Teleconverters and Telescopes

Discussion in 'Digital Photography' started by Dudley Hanks, Mar 23, 2009.

  1. Dudley Hanks

    Dudley Hanks Guest

    I have an old reflector type telescope and a T-mount adapter for my EOS
    Rebel XSi. As soon as it warms up a bit, I'd like to try taking some pics
    of the moon, etc, and I'm wondering if using a 2X TC would work with the
    scope. Or, will it make the exposure so long motion will be excessive?

    Anybody have any experience in such situations?
     
    Dudley Hanks, Mar 23, 2009
    #1
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  2. Dudley Hanks

    PixelPix Guest

    On Mar 24, 5:47 am, "Dudley Hanks" <>
    wrote:
    > I have an old reflector type telescope and a T-mount adapter for my EOS
    > Rebel XSi.  As soon as it warms up a bit, I'd like to try taking some pics
    > of the moon, etc, and I'm wondering if using a 2X TC would work with the
    > scope.  Or, will it make the exposure so long motion will be excessive?
    >
    > Anybody have any experience in such situations?


    The moon itself is as bright as a sunny day and exposures are
    generally quite short, so I think you may get away with using the 2x
    if it fits OK. Depending on your cam and it's noise characteristics,
    you also have the availability of using higher ISO to compensate for
    the 2x light loss.

    Cheers

    Rusty
     
    PixelPix, Mar 23, 2009
    #2
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  3. Dudley Hanks

    Dudley Hanks Guest

    --
    Take Care,
    Dudley


    "PixelPix" <> wrote in message
    news:...
    On Mar 24, 5:47 am, "Dudley Hanks" <>
    wrote:
    > I have an old reflector type telescope and a T-mount adapter for my EOS
    > Rebel XSi. As soon as it warms up a bit, I'd like to try taking some pics
    > of the moon, etc, and I'm wondering if using a 2X TC would work with the
    > scope. Or, will it make the exposure so long motion will be excessive?
    >
    > Anybody have any experience in such situations?


    The moon itself is as bright as a sunny day and exposures are
    generally quite short, so I think you may get away with using the 2x
    if it fits OK. Depending on your cam and it's noise characteristics,
    you also have the availability of using higher ISO to compensate for
    the 2x light loss.

    Cheers

    Rusty

    Noise doesn't seem to be too bad with the XSi high ISO speeds, so I wouldn't
    be afraid to use it. Also, I can switch in the optional high speed noise
    reduction routine -- haven't had to use it yet, so I don't know how
    effective it is.

    Thanks, Rusty, I'll give it a try and see what happens.
     
    Dudley Hanks, Mar 23, 2009
    #3
  4. Dudley Hanks

    Dudley Hanks Guest

    "Rich" <> wrote in message
    news:...
    > "Dudley Hanks" <> wrote in
    > news:dHRxl.18230$Db2.8994@edtnps83:
    >
    >> I have an old reflector type telescope and a T-mount adapter for my
    >> EOS Rebel XSi. As soon as it warms up a bit, I'd like to try taking
    >> some pics of the moon, etc, and I'm wondering if using a 2X TC would
    >> work with the scope. Or, will it make the exposure so long motion
    >> will be excessive?
    >>
    >> Anybody have any experience in such situations?
    >>
    >>
    >>

    >
    > Likely your old reflector is about 800-1000mm in focal length so putting a
    > 2x converter on it (won't hurt much optically, no more than a barlow lens)
    > might make to moon too large to fit into one (top to bottom) frame of the
    > camera, but it will get you closer. Just remember to let the scope reach
    > outside air temperature before shooting and to try to avoid shooting over
    > heated rooftops or pavement. Shooting over grass or water works best.
    >


    Thanks, Rich, appreciate the tips.

    Pulled the scope out this evening to check it out. My wife could only find
    the following info:

    Skywatcher
    d=130mm
    f=900mm

    Couldn't find anything written on the lens, but it came with 2 eye pieces
    with the following data printed:
    Super 10 Long eye relief
    Super 25 wide angle long eye relief

    Also, has the EOS t-mount for mounting Canon SLR cams.

    Probably won't get around to actually shooting anything for a week or two,
    since it sounds like we're in for a stretch of cloudy weather. As soon as I
    can get it out and take some shots, I'll give it a try.

    Once again, thanks.

