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Home Forums Observing and Imaging Group Fog on eyepieces

This topic contains 4 replies, has 3 voices, and was last updated by  Astrograph 2 months, 2 weeks ago.

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  • #16127

    ThObitz
    Participant
    Topics: 2
    Replies: 6

    Hi,

    Having a new telescope, I am struggling with what is probably the standard beginner’s issues – but there we go: I find that my eye pieces start fogging after some time. I know there are dew heaters similar to those for the front of the telescope – but I am changing eyepieces (and the one I am using is probably least likely to cool down), so not sure whether that is the solution.

    How are you dealing with this? Should I just put unused eye pieces into my coat pocket (with the cap on…)? There are 12V pet blankets on Amazon, that also sounds like a solution…

    Best

    Thomas

    #16134

    Astrograph
    Participant
    Topics: 27
    Replies: 101

    If you are regularly changing eyepieces then the easiest solution is to keep the caps on the eyepieces. If they fog in use then clean them (you should only ever need to do the ‘eye’ end. Wiping an eyepiece down is a much more straightforward task to cleaning the lens, or in your case, the corrector plate. That should not be done. Leaving that to dry naturally is the best solution.

    Putting them in you pocket works just as well although there is always the chance you can put your fingers on the optics when reaching for them.

    Dew heaters for eyepieces are only effective if sticking to one eyepiece. I never recommend this as a solution.

    You also need to be aware of your breath. It is quite easy to breathe on an eyepiece when lowering your head which naturally causes it to fog.

    #16135

    Tej
    Participant
    Topics: 36
    Replies: 582

    I use a 12V hairdryer for my eyepieces.   Works a treat to get that bit extra time of stargazing.

    https://www.amazon.co.uk/Boyz-Toys-RY871-12v-Hairdryer/dp/B00O4Z427E/ref=sr_1_8?ie=UTF8&qid=1493723949&sr=8-8&keywords=12+hair+dryer

    It gets bad reviews and justifiably so because frankly, its awful as a hair dryer.  The reviewers just dont realise that no hair dryer will dry hair quickly on just 12V.

     

    But as a dew remover on eyepieces, camera lenses and telescope object lens…its great!  The low heat is just right to quickly remove the dew without heating up the glass itself.

     

    I never wipe my eyepieces because the coating on eyepiece glass is supposedly delicate and wiping it may remove the coating (supposedly).  So I never risk it, despite having the dirtiest telescope lens in Flamsteed!

     

    EDIT:  I lie, I do wipe  my lenses but only when needing cleaning, not to remove dew.  At home, I use this Baader cloth and solution which work like magic.  I used it on my camera lens too.

    https://www.firstlightoptics.com/astronomy-optics-cleaning-protection/baader-optical-wonder-fluid.html

     

    For my telescope, I use a dew heater band.

    • This reply was modified 2 months, 2 weeks ago by  Tej.
    #16137

    ThObitz
    Participant
    Topics: 2
    Replies: 6

    Thanks for the excellent advice, both of you! I’ll probably put on the covers and put it into my pocket or under some cover.

    Tej, for the hair dryer I will probably need a bit more power than the 6A I have at the moment, but will give it a try.

    Best

    Thomas

     

    #16138

    Astrograph
    Participant
    Topics: 27
    Replies: 101

    Wiping EP’s is not a problem Tej. If the coating was so delicate it came off that easily it would indicate very poor quality. Modern coatings are pretty good. Not military grade perhaps but more than good enough for nomral use and cleaning. There is no harm in giving an EP a wipe but obviously you use a soft cloth like a microfibre and not one that has been used to clean your shoes beforehand. A bit of common sense is needed.

    All lens cleaner really is normally is isopropyl alcohol, sometimes watered down. This is a solvent which evaporates very quickly. Again common sense prevails. You don’t apply a gallon and leave to soak overnight!

    Best cleaning kits on the market is one of the Zeiss kits.

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