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Chasing the Midnight Sun

My June 2015 trip on Hurtgruten Ferry

Peter Hill

3/7/2015

 

All images at bottom of page, labelled as per text:

As the earth orbits the sun, at this time of year the earth’s axis is tilted towards the sun. For any point on the earth above the Arctic Circle 660 34’ N the sun is is now above the horizon for 24hrs, hence the midnight Sun.

Had just returned from the classic 11 day costal voyage on the Hurtigruten ferry, see image 1 (below - all images at bottom page), before last Fridays meeting, this took us from Bergen to Kirkenes, on the Russian border,  and back to Bergen, with a visit to North Cape the northern most tip of mainland Europe.

Images 2&3  show the marker for the arctic circle on Vikingen Island, passed on the northern passage at 07:20 16th June and 09:17 22nd June.

True midnight is when the Sun is due N of your position, same as true noon is when Sun is due S. To calculate true midnight requires knowing the Longitude of your position since every degree East will make midnight 4 mins earlier than at Greenwich. However Norway is in the central European time zone which is one hour ahead of BST and therefore two hours ahead of GMT or UT., so the difference due to this must be calculated as well as allowing for the effect of the equation of time that takes into account the variation in the earth’s orbital speed about the sun.

Local time of midnight Sun = Timezone (mins) – Longitude (mins) +/- EOT

Eg at Tromsǿ  69040’58” N 18056’34”E

Local midnight = 120 – (18.9 x 4) +2

                         = 46 mins

At Tromsǿ Midnight Sun occours at 00:46.

Height above Horizon = Latitiude – Artic Circle latitude

                                      = 69.7 – 66.56

                                       = 3.140  

As seen with the Solar graphs Damien showed last week, noon is not a sharp peak , more a gentle curve, equally midnight is a gentle dip to the minimum height above the horizon, so in Tromsǿ the Sun would appear  at about 30 above horizon for about 45 mins either side of the calculated time, i.e. between 00:00 and 01:30

To make life simple the effect of the equation of time can be ignored ( as it only accounts for at most 3 mins variation at this time of year) and the local time for midnight sun calculated as follows:

Local time of midnight sun =  Timezone (mins) – Longitude (mins)

And the sun will appear at its’ minimum height    for about 45 min either side of this time. This gave a variation in time of midnight sun at Ǿrnes of 01:07 and at Vardǿ  of 23.58.

Image 3 between Skjervǿy (00:30) & Ǿksfjord (00:32)  at 23:31 17/06/15, before local midnight sun time

Image.4 as above approx 700N 210E sun  3.50 above horizon at 00:30 18/06/15 near enough local midnight sun time

Image.5 Between Bǻtsfjord (00:03) & Vardǿ (23:58)   00:00 19/06/15  approx 710N 300E with Sun approx 40 above horizon.

Image .6  Night scene taken at 01:50 19/06/15 between Bǻtsfjord & Vardǿ , have not changed any levels with this , this is how it looked, you could sit out reading a book without any extra light.

Image.7 On south bound trip called into Tromsǿ (00:45) at 23:45 20/06/15 and attended a midnight concert, cloud had broken up enough when we returned to allow hazy sun to filter through at 1:25 21/06/15 about 40 mins after local midnight.

Image.8 unfortunately the next evening, 22/06/15  between Stamsund (01:06) and Bodǿ (01:04) the promising midnight sun was extinguished by low cloud but this was how it looked 50 mins  at 00::07 ,before it was due to reach lowest point (about 1 deg above horizon).

Image.9 On the evening of the 22nd June we had now passed the Arctic circle and any chance of sunset was unlikely as it was yet again cloudy (sound familiar??)  then a break produced these dramatic rays and we did get a glimpse of the setting sun on the horizon, Image 10 at  23:57  at approx 64.50N 110E between Rǿrvik  and Trondheim, courtesy of the atmospheric refraction.

On return flight from Bergen saw a wonderful halo and pair of sundogs as we passed between the sun and some high cirrus, unfortunately I had packed all the cameras away!!!!  Always keep one handy you never know what you’ll see.

Pete H

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Photo 8

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