fog in image centre

[libraryman]

Hi, i have been seeing a fog issue in my subs recently but i cant find the reason why its there.

Last night i was just running V curves @ -20c on my QSI through a LUM filter, obviously the moon was well up but this was taken well away from it and with an IDAS P2 Light pollution filter in the train.

This was a 15min sub @-20

looking at the filters, they show no obvious dew or issues on them...the optics were clean no dew obvious on the front element Tak 106ed.

I'm just looking at the possibility of  an issue with the sensor but even that looks clean.

any ideas anyone?

Ray

Beehive-001L.fit

[libraryman]

i have uploaded the same image, stretched in Images plus and saved as a  Jpeg.

this shows the issue far better.

i think it's dew somewhere in the optical train, i hope its not from the sensor.

Again; any input appreciated.

Ray

[Martin-Devon]

Ray - I'm pretty certain this is a thin film of condensation. I've had the same with my QSI/Tak set-up, it's an issue with these very humid cold nights as the temperature drops. I kept getting a film, almost identical to what you have, on the reducer (always on the glass side facing the CCD). The QSI cooler is very efficient/fast, so I've now taken to reducing the CCD temperature down to -20 in steps, so that it takes 30-45 minutes to get there. This slower cooling rate seems to have solved my problems. Maybe give this a try.

Martin

[Fay]

I can see the dark surrounding circle on this sub Ray.  hope Martins suggestion will sort you out 

Fay

[ollypenrice]

Chip window heaters are wonderful things. I have them on our Atik 11000 and, prior to that, on a pair of 4000s we had. All manufacturers should include them because, quite simply, they are necessary. 

Olly

[Scott]

Chip window heaters are wonderful things. I have them on our Atik 11000 and, prior to that, on a pair of 4000s we had. All manufacturers should include them because, quite simply, they are necessary. 

Olly

not heard of these. what should I be googling?.......Please

[libraryman]

Excellent Martin, I will try reducing the temperature slowly, ii. Certainly looks lke condensation... Its a pain.

Ray

I agree Olly though I did not realise they exist.