Above the “ISO” button is the “QUAL” button. Holding it down while scrolling with the rear wheel allows you to choose the quality of image setting. Choose “Raw” if you process your images. To see at a glance what all your settings are, press the “Info” button below the back wheel.
Note that the left-hand buttons have dual functions depending on the mode you’re using. For example, in live view mode, which you’ll use for focusing, “QUAL” will switch automatically to the “Zoom in” button. It’s marked with a “+.” The “ISO” button becomes the “Zoom out” button. It’s marked with a “–.”
When you turn on live view, you’ll see a square. Put your focus star into the middle of the square by using the directional dial under the “Info” button. Once centered, it will stay there as you zoom in to inspect the focus. Exit live view by pushing the “Info” button once more.
I’m often asked, “How do I know when I have the correct exposure?” My answer is by not looking at the image on the screen, but instead inspecting the histogram. The left-hand boundary is black, the right is white. If any of your graph touches those boundaries it means that parts of your image have no detail.
To view the histogram, first program the camera for this function. Go to “Menu” > “Playback menu” > “Playback display options” > “Histogram.” Make sure there is a checkmark in the square. When you exit the menu, the camera knows you want to see histograms.
After you take a picture, hit the button that has a triangle within a rectangle (on the back at top left) to bring up the image. Press the multi-directional button (the one with “OK” in the middle of it) up or down to bring up the histogram. Pressing that button left or right will toggle between your images.
As far as the lenses I use, I prefer the Sigma Art 14-24mm for my general imaging lens and the Samyang 12mm f/2.8 fisheye for 180° images. For higher power, any of the Sigma Art lenses work well with this camera. Remember that this camera has a full-frame chip when choosing a lens.
Make it better
To get even more out of your camera, have it converted so it can capture Hydrogen-alpha (Hα) light. I sent mine to Spencer’s Camera because they specialize in this kind of work.
I had them remove the camera’s infrared/ultraviolet blocking filter and install one that still blocks IR/UV, but also opens up a window for Hα wavelengths. One option I didn’t choose was the removal of the anti-alias filter. I also left the dust removing device intact.
With this modification, the camera will produce images with a red bias, but you can remove that in processing and still use it as a terrestrial camera. It costs about $500 and takes one to three weeks.
Top of the line
The Nikon D750 is a quantum leap in DSLRs for astroimaging. Low noise combined with ISO-invariant sensitivity is a real winner in the world of CMOS and astrophotography. With a converted camera, you’ll be even more amazed at the quality of your images.