Partly composed out of different emails to make it easier to read.

Andrew Young wrote:                                                  [Olaf SQUARRA wrote]
 

>  ...these days I put two images of mirages on my website.

Thanks very much!  These are really fine examples of superior mirages.
The miraged islands are somewhat similar to what I have seen from here,
looking at islands 125 - 150 km off the coast.  The "buildings" are
mirages of the "Fata Morgana" type.  In a few cases, you can see other
buildings near them; I assume these are really just farmhouses and
barns, for the most part.

> The photographs were taken in the morning of the ninth of January 2001,
> (rpt: 2001 / now I got a digital scan on CD) from the southern shores of
> Iceland.
> 
> We came from Reykjavik approaching Eyrarbakki arriving before sunrise.
> If it was possible to view the sea the whole time whilst travelling, a
> group of islands would have attracted attention. These islands were more
> than likely to be the Vestmannaeyjar Islands. 
> The Vestmannaeyjar Islands were visibly small on the horizon, but full
> of contrast with the clarity of the breaking dawn. If I remember...

Such distant objects at the horizon are often very plain when the Sun
is just below the horizon.

>  ...correctly, it was about one to three hands to the right, there was
> another mysterious sight that I experienced. As we travelled through
> several curves I sometimes lost the view. On our arrival at Eyrarbakki,
> I climbed some steps to see the view. It now looked different, not
> really like Vestmannaeyjar Islands at all.

Typical.  Mirages are critically dependent on the height of the eye.
Changing your height completely changed the appearance of the mirage.

Do you know how high you were above sea level when the mirage was
photographed?[Answer  further down]
 

> I searched for the islands a little more to the left but in vain. A
> little further around the view of the sea was lost. The small telezoom
> (f=105mm) that I was using, was of little help, but better than nothing!
> Yes - I thought it could be a mirage - but in reality I didn't know, I
> was surprised.

A longer telephoto lens would be useful.  It's clear from your
photographs that there are details still unresolved with this focal
length.

As I recall, your website mentions that it was much colder that day
than on previous ones.  This surface layer of cold air, underneath a
strong inversion, is responsible for these phenomena.

> Was I viewing Vestmannaeyjar Islands or not?? Is it possible to see them
> from that position? But a mirage cannot go around the corner
> (if I was right, then the V.-Islands would be more to the left)....
> One shouldn't see anything else in this direction.
> So to resolve this question I need to go there again….

Well, mirages certainly do not go around corners; but you may have been
a little disoriented in an unfamiliar place.  The first images on your
website show the Sun was a little to the left of the miraged islands.

If you noted the time, I could calculate the Sun's azimuth, and check
whether everything lines up properly.  But the appearance of the
islands -- plus the fact that you had seen them from a different height
-- certainly suggests that it had to be this group in the mirage
photographs.
... ... ...
... ... ...
... ... ...

Thanks very much for posting your mirage pictures, and pointing out
your pages!

Thanks for your detailed answer with a lot of information and
interesting remarks!
... ... ...
... ... ...

>Do you know how high you were above sea level when the mirage was
>photographed?
 

Good question! We climbed on a dike / dam (about 3 or 4m) and - ha ha - 
my eyes are in about 1,80m above ground. But the height above sea level?
I don't have a detailed map where I wanted to find the village and the 
view to the islands and maybe contours of height. But I assume that the
ground of the dike was about 3 to 7m above sea level. So all together my
eyes maybe were 8 to 13m above sea level (!?).
 

[Integrated out of a later answer:]
[Well, at least it's useful to know it was "about 10m" and not 50m.
It's often difficult to know how high one is above sea level,
particularly near a beach.  A gently sloping beach can put you several
meters above the sea and still look fairly flat to the eye.

I think this relatively low height is connected with the small angular
height of the mirages you photographed.  These phenomena require a
strong inversion not far from eye level; the shallowness of the
inversion is connected with the narrowness of the mirage strip at the
horizon.]
 
 

> ...but you may have been a little disoriented in an unfamiliar place.
>The first images on your website show the Sun was a little to the left of the
>miraged islands.

>If you noted the time, I could calculate the Sun's azimuth, and check
>whether everything lines up properly. ... ...
 

I believe that you are right! I sure have been disoriented.
Concerning the time: ...
 ...but on the slide I only found date and place. So I took my old pocket
calendar. "Effect during dawn before sunrise", was the only notice. 
A little bit later (I think maybe 20-40 minutes) we did a photo stop 
because of the view to Mount Hekla - and the Sun rose.
It was at 10:50(UTC). On the way back home I noticed 16:03 for the
evening sunset. I will test these data . . . when I found
the coordinates of the location. Then I will send it to you.

---Data Mirage Iceland 2001-01-09---
 

Hello again!

