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Help, strange artefacts in my images…

ZWO ASI2600MM Pro ZWO ASI6200MM Pro Equipment CMOS Artifacts
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Paul avatar
Paul avatar
I just got a new camera (6200MM, use to have the 2600MM) and never noticed something like this before.

It seems at the beginning of a session it starts to show this weird blob, and it gets worse as it gets cooler, if i turn the cooler off it gets better, or if i wait a while it gets better.  It’s been humid last couple of days so wondering if this is a condensation thing, but it just looks different to anything i’ve seen before.  It even looks weird in the image, like its artificial.

I have the Anti-dew turned on in the AA+.

Is this normal and what is it?  

Thanks!

Habib Sekha avatar
Habib Sekha avatar
I have this (sometimes) when humidity is high. It usually disappears in about 10 minutes.

One of the reasons I start to cool the camera at least 30 minutes before using it.
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Jeff Bennett avatar
Jeff Bennett avatar
Looks like condensation to me.  Its not the camera, its on your lens/corrector plate/secondary…  For me, running a small fan near the scope helps.
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Paul avatar
Paul avatar
ah ok, seems like nothing to worry about then

Is there anything to stop it happening or is it a case of just let the system startup for about 15-20min or so for temps to balance?
andrea tasselli avatar
andrea tasselli avatar
Reduce the cooling.
AmyWarble avatar
AmyWarble avatar
Your pics are kinda neat looking, they have the appearance of a bacterial colony.

Last winter I discovered a different cooling issue when I cooled my ASI2600MM camera to -28C.  There was snow on the ground so it was easy to reach that temperature.  I noticed these black, opaque snakes in the image.  I didn't retain the pictures, just imagine taking an astronomy photo into Microsoft Paint and asking a kid to draw a snake with a black marker.

I looped the camera on 2s exposures and could see them growing.  They grew longer faster than they did wider, so they took on the appearance of snakes or worms.  I reduced the temperature to -26C and they slowly went away.  

Ice crystals on my camera lens!
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Tony Gondola avatar
Tony Gondola avatar
It's ice crystals on your sensor or sensor window, hopefully the window. The fact that it gets better over time or at lower cam. temps proves it.
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Paul avatar
Paul avatar
Tony Gondola:
It's ice crystals on your sensor or sensor window, hopefully the window. The fact that it gets better over time or at lower cam. temps proves it.

That doesn’t sound good! Is it a cause for concern? Could it mean something is loose or set up incorrectly?

thanks all for your help so far!
Tony Gondola avatar
Tony Gondola avatar
Not really, it can happen when the humidity is high. It would only be something to worry about if the ice is forming directly on the sensor. The housing for that is supposed to be sealed and the air inside dry. If it's leaked then you would need to go through the procedure that ZWO outlines for drying it out, usually by recharging a desiccant. That said, Your camera does have a dew heater so just turn that on if the ice returns.
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andrea tasselli avatar
andrea tasselli avatar
It's on the sensor, obviously. But no need to fret about it.
Tony Gondola avatar
Tony Gondola avatar
Except that there shouldn't be enough humidity in there for that to happen. The camera's dew heater heats the window not the sensor….
andrea tasselli avatar
andrea tasselli avatar
How do you know there isn't enough? It isn't sealed for sure. Besides, the evidence is there to see. The dew heater is to prevent fogging of the window, not frosting on the sensor as they are thermally insulated from each other, as they should be.
Blue avatar
Blue avatar
That looks like ice on the sensor to me, not the window. I used to get that on my ASI294MC Pro when it needed the desiccant changed or dried out but my 5 year old 2600MC Pro has never shown that.

What sensor temperature are you cooling to? I use -10 on my ASI2600 as there is little point going lower than that in terms of dark current reduction and I think the 6200 is very similar in that regard. The colder you set it the more likely it is for ice to form on the sensor.

Some people report better results by cooling the sensor more slowly if they get ice forming but I have not had it with my 2600 at all so I can't comment on how effective it is.
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Tony Gondola avatar
Tony Gondola avatar
andrea tasselli:
How do you know there isn't enough? It isn't sealed for sure. Besides, the evidence is there to see. The dew heater is to prevent fogging of the window, not frosting on the sensor as they are thermally insulated from each other, as they should be.

andrea, that's exactly what I said. By "in there" I was talking about the sensor enclosure. I also said "The camera's dew heater heats the window not the sensor" I really don't know what you're on about...
Paul avatar
Paul avatar
I’m cooling to 0 and -10, its about 21C during the day but quite humid (in the UK) and around 12C at night.

Shouldn’t be a problem i think, but also the camera is only a week old - wondering if I should be contacting the retailer? As it seems like it isn’t normal for such a new camera? I never had it with my 2600 at all, but within first week of use of my 6200 its happened every night.

I use the Asiair+, so I have cooling come on at startup and the dew heater too, but it takes about 20min for everything to settle down.
andrea tasselli avatar
andrea tasselli avatar
Exchange it for a new one right away, that is my advice. Modern cameras shouldn't have an issue cooling to -10C in a UK summer night. Older models do, so I'm cooling at 0C.  By the way, the critical issue is daytime temperatures, not night-time's.
Paul avatar
Paul avatar
Contacted the retailer and getting it exchanged, thanks all for your help!
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