Understanding Dew Prevention
Hi all, thanks for allowing me to join this forum. I hope not be be a pest, just want to learn and get advice. I have ordered a new Celestron Advanced VX 8" Newtonian. Living in South Texas dew is going to be a problem for me. So any kind of knowledge anyone has and can pass my way would be appreciated. Question is do I get a dew shield and heat straps placing them near the primary mirror and the front of the tube? Have not been able to find info for a Newtonian.
Welcome aboard, and thanks for pointing out the signup problems with the forum. I have been so busy with other things and no one else let me know. Hopefully, we can get the forums up and active again.
To your question, Newtonians can be a pain to heat. A dew shield on the front will absolutely help, a dew strap probably will not. On the rear, a dew strap will fix the issue with the primary but you still have the secondary to contend with.
If you are handy, you can make your own something like http://www.deepskywatch.com/Articles/newtonian-dew-heater.html . The idea is to just heat the secondary up just enough to stop the dew. You never want to add more heat than is required for the job as it can introduce defects into your imaging.
Kendricks makes some for Newtonians https://www.kendrickastro.com/newtonian.html .
You may also need some heaters for guidescopes and diagonals & filters in the optical path.
Lastly, speaking from LOTS of experience with Texas dew, you need to protect your laptop. I have a box I made that has four sides: top, left, back, and right. This does a good job. I also keep a hand towel over the keyboard/trackpad.
Let me know if you need more information. Clear skies!
Thank you Allan this will help me when I get everything together. One other thought. When all set up all equipment on, balanced and polar aligned can the bahtinov mask be on the dew shield?
Since I have almost always shot with a refractor my answer is less than conclusive, but my mask has always been used on the end of the extended dew shield. My only concern with moving that experience over to a Newtonian is the dew shield is probably not rigid and may not be as close to a perfect perpendicular angle.
I absolutely would try that though.
@asadmin I guess I will try it without the dew shield 1st get it focused, then put the dew shield and see if there is a difference. Of course doing this is down the road when I get my new equipment. Thanks for your help Allan.
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