Camera cooling impeded on a RASA with dewshield

[tomato]

Tonight I  fired up my QHY 268c on the RASA 8 fitted with an Astrozap type flexible dewshield,   I set the temp to -20 deg C. The cooler was running at 83% initially and NINA warned me it wouldn’t be able to maintain the temp and sure enough over 20 mins it ramped up to 100% and the temp started to warm up slowly from the set point.

I thought the most likely cause was the dewshield impeding the air flow through the camera and sure enough with it removed -20 was maintained with 65% cooling.

Simple solution is to run without the dewshield, I’m sure the warm air from the fan will keep any dew at bay on the corrector plate. However, the dewshield is very handy for placing the dust cap back on the scope, not possible to do otherwise when a camera is attached. Not too big a deal to replace at the end of the session, I just wondered if any other RASA owners had encountered this?

[Adam J]

59 minutes ago, tomato said:

Tonight I  fired up my QHY 268c on the RASA 8 fitted with an Astrozap type flexible dewshield,   I set the temp to -20 deg C. The cooler was running at 83% initially and NINA warned me it wouldn’t be able to maintain the temp and sure enough over 20 mins it ramped up to 100% and the temp started to warm up slowly from the set point.

I thought the most likely cause was the dewshield impeding the air flow through the camera and sure enough with it removed -20 was maintained with 65% cooling.

Simple solution is to run without the dewshield, I’m sure the warm air from the fan will keep any dew at bay on the corrector plate. However, the dewshield is very handy for placing the dust cap back on the scope, not possible to do otherwise when a camera is attached. Not too big a deal to replace at the end of the session, I just wondered if any other RASA owners had encountered this?

Thats really interesting but I remain skeptical. Do you have a picture of your setup? I would have throught that unless the dew sheild is very long there would be sufficient air circulation within that space to prevent the air temperature from raising too much. Suppose you could sirect a fan at the front of the setup with the sheild in place to enhance circulation and se if it helps.

Have you done any other testing?

Adam

 

Edited November 15, 2020 by Adam J

[tomato]

This is a photo with an Atik Horizon in place. The 268 is wider and a bit shorter. There is no question the dewshield was causing the problem, the temperature and cooling capacity improved immediately once it was removed. I can see how the shield can promote recirculation of the airflow and hence cause a problem. I could cut some slots in the dewshield but being a flexible Velcro design, it’s no problem to put on and take off.