By: David Keller
For those of you that want to try your luck at photographing comet NeoWise, and are not experienced astro-imagers, here are some suggestions:
Tripod: You absolutely require a tripod or an equivalent way to hold the camera still, and that’s because to get a decent photograph, you will need an exposure in the range of 2-6 seconds. If you’re using a smartphone, many inexpensive camera holders are available on Amazon. If you’ve a DSLR (or a mirrorless equivalent), Southeastern Camera & Video is probably your best bet for a “get it today” local source. Otherwise, you may be able to get one off of Amazon within a couple of days from ordering it.
Camera: While it is possible to take an image of the comet with a cellphone camera so long as your particular model will allow you to take a relatively long exposure, it will be considerably easier to photograph this object with a dedicated camera – a DSLR, mirrorless “prosumer” or “point and shoot” model. The only real requirement here is that you have a way to manually focus the camera/lens, and a manual setting that allows you to manually adjust the exposure time and ISO equivalent speed. You also need some way of remotely triggering the camera so that the act of triggering the shot doesn’t induce vibration that ruins the shot. Many point and shoot and DSLR cameras come with a dedicated remote control for this purpose, but almost all cameras also come with a delayed-trigger timer, and that works very well with a 2-5 second shutter delay to prevent motion blur in the imaging setup.
Focusing: This is probably the aspect that is the most troublesome with even a pro-level DSLR. Specifically, all but the most expensive professional cameras will not have enough light to auto-focus. Instead, if your camera has a “live view” option and a way to set the camera lens to manual focusing, you can point the camera at a bright object, such as Jupiter, one of the bright “constellation” stars, or even the Moon when it comes back next week, use the live-view to zoom into the bright celestial object, and manually focus the camera. For a star, you simply want to get the minimum size of the star in the viewfinder at max zoom. Those that want to do this on a regular basis with a DSLR or mirrorless camera might want to consider a Bahtinov mask, which is a focus aid that fits over the front of the lens, and produces a 6 pointed star-shaped diffraction pattern on the imaging chip when the camera is pointed at a bright star. When the focus is adjusted, the center spike moves to the left and right of the two other diffraction spikes. When the lens is optimally focused, the vertical spike exactly bisects the two other spikes.
Exposure: To start, and based on my experience Thursday evening photographing the comet at Jordan Lake Dam, I would suggest an ISO of 1600 and a 4 second exposure at F4. Depending on the time of the evening, the focal length of your lens (or where you have your zoom lens set to), the f-stop of your lens, and the sensitivity of your camera’s imaging chip, you may need to adjust the exposure time and/or ISO from there, but 4s at ISO 1600 will give you a good starting point. Note that in my case this was at a focal length of about 80mm. The exposures will need to get longer and/or the ISO speed will need to be increased the longer the focal length of your lens. One tip – bring something that will allow you to examine your shots as they’re taken. That could be a laptop, a tablet, or even a cell phone if you have a modern camera that comes with a cell phone app. You want to do this so that you can closely examine the focus and the amount of star-trailing you have while you’re taking shots. It can be quite disheartening to go to the trouble of finding a location that has a good horizon, packing up your gear, doing the photo shoot, and getting home to realize that all your shots were out of focus, or they were taken at a sufficiently long focal length and long enough exposure that all of the stars (and the comet) have been blurred by sidereal motion.
Location: I took my shots from the Jordan Lake Dam, but any location that has a clear view of the NorthWestern horizon down to about 5 degrees from the horizon will do. The comet is currently about 20 degrees above the horizon at about 9:30, and will of course get closer to the horizon as it gets darker from sidereal motion, so you will want to plan for this when scoping your location.