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Zenithstar ll 80mm ED APO

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  • w.stanley07
    I would appreciate advice on lens cap. After using my telescope in cold weather , when I return home should I leave the lens cap on or off as it warms up with
    Message 1 of 4 , Jan 1, 2007
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      I would appreciate advice on lens cap. After using my telescope in
      cold weather , when I return home should I leave the lens cap on or off
      as it warms up with indoor air ? Thanks and Happy New Year with lots
      of clear skies.
      William
      Toronto, Canada
    • Rob Trudel
      William, I have the WO Megrez 80II SD and 90 APO and live in New England (prone to cold moist nights). What I have found to work best is to take my equipment
      Message 2 of 4 , Jan 1, 2007
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        William,
         
        I have the WO Megrez 80II SD and 90 APO and live in New England (prone to cold moist nights). What I have found to work best is to take my equipment outside on cooler/cold days closed up in their cases and let them acclimate to the outside conditions before opening, then after use, before going inside I place the lens cap back on and and close it up in the case. Once brought back inside it will slowly acclimate back to indoor temperature and humidity without condensing on the lens. It is VERY VERY important to ensure the lens has no moisture on it when placing the lens cap on before closing it up in the case so you must check for dew. If dew has settled it is important to remove all of it before putting the lens cap on or to bring it indoors and wait until all moisture has evaporated.
         
        I had an experience bringing in the telescope after use one night on a cool night this fall without the lens cap on and the lens fogged. What I noticed is that this fogging caused the little bit of dust to bond to the lens such that an air bulb (that I use after each use) would not remove some of it.
         
        I also now use silica gel to remove any unseen moisture (again - if you can see any moisture on the lens you must be sure it is all gone before putting the lens cap back on) - I located a great product called DDCAP from Particle Waves Technologies http://www.pwtec.com/ddcap.htm that inserts into the focuser like an eyepiece and holds the silica gel packets. At least this takes care of the inside of the optical tube. I also keep some inside the case as well though I am sure that it loses it's effectiveness rather quickly. I wish they made a similar product that replaces the lens cap and holds the silica gel packets but when I asked them about this they said it would not be practical based on the different sized lens caps in the market. (Maybe William Optics could look into this and offer it for their line of telescopes. I know I would purchase one for each telescope). 
         
        I also do not use the telescope on nights that have a chance of dewing for very long and plan as my next purchase to get some type of dew heater / removal system. Anyone who has experience with these products and could recommend one is welcome to comment - I would appreciate it.
         
        Rob 
        -----Original Message-----
        From: William-Optics@yahoogroups.com [mailto:William-Optics@yahoogroups.com]On Behalf Of w.stanley07
        Sent: Monday, January 01, 2007 10:04 AM
        To: William-Optics@yahoogroups.com
        Subject: [William-Optics] Zenithstar ll 80mm ED APO


        I would appreciate advice on lens cap. After using my telescope in
        cold weather , when I return home should I leave the lens cap on or off
        as it warms up with indoor air ? Thanks and Happy New Year with lots
        of clear skies.
        William
        Toronto, Canada

      • Dan
        Technically, you should leave the dust cap off until the optics reach ambient temperature.
        Message 3 of 4 , Jan 1, 2007
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          Technically, you should leave the dust cap off until the optics reach ambient temperature.
          --- In William-Optics@yahoogroups.com, "w.stanley07" <w.stanley07@...> wrote:
          >
          >
          > I would appreciate advice on lens cap. After using my telescope in
          > cold weather , when I return home should I leave the lens cap on or off
          > as it warms up with indoor air ? Thanks and Happy New Year with lots
          > of clear skies.
          > William
          > Toronto, Canada
          >
        • Scott Walker
          Dan I do not understand your reasoning. As long as the lens is dry I would put the cap on. This will keep dew from forming on the lens due to the warm humid
          Message 4 of 4 , Jan 1, 2007
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            Dan I do not understand your reasoning. As long as the lens is dry I would put the cap on. This will keep "dew" from forming on the lens due to the warm humid indoor air. It also reduces thermal shock. I bring my case outdoors with the scope. When I am done for the night I make sure the lens and scope are dry. I put the lens cap on and put the scope in the case. In the case I keep desiccant. I close up the case and bring it inside. When the air in the case warms its relative humidity should be quite low. The desiccant will ensure this. In my situation it might be better to have holes in the lens cap to let the front of the lens to "breath", but this is because the case protects the lens from the humid air. Some use special lens caps with a built-in holder for desiccant. I remember one member saying he puts his scope in a giant zip lock bag before taking his scope indoors.This protects the scope from the humid air. In the morning his opens the bag. Here in California the problem is not as severe since it does not get that cold. One uses in the mid west told me that after coming in one night the scope quickly started to form frost.
             
            Scott Walker
            ----- Original Message -----
            From: Dan
            Sent: Monday, January 01, 2007 8:30 AM
            Subject: [William-Optics] Re: Zenithstar ll 80mm ED APO

            Technically, you should leave the dust cap off until the optics reach ambient temperature.
            --- In William-Optics@ yahoogroups. com, "w.stanley07" <w.stanley07@ ...> wrote:
            >
            >
            > I would appreciate advice on lens cap. After using my telescope in
            > cold weather , when I return home should I leave the lens cap on or off
            > as it warms up with indoor air ? Thanks and Happy New Year with lots
            > of clear skies.
            > William
            > Toronto, Canada
            >

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