QHY-8 window fogging up

kinetic (Steve) · #1 07-08-2010, 02:53 PM

I think I have moisture within the sealed case of the QHY-8
and it quickly fogs up on the INSIDE face of the IR filter
when I turn on cooling on these cold nights.
A homemade dew heater wrapped around the nosepiece /MPCC
arrangement seems to make it dissipate but VEEEERY slowly.
Last night it took about an hour before the dew heater had
made it disappear completely and that was even with a full 12v
and obvious warmth even heating up the camera body.

I have never opened the camera and so cannot work out how
moisture got in.

I suppose it's time to read the instructions and fire up the dessicant
heater for the first time...

any advice would be very welcome.

Steve

mill (Martin) · #2 07-08-2010, 03:12 PM

One way or the other, moisture will find it's way into a camera.
You can open the chamber and let it dry out, then close it again with some hot air blowing on it from a hairdrier.
The biggest problem with doing it this way is dust

Another way of doing it is placing the whole opened camera in a zippy bag with some silica bags and wait a couple of hours.
Then with the camera still in the bag, reassemble it.
I use the hot air method because it is quick and works for me everytime.

PS: You could also fire up the heater a while before powering the camera (if it has it's own power).
I own a QHY9 and the heater board is directly on top of the ccd chamber glass.

TechnoBill · #3 07-08-2010, 03:26 PM

Hi Steve,
I have had similar issues. There are two Basic models of the QHY8, one from a mob in the USA is a sealed system, but the normal run of the mill QHY8 is not a sealed system. So air can get in through the joints and plug holes. If it is moist air then that spells trouble.

Most users tend to store the camera in a plastic ziplock bag with dessicant packs when it is not in use. This makes sure the air in the camera is dry. Simply take the camera out of the bag when you are ready to use it and then put it back in at the end of the evening. This also removes any moitsture that may have accumulated in there and prolongs the life of the camera.

Rule number one with that camera is never ever take the filter (or front glass) off when you are out in the field. This lets damp air in and will ruin the evening instantly if the camera is cold.

The coolers on these things are amazingly good and thats part of the problem. There is setup in there called a cold finger that gets cold first and is supposed to hold the ice that may form before it can get to the CCD or the filter. The problem is, that it gets so cold in there so quick everything can ice up before it can collect on the finger.

If you store the camera in a sealed bag with dessicant packs this reduces the problem alot (there is also a small rubber plug on the side that you can remove while its in the bag to let the crystals do their magic more efficiently). Just remember to fit it back in before you take the camera out of the bag :-) .

Also I use a different controller for mine. The standard controller is the DC-101. I bought a DC-102 separately (about 100 bux au). Its for their thermostatically controlled QHY9, but is pin compatible with the QHY8. As the QHY8 does not have a thermostat it still cant thermostatically control the camera, but it does let you manually control the current to the cooling system. When I setup for the night, I set it to barely cooling at all initially for the first 10 mins or so while focussing and setting up, etc. Then increase the cooling power to 50% or so if required depending on the temp outside. Since doing this I have not had iceing issues and still have beautiful clean darks and no background noise.

I hope this helps
Regards
Bill D

marki · #4 07-08-2010, 03:30 PM

Steve if you have the supplied desicant heater from QHY use that it works well. When I had one I used to take the nose piece off the camera and place it chip down in the case. It was then a simple matter to heat and dry the crystals and place that in the box closing the whole lot up for about and hour. Put it back together as soon as you open the case (in a dry environment) and hey presto it's done. I used to do this regularly and never had a problem with dew although Perth is pretty dry most of the year. I think Theo is selling a dedicated dew heater for the QHY8 for people living in areas that have high humidity. Either that or you can give your own a bit more oomph. As Mill said the 9's have them on board and mine has only ever fogged up once when maxim went mad and applied full power to the peltiers at startup. Camera got to about -35 in less then a minute and the chip iced up. Teach me not to keep my eye on things.

