Star Tracker

Enjoying Astrophotography in 2020

Photography by heart is my way of describing the joy of photography. It encompasses not only the camera experience but the planning and the post processing steps. Astrophotography does not usually fall into the beginning photography classes because it involves some advanced steps within each stage of the workflow: planning, photographing, and processing.

In this article I’m going to describe my current workflow steps in very general terms to give you an idea of what I use and do in order to make astrophotography something fun and relatively simple to teach when coaching photographers just getting started with it. In the future I hope to add some instructional and resource materials that will go a little deeper into the workflow so you can see if anything I do might be useful for you in your own astrophotography workflow.

PLANNING PHASE

Try and imagine, if you will, that you have access to a host of sight seeing tours accessible by bus. The bus for each tour leaves on time and ends on time. However, each day the schedule is slightly different, and each season it’s slightly different and some tours only run in certain seasons in your area. And they are all weather conditional, plus there are frequently one of a kind events available at certain places and specific times from year to year. It’s nearly impossible to keep up with all the day to day variations so wouldn’t it be great if there was an app for your smartphone to help with scheduling and planning your visits to see the sights?

Apps are critical for keeping the planning phase manageable and allowing the astrophotographer to quickly evaluate upcoming astro events and decide whether or not to make the attempt to witness and/or photograph them. My goto app is Photo Pills. It’s by far the best commercial purchase I’ve made for an app on the smartphone. It is an app designed to plan your events you wish to photograph, including sun and moon calendars, exposure times for each model of camera and lens you might use, depth of field and angles of view calculators, table for focus and hyper focus, and various additional calculators to speed your setup plus virtual reality views to visualize the night sky at any point from any angle on any given date at any given location you might be interested in.

Another app I personally depend upon for long session deep space or lunar astrophotography is Xasteria which is a detailed weather reporter for atmospheric conditions including temperature, transparency, humidity, clouds, wind, and overall seeing ability taking the atmospheric conditions into account. It’s helpful to know what we might be up against if we need to see faint objects in the night sky that may be partly obscured or diminished by humidity, haze, or moonlight in the sky. There is also an excellent astronomy weather site you can use from any browser that’s excellent for planning: Clear Sky Chart.

SETUP AND SETTINGS

I recently purchased a very small and portable star tracking mount from Move-Shoot-Move to use in lieu of my larger and heavier mount, an iOptron Star Tracker, which uses a polar scope to get very precise alignment of the device on Polaris and can handle up to 11 pounds of camera and lens. The MSM Rotator, from Move-Shoot-Move is not designed for that kind of heavy transport and I selected the entry level package without the polar scope but having a laser pointer instead for very quickly aligning the device for wide field astrophotography or some modest deep space photos of fairly large, close, and bright objects. It’s ideally suited for a smaller mirrorless camera such as my Olympus OM-D E-M1 Mark II and lenses up to around 135mm f/2.8 or so. Keeping it around 3 lbs or less is my target for this kit.

You might reasonably ask why I’m including a star tracking mount in a beginning astrophotography writeup when it’s been possible to take photos without one using a tripod, camera and lens and remote shutter or intervalometer for decades? Why add this level of complexity to a relatively simple kit for photographing something like the Milky Way core?

And this is my answer. Quite a number of people who come to me wanting to try their luck at photographing the night sky are coming with a basic entry level to mid-level DSLR or mirrorless camera with a decent kit lens and with modest or very little post processing skills using popular off the shelf software to spruce up their sunrises or sunsets or landscape and travel photos. When they hear someone talk about f/2.8 or faster aperture lenses shooting at ISO3200-6400 for 30 seconds, then all the steps needed such as taking a stack of 20 to merge and reduce noise or specialized software needed to process such high ISO images plus the workflow to manage light pollution in order to bring out the Milky Way in a visibly aesthetic way, they realize their basic camera and lens may not be very ideal for this kind of work compared to what experienced astrophotographers are using for that kind of workflow. The cost in new camera and faster lens will likely be in the thousands of dollars. Whereas, a star tracking mount like the MSM Rotator for $200-$250, will allow modest zoom lenses at f/4-f/5 to track for 60 seconds to a few minutes with pin point stars, low ISOs, better dynamic range of colors in the stars, and easier to process raw files from any DSLR made in the past 10-15 years. Even a young student interested in starting photography for this sole purpose could get into it for a modest outlay knowing this information.

Here is my basic setup designed to get nice clean and detailed photos of the Milky Way or deep space objects such as Orion’s Nebula. I have two carbon fiber tripods that are very stable yet lightweight and easy to carry with me into the back country. My preferred tripod for using the MSM Rotator is a Manfrotto MT190CXPro3 with MHXPro-3W 3-way pan/tilt head and a PB70 panning mount with Arca Swiss clamp. I like this arrangement because it’s important to get a very level base and the three way lets me orient the head so that I can tilt the base toward the North Star (Polaris) without causing the mount to tilt sideways at all, which is difficult with just a ball head mount.

