do dew zappers affect planetary imaging?

[Robert_T]

To quote hitchiker below from previous thread on temp sensing for SCTs

Originally Posted by Hitchhiker

I've always wondered the same thing. It seems to me that if you're pumping heat into your corrector plate you're driving the optical components away from equalising with the ambient temperature.

Perhaps that is something else that we could test - try and image under the same conditions but with the dew heater on and with it off. I don't have enough experience at imaging yet to have formed an opinion on the effect of the dew heater - in fact, so far, when I have done imaging of the moon or planets I have been lucky and it has not been dewy. I would be interested to know what the more experienced SCT owners think of the effect of a dew heater on seeing or imaging fine planetary detail.

Any thoughts, comments out there guys?

cheers,

[bird (Anthony Wesley)]

I have always thought that dew heaters must have an adverse effect, sort of like sticking your hand in front of the tube causes visible heat shimmer.

But I've never used a dew heater so I can't give any solid answer - the closest I come is to use a hairdryer to remove condensation on my secondary, and I know that totally destroys the imaging ability of my scope for about 5 minutes afterwards until the air around the secondary has cooled down.

Bird

[beren]

Without a heater on a SCT you ll get 0 chance of success if Dew rears its head , there would have to be some impact I guess but depending on your dew control system you can lessen the chances with a adjustable controller like the kendricks or dew-buster . Interesting i was out two times in the last week imaging Mars and the first night i had the scope out in the afternoon to cooldown and the conditions where good in the evening with no dew but I got better results the next night when i got home late from work and virtually set the scope straight away from the garage and had to use my heater

[astronut (John)]

I have a homemade dew zapper on my Unitron 4" refractor. The Main objective, eyepiece, Finder objective and eyepiece are all protected. Before installing the heaters my observing session on any resonably moist night would end after about half and hour. After installation no dew all night, even on the most moisture laden atmosphere.
You just have to be careful not to turn the heater control up too much.
Where you set it will come with experience. Cheers, John

[Striker (Tony)]

For a dew heater to work...it only has to create a differnce of temperture in end of the tube of a couple of degrees.....as long as you dont have it too hot I cant see it making a difference.