QSI advice anyone... Ice or debris?

[Sp@ce_d]

Weird one with second light on the QSI tonight. Nothing obvious in the optical train so I'm thinking either icing up or a piece of floating debris inside the camera. After a visual inspection & a reboot its running fine now. Had to reboot as it disappeared from windows after disconnecting from Maxim. Power cycle didn't help & left it with fans running full blast. Maybe a sign of not passing POST properly? I've never had issues with icing up on the Atiks so not sure what to make of this. I was running it at -20 as I did for first light at the weekend....  Now set it to -10 & currently running fine.  Any ideas?

20s Luminance

900s Ha

[r3i]

Weird - my guess would be some kind of frosting or dewing up, because as you said it disappeared when you were running the CCD at a higher temperature.  Not sure what the conditions were like in Scotland were like last night but there was loads of dew down here, it was dripping off the scope.

I don't think it is debris as that would look more well defined black blobs.

[Zakalwe]

It looks like frost on the sensor to me. Is the desiccant replaceable in the sensor chamber?

You can also cool it down in stages while running the camera on really short exposures. This will keep the sensor warmer than the cold-finger so moisture will condense on the cold finger rather than the sensor.

[Herra Kuulapaa]

Looks a dew or frost to me. Starts in the middle and expands towards the warmer edges.

[ChrisLX200]

That will most likely be the CCD Chamber window misting over, it's not on the sensor but close to it. At -20 on a dewey night this can happen, and indeed it did to me last night. Does the camera have a window heater? If so you should turn it on.

ChrisH

[Zakalwe]

That will most likely be the CCD Chamber window misting over, it's not on the sensor but close to it. At -20 on a dewey night this can happen, and indeed it did to me last night. Does the camera have a window heater? If so you should turn it on.

ChrisH

It looks quite sharp, so the window must be very close to the sensor?

Wrapping a dewband around the extension tube (if there's one in the optical train) might sort it too.

[ChrisLX200]

It looks quite sharp, so the window must be very close to the sensor?

Wrapping a dewband around the extension tube (if there's one in the optical train) might sort it too.

It would look a heck of a lot sharper if it were on the sensor :-) (BTDT). Yes, heating the extension tube may help, or it might not... Depends whether the heat will transfer to the chamber window readily.

ChrisH

[Zakalwe]

It would look a heck of a lot sharper if it were on the sensor :-) (BTDT). Yes, heating the extension tube may help, or it might not... Depends whether the heat will transfer to the chamber window readily.

ChrisH

It'd only need to keep the air in the tube above the dewpoint, so it'd only take a very gentle warming. Unless the ice is on the inside, and then we are back to the desiccant in the sensor.

I had a QHY camera that used to freeze the outside of the sensor window on dewy nights....the dewstrap around the tube used to work well with it.

[ChrisLX200]

It'd only need to keep the air in the tube above the dewpoint, so it'd only take a very gentle warming. Unless the ice is on the inside, and then we are back to the desiccant in the sensor.

I had a QHY camera that used to freeze the outside of the sensor window on dewy nights....the dewstrap around the tube used to work well with it.

This is a good idea - and something I will try because I have been plagued by the same thing. I have to use -20deg with the Kodak 16803 and it's a very large surface area sensor. It's OK on a dry night but when it's dewey the window heater barely copes. I don't really know whether it's on the inside or not, Moravian cameras are not sealed but there is a desiccant plug, they seem to think that by incorporating a 'cold copper finger' on the inside any misting will happen there and not on the window or sensor. I'm not convinced...

ChrisH

[Zakalwe]

This is a good idea - and something I will try because I have been plagued by the same thing. I have to use -20deg with the Kodak 16803 and it's a very large surface area sensor. It's OK on a dry night but when it's dewey the window heater barely copes. I don't really know whether it's on the inside or not, Moravian cameras are not sealed but there is a desiccant plug, they seem to think that by incorporating a 'cold copper finger' on the inside any misting will happen there and not on the window or sensor. I'm not convinced...

ChrisH

Try cooling it gradually whilst running a series of looping exposures (shortest possible length) -  in a "Frame and Focus" mode. That will keep the sensor and electronics active and warm. The cold finger will then become the coldest part and the moisture will condense on the cold finger.

QHY used to make a sensor window heater that could be retro-fitted....let me see if I can find it.

[Zakalwe]

Here you go:

http://tienda.lunatico.es/M42-M42-heater-ring

[ollypenrice]

The large format Atiks, of which I've used four, have an integral chip window heater and this is so important a feature that I'm amazed by its absence on many makes of camera. The hearted ring looks promising though.

Olly

[Sp@ce_d]

I think this must have been frost.. seemed ok when I left it in the hands of ACP for the night running on a selection of test targets. I've yet to go through them all as at work now.

I guess I need to adjust things to provide a gentler cooling down. I've got power & cooling scripted. Only had the camera a week it was happy on Sat running -20. The chamber is filled with Argon & desiccant. Looks like it has to go back for refilling, (they charge $150) so hoping its not the seal. The scope was dry when I went out to check everything however, it was warm & dew was forming on the cars & obsy roof but I don't normally have a problem with dew on the scopes and of course it all lives in the Obsy so no shock from the house.

  Theres no nose piece to put a dew band on. Its a 683wsg-8 so you can't get near the sensor (mechanical shutter too) the front of the FW goes straight onto the Flattener. I guess the cooling is far more aggressive on this than my Atiks & I need to stick a gentler cool down in my script. I'll give Ian King a call when he's back next week for a chat. Course theres also the question do I really need to take it down to -20 anyway. Not had change to compare with -10 yet.

[Phillyo]

I've got the 583 and I've compared lights and darks at both -20 and -10 and I couldn't really see a discernable difference between them so I stuck to -10 so i can use it all year round

Phil

[swag72]

I only cool down to -15 degrees. I set SGP to cool down in 5 minutes and also warm up in 5 minutes. I've never had an issue, but then I don't get the dew that you guys get.

[libraryman]

i also run the 583, when i used Maxim, i saw something akin to the image you show, perhaps not quite as bad but nevertheless still there...i now use SGpro, i cool down over 15 mins and any issues that i felt were there have disappeared.

I'm not sure what the issue was but i did not like the way it looked.

Ray

[Davey-T]

Only just started with QSI683 using APT and setting a cooling / warming scheme.

Dave

[rockyraccoon]

As some have said before, it's simply condensation resulting from cooling the sensor too quickly. On humid nights try to leave the camera running uncooled for 20mins or so and then ramp it down gradually to your desired set point.

Sent from my iPhone using Tapatalk

[opticalpath]

I started to get occasional dewing in my QSI 583wsg after about 2-3 years use.  I removed the desiccant plug and regenerated the molecular sieve material according to the directions in the manual.  Have not had the problem since then despite some pretty damp nights.

Up till now I have just allowed Maxim to control the cooling down to -20 C without pause.  Cooling is rapid.  I've had no problems so far but I take note of the comments others have made about cooling more gradually and I may do just that from now on.

Adrian

[tony210]

Hi -I have had the same problem when creating Flats the next day after imaging- it is moisture! I am sure cooling slowly is the answer - best wishes Tony

[Sp@ce_d]

Yes, It's caused by condensation on the outside of the optical window or sometimes the reducer. I spoke to IK about it. Best way to deal with it is to turn off the cooler for a bit to let it return to ambient, then power on again. Which is in effect what I did when checking it. I've never had this problem before because the Atiks I've had just don't cool down as rapid and are as well insulated I guess. I've not had the problem since this & I think the air was just particularly heavy with moisture at the time.