How to Capture Starlight

Introduction:

Many people who own DSLR’s are left in the dark when it comes to capturing starlight.  Their results vary from completely blurry, to light trails, to completely blank.  The object of this entry is to help you to capture some amazing shots of the night sky by using a few basic but key accessories.  I will give you these in list form.  All items that are absolutely essential will have an * at the beginning of the explanation.  I will also include instructions for proper post editing…

  • Use a tripod – * This is an absolute necessity because you can’t possibly hold the camera steady enough yourself, for the time duration it takes to capture enough light, and keep the star points concentric (round).
  • Exposure – The Earth is always moving, and the stars are moving as well.  So the I prefer 5 seconds, but can push it up to 8 seconds, and still get concentric star points.  This time frame is important because any longer and you’re going to get trails (movement), and any shorter, and you won’t capture as many star points.  The human eye creates a new picture every tenth of a second.  So leaving the shutter open for this amount of time will capture stars up to 3 more magnitudes than you can visually see!  This may not sound like much, but it is…
  • ISO – *  It’s advisable to set your ISO to 3200 to make the sensor as sensitive to light as possible.  If your camera only provides 1600 ISO max., adequate pictures can still be attained with 8 second exposures, though a reduction in size will be a must in the post processing stage…
  • F Stop – Again, you want the camera to pick up as much light as possible, so open your lens all the way to at least f 5.6.. If you can get it lower at f 4 or below, so much the better!
  • Lens – Contrary to popular belief, you may think the longer the lens in the telescopic range, the more starlight you’ll gather.  This is true, but your field of view is very limited.  So although you will see stars that are further away, there will be very few of them in your field of view!  Use as wide an angle lens as you have.  I used as 24mm to 105mm zoom lens set to 24mm to capture the most stars.
  • Focus – You’re not going to see a lot through your view finder.  To obtain clear focus, set your focus ring to infinity: that’s the sideways 8 shown on your lens.  Do this along with all of your other camera settings before you go out because it’s dark out there, and a flashlight will only blind you more! 
  • Cable Release – * This is an optional accessory that most people have to buy separately for their camera.  When you click the button on your camera to take a picture, this transfers any shake in your hand, to the image, producing ‘ghosts’ beside each star point.  A cable release is relatively inexpensive, and essential for every day use as well!
  • Mirror Lock – * Unfortunately, it’s essential that your camera has this feature!  Just before the exposure is taken, the mirror flips up, causing camera shake that is avoided of you have a ‘mirror lock’ feature.  This way, you set your camera to ‘bulb’, press the cable release once to lock up the mirror, wait 2 seconds, and then hold the button down for the duration of your exposure, and then let go: else-wise, your camera will try to focus on nothing, which is why you get those blank shots!  Alternatively, set your camera to ‘Manual’, and uncouple your exposure from your focus points on the camera, if your camera provides for that…  The newest cameras are now mirror-less to avoid the problem completely.
  • Black Mat – Not many cameras have this feature.  Mine does.  At 3200 ISO, artifacts, or ‘digital noise’ becomes a very real problem.  With this feature, a camera can take a black mat background shot first, and then superimpose the foreground on that, virtually eliminating all noise.  Though you may loose a few star points, I’ll show you a way to achieve something similar in the post processing phase.
  • Seeing – ‘Seeing is a term that describes the number of stars visible on any given night.  Sometimes you will see lots of stars, and on other nights, not so many.  I purposely picked a night when the seeing was poor, so I could show you only the tip of the ice-burg of what your camera is capable of!  The real name for the sensor that determines the number of mega-pix you can capture is called a CCD, or ‘charged couped device’.  Astronomers immediately switched from conventional emulsion film to CCD’s as soon as they came out.  This was long before commercial cameras were using them.  So you have the perfect astronomical instrument right there in the back of your camera.  CCD’s are far more sensitive to light than conventional film.  The catch is, if you own a cheap camera, you probably have a crumby CCD chip as well.  I paid $8000 for one of the best cameras there is, so I have everything listed above, including an excellent, full 35mm frame CMOS CCD chip…

Post Processing:

It’s best to shoot these in RAW format.  I then save it as a dng. extension which stands for: ‘digital negative.’  This retains the ability to still work with the image in your RAW utility without loosing data, except now, it’s an actual image that can be processed.  Next, I save a copy to png. format because it retains 16 mega-pix of data, and is presentable in WordPress format.  Jpgs. are only 8 bits which equates to presenting someone with an image capable of defining 65,000 colors, as apposed to 256 colors in jpg format.