In a computer program I found the following data:

2001-01-09:

Eyrarbakki coordinates
63° 52' 12" N
21° 09' 00" W

approximately time of the photographs:
10:10-10:30 UTC
(Height of the Sun at 10:25 UTC minus 3°17'  /  Azimuth 137°30')

OK -- that puts the Sun 47 degrees and a bit more south of east.
... ...
On the map I looked at, the islands were not so far to the
south, it seemed to me.  But I need to go to the library and look at a
large-scale map to be sure.

Sunrise:
11:00 UTC (Azimuth 145°14')
(Height of the Sun minus 0°52' (!) said the program / maybe the first
limb of the sun at/on/above the horizon - the rest below)

Yes; this assumes you are at sea level, with "standard" refraction.  So
the Sun's center is 16' (its radius) + 34' (the horizontal refraction)
below the horizon.  This nominally puts the apparent (refracted) upper
limb exactly at the astronomical horizon.
 

(My notice for the sunrise was 10:50 UTC; at that time we were a little
more east of Eyrarbakki / and maybe refraction effects)

Partly.  But also, there is the dip of the horizon, because of your
height above sea level.

(Sunset Eyrarbakki: 16:04 UTC)
 

The distance to the islands has to be 60-70km; rough measured on a
little map.

Maybe it's of interest for you.

Of course!  That distance to the islands is about half of the distance
to the offshore islands I occasionally see miraged here in San Diego.

> Eyrarbakki coordinates
> 63° 52' 12" N
> 21° 09' 00" W

I got to the maps in the library today.  Those coordinates are very
close, but might be 1 or 2 km back from the coastline.

> approximately time of the photographs:
> 10:10-10:30 UTC
> (Height of the Sun at 10:25 UTC minus 3°17'  /  Azimuth 137°30')

I have not checked these numbers, but they appear reasonable.

Because of the high latitude, the Sun's motion is almost parallel to
the horizon; so the azimuth changes by a degree in a little over 4
minutes of time.  An uncertainty of 10 minutes is not quite 2 and a
half degrees in the azimuth.

I think the earlier part of your time interval is fairly consistent
with what the picture shows.  It is, after all, a bit difficult to be
sure of where in the picture the Sun would be, if you could see it.
 

> The distance to the islands has to be 60-70km; rough measured on a
> little map.

I measured on a bigger map of Iceland.  The distance is about 60 km
from where I think you were, about at Stokkseyri.

The azimuth to the biggest island is just about straight south-east
(135 degrees azimuth).  As the coastline runs nearly in that direction
-- as you can see from your photos, in which the islands appear *just*
to the right of the coastline -- this is quite insensitive to your
exact position along the coast.

But the whole chain of islands subtends about 25 degrees of azimuth as
seen from where you were.  I wish I knew the scale of your photograph
better.  I don't know whether the features in the mirage are separate
peaks on that one island, or features on several adjacent islands.  The
whole string of islands is very nearly perpendicular to your line of
sight, so all were nearly at the same distance.  Probably Surtsey is
off the image at the right side somewhere.

Most of the islands seem to be little more than large rocks sticking up
out of the water, so probably what you show is just the one big
island.  It is itself about 6 degrees wide as seen from your position.

The interesting thing is that, although there are considerable
variations in the heights of the features you saw, they all look so
similar in the mirage.  One might have expected the highest part of the
island to be visible above the mirage layer, but it was not.  I need to
find more detailed information about the topography of the islands.
But it appears that the summits were in fact all hidden by the mirage
layer.

> I just read your second mail of yesterday. I only can say
> very very interesting story for me! But I have to read it
> sometimes more to see the "reality" more clear in front of me.

Sure.  It helps to be *looking* at a large-scale map.  Anyway, I think
the map answers your original doubts completely: the general direction
of the coastline is a few degrees to the left of the islands, so they
should indeed appear just off the coast, as they do in your pictures.
I think there is no doubt about what is miraged here: those islands
certainly must be the objects you saw.  The only uncertainty had to do
with the azimuth of the Sun, and that depends on the exact time of the
observation, which seems to be uncertain by enough to accommodate the
apparent direction to the Sun indicated by the brightness distribution
over the sky.
You also alluded to having the impression of something else interesting
off to the right of the prominent islands by a hand-span or two.  That
almost certainly would be Surtsey.

> I think it is an interesting dialogue and contents in that
> mail. I would like to put that as a link for more interested
> visitors on my site. Would you agree for that?

Yes, of course.  I think it's always useful to show people the path
taken in such detective work.
...
...
I think it's useful to "de-mystify" this process.

> ... ...
> Best wishes,   Olaf S.

Thanks for your help in understanding these mirages!
  -- Andy