TheSkySearchers

cold winter nights,how do I look after my telescope when I finish stargazing,against condensation, do I pop back on the lens cover or leave it off,at the moment I have started to use a heated dew shield a small wrap around cloth that obviously heats the large top but leaves the eye piece section exposed to the temperature outside,I,m worried that this might do more damage than good.I understand that I must let the scope warm up first by ambient heating in other words I leave the scope for about 40 min in our un heated sun room ,before bring it in to our main dwelling.I read that you should completely seal the telescope while still out side then bring it in,not sure if this is helpful..looking for guidance here on the right procedure.I have a Celestron 80 explorer LT, I don't want to strip it down,but to be able to keep it all together with the tripod..Many Thanks.

When going from very cold to warm environment you want to slow the warm up process to prevent dew on the optical components. The reason for this is that if the air has any particulates in in then when it dews up those particulates will be in the dew and when the dew dries then you have some residue left on the optical components that over time will need to be cleaned. With my refractors I just cap them and leave dew shield extended, as well as wrap a blanket around them to slow things more. With a SCT, given the corrector is so close to the cap, I would wrap the OTA in a blanket then bring it in and leave it that way til morning. On testing I found that the blanket wrap did prevent dewing inside. I'm sure others have other approaches, but this was easy and I found worked for me.

FYI, I do the above when there is a fairly marked difference in temp between outside and inside, something akin to a 30 degree F or 17 degree C delta or more. Less than than and I just cap them outside before I bring them in.

Steve wrote: ↑Sat Nov 27, 2021 2:54 pm cold winter nights,how do I look after my telescope when I finish stargazing,against condensation, do I pop back on the lens cover or leave it off,at the moment I have started to use a heated dew shield a small wrap around cloth that obviously heats the large top but leaves the eye piece section exposed to the temperature outside,I,m worried that this might do more damage than good.I understand that I must let the scope warm up first by ambient heating in other words I leave the scope for about 40 min in our un heated sun room ,before bring it in to our main dwelling.I read that you should completely seal the telescope while still out side then bring it in,not sure if this is helpful..looking for guidance here on the right procedure.I have a Celestron 80 explorer LT, I don't want to strip it down,but to be able to keep it all together with the tripod..Many Thanks.

Bringing the scope into an unheated space is the same as leaving it outside: it will do nothing.

The speed of warming is not important. What matters is that you keep humid indoor air away from the cold surfaces, in order to avoid condensation. So capping the optics while still outdoors is helpful. Once the scope has warmed up to room temperature with the caps on, remove them, and allow any of the outdoor moisture that is left to evaporate. Then, re-install the caps and pack it away untill next session.

I think the best way would be putting the gear in an airtight container or plastic pouch. The cold air outside has much less water that the warm air inside the house, even if the relative humidity was high outside. Then the condensation happens on the container or plastic pouch, and the already dry outside air inside becomes even drier (relative humidity sinks) when the air inside warms up. After the inside of the container (and the gear) get as warm as the air inside the house, there's no danger of condensation.

Thanks for the advice K and T will follow your recommendations.

Found it...
https://commons.wikimedia.org/wiki/File ... midity.png

I think the blanket helps by creating a blanket-thick transition layer. When the moist room air penetrates the blanket it cools, and the blanket absorbs most of the excess humidity.

Keep the lenscap on!