Comets pass through the inner solar system almost every year. Rarely, about once in every one or two decades, does a comet become so bright that it can easily be seen by the unaided eye. Comet NEOWISE has become one of these bright comets after passing 27 million miles from the sun on July 3rd. It is now making its way back to the outer solar system and would have passed closest to Earth on July 22-23 at a distance of 64 million miles.
Comets consist mainly of icy compounds, rocks and dust; materials left over from the formation of the solar system approximately 4.6 billion years ago. Comet NEOWISE is roughly 5 miles across. The sun’s heat melts the ices and ionizes some of the compounds on the comet and the solar wind carries the debris off into interplanetary space forming tails that stretch out in the opposite direction of the sun from the comet. There are usually two tails, the dust tail and the ion tail. Comet NEOWISE’s tails currently stretch approximately 12 arc degrees across the sky which is about 24 times the width of the full moon.
Amateur astronomers and astrophotographers across the northern hemisphere have been imaging comet NEOWISE every chance they get and producing breathtaking images. It is possibly the most photographed comet ever which is due largely to the availability of photography equipment, and that is including smartphones. The comet has recently become visible in Guyana. It can be seen very low over the northwestern horizon as soon as the sky gets dark enough in the evening for it to be visible. As the comet makes its way further away from the sun, it will rise higher over the horizon.
The star chart below shows the comet’s position in the sky up to 8th August, 2020. If you can find the Big Dipper, then you can find the comet. The best place to see it is probably from the seawalls because it will be visible over the ocean and there are no lights out there to obstruct the view.
The comet can be seen by the unaided eye but even better through binoculars and small telescopes at low magnifications. Long exposure photography can capture the entire tail of the comet if the sky is dark enough.
I have imaged the comet on two occasions so far from light polluted skies in New York. First I used my canon SL1 DSLR and lens and another time I used my DSLR camera mounted to a small telescope, the pictures are shown below. On both occasions, I had the imaging rig on an equatorial telescope mount to track the comet in order to avoid star trails during the long exposures. I must say that imaging with the lens was better in this case because the telescope’s field of view is too small to capture the entire tail of the comet. A 135mm focal length lens works very well and short exposures of a few seconds can be stacked together to create a brighter image.
A tracking mount to image the comet is not necessary, though a stationary tripod can work for wide field imaging and using shorter exposures. If you do not have a DSLR camera, check your smartphone to see if the camera has a “pro” mode that allows exposures of a few seconds. (Just be sure to get the ISO higher for shorter exposure, usually 800-1600 is fine).
The comet has been imaged this way as well. I think a great idea for an image would be to photograph the comet low over the horizon with a ship out in the ocean. That would be an awesome shot! A comet’s brightness can be very unpredictable and as it gets further away from the sun, its brightness will diminish until it is no longer visible. Therefore, it is best to catch a glimpse of it as soon as possible.
Comet NEOWISE has traveled over 50 billion miles to get to the inner solar system, that means it came from a region more than sixteen times further away than Pluto and it will not return for another 6,800 years! Its journey is one of truly epic proportions and we rarely ever get the opportunity to witness such an event. I hope you get the chance to see it for yourself and, if you can, to take pictures as well. Be sure to share with your astronomy pals at the Amateur Astronomers Association of Guyana.
Good luck and clear skies!
Mahendra Mahadeo is a Guyanese Astrophotographer and Optic Engineer at U.S. telescope and lens manufacturing company, TeleVue.