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Merlin66

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Posts posted by Merlin66

  1. Hmmm

    OK

    My central bolt is fixed in the pier...

    I then assemble the extension and "wind" it down hard using the BOA around it....

    If you can jamb the central bolt/ knob/ between the tripod legs you could probably use the same method - or a BOA on each?.

  2. I've recently replaced the tripod on the NEQ6 with a pillar. This has a M12 x 1.75 central bolt.

    The extension just screws onto the bolt (with the bottom disk inverted) - the BOA pulls it up nice and tight! - I don't think you'll break an M12 bolt!

    Looks MUCH better than those "Owl Cage" attachments.

    IMHO the rubber is too soft, and when you tighten down hard it will just shear.......

  3. I use one of these on my NEQ6pro mount.

    The C11 and spectroscopes needs 4 counterweights, so there's a fair load up top.

    It works very well. No issues, no drama.

    (I'm about to set-up a permanent pier - it will have a M12 x1.75 centre bolt to take the extension (rather than having the complex?! Owl cage arrangement) Much neater and functional)

  4. Probably does.....

    Any element corrector/ reducer etc. has a design spacing to the CCD chip to give optimum performance.

    When the filter is introduced between the element and the CCD then the change to the optical length  needs to be considered.

    Andrew's answer above gives the solution, taking into account the effect of the filter.

  5. Andrew,

    The reason I didn't use the "optical" path for the corrector was that the corrector "doesn't" see the filter, and, as far as it's concerned it's still functioning as if it were at a 55mm spacing. The filter just takes the focus from the corrector (at 55mm) and moves it by 1mm to reach the CCD.

    Think through the set-up if the filter were 18mm thick!

    The 6mm change in the focal position would not change the design of the corrector.....it would be (55+6=61mm) from the CCD.

    Yes No??

  6. Guys,

    Stop.

    Think about it slowly and clearly....

    The two "issues" are - mechanical "fixed" distance and "optical" path distance.

    The difference is +/- the filter "correction" depending on your frame of reference.

    I'm thinking with a corrector ( as distinct from a reducer) - the optics of the corrector are designed such that when placed in the optical path (somewhere) that the design distance from the corrector to the focus, and hence the CCD is a fixed distance.

    If we then place a filter element (say 3mm) between the corrector (say requiring 55mm spacing) and the CCD; looking at the optical path the design distance for the corrector remains unchanged but the "optical" path increases by 1mm. To me this says that with a filter the 55mm spacing would actually be 56mm - the corrector still functioning at it's 55mm plus the, added 1mm.

    If we maintained the "physical" spacing of 55mm, the corrector would have to be placed (55-1=54mm) from the CCD, which is not it's design position.

  7. Themos,

    I'll see what I have.

    The electronic finder set-up I have is a Zuiko 200mm f4 lens with an ATiK16ic camera.

    FOV = 63 x 84 arc Min

    The fits header info:

    AVISUMIN=                280.0
    AVISUMAX=                426.0
    AVISUTYP=                  0.0
    APOLY0  =  0.43113530426640000
    APOLY1  = -1.01591339168100000
    APOLY2  =  1.109754879585E-005
    APOLY3  = -3.508152104379E-005
    APOLY4  =  0.00500787253995900
    APOLY5  = -3.507013049586E-005
    APOLY6  = -1.102732033609E-005
    APOLY7  =  0.01427973577929000
    EQUINOX =               2000.0
    CTYPE1  = 'RA---TAN'
    CTYPE2  = 'DEC--TAN'
    CRVAL1  =  24.7022333335500000
    CRVAL2  = -58.2075496941600000
    CRPIX1  =  330.514907382500000
    CRPIX2  =  247.987018971600000
    CD1_1   =  6.358427089425E-004
    CD1_2   = -0.00201002309470900
    CD2_1   = -0.00200937046438600
    CD2_2   = -6.318189145967E-004
    CDELT1  = -0.00210757339460800
    CDELT2  =  0.00210698552014600
    CROTA1  =                  0.0
    CROTA2  = -72.4954476428000000
    END

    post-2614-0-79023500-1416695438.jpg

    It would be much easier to supply the plate solved fits file....drop me an email.

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