One of the features of my version of this scope is the open "mirror box". This allows quick cooling without the need for fans. In most instances, this works very well. Even in an area with some ambient light, a street lamp for example, as long as light isn't reflected directly into the eyepiece, the open mirror box works fine......... B-U-T---

Many areas of the country are humid and with humidity in the air, "dew" can cause it's own problems. Even to the point of cutting an observing session short. There are some ways to deal with dew: 1) to remove it once it's formed, and 2) dew prevention. Obviously, dew prevention is the better solution.

Here's a couple of "dew solutions" you might consider .




1) A simple solution: This example shows a regular ole' dew shield for an 8" Schmidt Cassegrain telescope. But, it works nicely and these ready made dew shields are available from a wide variety of vendors.

I've just taken the dew shield, put it in the mirror box and around the mirror and let it expand. These kind of dew shield are available off the shelf up to 14" in size. Other sizes can be custom made. I've also seen effective dew shields made from automobile sunshades.




2) Here's a solution for those of you who want to take a bit of time. I've disassembled the mirror box and routed a groove in the mirror board. The groove has the same inside diameter as the ring just above it -- in this case, 14 inches The rest of the dew shield is very simple. I've taken a piece of 1/16" Kydex 12 inches wide and long enough to make a complete Kydex "tube" to act as the dew shield (remember to add an inch or two for the overlap). While the mirror box was disassembled, I used the tube-ring to help form the dew shield. Since this material is ABS, I've used ABS cement to join the ends. A couple of "C" clamps help hold the Kydex is place.

Finally, reassemble the mirror box, slide the newly made dew shield down into the groove below. I used a staple gun to affix the dew shield to the top ring of the mirror box. In my case, I am continuing to use the mirror cover I've used all along.

SPECIAL NOTE:  I have since found that, instead of using a staple-gun to affix the dew shield to the mirror box, I just slide the dew shield down into place. If it's the right size, it fits nicely and stays put. This way, the dew shield can be removed and replace easily and you'll be able to gain access to the mirror and mirror cell easily.

For future builds of these scopes, I will include the "groove on the mirror board ".


3) Brian Medeiros, West Greenwich, Rhode Island and his 14-inch telescope with a neat dew shield solution. Here's what Brian has to say:

"...and I got everybody on the site going nuts over this scope, they LOVE it! as I do too. Me and my dad just made a cool dew shield. It cost me 13 bucks to build, and is made out of thin sheet metal, button rivets, no butts on the end, like a button, and a can of black flat spray paint."


Here's a list of vendors you may wish to visit:

Of course, there are many more, including Meade and Celestron. All of the telescope vendors I know about sell 2 or more brands of dew shields.

While KYDEX is a brand name, there are a variety of plastic dealers who provide Kydex-like material. I've found TAP Plastics to be a good source for this material. They sell a 1/16" thick ABS plastic in 4'x8' sheets. They will cut the material to size for you in the store. You can find a vendor near you by using one the search engine of your choice.

Please let me know if you've found an interesting or different dew solution.


For more information call or email anytime:
--Dennis Steele
--Tel: 650-315-6578
--Email: densteele@dobstuff.com

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