[AZ-Observing] Dew Shield

For those with SCT's, even though Arizona is mostly very dry, there 
are wet times and there are times when there is dew. Dew is a real 
killer for photometry with a SCT, but can also degrade visual 
observing. If you have looked at commercial dew shields you may have 
suffered sticker shock. They vary from $35 to over $150.

Rather than spend my limited financial resources on a commercial unit 
I decide to make my own. For under $1 you can have a sturdy, 
lightweight and effective dew shield.

To make one or several, go to a hardware store, e.g., Home Depot, and 
purchase a small 12" wide roll of aluminum flashing. This can make 
several dew shields. Measure the front circumference of your SCT. 
Just use a string if you wish. Layout the string/measurement on a 
strip of the flashing. Mark it about an inch larger. Use a paper 
cutter (board with big knife cutter) to cut the flashing and you will 
get a nice square even cut. Now wrap the flashing around the front 
end of the telescope and mark where it over laps. Make sure there is 
about a half inch over lap. If too much, trim on the paper cutter. 
Now comes the hard part. Clamp one end so the diameter is that of the 
telescope for a snug fit. Drill an 1/8" hole near the bottom of the 
overlap and use an 1/8" pop rivet with washer to secure it. This will 
be the top end of the shield. Now do the other end, but make sure the 
hole is up an inch or so from the bottom so you have a tight fit on 
the telescope at that end of the shield. Drill and pop rivet again. 
Do at least one more in the middle of the overlap or if you want, 
make a total of 5 evenly spaced holes and pop rivets. Now spray the 
inside with flat black paint. Spray the outside whatever color you 
want or leave plain. If 12" is not long enough (12" should be fine 
for AZ), just add another section on the first. This will produce a 
ridge and light weight low cost dew shield. I've been using one of 
these for a while and it works well.

Jeff


-- 
Jeff Hopkins
HPO SOFT
http://www.hposoft.com/Astro/astro.html

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