    Take Care,
    Dudley
     
    Dudley Hanks, Mar 24, 2009
    #4
  5. Dudley Hanks

    Dudley Hanks Guest

    >> Pulled the scope out this evening to check it out. My wife could only
    >> find
    >> the following info:
    >>
    >> Skywatcher
    >> d=130mm
    >> f=900mm

    >
    > That's about an f/7 f-ratio.
    >
    > There's this free program here:
    > http://www.newastro.com/book_new/camera_app.php
    >
    > direct download of application here:
    > http://www.newastro.com/downloads/ccdcalc/ccdcalcfull.exe
    >
    > You can type in your scope's focal length and aperture, camera's
    > sensor size, pixels etc, and from a drop down box select
    > different astronomy targets like galaxies, common nebulae, and
    > the moon, to see how much of the frame they'll fill.
    >
    > Without the teleconverter, with a 30D and 900mm scope you'll fill
    > a lot of the frame - probably half of the short side. Should get
    > pretty good detail out of that.
    >
    > Little tip - the full moon is pretty boring. Get it just before
    > or just after full moon. You get some better shadow lines on the
    > craters, nicer textures.
    >
    > Oh, make sure you don't take too much time between composition
    > and shooting. You'd be surprised how quickly the moon moves at
    > those sort of focal lengths.
    >
    > Another tip - for rough exposure calcs for the moon:
    > http://www.adidap.com/2006/12/06/moon-exposure-calculator/
    >
    > Hope that helps.
    >
    > --
    > Troy Piggins




    Thanks, Troy, those links sound very interesting. I'll check them out while
    I'm (im)patiently waiting for a chance to set it up and click some pics.

    We've had the scope for a number of years, but never took any shots with it.
    Set it up a few times for the kids to look through, but (with the help of
    the LCD on the back of the XSi), this will (hopefully) be the first time
    I'll be able to see anything through it.

    Take Care,
    Dudley
     
    Dudley Hanks, Mar 24, 2009
    #5
  6. Dudley Hanks

    Twibil Guest

    On Mar 23, 10:36 pm, Troy Piggins <> wrote:

    > Oh, make sure you don't take too much time between composition
    > and shooting.  You'd be surprised how quickly the moon moves at
    > those sort of focal lengths.


    Hint: read up on your Galileo.

    ~Pete
     
    Twibil, Mar 24, 2009
    #6
  7. Dudley Hanks

    Dudley Hanks Guest

    "Rich" <> wrote in message
    news:...
    > "Dudley Hanks" <> wrote in
    > news:Bo_xl.19403$PH1.7023@edtnps82:
    >
    >>>> Pulled the scope out this evening to check it out. My wife could
    >>>> only find
    >>>> the following info:
    >>>>
    >>>> Skywatcher
    >>>> d=130mm
    >>>> f=900mm
    >>>
    >>> That's about an f/7 f-ratio.
    >>>
    >>> There's this free program here:
    >>> http://www.newastro.com/book_new/camera_app.php
    >>>
    >>> direct download of application here:
    >>> http://www.newastro.com/downloads/ccdcalc/ccdcalcfull.exe
    >>>
    >>> You can type in your scope's focal length and aperture, camera's
    >>> sensor size, pixels etc, and from a drop down box select
    >>> different astronomy targets like galaxies, common nebulae, and
    >>> the moon, to see how much of the frame they'll fill.
    >>>
    >>> Without the teleconverter, with a 30D and 900mm scope you'll fill
    >>> a lot of the frame - probably half of the short side. Should get
    >>> pretty good detail out of that.
    >>>
    >>> Little tip - the full moon is pretty boring. Get it just before
    >>> or just after full moon. You get some better shadow lines on the
    >>> craters, nicer textures.
    >>>
    >>> Oh, make sure you don't take too much time between composition
    >>> and shooting. You'd be surprised how quickly the moon moves at
    >>> those sort of focal lengths.
    >>>
    >>> Another tip - for rough exposure calcs for the moon:
    >>> http://www.adidap.com/2006/12/06/moon-exposure-calculator/
    >>>
    >>> Hope that helps.
    >>>
    >>> --
    >>> Troy Piggins

    >>
    >>
    >>
    >> Thanks, Troy, those links sound very interesting. I'll check them out
    >> while I'm (im)patiently waiting for a chance to set it up and click
    >> some pics.
    >>
    >> We've had the scope for a number of years, but never took any shots
    >> with it. Set it up a few times for the kids to look through, but (with
    >> the help of the LCD on the back of the XSi), this will (hopefully) be
    >> the first time I'll be able to see anything through it.
    >>
    >> Take Care,
    >> Dudley
    >>
    >>

    >
    > Forgot one thing, use the camera's mirror lock up function if it has one
    > and fire the shutter with a remote or with the self-timer, to eliminate
    > as much vibration as possible.


    Yep, the XSi has mirror lockup, and I've got fairly easy access to that menu
    item. My camera actually has a fairly wicked kick when the mirror moves
    around, especially when using Live View, so I'll probably have to compose
    shots in Live View, and then go back to regular mode and shoot with mirror
    lockup.

    I want to pick up a remote control so I won't have to depend on the 2 sec.
    timer.

    Take Care, and thanks for the tip.

    Dudley
     
    Dudley Hanks, Mar 25, 2009
    #7
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