Dew prob?

[redfox1971]

My celestron cpc800 seems to be dewing up on the inside,it's clear at first with the dew heaters on but then dew on the inside starts to work its way from centre out.i don't fancy removing focal reducer and useing hair dryer as it may blow dust in aswell,will leaving rear cell open when finnished dry the inside out?

[jonathan]

Do you mean the front corrector glass is dewing up from the centre outwards, on the inside?

I would just leave it to dry out naturally, otherwise you are inviting dust inside. You can probably just use a hair dryer on the outside of the scope to raise the temperature slightly, should be enough to keep the dew away, but try not to heat it up too much otherwise thermals will destroy your view. How about a thermal blanket for the main body of the scope? Won't hold off dew indefinitely, but may help for a bit. What dew shield are you using?

[Monty]

Buy yourself one of these...

http://www.firstlightoptics.com/dew-prevention/flo-2-inch-desiccant-cap.html

Store with corrector down so as the moisture warms and evaporates it migrates towards the dessicant.

[redfox1971]

Hi Jonathan that's what i mean,yes a hair dryer does move it but comes back in no time at all,At the mo i have removed rear finder to allow air to enter whitch might help and covered scope with old electric blankit.Thanks for the link Monty maybe I could make one with a spare 2inch sleave with a desiccant bag tucked inside.dose anybody have a link to buying reusable desiccant?

[MJP]

Most chemists will sell you silica gel crystals.

Mike

[starnut]

silica gel crystals - have a look on ebay

[eid]

Don't use calcium chloride...like I did. <blush>

Not one of my brighter moments.

[jonathan]

Hi Jonathan that's what i mean,yes a hair dryer does move it but comes back in no time at all,At the mo i have removed rear finder to allow air to enter whitch might help and covered scope with old electric blankit.Thanks for the link Monty maybe I could make one with a spare 2inch sleave with a desiccant bag tucked inside.dose anybody have a link to buying reusable desiccant?

As far as I know, all of those little desiccant bags that come in deliveries and such are re-usable, they will absorb moisture and then release it slowly under warm / dry conditions.