24 Bits produces 16 million colors, and 32 bits introduces 22 million colors, which is the full extent of what the eye can discern.  So if you’re shooting for 64 bit pix., it’s over-kill…  Anyway, 16 bits makes for far more latitude in the post processing stage without the image deteriorating or developing artifacts…

At the bottom of your RAW utility window in Photoshop, you’ll see a statement highlighted in light blue, assigning 8 bits to your photo.  You don’t want this.  You want 16 bits until you intend to save a jpg. copy. By right clicking this ‘statement’, it will give you the option to convert images using 16 bit format.  This is where you need to be.  Select it, and leave it that way.

Temperature – Star colors used to be very hard to achieve without a high powered telescope.  Not anymore!  There is a trick to it though.  You’ll find, if you examine your ‘Histogram’, that all of the pixels in star shots are all slammed up against the far left hand side.  This is naturally where all your shadow content would be, and the favorite place for blue light. There’s a ‘temperature gage on the first tab in the RAW utility.  You will see it’s at the blue side of things.  Reset it to 5200 K. so that you will get the correct color of stars that aren’t apparent just yet.

Color – In the same tab, you’ll find a saturation control and a vibrancy control.  I set the vibrancy control to 45% and the saturation level to 40% and I still had to add 40% more saturation in Photoshop for star colors to become apparent!  Still, most of them are subtle differences because stars go from very faintly colored to extremely colorful on a scale from 1 to 9. The designations are: OBAFGKM.  

The sentence to remember the order is: ‘Oh be a fine girl, kiss me!’  ‘O’ stars are white. ‘B’ stars are progressively more blue: 1 being the faintest, and 9 being the most saturated.  ‘A’ stars are cyan. ‘F’ stars are Gold.  ‘G’ stars are yellow.  Our star is a G2 star. ‘K’ stars are orange and ‘M’ stars are red dwarfs.  Over half of all stars are red dwarfs.  Over half of all stars are double stars orbiting about each other  Castor in Gemini, is a six star system!

In one shot, on the bottom left hand side, near the tree, you’ll notice the big dipper, and that a couple of the stars on the handle show their double star companions.  The Big Dipper BTW is within the region of space in which we reside.  Because they’re so close, the ‘proper motion’ of these stars will radically change their position by 2050, so it won’t resemble its present shape at all…

You’ll notice subtle shades of purple and green, but you’ll have to look close!  Other stars will jump right out at you as beings deep blue or red or yellow…  Experiment with a 50 mm macro lenses you can stop down to f 1.2 in some cases.

Contrast – This is where I was telling you earlier, where you can take out the noise.  adjust your contrast in your Raw utility, to +40.  That should remove the noise, and leave the actual stars.  Do not adjust any other controls.

Get out there now and try your hand at this wonderful field of night time photography!  I took a picture here of a bright star, and to my delight, I captured an ‘Open Cluster’ of older, yellow stars beside it.  So you never know what surprises are in store!  Like I said before…  There were only a few of stars visible the night I took these pictures.  Imagine what you would capture on nights when you can see The entire Milky Way sprawled out above you!

In Conclusion:

Since the star points won’t be visible in the slide show, it’s important that you choose ‘view full size’ on the bottom of your slide show screen, and then click the photo with your little magnifying glass icon to view it full size.  Then to save it, right click and chose: ‘Save Image as’…

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2 thoughts on “How to Capture Starlight

    • Thank you! If you can see that, I’m sure others can too… I was just going to help this nutbar I know in person, to post process a few of her pics. for her and she went snakey on me! I have washed my hands of her. Too cruel and vindictive to be repaired…

      I have an $8000 camera: one of the best on the planet! What on Earth would I want with her scruffy, cheap camera, tiny pictures??? My brother was a pediphile 30 years ago! He is dead now, and square with the house, so I have forgiven him…

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