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Photos Astrophotography - Lenses and Mounts

Discussion in 'General' started by notmeagain, 14 Sep 2015.

  1. notmeagain

    notmeagain Member

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    Hi All,

    Bit of a long reach/split question here...

    Had a DSLR for 8 years, and recently upgraded to a 70D, and rediscovered my love for taking pictures of pretty things.

    I've got a couple good lenses already:

    50mm F1.8 Prime (Captured this timelapse in London with it! https://www.youtube.com/watch?v=oAXUGaV9yto)
    18-135mm F3.5-5.6 STM
    55-250 F3.5-5.6 STM
    500mm Mirror (great for moon shots)

    I'm looking for a good telephoto lens with a fast aperture that's not going to break the bank for some astro photos, any recommendations?

    To go alongside the lenses, it's apparent that i'll need me a decent (cheap) tracking mount.
    I'd researched some of the options and this seems to fit my budget/mindset:
    http://www.garyseronik.com/?q=node/52

    However, I lack the resource to build one - any bit-techers out there want to be commissioned into constructing this piece of kit?
     
  2. chrisb2e9

    chrisb2e9 Dont do that...

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    You would be better off in the photo section I think, but i'm happy to share what little I know.

    What do you want pictures of? The moon, sure you can get a cheaper telephoto that will let you do that. you don't really need tracking equipment for the moon though, it's plenty bright and you wont need the longer exposure times. Other planets? forget it, you need a telescope. A long enough camera lens will set you back a lot of money. I have a 70-200 2.8 and it's not even worth it for the moon. And it still cost over 2,000.
    Here is an example of that, the moon back when smoke from forest fires was making it red
    [​IMG]
    So that's 200mm and likely 8 to 6 seconds. an ok'ish pic, but 400 or even 600 would have been much much better.

    But for pics of stars, you don't really want a telephoto for that. Makes for a boring pic if there are just a handful of stars.
    A really wide shot, with a lit foreground is generally what people want to see in a night shot.
    Here is one of mine as an example. Although it's not the best... It's my parents back yard and it could be composed a lot better to have more of the backyard in there. But it was late and I was tired.
    [​IMG]
    Anyway, that's a 14mm lens which is quite cheap (its also full manual and has a learning curve to get the exposure right(but you get what you pay for))
    http://www.bhphotovideo.com/c/product/769532-REG/Rokinon_FE14M_C_14mm_Ultra_Wide_Angle_f_2_8.html
    The canon equivalent 14mm, is over 2,000. If you check comparisons, I think that this lens beats the canon for image quality. But not user friendliness.
    The great thing, is that it's 2.8 and that was a 30 second shot. No moving gears or anything. And to be honest, you need no moving parts unless you are tracking stars. Which at 30 seconds and 14mm you don't need to do. But it's really the limit time wise. There is a formula which will tell you how long the exposure can be before you get star trails. But I can't remember it now and have to get going to work.

    Anyway, I have looked into doing astrophotography before. And my take away, was that if you want to track stars. Buy a proper motorized star tracking mount(ie, expensive and well made). It will set you back cash. but it's worth it over a home build.
    If you want to take pics of far away objects, buy a telescope and dslr mount.
    Scenery shots, wide and fast lens are the way to go.

    Hope that helps!
     
    Last edited: 14 Sep 2015
  3. notmeagain

    notmeagain Member

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    Great response, much appreciated.

    I've come to the same conclusion about focal lengths, the best for me would be a 5-800mm, setting me back a couple of grand.

    I'm not looking for hubble images of the pillars of creation, but I want to image things like Andromeda, constellations, and certain other gaseous nebulae in H/S/O long (1m+ )exposures, stacked (ala this.

    I can't justify the expense of a telescope, equatorial tracker, controller, motors when I've seen verifiable results using the Haig/Barn-door mounts.

    The equation is similar to this: 500/Focal-Length(*1.6 if cropped sensor) = Longest exposure before trailing.

    For example:
    18-135mm lens, @18mm on Cropped Sensor = 28.8mm focal length
    500/28.8 = ~17.4 == 17s exposure.

    I've had good results in London with my 50mm @ f1.8, but the issue is I want a tighter picture, hence the 55-250, 400mm equivelant - max 1.25s exposure before trailing, and this lenses slow aperture means I'm not capturing the light I need in a 1s exposure.

    The Haig mount *should* fulfil my immediate broke-ass desire to take some pretty star pictures, without the neccessity of buying a new f2.8 lens at great cost.

    Mods - could you kindly phase shift this thread into the Photography section?
     
    Last edited: 14 Sep 2015
  4. samkiller42

    samkiller42 For i AM Cheesecake!!

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    What's your budget on a lens? Few options, 2nd Hand from either ebay or a camera shop (Park Cameras or London Camera exchange are in London) Orrrrr, Grey Import (Can be risky) But, Canon 70-200 f2.8 L IS 2 is under £1400, or the alternative is a Sigma 70-200 f2.8 APO which is £640, Spending a bit more, Is the Canon 100-400 f4.5-5.6 L IS USM for under £1000.

    Ultimately though, still need to know what sort of budget your considering before pelting out recommendations.

    Sam
     
  5. Pliqu3011

    Pliqu3011 all flowers in time bend towards the sun

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    I don't have any experience with astrophotography, but if you're shooting at infinity anyway, do you really need an autofocus lens? Same for stabilization, since you're going to be shooting on a tripod you'd need to turn it off anyway.

    There are a lot of good older tele primes you can get for much less than a more modern Canon lens if you look around a bit. Of course very fast teles are always very expensive (because of the sheer amount of glass), but for example the excellent Tamron SP 400mm F/4.0 LD-IF is around $850 according to this page.
    A Carl Zeiss Sonnar 200mm f/2.8 is about £200.
    Even cheaper, you can easily find a Tair-3 300mm f/4.5 for under 100 pounds.
    You can find tons of other really nice older lenses if you do a bit of research. Will they be as good as a modern lens? Probably not in every case (especially coatings have improved a lot, so flare is sometimes more of a problem), but they're often great value for money.
    Additionally these lenses don't lose value any more (if anything, they've gotten more expensive over the last years), so if you don't like one you can always sell it for pretty much what you bought it for (or more).

    But as I said, I've never done astrophotography, so feel free to point out if there are in fact significant advantages to a modern autofocus (zoom)lens.
     
  6. notmeagain

    notmeagain Member

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    You know, I didn't even consider that.
    My primary concern was a fast aperture to collect as much light as possible in the shortest time frame, reducing my exposure time and therefore limiting blur/star trails (https://silverstrandphoto.files.wordpress.com/2010/06/aperture_shutter_speed_overall_exp.gif).

    With the stuff below, I might be able to get ahold of an f6/8 800mm mirror lens for a couple hundred quid and get some good pictures.

    I've been looking at mounts such as the Sky-Watcher "Star Adventurer", Vixen Polaire, and the iOptron variant.

    These should allow me to use an f4/5.6 lens (250mm@380mm equivelant) for n-Minute exposures with minimal issue, which means my expense has gone from thousands to hundreds.

    If I go for the Star Adventurer, I get a tracking mount, that can be converted to an EQ Mount for a ~5kg reflector telescope.

    I hate choice.
     
    Last edited: 16 Sep 2015

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