Mark

kinetic (Steve) · #5 07-08-2010, 04:09 PM

Thanks guys for the in depth replies, great insights and saves me a
lot of time.
I'll go and get a universal travel adaptor I think I need to allow the
dessicant heater to plug into 240v mains. (it seems to have US style
110/120v parallel pins on it)
It's rated on the label as 120-240v .
I will let you know how it goes first night out

many thanks,

Steve

multiweb (Marc) · #6 07-08-2010, 04:46 PM

Yep - the secret of it all is to keep it dry inside. Any water, dirt on the sensor will ice up eventually. Keep it super clean, silicon around the USB/s-video/power plugs, electrical tape all around the body to seal it off and store it open in the dessicant box when not using it. Just blowdry it prior to use it everytime and you'll never have a problem again.

renormalised (Carl) · #7 07-08-2010, 04:56 PM

They need to make hermetically sealed cameras with argon or nitrogen gas in behind the glass to keep the CCD's dry. I know with the top of the line cameras (with some makes) they do this (seal the CCD chambers and pump gas in there), but it should be done with all cameras. Desiccant, hell with the humidity I get up my way, I'd need a semitrailer load of desiccant to keep a camera dry!!!

Alchemy (Clive) · #8 07-08-2010, 04:59 PM

Hot hair dryer method for me, I haven't had an issue for months, but if you reassemble it when it's hot, there's effectively no humidity inside. As for dust, a high quality artists brush gently swept across the chip does wonders. If younget any oils or such on the chip it will cause it to ice up.... Clean with metho

I tried the silica gel, but quite frankly , opening the casing all the time let's dust in and changes your flat frames all the time. I can go months without an issue done by the above method.

kinetic (Steve) · #9 17-08-2010, 06:15 PM

A few niggling questions still people, sorry..............

Is it normal for the supplied QHY dessicant heater to only JUST
make contact with a typical generic 240v Aus to US adaptor as shown?

The slightest bump and the pins on the heater fail to make contact.
The LED goes out..with such a dodgy connection surely it's a touch
and go affair if it is even doing its job...not only that, a fire risk.

Also, from what you people have suggested, an appropriate way to
house the QHY8 in a case before and after an imaging session is as
shown below in the yellow pelical clone case?
Rubber grommet removed and dessicant heater sharing the same
removed void of foam with the camera?

thanks in advance for any advice.

Steve

multiweb (Marc) · #10 17-08-2010, 07:51 PM

Quote:

Originally Posted by kinetic

Is it normal for the supplied QHY dessicant heater to only JUST make contact with a typical generic 240v Aus to US adaptor as shown?

Yes - it's a cheap heatbox but it does the job.

Quote:

Originally Posted by kinetic

Also, from what you people have suggested, an appropriate way to
house the QHY8 in a case before and after an imaging session is as
shown below in the yellow pelical clone case?
Rubber grommet removed and dessicant heater sharing the same
removed void of foam with the camera?

thanks in advance for any advice.

Steve

Yes that's fine. I also remove the nosepiece and have a thin piece of mesh in front of the hole so the camera breathes. Side plug off, all the time when stored. Keep your sensor super clean. Slightest grease, finger print will ice up. It's glass you won't hurt it. Spray some alcohol on a wipe then one swipe across the length - that's all.

As Clive said I also blowdry it when assembling and that's it. No worries. Ever.

kinetic (Steve) · #11 18-08-2010, 07:04 AM

Thanks Marc!

Steve

seeker372011 (Narayan) · #12 18-08-2010, 05:55 PM

is there a sequence to follow when powering off?
The only time i have ice issues is when i have to poweroff-say i have to deal with a meridian flip amd dont want to attempt that with the qhy cables in place-thats when i have fogging up issues-usually the only way out is to take it in and blowdry it
Can i avoid this by following a particular shut down sequence?

mill (Martin) · #13 18-08-2010, 06:02 PM

Quote:

Originally Posted by seeker372011

is there a sequence to follow when powering off?
The only time i have ice issues is when i have to poweroff-say i have to deal with a meridian flip amd dont want to attempt that with the qhy cables in place-thats when i have fogging up issues-usually the only way out is to take it in and blowdry it
Can i avoid this by following a particular shut down sequence?

I dont think so, because powering down is just that, powering down.
Why cant you do a meridian flip with the cables on?
PS: I never do a meridian flip so my scope is normally upside down in the morning

(And it is working well for me).