dew heater ? etc

[glyn lacey]

Hi all,sorry for my absence,been on a weekend break ,scope free , dew ! ,To the bad weather ,urgh , can I also add to the original question ,will the dew leave marks on the primary ? Resulting in the need to cleanclean ?

[ChrisLX200]

Hi all,sorry for my absence,been on a weekend break ,scope free , dew ! ,To the bad weather ,urgh , can I also add to the original question ,will the dew leave marks on the primary ? Resulting in the need to cleanclean ?

Generally no, the water so formed is effectively distilled and (mostly) free from impurities like dissolved salts etc. What it does do though is attract dust which is then left behind after the water evaportates, so it's best to get rid of it as soon as possible (use a hairdryer if nothing else available).

ChrisH

[MrFinster]

Also be aware that when observing near trees, depending on the time of year, pollen also becomes an issue. Its present in the air and settles out with the water vapour on your scope, its naturally sticky in its own right and is abrasive which is not good news for optical coatings.

I had problems from pollen grains creating condensation nuclei on the corrector plate which are surface irregularities that airborne water vapour finds it easier to start condensing from.

I cleaned 3/4 of the corrector plate on my SCT with a cleaning mix and method recommended by the scope manufacturer and set it up outside, the dew distinctly started forming on the uncleaned quarter first.

I applied a hairdryer to remove it and switched on the dew heater which kept it clear until the power tank  gave up the ghost a couple of hours later, that was enough proof for me that I hadn't wasted a chunk of my equipment budget. 

The way I see it is no dew = no residue therefore no scary cleaning

[ChrisLX200]

I agree about setting up near trees - especially Poplar trees! They exude airborne droplets of resinous sap which is an absolute pig to clean off. There may be other types that do this but it's Poplars that got me once.

ChrisH

[MrFinster]

I agree about setting up near trees - especially Poplar trees! They exude airborne droplets of resinous sap which is an absolute pig to clean off. There may be other types that do this but it's Poplars that got me once.

ChrisH

Try parking under a lime tree