Photographing Mars' grand show

Discussion in 'Digital Cameras' started by Roger N. Clark, Aug 10, 2003.

  1. All:

    This month and into September, Mars will be very
    close to the Earth, in fact the closest in recorded
    history. Normally, you need a telescope to see much
    detail or photograph anything on Mars, but because
    it is so close, it is possible to photograph detail on Mars
    with telephoto lenses, if you can get to 700mm or longer.

    This morning I went out and
    photographed Mars before sunrise with a 500mm f/4 lens
    plus 1.4x and 1.4+2x (stacked) teleconverters and Canon
    10D camera. Note the 10D has spatial resolution similar
    to Fujichrome Velvia (ISO 50) film.
    Before you say the 1.4+2x image is fuzzy, note the
    image is enlarged 4x and diffraction limited.
    Below that image is an image of Mars with the 1.4x taken
    a couple of days earlier (the ones from this morning
    look similar).

    http://clarkvision.com/astro/mars.2003

    Roger
     
    Roger N. Clark, Aug 10, 2003
    #1
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  2. On Sun, 10 Aug 2003 08:49:28 -0600, "Roger N. Clark"

    [snip]
    That's pretty amazing. I tried my 400mm lens last night but I didn't
    get much...you said 700mm and you weren't kidding! Of course your "L"
    lens helped...superb optics. I'm still waiting for my friend's
    telescope, but I think that it's gonna be cloudy for the next couple
    of days.

    --
    Kulvinder Singh Matharu
    Contact details : http://www.metalvortex.com/form/index.htm
    Website : http://www.metalvortex.com/

    "It ain't Coca Cola, it's rice" - The Clash
     
    Kulvinder Singh Matharu, Aug 10, 2003
    #2
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  3. Yes, an T-mount will work well. I've used them too for many
    telescope images. I have them for the 10D but haven't
    drug the telescopes out yet (12.5-inch aperture f/6 and
    8-inch aperture f/11.5).

    Regarding exposure:
    Remember Mars is illuminated by the sun. Mars right
    now is about 40% further from the sun, so the light
    level is 1.4*1.4 ~ 2x fainter (one stop).
    The sunny f/16 rule for the Earth would say 1/100
    sec at f/16 for ISO 100 or 1/200 at f/11. For Mars
    one stop fainter should be close.

    Roger
     
    Roger N. Clark, Aug 10, 2003
    #3

  4. Certainly better than I thought it could be! This could be worth
    trying out...

    I've noticed in the past that, with my 170-500mm and 2x converter,
    good focus in the viewfinder is not always best focus on the film, leading
    me to believe my focus screen is a smidgen away from ideal (Elan IIe, so
    it's non-removeable - ain't gonna fix it myself). I'll have to try focus
    bracketing.

    Even better, when helping a friend move the other day, I couldn't
    help but notice she has a Dobsonian telescope, halfway-decent size, "never
    been used". Yes, I'll be calling her up to borrow it, then trying to figure
    out what's needed to get my camera onto it.

    For those who are really into messing with night shots, full moon is
    August 12 (see http://aa.usno.navy.mil/data/), and Perseids peak the 13th
    (http://www.meteorscatter.net/metshw.htm). Maybe catch a satellite or two
    in there (http://www.heavens-above.com/).

    And not long ago, the moon occluded Mars in some sections of the US,
    see http://antwrp.gsfc.nasa.gov/apod/ap030724.html for a fantastic shot.

    Good luck all, and thanks Roger!


    - Al.
     
    Al Denelsbeck, Aug 10, 2003
    #4
  5. If your optics are good, you should get similar results.
    With a 2x, you'll be shooting at f/22, similar to me
    (I corrected a small error in the f/stop numbers on my
    web page). There are catadioptric telescopes (designs like
    your mirror lens) that are diffraction limited.
    It's just hard to make that optical design faster than
    about f/10.

    Note: the rotation of the Earth could cause smear if
    your exposure times are less than 1/30 second. Mars is
    moving at a rate (due to earth's rotation) in the sky of
    about 14 arc-seconds per second, and mars is a maximum
    25.1 arc-seconds across this month.

    Roger
     
    Roger N. Clark, Aug 10, 2003
    #5
  6. Roger N. Clark

    Glenn Shaw Guest

    Roger N. Clark wrote in rec.photo.digital:
    Um, Roger, don't you mean that the image would smear if your exposure times
    are *longer* than 1/30 second (like 1/15 second)? IIRC, shorter exposure
    times would result in sharper, less blurry but dimmer images (unless one
    compensates for the dimness by using a larger aperture).
     
    Glenn Shaw, Aug 10, 2003
    #6
  7. oops. you are right.
    Roger
     
    Roger N. Clark, Aug 11, 2003
    #7
  8. Roger N. Clark

    John Eyles Guest

    Despite all the hype about this Mars business, I can't seem to
    find this simple piece of data: how close to Earth will Mars be,
    and what is its typical distance from Earth over the course
    of a year ?

    Thanks, John
     
    John Eyles, Aug 11, 2003
    #8
  9. Roger N. Clark

    Bob O`Bob Guest

    STFW, man.

    http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

    I went to google, entered "mars earth distance" and that came up first.
    And the next link after that one was even BETTER.
     
    Bob O`Bob, Aug 11, 2003
    #9
  10. Roger N. Clark

    SBM Guest

    I read 34.65 million miles on the 27th.... from sci space newsgroup.
     
    SBM, Aug 12, 2003
    #10
  11. Nice image. What was the effective focal length?
    In netscape, there was an error and all I got was:

    The parameter is incorrect.

    but mozilla showed it fine
    Roger
     
    Roger N. Clark, Aug 12, 2003
    #11
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