Explained: Two Suns at Sunset - Harrow, UK [Reflection Off Building]

Mick West

Staff member

What looks like two suns, one bigger than the other, were observed in Harrow, UK, recently. Video was show at:

Posted on April 11 2017, 03:15, so was likely from the previous day, April 10th.

An opposing sunset is usually a cloud lit by the sun. This one looks a bit unusual though.


It's actually the sun reflecting off this building:


The building has been identified by @Trailblazer as a recently built apartment building, The Stay Club, a 19-storey block of student accommodation which has a lot of glass facing in the right direction: http://www.thestayclub.com/students/colindale/

On the day the video was taken (29 Dec 2016) the sun was perfectly aligned with the building. This animation by @Trailblazer shows the direction of the sunset and the alignment of the building (under construction in the satellite images).
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It's a bit fiddly to find out which building it is as there's incomplete 3D building data in Google Earth, and some new construction of tall building which are candidates.

Maybe someone could pop over there with a P900 :) Roundabout at the top of Preston Hill, about house 226. The light colored building next to the dark one

I Suspect this:

However there's several similar buildings, and some new ones.
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From my desk I look out of an east-facing window, and I sometimes get a very similar effect close to sunset, as the sun reflects off a building giving the impression of the sun setting in the east at the same time as it is setting in the west behind me.


Add a bit of overexposure and it would look like a proper sunset.

(The double image in this pic is just due to double glazing)
It's a bit fiddly to find out which building it is as there's incomplete 3D building data in Google Earth, and some new construction of tall building which are candidates.
From the historical Street View, you can see that the building was not there in August 2014:


but was there by October 2016:


There is also imagery from July 2015 but it's not very clear as there is a bus in the way from the same viewpoint. It looks as though the white building is not there but there may be a crane there:

These two distinctive buildings should help to identify it:


The brown building is the HGSI Institute (Masons House, on Valley Drive) - https://www.google.co.uk/maps/@51.5850094,-0.2748772,226a,35y,50.05h,26.71t/data=!3m1!1e3?hl=en

The blue circular building is the northern end of the JFS school - https://www.google.co.uk/maps/@51.5816062,-0.2820602,136m/data=!3m1!1e3?hl=en

I suspect it could be this new tall building in Colindale which is only shown partially in 3D on Google Maps, as it was under construction when the 3D imagery was captured: https://www.google.co.uk/maps/@51.5955859,-0.2507374,184a,35y,350.56h/data=!3m1!1e3?hl=en


Drawing a line from there back to the camera position lines up well with the other two buildings, circled in yellow:


In October 2016, it has glazing facing in the right direction:


It's not there in Aug 2014:


And (from a different angle) in July 2015 it has just the central core and the crane, as seen in the historic Street View from that date in Preston Hill:

I'm pretty certain that is the right building. Comparing Street View from summer 2015 on Preston Hill


with a closer view from a similar direction at a similar time, only the thin core and crane are visible:


By autumn last year, the whole building is there:



The building in question is called The Stay Club, a 19-storey block of student accommodation: http://www.thestayclub.com/students/colindale/

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Using Suncalc to show the direction of the sunset on the day in question, and overlaying the orientation of the front of the building (shown by the red steel framework) shows that the sun would have reflected back in the right direction:

Excellent work! I've updated the OP.

Putting in some rough polygon building for the School and the HGSI buildings shows that the Stay Club building core is in the correct place

Nice analysis, guys!
However, I don't understand the Suncalc thing...could you perhaps describe it in more detail?
Suncalc is a website that shows you the direction of the sun at any given time: http://suncalc.net

For example, using the location of the camera in this video, the site shows today's date, and yellow, orange and red lines:


The yellow line shows the direction in which the sun will rise. The red one shows where it will set, and the orange one shows the direction of the sun at the time shown on the slider at the top (in this case about 11.40am local time)

The orange arc shows how high the sun is in the sky compared to its highest and lowest points throughout the year (closer to the centre is higher in the sky - so in this case the sun is slightly higher in the sky than the midpoint for the year).

And with the building being nearly exactly opposite the sun relative to the camera, and with the building face aligned in that direction, it maximizes the amount of light it will reflect back, making it seem brighter. With the camera on a hill that's a near perfect situation.

An interesting experiment might be to set up a mirror at a reasonable distance and photograph the sunset in it. Hmm.....
How would it be possible for a sun spot on a building to reflect the sun if the sun was 93 million miles away ..i mean how does the sun hit that building directly and not flood the area with sunlight ?
How would it be possible for a sun spot on a building to reflect the sun if the sun was 93 million miles away ..i mean how does the sun hit that building directly and not flood the area with sunlight ?

It's just reflecting an image of the sun, like looking at the sunset in a mirror.

Try looking at the sunset in a mirror to see what this is like. Move the mirror further away from you. Imagine a very big mirror that's far away.
Of interest, mirrored glass buildings can create problems because of their reflection, especially if they are concave shaped.
London's "Walkie-Talkie" building is mirrored "plus" being convex shaped....so much so that at certain times of the year it can beam-down a concentrated sun reflection that can produce a 90*C hot area, on the street.

This does not explain "second sun" in the original post, but it does show the reflective power of mirrored glass buildings when sun is at the correct angle.

Here is a photo I took of my niece, in Dallas TX, where a large (flat) reflective glass building provided "extra" light, bounced off the building, 180 deg. opposite from the natural sun....

Light on the right side was natural sun.
Light on the left side was from the building's reflection.
(phone camera, no photo processing)
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and with 'two' sunsets there would have been many more videos clips from others in London.