C14 mirror flop

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  • #574653
    Jack Martin
    Participant

    Where can I obtain mirror locks?

    Regards,

    Jack

    Essex UK

    #582678
    Peter Anderson
    Participant

    My C14 (in 2014) came with these bolts to secure the mirror. They were screwed through the back of the tube to secure the mirror fixed in place and needed to be removed or at least loosened so the telescope could be operated.  There were strict instructions that they should not be used to lock the mirror during observations. Celestron said it was okay to remove them completely. (Unless the telescope was to be shifted – which was what they were designed for, they were not to be used.) So I removed them completely and stored them appropriately labelled. I covered the holes with adhesive rubber pads.  I don’t know whether this has helped… Maybe they can be safely used by a responsible adult… Where to get them? Perhaps from Celestron or a dealer. You can see the ‘mirror lock screws’ in the attached image.

    I seem to have very little image shift anyway, but my work is not critical. 

    #582679
    Peter Anderson
    Participant

    #582680
    Daryl Dobbs
    Participant

    Rother Valley Optics or 365 Astronomy might be worth contacting, I needed similar fixings but can’t remember which one had them? Both companies were very helpful.

    #582683
    Jack Martin
    Participant

    Peter and Daryl,

    Thanks for your replies.

    Jack

    #582702
    David Arditti
    Participant

    The bolts that are supplied with the telescope are about 2″ long, smooth-shanked and threaded with a ¼” Whitworth thread in the top ½”.

    They work by the thread engaging with the mirror cell while the unthreaded section passes through the hole in the back of the scope and the knob clamps tight. Owing the varying mirror position at different focus points, I am not sure if they would succeed in in locking the mirror at any point in its focus range, or not.

    Assuming they do, and assuming you are using one optical configuration with camera at a fixed distance out in a Crayford or similar focuser, I don’t see why you should not lock the mirror in position with these screws after you have established the approximate focus point for the mirror, with the Crayford in the middle of its range, to give a bit of temperature compensation around that point. However, I have not tried this. I tend to do my critical work around the same part of the sky, the meridian, so the collimation does not change much.

    #582704
    Jack Martin
    Participant

    David,

    These bolts were not supplied with my previously owned C14.

    I just have the 2 transport locking bolts 1″ long.

    Rother Valley optics cannot obtain these accessories. I will try 365 Astronomy.

    Regards,

    Jack  

    #582707

    Hi Jack,

    I hope you don’t mind but I thought I’d ask what problem it is you are trying to solve.

    I remember you were having issues with wavelength shift in your spectrograph. If this is the problem then I don’t think mirror flop in the telescope is likely to be the cause.

    Of course if you are having trouble with shifting position of the star when you cross the meridian then that would be fixed by solving mirror flop.

    Cheers,

    Andy

    #582708
    Jack Martin
    Participant

    Andy,

    I don’t mind at all.

    I thought Schmit C’s suffered from this, there was an issue with focussing, after winding the focussing knob backwards and forwards a few times (which has to be done regularly), spectra are much sharper, perhaps it was that.

    Regards,

    Jack 

    #582709
    Roy Hughes
    Participant

    I was curious. So I googled around and found this site giving a DIY version of what you are trying to do.

    Certainly looks do-able, advisable?, who knows.

    https://www.skyimager.com/mirror-lock.html

    Hope this helps.

    Roy

    #582710
    Michael O’Connell
    Participant

    I use a pair of eye bolts and they work very well.

    #582713
    Jack Martin
    Participant

    Astroshot,

    Ingenious ! how long and what thread are the eyebolts ?

    Regards,

    Jack

    #582714
    Jack Martin
    Participant

    Roy,

    Thanks for the link, very informative.

    Regards,

    Jack

    #582715
    Jack Martin
    Participant

    Astroshot,

    What do you use the secure the eye bolts, can see something but not in detail ?

    Regards,

    Jack

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