Forums General Discussion filters

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    Stan wright

    HI All,

    i have just bought my first telescope (celestron 150) i would like to observe the eclipse in march can someone explain what filter/s i will need to do this safely  


    stan wright (Newbee)




    Nick James


    The key point is that any filter must go over the front end, or objective, of the telescope. It is not safe to use filters at the backend, i.e. near the eyepiece.

    I have a C6 and observe the sun using a full-aperture filter made from Baader Solar film. You can buy this film from a number of UK suppliers and make it into a filter that fits over the objective of your telescope. I made a suitable filter using cardboard and tape as shown in the picture below. Make sure that this fits snugly over the objective so that there is no danger of it coming off when you are looking through the scope.

    Let me know if you need any more info.


    Robin Leadbeater

     Hi Stan,

    A couple of other safety tips. 

    Keep the front cap on the finder scope or make another filter for it from the offcuts of solar film

    Be sure to put the filters on before aiming at the sun and remember to swing away from  the sun before taking them off. (Seems obvious I know but I forgot once when packing up some time after an eclipse that the mount  was still faithfully tracking the sun and within a couple of seconds of removing the filter the eyepeice cap had a nice neat pinhole melted through it! I keep it as reminder as to why you should never look at the sun through an unfiltered instrument.)


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