Once the tripod is level and I have the tilt handle pointed toward Polaris, I mount the MSM Rotator to which I’ve attached a 70mm Arca Swiss plate. I have a small ball head attached to the Rotator’s drive mount and the bracket for the laser pen is attached and the pen inserted and secured. I’ve locked down the 3-way pan/tilt head so it can’t pan and only tilts up toward Polaris. The PB-70 panning head allows me to make very fine adjustments to get the laser beam fine tuned onto Polaris with the vertical tilt axis on the 3-way used to get the beam in the right place vertically. Note, an actual geared 3-way head would be a better option here, but they are a little more expensive. Someday…

Once the laser pen is turned on and the 3-way head is manipulated to place the beam accurately onto Polaris, I turn off the pen and add my camera and lens to the ball head mount I had previously attached onto the Rotator’s tracking mount plate. Now I can situate the camera and point it in the direction of what I’m going to be shooting and then tighten down the ballhead. Once again, I turn the laser pen back on to ensure it’s still aligned properly and the weight of the camera and lens and manipulating it previously, has not slightly misaligned the Rotator. After making final adjustments, I turn on the MSM Rotator and begin to get the camera ready to take exposures.

My usual practice is to set up my camera or cameras before I even leave for the astro shoot, getting them into the basic configuration I’ll use for the kinds of images I want to take. I will explore these settings more specifically in a separate post, as they are pretty specific to the abilities and features of my Olympus cameras and will be most helpful to Olympus shooters. I can always tweak settings once I start doing some test images but at least they are set up close to what I should use. If you are familiar with the 500 rule which we use to determine how long the shutter can be open before noticeable star trailing begins, I find that with a fairly accurate alignment of the laser pointer, I can get a 10 times longer exposure before the stars begin to elongate into trails. According to the 500 rule, if we want to photograph with a 24mm lens (convert to 35mm focal lengths if using a crop sensor), 500 divided by 24 is 21 seconds. Without the ability to track with the stars, a camera with a 24mm lens on a fixed mount could keep fairly sharp stars without noticeable trailing caused by the earth’s rotation if the shutter speed is no more than about 20 seconds. With a star tracker like the MSM Rotator, this could be very likely extended to 200 seconds or possibly longer. Note that a 24 mm lens on a full frame 35mm equivalent sensor is analogous to using an 18 mm lens on an APS-C sensor camera or a 12 mm lens on a micro four-thirds sensor camera.

Since 20 seconds is not very much time to collect adequate light from a night sky at the camera’s base ISO, we usually have to push up the ISO to quite high numbers, depending on the lens aperture. This is one reason most recommended astrophotography lenses offer a fairly wide aperture of f/2.8 or faster. Even at f/2.8, it’s likely it would take an ISO of 3200 to 6400 to collect enough light to expose the Milky Way adequately in a reasonably dark sky area within 20 seconds. But mount the camera on an MSM Rotator aligned and running, that 20 seconds can turn into 200 seconds if needed, and sometimes longer.

How do I determine these settings? Well, if the camera’s ISO can reach 6400 or higher, it’s best to just do a test by establishing accurate focus (see earlier post on how to autofocus with mirrorless cameras on the stars) and setting the ISO to 6400, shutter to the maximum time we can use and still expect round stars, aperture at its widest or optimum setting, and do a test exposure. There are various ways to evaluate this in the camera but a histogram reading can surely help. If it is looking okay at ISO 6400 and 20 seconds, it would look a little better at ISO3200 and 40 seconds and even better at ISO1600 and 80 seconds and what about ISO 800 and 160 seconds? I have some f/1.2 lenses and have been able to shoot Milky Way scenes at the base ISO 200 for my particular brand of cameras. With the live view of most mirrorless cameras, using my Olympus cameras’ Live Time, I can simply open the shutter and watch the image develop on the LCD and once it’s looking great, close the shutter.

Using the. MSM Rotator, I can now shoot the Milky Way with my camera’s best ISO performance range, achieving the best dynamic range for colors in the camera. This also speeds up the next phase: the editing phase. Having lower ISO, cleaner, more colorful raw files, allows me the opportunity to process the images with better results in less time.

POST PROCESSING

MyPanel from f64Academy

I routinely shoot in RAW and process the RAW files in Photoshop CC. I’ve seen beautiful prints processed in about every program you’ve ever heard of and some you’ve likely never heard of. There is a very accomplished dedicated astrophotographer I have been told who processes his images in Microsoft Word. I’m not kidding. I’ve no idea how he does that. I use a set of actions in Photoshop to bring forth the contrast, raise the brightness of the stars and push back the deep space to give the night sky it’s brilliance. If you are a dedicated Photoshop user like me, I highly recommend looking into MyPanel for Photoshop CC.

For landscapes with the Milky Way, using the MSM Rotator, it’s going to require one long exposure with the Rotator turned off to photograph the foreground and then with the Rotator turned on, photograph the sky and replace the foreground photo’s sky with the tracked starry sky.

The main reason to use a star tracking mount to get longer exposures of stars is that is increases the quality of the resulting image by 1) keeping ISO lower to ensure maximum dynamic range and 2) allowing better color fidelity and details by mitigating some of the atmospheric disturbance present in our atmosphere. The better the image output from the camera, the better our starting point in post processing.

CONCLUSION

Although I’ve only had the rotator for a couple of weeks and rainy weather has prevented me from doing a lot of shooting with it, I’m impressed overall with the product quality and ease of use for most night photography that interests me. Not only is it easy to set up and handle, even with gloves in cold temperatures, it’s easy to recharge in the field and it seems reliable for getting up to 10x the exposure time I’d be limited to using on a fixed mount. I’ve tested it with the Orion Nebula so far and I was pleased with my initial results. Having two tracking mounts to use will allow me to compare them over time and I’ll revisit this topic from time to time and update my impressions. I welcome comments and questions.

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