Is this condensation/frost?

[Anthonyexmouth]

Thought this might be frost on the lens but cant see anything when i take the camera off while still cooled. I tried drying the desiccant yesterday bit now looks like i might have a couple of dust specks in there.  Zoomed in pic. 

[Anthonyexmouth]

heres the image unzoomed. 

[tomato]

It does look like a bit of moisture on the sensor window, what temperature were you running the camera at?

[Anthonyexmouth]

losing the will to carry on. 

Installed new dessicant tablets from FLO and also added a dew heater for the camera but still got the same problem. Slowed cooling to 15mins in NINA.

Had just saved up for a new scope when the mount board got fried so had to buy a new board £140 and now another £40 on this which didn't fix the problem. 

Anyone got any ideas? 

[skybadger]

What does a flat field look like without cooling ?

 

[Anthonyexmouth]

Just now, skybadger said:

What does a flat field look like without cooling ?

 

Was looking fine.  I'll pop out and stick the panel on now and take some new ones. 

[symmetal]

Frost or dew on the sensor is pretty much in focus as it's only the sensor cover slip thickness away from the pixels. Flat frames will display it clearly if it's present.

Alan

[skybadger]

And what camera is it ?

I have a qhy9 that needed extreme measures but the cooling rate didn't matter, just the achieved  temperature. 

 

 

[skybadger]

12 minutes ago, symmetal said:

Frost or dew on the sensor is pretty much in focus as it's only the sensor cover slip thickness away from the pixels. Flat frames will display it clearly if it's present.

Alan

That depends on the camera. There are other optical surfaces that get cold. 

[Anthonyexmouth]

Ok, heres cooled and uncooled flats, -10 cooled over 10 mins. nothing on the uncooled image.

 

JPG to show the area. 

Cooled Flat.fitsUncooled Flat.fits

 

[Anthonyexmouth]

1 minute ago, skybadger said:

And what camera is it ?

I have a qhy9 that needed extreme measures but the cooling rate didn't matter, just the achieved  temperature. 

 

 

294MC. 

[symmetal]

Yes, that looks like dew on the sensor as the spots are in focus. Possibly ice, though I've found the ice generally forms streaky patterns rather than distinct spots. My ASI071 is very prone to ice unless I store it when not in use in an airtight container with a large desiccant bag, and the access port on the side of the camera open, to allow the internal desiccants to dry out.

Alan

[Adam J]

On 07/08/2022 at 21:55, Anthonyexmouth said:

heres the image unzoomed. 

My guess is no simply because frost and consideration normally form dead centre of the chip and that is offset to the side. I think my first move would be to give all optical surfaces a good clean. But to be honest the definitive way to tell is really easy, just take a flat with the cooling turned off. 

Edited August 20, 2022 by Adam J

[Adam J]

34 minutes ago, symmetal said:

Yes, that looks like dew on the sensor as the spots are in focus. Possibly ice, though I've found the ice generally forms streaky patterns rather than distinct spots. My ASI071 is very prone to ice unless I store it when not in use in an airtight container with a large desiccant bag, and the access port on the side of the camera open, to allow the internal desiccants to dry out.

Alan

ZWO state that poet on the side is not for customer use. Also you can't dry desiccant out like that, it needs to be removed and heated in an oven. 

 

[symmetal]

44 minutes ago, Adam J said:

My guess is no simply because frost and consideration normally form dead centre of the chip and that is offset to the side. I think my first move would be to give all optical surfaces a good clean. But to be honest the definitive way to tell is really easy, just take a flat with the cooling turned off. 

Anthony has posted a flat with no cooling and the patch is not present. My ASI071 ices up from one edge of the frame initially and works it way across.

38 minutes ago, Adam J said:

ZWO state that poet on the side is not for customer use. Also you can't dry desiccant out like that, it needs to be removed and heated in an oven. 

The instructions for the original ASI1600 was to put two desiccant tablets in the port adapter to dry out the camera internals. This was actually ineffective as two dry tablets will do little to dry out the four internal saturated ones and they will all equalize to around 75% saturation each at best and also take a long time. This is probably why Zwo don't include the port adapter anymore and have said not to use it.

Silica gel is a moisture buffer. It will absorb moisture from moist air and release moisture to dry air until an equilibrium is reached. I've put saturated small silica gel sachets in a sealed container with a large bag of 'dry' silica gel and a RH meter indicating 20%. After a few days the sachets change colour and indicate recharged and the RH has increased to around 22% or so. 🙂

Putting the camera in the container it would likely take a week or more for the internal tablets to reach equilibrium as the access port area is small.

Heating them just forces the water to be released quicker as the water molecules will have more energy and the RH of the surroundings is very low, as long as there is adequate ventilation to let the released water vapour escape. Microwaves aren't so good at ventilating the water vapour I've found, as the inside is left wet and the silica gel pack very hot and moist, unless it's left in well beyond the recommended 'cooking' time.

Alan

[Anthonyexmouth]

The patch always appears in the same spot.

I originally tried oven drying the tablets. When that didn't work I popped into FLO and got a packet of new ones and also added a zwo dew heater. 

I don't know what else to try now. 

 

 

[Adam J]

4 hours ago, Anthonyexmouth said:

The patch always appears in the same spot.

I originally tried oven drying the tablets. When that didn't work I popped into FLO and got a packet of new ones and also added a zwo dew heater. 

I don't know what else to try now. 

