How to get great night sky images using a basic star tracker with Shelly Leigh, professional astrophotographer from Michigan who has partnered with the band.it team!
By the time you buy a tracker, you are seeking more than the average 30 second night exposure will get you!
The setup can be quite confusing, and even discouraging to some when first looking at trackers and the different options some have.
I start by simply leveling a tripod like anyone else. After that I assemble the two pieces that make up the body of the tracker. The alt/az base, which is basically a wedge I use to set my latitude and correctly place Polaris within the reticule, rotates in the right to left direction with two thumb screws at the base. Recently, I discovered an app called Clinometer that makes setting the correct latitude on the adjustment wedge a breeze. To the right is a photo of the clinometer app.
A NEW EXPERIENCE
Next I roughly align the polar sight with Polaris. If you can’t find Polaris you’re no different from me most nights I’m on site at a location. There are usually thick trees not allowing me to see the pole star to align to it. In this case you just use an app. I use star chart. In the above instance my tracker was poorly aligned due to trees obstructing my view. That’s something people might find as a discouraging selling point against buying a tracker… however in my experience a rough alignment is just fine for tracking under 5 minutes with 14mm and 24mm lenses. To the left is an image of what the reticule looks like when looking through the pole scope.
After the rough alignment is done, I use the included polar scope and an iOptron app to place Polaris within the reticle of the polar scope at its dedicated position. I do this with the two alt/az screws on the base. When set to the proper latitude and aimed correctly, Polaris should be in the polar scope viewing circle. When the tracker is pointing towards Polaris and the correct latitude is set, you should only need to do a fine adjustment. Every object beside the dial in a polar scope is a mirror image, which just takes some getting used to when moving your alignment.
The Finished Setup
Next, I attach a regular tripod ball head to the skytracker. There is a rotating circular mounting plate it attaches to directly. After that I mount my camera to the ball head. I use the ball head from iOptron, the maker of my tracker. Pictured to the right are photos of the tracker with the ball head and with the camera attached.
The rest of my process is just like shooting those single night sky exposures, only a lot longer! A strong tripod is key. I use one that is rated for up to 45 lbs. I experienced plenty of wind and flex related issues with the cheap few tripods I had tried prior. Just use a good one and you’ll save yourself a lot of headache!
A Simple Innovation
I use F&V filtered LED panels for my foreground light a large portion of the time. One is almost always sufficient. I use the warm filter on these lights and most of the time cover them with a white T-shirt to dim them down even further. Another important accessory I use in my setup are camera zoom creep bands by camera bandit. I use these bands for an off-label type of application.
I almost exclusively use prime lenses, and although prime lenses can’t suffer from zoom creep-they do suffer from focus shift. The issue of focus shift with a tracker is further exacerbated by a rotating camera and lens as the torque can twist the lens in such a way that gravity can pull enough to make your prime lens lose its perfect focus. Autofocus is not generally something that I suggest using at night as it will never truly give you what you’re after. In my professional opinion, focus slip is a lot more detrimental than zoom creep.
To the left is a photo of how I orient the bands. It serves 2 functions for me. They lock the barrel in place not allowing focus shift to happen, and they also serve to protect my aperture setting from accidentally being changed throughout the night.
Troubleshooting Your Images - Focus Slip
The photo here is exactly what happens when I’m out for a night of imaging and not using the band.it. This photo is a jpg unedited version of my raw file with focus slip. I let another photographer have two of my band.its the night prior, so I did not have them on my 24mm lens for the picture to the right. In the past, I’ve tried rubber band bracelets, asparagus bands, and tape all trying to achieve what the band.it achieves easily. With no band.it on my lens, as my tracker moved my camera and lens to a different position gravity took its toll on my images.
With night sky images, focus is so crucial that the smallest movement in the lens barrel can be detrimental. You don’t need to have a tracker for this to happen; it’s just more pronounced with one. As my focus shifted, you can see Jupiter - the brightest, biggest object in my sky shot began to take on a UFO like appearance. Had I not caught the problem then, every star would have changed shape. If I had band.its on my lens, I would not have wasted 25 minutes this night. And, 25 minutes may not seem like much, but when you only have one week a month, 3 hours of total darkness per night, for 4-5 months to shoot ... 25 minutes can make or break a nightscape image.
Grip The Moment
Photos Taken by michiganmilkywayphoto © 2019