It's midnight at the oasis and I'm seeing stars. Lots of them. Bright ones. Just like it says in the Sahara desert guidebook.
But these are in my head, not the night sky, because I've just tripped over a rock and smacked my head on a branch.
I have a condition, you see, that makes me see stars.
And makes me not see stars.
Retinitis pigmentosa is its name - RP for short or Arsey when it's naughty - and it has two big impacts on my vision.
Tunnel vision is one. Normal eyes give you 160 degree sight; mine only 30. That's not enough to stop unceasing ambushes by solid objects. A cupboard door in the forehead, a low wall in the shin, a bollard in the...
You can see why stars are something I see quite regularly.
But while that's a daily and painful inconvenience, it's a lack of stars that invokes my most visceral curses against the faulty genes which are gradually destroying the rod and cone cells of my retinas.
The rods are the ones that should kick in when it gets dark and their untimely death leaves me floundering in dimly-lit rooms let alone trying to make out far away constellations.
So why go to the Sahara at all?
Simple - to help find a way to halt this infuriating disease in its tracks by raising money for research into finding a cure or at least a treatment to slow its progress.
Defying varying degrees of sight loss right up to almost total darkness, a group of us are trying to trek 100km across the Moroccan desert in aid of RP Fighting Blindness.
The charity not only funds increasingly promising research but provides support for those who find it harder to cope with the life-changing discovery that you are going blind than those of us who take it by the horns and refuse to be bowed.
And there are many of them: RP is officially now the most common cause of blindness in the working population.
So the next time you find yourself staring in wonder at the magnificence of the night sky, remember those of us who can't enjoy it and think about giving a helping hand to our fight to see stars only when we want to.
Please donate to help fight RP at justgiving.com/rpsahara
Follow Joe Churcher on Twitter: www.twitter.com/joechurcher