Paul,
The answer to your question is YES!!
You will need dew heaters if you want an uninterrupted observing session, whether it's summer or winter.
You can either make them yourself, or purchase the system commercially.
I have heaters for both ends of the finder, main eyepiece, laser, secondary mirror and the filter slide..........oh, also leave the fan running the whole time.
Whilst others are having to pack up, or are trying to dry off their optics to continue viewing, my optics are dew free all night.
