What's going on here - advice please

[AndrewRrrrrr]

Evening All,

Just got a new pegasus power box and moved to "proper" dew control. Also got a heater for the front of the AA 183M camera. Have the camera cooled to -10C.  (also got a new 0.8 reducer as well - haven't done my flats yet.)

The scope is an AA Wave 80. 

This is a 15% stretch of one of the lights. 

I have the dew heaters on maximum  and there is no dew at all on the front of the objective lens.

The humidity is really high at the moment down here in West Sussex (powerbox says 99%), everything is dripping! Does it ever get too bad and just not worth bothering trying to take subs?

Any ideas what this is? Ice on the sensor? 

Any handy tips on troubleshooting would be welcomed. 

yours Andrew

 

 

 

[Stefan73]

Certainly looks like the subs with my ZWO 2600 last night.  Cambridge was pretty damp too. 

You could see the mist gathering on the front of the camera glass almost immediately after I cleared it.  Did you have a look at the little window on the front of the camera?  Should be obvious if it's mist or ice.

I've ordered a heater for it but I'm not massively optimistic it would have solved last night's problem.  Trying cooling to a higher temperature is worth a go too.

My DSLR seemed to manage OK though but then it clouded over so I gave up!

[tomato]

The shadows look quite intense so what’s causing it is close to the sensor. Given the humidity levels you described, I would agree it’s most likely ice on the sensor window.

[MillHey Nebula]

I read somewhere a while ago that when the relative humidity climbs above 92%, it is time to pack up and go to bed.

[Elp]

You shouldn't need a dew heater for the 183, it's designed so heat from the tec radiates through the camera. Ive used mine throughout the year and its never misted or frozen over whereas the telescope or camera lenses do very quickly. I do not however keep it outside when not in use which could be a factor.

The pattern in the image is similar to a mist formation where it's greyed out but I find it starts from the centre and radiates out like a radial blur, it will end up looking like there's cloud covering the stars over the whole frame. Did you use a filter at all?

[Grant Fribbens]

I have had this with an ASI2600MC equivalent the Altair 26C. This was taking the camera down do -15 and I had the dew heater turned on on the camera  as well as a dew strap around the lens of the scope but I got a fog that appeared during imaging which got larger and larger. Some say that you have to do the cooling down slower which can help or that you may need to insulate the area between the camera and the scope or even include a dew heater at this point on a very LOW setting so as not to introduce nasty thermals in the system. Even though it has been clear the last couple of nights I have not bothered as everything is covered in dew.

Edited November 14, 2022 by Grant Fribbens

[ONIKKINEN]

9 hours ago, MillHey Nebula said:

I read somewhere a while ago that when the relative humidity climbs above 92%, it is time to pack up and go to bed.

This would mean that 90% of nights are not usable for many folks in humid climates so not really an option for many. The remedy is to not cool down as far down below ambient and/or fit a camera body heater like the one FLO sells for ZWO cameras. That one just glues onto the face of the camera and keeps the sensor window from dewing/frosting up.

With my Rising Cam 571 (same/similar to altair 26C) i cool down only to -10, but then again ambient temperatures here are often very low. It may be necessary to cool to -5 for some folks if one wouldn't want to introduce the extra heater to the mix.

[symmetal]

Look down the scope with a torch and see on what surface the dew is forming. In my experience, dew or ice on the sensor itself tends to form from one edge and progress across the sensor. I would get these circular dew patterns forming on the rear of the field flattener with my FLT98 when used with the Atik One CCD camera with the in-built filter wheel. On cooling the camera below zero, the sensor cover and filters would be fine but the field flattener would start dewing up from the centre outwards. When this happened, removing the camera and warming the FF rear with a hair dryer until the dew was gone would then keep it clear for the rest of the night with the cooled camera re-attached.

Tried a dew band around the FF, or putting desiccant sachets behind the FF when not being used, but neither of these had any effect.

When I used newer cooled CMOS cameras though the problem never occurred. 🤔

Alan 

[newbie alert]

How fast are you cooling? Take it you're using a capture software, ie Nina or Apt or something ? You can control how slow or fast you cool, too fast and it can cause frosting 

[AndrewRrrrrr]

14 hours ago, Stefan73 said:

Certainly looks like the subs with my ZWO 2600 last night.  Cambridge was pretty damp too. 

You could see the mist gathering on the front of the camera glass almost immediately after I cleared it.  Did you have a look at the little window on the front of the camera?  Should be obvious if it's mist or ice.

I've ordered a heater for it but I'm not massively optimistic it would have solved last night's problem.  Trying cooling to a higher temperature is worth a go too.

My DSLR seemed to manage OK though but then it clouded over so I gave up!

thanks Stefan, next time i will take the camera off and have a look and yes will try at zero degrees also

[AndrewRrrrrr]

12 hours ago, Elp said:

You shouldn't need a dew heater for the 183, it's designed so heat from the tec radiates through the camera. Ive used mine throughout the year and its never misted or frozen over whereas the telescope or camera lenses do very quickly. I do not however keep it outside when not in use which could be a factor.

The pattern in the image is similar to a mist formation where it's greyed out but I find it starts from the centre and radiates out like a radial blur, it will end up looking like there's cloud covering the stars over the whole frame. Did you use a filter at all?

hi there, yes a plain old L filter for my mono camera. i don't keep my camera outside either. will take the camera off to take a closer look next time it happens......

[AndrewRrrrrr]

12 hours ago, Grant Fribbens said:

I have had this with an ASI2600MC equivalent the Altair 26C. This was taking the camera down do -15 and I had the dew heater turned on on the camera  as well as a dew strap around the lens of the scope but I got a fog that appeared during imaging which got larger and larger. Some say that you have to do the cooling down slower which can help or that you may need to insulate the area between the camera and the scope or even include a dew heater at this point on a very LOW setting so as not to introduce nasty thermals in the system. Even though it has been clear the last couple of nights I have not bothered as everything is covered in dew.

thanks Grant, think taking the cooling a bit slower and not as cold a target temp. 

[AndrewRrrrrr]

4 hours ago, symmetal said:

Look down the scope with a torch and see on what surface the dew is forming. In my experience, dew or ice on the sensor itself tends to form from one edge and progress across the sensor. I would get these circular dew patterns forming on the rear of the field flattener with my FLT98 when used with the Atik One CCD camera with the in-built filter wheel. On cooling the camera below zero, the sensor cover and filters would be fine but the field flattener would start dewing up from the centre outwards. When this happened, removing the camera and warming the FF rear with a hair dryer until the dew was gone would then keep it clear for the rest of the night with the cooled camera re-attached.

Tried a dew band around the FF, or putting desiccant sachets behind the FF when not being used, but neither of these had any effect.

When I used newer cooled CMOS cameras though the problem never occurred. 🤔

Alan 

will take it apart next time it happens and see what's going on. thanks Symmetal

[Elp]

13 minutes ago, AndrewRrrrrr said:

hi there, yes a plain old L filter for my mono camera. i don't keep my camera outside either. will take the camera off to take a closer look next time it happens......

Considering how quickly they fog up when I'm changing them manually i wouldn't be surprised if they did too whilst imaging, though I don't ever recall it being reported as they are enclosed in their holders.

[AndrewRrrrrr]

1 hour ago, newbie alert said:

How fast are you cooling? Take it you're using a capture software, ie Nina or Apt or something ? You can control how slow or fast you cool, too fast and it can cause frosting 

using APT, not sure what the cool down settings are , I think they are the defaults. will have a look at slowing things down and seeing how that goes. cheers!