Weird Sunset

[MarkS]

Here's a sunset I took over the Dead Sea on holiday in Jordan - I arrived back last night.  In the foreground is the hotel's infinity pool and then the Dead Sea extends to the base of the mountains. The sun and mountains are reflected in the sea but there are extra reflections of the sun and sky over on the far side of the sea which I think must be caused by some mirage-type bending of the light rays.



Here's a larger version of the region of interest:



I've never seen anything like it before and I don't know if it is common over the Dead Sea.  The sunset on the second night had perfectly normal reflections.

For fun, here's a typical "holiday snap" picture:



Mark

[Carole]

Weird sunset as you say, also it must have been a weird sensation floating in the dead sea.

Hope you had a nice holiday.

Carole

[MarkH]

Really nice pictures Mark, is the book by Andrew Smith? If so what was your opinion of it.

[MarkS]

Yes, floating in the Dead Sea is weird but really relaxing - I floated around for at least 45 minutes on the second day there.  I did try swimming on my front but it forces one's bum in the air so I had to strain my neck upwards to keep it above water.  We covered ourselves with Dead Sea mud and let it dry - I've now got skin as soft as a baby's bum!

The Dead Sea and the ancient city of Petra were real highlights.  We also spent a night in a Bedouin tent in the Wadi Rum desert, famous for its Lawrence of Arabia connection.  The Milky Way was stunningly bright out there. Visited other Roman ruins, Crusader and Muslim castles.  I would thoroughly recommend Jordan as a great all round holiday.

Mark, I read the Andrew Smith book whilst relaxing at Aqaba and really enjoyed it.  It is his account of the interviews or brief contacts he made with all 9 remaining moon walking astronauts (9 at the time of writing) to find out how the experience affected their lives.  Lots of interesting facts and anecdotes.

Mark

[Carole]

The Milky Way was stunningly bright out there.

Did you manage any widefield imaging with your AA mini mount and tripod?

Carole

[MarkH]

Cheers Mark, I have a stack of similar books, I'll have to add it to the collection.

[MarkS]

Did you manage any widefield imaging with your AA mini mount and tripod?

No, I didn't take the ioptron skytracker and didn't have room for a tripod.  I meant to buy a mini-tripod at the airport but forgot    Once out there, I never found a camera shop.

So I took a few shots with the camera perched on a rock, from the natural rock terrace next to the camp.  All are Canon 600D 18mm 150sec f/3.5 ISO1600 and the images are straight out of the camera with no processing.  To focus I sent Dee to the other end of the camp with a head torch!







All lighting in the camp was candlelight and light from the camp fire plus our head torches. There is a tiny amount of light pollution near the horizon but I cannot detect any looking straight up (3rd photo) where you can also see the outcrop of rock above the ledge we were sitting on.

The 4th picture was taken from outside the tent in the middle of the night after the moon came up - looking upwards.
30sec f/4 ISO1600



Mark

[ApophisAstros]

stunning a different world......is it right that the higher the iso the more noise?

[Carole]

That's correct Roger, but I think it only matters with long exposure imaging.

So you were sleeping in a tent?

We did that in Kenya on one of the Safari's, a rather luxurious tent with an added bathroom and aircon. 

Carole

[MarkS]

is it right that the higher the iso the more noise?

It depends what you mean.  If you take the same length exposure at the same f-ratio at 2 different ISOs then all sources of image noise are exactly the same, except that the read noise generally reduces with higher ISO.  If the higher ISO image appears to be noisier it is only because it appears brighter.

For the same length exposure at the same f-ratio, ISO does not change the number of photons collected by the sensor: it only changes their conversion into final pixel values in the image.

However, if changing the ISO results in a shorter length exposure then fewer photons hit the sensor and the image will be noisier.

So you were sleeping in a tent?

Yes, a Bedouin style tent with raised wooden floor.  A couple of floor mats and a couple of simple beds.  Not luxurious.

Mark

[MarkH]

Mark after a bit of thought I remember seeing something on TV about atmospheric refraction and a " green flash" at point of contact/disappearance of the sun at the horizon at dawn and dusk. If I remember rightly you see the sun before and after contact with the horizon in real terms. I wonder if this is a variation of the same phenomena.

[Fay]

I watched a film called The Sheltering Sky, Debra Winger and John Makeovitch, (wrong spelling) set in the 40's about a long holiday around north africa, more of an adventure then, would have been a good book for Dee to read, she would have enjoyed it,  especially the bit where the woman ends up cadging a lift with an arab camel caravan, because her husband dies,  and ends up being a concubine, for a while, of the leading, young, extremely handsome, dressed all in black, just dark twinkly eyes showing,  arab.

Got a bit carried away there.

[MarkS]

As a direct comparison, here is an image of the same area of sky taken from High Halden taken tonight with the same camera, same lens and same settings.  The SQM reading was 20.8, which is average.  Both images are straight out of the camera with no post processing.

High Halden:


Wadi Rum, Jordan:


To be honest, I'm surprised the difference is not greater.

Mark