Problem OIII subs from Running Rivers, a big Sadr

[Fay]

well it does look like dew was the problem. i used dew strips, and the lens looked clear. could it have reached the filters, if so, not had that before.

15x480 Leitz 180mm, QSI OIII filter

[Carole]

I had the same problem on my Oiii filter after I had dried out the aperture of the scope which was still clear - blown out stars and a big halo (where yours is).  In my case I was also using dew strips but a new dew controller that has worked well at home, but it was the first time I had used it in the field, and I think I probably didn't have it turned up high enough.

I have never known it so damp and I am sure it had penetrated onto the filters, again as you say never had that before, it was an exceptionally damp night. 

Carole

[Fay]

i had my dew strips at 75, so high

[Carole]

i had my dew strips at 75, so high

Well it can't be because I didn't have them turned high enough then. 

I have never ever had a problem with dew using dew heaters before, I think it was a really exceptionally damp night.

Carole

[mickw]

If you assemble everything in a humid/damp atmosphere, as soon as you cool the camera, any moisture will start condensing.

I think Starlight Express get round this by using an attachment with silica-gel to absorb any moisture - your camera makers might have similar.

You could try using a hair dryer to warm everything up slightly before assembly.

[Mike]

Also keeping it in a warm place and then taking it out into the cold is a disaster.

Always try and keep your kit at ambient temperature. Never store it indoors if at all possible. Keep it in a shed or observatory. When camping keep it in your car, not inside your tent.

[Mac]

When camping keep it in your car, not inside your tent.

Hmmmmm, Cars get VERY VERY Hot, but at least its a dry heat,
The tents probably a cooler place, and will also cool down quicker then your car.
It's a no win situation.

One other tip, when taking equipment from outside to inside, i.e. cold to warm, put them in a bag outside and seal it,
that way any condensation will normally form on the outside of the bag and not inside.
Once they have warmed up remove from the bag.

Another tip i found is if you have some thing that is very wet, sticking in in the oven at about 40-50 deg normally dries it out.

Mac.

[RobertM]

I think Starlight Express get round this by using an attachment with silica-gel to absorb any moisture - your camera makers might have similar.

Nope, they have not caught up on dessicants yet...

You could always put a low temperature dew band around the camera attachment, something like those designed for eyepieces.

Robert

[Mike]

Hmmmmm, Cars get VERY VERY Hot, but at least its a dry heat,

Yeah, loads of moisture inside tents. Cars do get hot but they also cool down very quickly.

Mick I think you mean the QHY cameras. I know mine has a desiccant tube.

[mickw]

Mick I think you mean the QHY cameras. I know mine has a desiccant tube.

Oops you're right, I forgot QHY

[Rocket Pooch]

I blame Russia.

[Carole]

Set up earlier in the day, hours before it got cold and damp.

Carole

[MarkS]

From the image it is clear that the central area of one of the optical components very close to the CCD has misted up (because the stars outside this area are unaffected).  So it's either moisture condensing on the optical window of the camera itself or on a filter.

[Fay]

I will open it up and see if there is any evidence after the event, today, Mark

It says 500 temp, i assume that is F and =260 C. My oven only goes up to 200

[Mac]

So long as its above 100C the water will be driven off, but 500F for 5 hours, Thats a long time.

I would stick the pack in the oven and fill a baking tray with a lot of water.

stick it in on 200 and keep checking back

once the water in the tray has gone, you know the small amount of water in your pack has also gone.

Mac.