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Fighting The Dew

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9 replies to this topic

#1 Colinstar

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Posted 28 February 2020 - 06:01 PM

We had amazing skies over our Bortle 2 site at Clayton, South Dakota last Saturday night. 

 

But alas, viewing was cut short by dew by Midnight.

 

This Saturday I will use my Orion light shroud to battle against the dew on my 12" Skywatcher collapsible Dobsonian reflector...

 

...and...

 

I am also looking to get some foam, based on this Sky and Telescope article:

 

https://skyandtelesc...aling-with-dew/

 

Is that called foam core?  Foam-rubber?  Or what exactly do I need to tell the store I am looking for?

 



#2 eyeoftexas

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Posted 28 February 2020 - 06:38 PM

Those extensions are mainly for SCT scopes, not reflectors.  The tube holding your primary mirror is already serving the purpose of that foam extension.  I find that if anything dews up on my 12", it is either the secondary mirror or the eyepieces.  I use a secondary heater from Kendrick (http://www.kendricka.../newtonian.html) and Astrozaps on the eyepieces, both run with an Astrozap controller (https://astrozap.com/products/dew-controller).  There are other brands, like Dew Not.

 

While I sit under my Bortle 7/8 skies tonight, I'll dream of your 2 skies.


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#3 MikeTahtib

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Posted 28 February 2020 - 06:46 PM

After losing a few nights to dew at my Bortle 4 dark sky site (no, i'm not jealous) a fw years go, I bit the bullet and bought a complete dew heater system for secondary mirror, eyepiece, and telrad, for both scopes.  It was a lot more expensive than I expected by the time I was done picking ut all the littel bits and peices, but it allows me to use the telescopes on those rare clear dark nights in the summer.  It was worth it.


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#4 Carol L

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Posted 02 March 2020 - 11:29 PM

We had amazing skies over our Bortle 2 site at Clayton, South Dakota last Saturday night. 

 

But alas, viewing was cut short by dew by Midnight.

 

This Saturday I will use my Orion light shroud to battle against the dew on my 12" Skywatcher collapsible Dobsonian reflector...

 

...and...

 

I am also looking to get some foam, based on this Sky and Telescope article:

 

https://skyandtelesc...aling-with-dew/

 

Is that called foam core?  Foam-rubber?  Or what exactly do I need to tell the store I am looking for?

 

 

The foam you want is a sleeping bag mat. I bought one at Walmart years ago for about $5. It comes in a roll and is made to go under your sleeping bag to insulate and protect you from ground dampness when camping.

 

The mat is large, and there was enough to make dew shields for all of my telescopes, including a 16" Dob. Usually people don't think of needing a dew shield on a Dob, but the secondary mirror is way up there in the upper tube assembly and might get dewed up, so it's best to be cautious. 

 

My Dob's dew shield isn't cylindrical. Instead, it's a half-circle that's deep enough to cover a good portion of the upper tube assembly. It's secured with an adjustable webbing strap that's snug enough to keep the shield from flopping off, but loose enough not to squeeze the tube and throw my secondary alignment off. Notches were cut out of the shield to accomodate the finder scopes.

 

Hope this helps!

smile.gif


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#5 havasman

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Posted 03 March 2020 - 01:16 AM

Good on ya' if you can get along w/o it but I have active dew control on everything I take out for observing because I lost so many nights to dew on secondaries, refractor objectives, eyepieces and finders early on in my dark site excursion experiences.

 

Active dew control works.


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#6 KI5CAW

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Posted 08 March 2020 - 11:43 AM

I live in New Mexico. What is dew?smile.gif


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#7 MikeTahtib

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Posted 09 March 2020 - 09:01 PM

I live in New Mexico. What is dew?smile.gif

LIke the inside of a barrel cactus, all over your telescope.

Edited:  This seemed really funny inside my head.  Not so muchnow that I see it in print.scratchhead2.gif


Edited by MikeTahtib, 09 March 2020 - 09:36 PM.


#8 tphili1959

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Posted 10 March 2020 - 08:16 AM

I made one also from a foam camping mat and it helps a lot to minimize dew on the s we contrary mirror of my 12 inch fob. I superglue it together and simply slide it on or off..its been staying together going on 2 years now

#9 RRMichigan

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Posted 10 March 2020 - 08:19 AM

We had amazing skies over our Bortle 2 site at Clayton, South Dakota last Saturday night. 

 

But alas, viewing was cut short by dew by Midnight.

 

This Saturday I will use my Orion light shroud to battle against the dew on my 12" Skywatcher collapsible Dobsonian reflector...

 

...and...

 

I am also looking to get some foam, based on this Sky and Telescope article:

 

https://skyandtelesc...aling-with-dew/

 

Is that called foam core?  Foam-rubber?  Or what exactly do I need to tell the store I am looking for?

If you happen to have a Five Below store near you, they sell a foam yoga mat in a roll, 1/4" thick, in several colors (including black) for $5.00. There is enough in that roll to make perhaps 4 or more dew shields for an 8" aperture scope (assuming 31" long x 21" deep), even more if for small scopes. I am sure other stores carry this type of mat as well, but most likely for a higher cost.


Edited by RRMichigan, 10 March 2020 - 08:22 AM.


#10 Island_Universe

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Posted 16 March 2020 - 08:32 AM

With great seeing comes great humidity.




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