mvandervorst Posted June 25, 2019 Report Share Posted June 25, 2019 Hi, I have the 12-inch Newtonian located in a remote observatory in San Diego. This year has been unusually humid. I currently do not try to image when the humidity goes above 80%. I'm thinking (actually hoping) that may be a little conservative. I assume the rear fan will help a little. I'm curious about others experiences about at what point dew forms? Thanks, Michael Link to comment Share on other sites More sharing options...
MarkS Posted July 4, 2019 Report Share Posted July 4, 2019 Hi Michael, Predicting dew formation is a complex subject, but here is some relevant experience: I use a hood on my ASA10, more for stray light exclusion than dew protection, but it does help a little. The fan is a help, and I control the speed, depending on the conditions. It is best not to use it if possible. I regularly encounter very high humidity - often 80% and above. I have successfully imaged when humidity is >90%. My record, at the end of a run I really wanted to complete, was 99%. The alarm on the humidity sensor was flashing and all the outer surfaces of the gear were very wet, but not the mirrors! I don't make a habit of this, but I would expect that you'd be OK up to 90% RH. Just keep everything cold and run the fan for some time after you finish. Mark Link to comment Share on other sites More sharing options...
mvandervorst Posted July 19, 2019 Author Report Share Posted July 19, 2019 Thank you Mark. I've been imaging to about 85 to 90% humidity recently without a dew shield. The results look OK. In your experience, why should the fan not be used all of the time? Thanks, Michael Link to comment Share on other sites More sharing options...
MarkS Posted July 20, 2019 Report Share Posted July 20, 2019 Theoretically, you don't want any air turbulence in the OTA, so there's a trade-off. I don't really know where the trade-off is on any particular night, so I just try to keep the fan speed down. Mark Link to comment Share on other sites More sharing options...
caober Posted December 22, 2020 Report Share Posted December 22, 2020 What are you using to control the fan speed? Is that a feature when combined with an ASA mount? Link to comment Share on other sites More sharing options...
Waldemar Posted December 23, 2020 Report Share Posted December 23, 2020 In AutoSlew, the software for ASA mounts, there is a feature to control the fan speed through a connection on the mount. Link to comment Share on other sites More sharing options...
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