 

 

Oven will have dried them out so long as you had it hot enough for long enough. I have had to do that once in four years on my 1600mm pro. But the larger aps-c sensors seem to cause ZWO issues. If it's not sealing and frost it's oil on the sensor. I have always had it in mind that I would buy another brand if I ever got a large chip (unlikely). 

[Paul M]

10 hours ago, symmetal said:

My ASI071 is very prone to ice unless I store it when not in use in an airtight container with a large desiccant bag, and the access port on the side of the camera open, to allow the internal desiccants to dry out.

Oh dear. I've had trouble with my 071 and didn't even cool it last time out. I've just received one of the bespoke heater elements from FLO but I've not fitted it yet. I was hoping that'll be the end of the matter.

The camera lives on the OTA full time in an integral garage that houses the boiler also. Very dry in there. Always just a tweak away from focus and less risk of accidents and getting dust on the sensor.

Your findings don't fill me with confidence going forward!

[Anthonyexmouth]

5 minutes ago, Adam J said:

Oven will have dried them out so long as you had it hot enough for long enough. I have had to do that once in four years on my 1600mm pro. But the larger aps-c sensors seem to cause ZWO issues. If it's not sealing and frost it's oil on the sensor. I have always had it in mind that I would buy another brand if I ever got a large chip (unlikely). 

dried them in my airfryer for an hour. when that didn't work I got fresh ones from FLO, it's so frustrating having a string of issues all at once. Sent my 290 off to be repaired in May and it only got to ZWO last week. 

[Anthonyexmouth]

1 minute ago, Paul M said:

Oh dear. I've had trouble with my 071 and didn't even cool it last time out. I've just received one of the bespoke heater elements from FLO but I've not fitted it yet. I was hoping that'll be the end of the matter.

The camera lives on the OTA full time in an integral garage that houses the boiler also. Very dry in there. Always just a tweak away from focus and less risk of accidents and getting dust on the sensor.

Your findings don't fill me with confidence going forward!

mine lives outdoors on the pier year round, been like that for 4 yrs and never had an issue. didn't even creep up on my. The ZWO heater band didn't make any difference, nor did new tablets. 

[Paul M]

12 minutes ago, Anthonyexmouth said:

mine lives outdoors on the pier year round, been like that for 4 yrs and never had an issue. didn't even creep up on my. The ZWO heater band didn't make any difference, nor did new tablets. 

Even with my gear living indoors when not in use I find I need dew bands on my OTA just about all year round. Otherwise my 10" primary looks like it's sweating!

[Anthonyexmouth]

50 minutes ago, Paul M said:

Even with my gear living indoors when not in use I find I need dew bands on my OTA just about all year round. Otherwise my 10" primary looks like it's sweating!

I meant the anti dew ring for the camera. Where it's kept when not in use doesn't make a difference to dew issues. 

[symmetal]

The anti-dew ring for the camera is to prevent condensation on the front surface of the camera protection glass only and won't have any real effect on dew on the sensor.

If the camera sensor chamber isn't airtight as seems the case on my 071 then it will over a few days or maybe weeks, end up at the average daily RH of the outside air. During the night as the temperature drops some moisture may condense out even if not cooled.

Keeping the camera in an airtight container with large desiccant bag until just before being used means the sensor and tablets are around 25% RH so can then be left on the scope for several days without problems, defore going back in the container. The chance of more than a few days of imaging time in a row being rare this works for me. 🙂

It means the camera doesn't have to be opened to change the tablets, which wasn't successful for me on the icing, and end up getting dust on the sensor as happened when I tried it. The DSLR sensor cleaning kits with the one use pads on a stick work very well though.

Alan

[skybadger]

I think there are a number of ways to address this : 

The dew preferentially forms at the same spot on one of the surfaces: potentially because there is a film of something on the glass there - give it a good clean and it may delay the formation of dew but wont prevent it. 

Any internal dehumidifiers arent working. Replace them and reseal the camera or bring the camera in and wrap in a large warm bag of dehumidifier in a sealed box for a few days.  It will take that long if not longer to pull the moisture out of the internal ones . 

Take the internal ones out and microwave them if they accessible and are silica, on warm for 10mins. Works very well on an open plate (the granules need to be loose rather than in a bag). If they are zeolite strips, they need heating in an oven at 160 degree in a closed tin filled with silica granules to dry them properly. 

Seal the camera properly if you can find the leak. Add a gasket to threads like ptfe tape if they are a sealing surface.

I ended up replacing the dehumidifier strips on my QHY 9 with zeolite strips inside the internal sealed (clearly not very airtight)  cell, coating the inside of the camera with styrene resin to seal the pcb connector openings and have a much larger external reservoir of silica used to extend the camera internal plenum dry time to something useable. I also purge with argon gas through the silica reservoir to remove any water in the argon during purge.  Purging gently from the bottom up enables the heavier argon to push out the damp air. That typically lasts about 6 months. These cameras are not sealed well!

While I am sure your ASI is better than this, the only camera thats not likely to eventually leak is a vacuum sealed camera/sensor and even they are not infallible. 

HTH. 

 

Edited August 22, 2022 by skybadger
addition

[Anthonyexmouth]

Ok. I'm going to try a sensor clean. It looks totally clean to the eye, even under a magnifying glass I can't see any imperfections but I'll try anyway. Just wondering if there's any benefit in doing an argon purge when I put it all back together.