reflected but essentially a tilted straight line makes no sense. I think the ground, assumed to be grass was wet from dew, this still makes no sense.

The ground long wave signal is high frequency noisy during the middle of the day. In the sky signal this is related to water but whether this is variation is incident radiation or to do with say wet grass is unknown.


Figure 2. Meteorological data.

I’ve omitted wind direction as awkward to plot, add no useful information.
Littleof interest is in these plots other than a slight temperature effect during the eclipse.


Figure 3. There are three instruments here.

The pyrheliometer (narrow view of solar disk) could not see more than a tiny effect which I have brought out.

A pair of pyranometers observe the whole sky but one has the solar disk obscured. These track closely until the sun comes out. I’ve extracted the difference signal during the eclipse, shows a small instrument offset and what has to be taken as noise, no sensible eclipse signal.

The instrument absolute accuracies are not good enough for critical appraisal but do give a broad indication. (instrument documents can be download from Kipp & Zonen, have previously been referenced on the Talkshop)

A null result is presented for the record.

Data provided by Chilbolton Observatory via BADC archive.
Chilbolton Observatory

I wish to thank them for making this data available.


Data from other instruments remains to be analysed, such as the microwave sounding of water vapour.

Post by Tim

  1. I blogged on this – the effect on my instruments was miniscule because of the cloud. I did manage to do a comparison with the previous day which shows the effect of the moon obscuring the sun. It is a shame it didn’t occur later in the year

  2. vukcevic says:

    Get out your solar eclipse glasses. There are some large sunspots that will be visible by using protective glasses with ‘naked’ eye during next few days.
    DO NOT LOOK DIRECTLY!! Not even with the darkest of sunglasses!!

  3. vukcevic says:

    Click on the above image to see one up to date, it appears that the WP is fetching ‘cashe’ one.

  4. tchannon says:

    Good spot there vuk

    Cycle 24 is proving strange.

  5. oldbrew says:

    Looks like Cycle 24 is nose-diving now…

  6. Michele says:

    Two planetary alignments + input alignment Jupiter-Venus-Sun