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  1. #91
    Senior Member
    J-see's Avatar

    Re: Star Photography One on One

    I didn't know one of the Three Sisters was a double-star. I guess the Tam is at least sharp enough to distinguish that.

    Star Photography One on One-_dsc1856.jpg


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  2. #92
    Senior Member
    J-see's Avatar

    Re: Star Photography One on One

    Testing what high ISO does.

    Star Photography One on One-091.jpg

    That's the Three Sisters and that bright area to the bottom is the Orion Nebula I think. Or whatever it is called in English. The 200mm is a bit short and the 600's shutter too fast to get enough data.
    Last edited by J-see; 12-31-2014 at 11:47 PM.

  3. #93
    Senior Member
    J-see's Avatar

    Re: Star Photography One on One

    Just tried some shots to check how the lens does. Too long shutter for this length and too close to the buildings to get depth wide open. Too much moon too. But all in all the stars it grabs is not too shabby at that ISO.

    Star Photography One on One-003-2.jpg

  4. #94
    Senior Member
    Bourbon Neat's Avatar

    Re: Star Photography One on One

    Quote Originally Posted by J-see View Post
    Does anyone know how to calculate the exact shutter limit I can use with each lens/sensor?

    I read about the rule of 600 at the one place, the rule of 500 at another yet none of them seems to be very correct in my case. I used the 18mm for 20s and even while that's just 360 and within range of both rules, when I check 1:1, I see the stars stretch. The full shot is ok but the moment I want to crop it's a no-go.

    Strangely when shooting my 200mm at 2s shutter they're pretty ok even at 1:1.
    In respect to the 500 or 600 rule to plan your shutter speed. My curiosity went further as I wasn't satisfied with the results using those rules. I need to know how far the movement of the stars is on the sensor in time. Luckily, like most things, a little arithmetic can get ya there.

    This formula will give you more to help in determining your shutter speed. Notice that considering the crop of a sensor is not necessary.

    D=T x FD/13750 x is the sign for multiplication

    D is the distance of (or size of a pixel)

    T is time, what we want to know (How long does it take for the light of the star to move one pixel on the sensor).

    FD is focal distance

    13750 is what I call hard arithmetic, someone else figured out the movement of the sky as we see it during the rotation of our planet.

    To determine D: Take the sensor horizontal dimension and divide by the pixel count across the sensor. Example of the D5500 and D7200: 24.1mm / 6000 pixels = .00392

    0.00392=T x 24(24mm lens)/13750

    0.00392=T x 0.00174

    0.00392/0.00174= T

    T= 2.25 seconds the time the light on the sensor moves one pixel.

    Using the rule of 500, 500/24=20.83.....20.83/1.5 (crop sensor)=13.88 seconds of exposure. 13.88/2.25=6.16 pixels of travel across the sensor. A 10mm lens will bring that camera up to 5.37 seconds per pixel.

    Roughly, with the D5500 and 24mm lens, stars are between 5 and 30 pixels wide at a 13 second exposure. So, knowing that, you can decide how much trailing is acceptable to you.

    As you can imagine, high pixel sensors may or may not be the best for night sky. Fat pixels good and slim pixels not as good. With a D4 and a 24mm lens, you get 4.82 seconds of exposure to one pixel of movement (a 12.1mp FX sensor). With that said, we are using the pixel as a measuring unit when each sensor may have a different pixel size.

    The D810 and a 24mm lens, will get you 2.80 seconds of exposure to one pixel of movement (a 36.3mp FX sensor).

    Note that lens size has an impact too: 10mm very good, 50mm not so good.

    Disclaimer......This is just a few cents from a large bottle of pennies, don't take it too serious.
    Last edited by Bourbon Neat; 03-28-2015 at 03:48 PM.

  5. #95
    Senior Member
    wornish's Avatar

    Re: Star Photography One on One

    Looking North - front window bottom right.

    Star Photography One on One-great-bear.jpg

  6. #96
    Senior Member
    oldsalt's Avatar

    Re: Star Photography One on One

    Star Photography One on One
    Looking South towards the city (and it's lights)...
    Star Photography One on One-untitled-1-444.jpg
    Thanks/Like wornish Thanks/liked this post
     

  7. #97
    Senior Member

    Re: Star Photography One on One

    Star Photography One on One
    Star Photography One on One-fb_img_1520109049556.jpg
    AT 802 Fire Bomber D750 Rokinon 14 mm 30 sec f2.8 iso 3200
    Last edited by Scoupe; 03-23-2018 at 03:48 AM.
    Thanks/Like Dawg Pics, tex.4810 Thanks/liked this post
     





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