Shooting Comets Like Neowise

In Master Photography Roundtable by Jeff Harmon4 Comments

What is Neowise?

Neowise is a comet. One that scientists say only comes around once every 6,800 years! It has been something that the photography community has been writing about for a couple of weeks now. Photographers have a couple more weeks here in July 2020 to shoot the comet.

Check out this link for more information on the comet

https://earthsky.org/space/how-to-see-comet-c2020-f3-neowise

Tips For Creating Photos Of Neowise

Now let’s talk about tips for how a photographers can create photos of Neowise – even if they have never done astrophotography.

You need a fast (f/2.8 or better) telephoto lens at 100mm or more with a shutter speed of under two seconds and ISO set at 1,000 or higher to create a photo of the Neowise comet.

Lens For Shooting Comets

The first thing a photography needs for shooting comets (astro) is a suitable lens. There are two things photographers should look for in a lens that makes it suitable for creating photos of a comet like Neowise

  1. Fast. Look for a lens that has a maximum aperture of f/2.8, f/1.8, f/1.4, or even f/1.2. You can shoot astrophotography with a lens that has a maximum aperture of f/4.0, but this would mean that your ISO will have to be a lot higher and would be a challenge if you have an older camera.
  2. Telephoto. Usually a photography should look for a lens that most would call a “wide-angle” and has a focal length between 14 and 35mm. Usually, in a pinch if the fastest focal length you have is a “nifty 50”, that goes f/1.8 or faster, give it a try. For Neowise (and presumably other comets) you are going to need telephoto. Something over 100mm most likely. So that 70-200mm lens that goes f/2.8 is going to be a great choice. 50mm can sort of work, but Neowise is pretty small and at 50mm it will barely look like a comet.

Camera Settings For Shooting Comets

One of the reasons photographers should give astrophotography a try is the challenge it will pose. You have to really understand the exposure triangle for things to go well as you create astro photos. Even if you think you understand the exposure triangle well right now, if you haven’t tried astro you should give it a go and you will be surprised how much you learn.

Astrophotography needs a different approach than most any other genre. You are shooting in low light. As low light as you can possibly get in. In fact, you should look into seeing if there is any reasonable way for you to travel to a spot where there is less light pollution.

Here are the settings you should consider as you attempt to shoot the comet.

Aperture

As always, after deciding the focal length of the lens you are going to use as you create photos, the next most important setting to me is aperture. This is really easy in this case, you want to shoot as wide open as you possibly can.

This is why the recommendation was to use a lens that is both wide and fast. F-stops of f/2.8, 1.8, and 1.2 are going to be the best here. Even if you can get better sharpness stopped down some to f-stops of f/4.0, f/5.6, or f/8.0 you just can’t do that with astrophotography.

There really isn’t any deciding to do here, you want to open up that f-stop to the widest it can be (the smallest number possible).

Shutter Speed

You end up not really having much of a choice with your shutter speed either. Light is such a premium you want to have your shutter open for as long as you possibly can. Trouble is, the earth isn’t standing still and it means those stars are moving in the scene. If you drag that shutter (hold it open) for too long those stars stop looking like stars.

This can produce a different type of image that is also fun to create called star trails, but that isn’t what you want here as you are trying to create a photo of the comet. So how do you know how long you have before those stars go from being dots in they sky to trails? The 500 rule can help you there.

The 500 rule is a generic rule-of-thumb and is dividing 500 by the focal length of your lens. If you are shooting at 24mm then it is 500/24 = 20 seconds. If you are shooting at 18mm 500/18=27 seconds.

The formula is an easy one, but with modern cameras it really doesn’t help a lot. It doesn’t account for the size of the photosites in the camera and how far apart they are. You can try using the 400 rule instead, which should get you a little closer. If you shoot a crop sensor then you can try adding the crop factor as well. For example, for a Canon crop sensor if you are shooting at 18mm then you have to apply the 1.6x crop factor 18*1.6=29mm and your 500 rule then is 500/29=17 seconds. You have to use 10 seconds less time on the shutter speed.

If you follow the 500 rule or 400 rule you may notice when you get your images on the computer that the stars still don’t seem perfectly sharp. Some of this is going to happen because lenses aren’t as sharp on the edges as they are in the middle – especially when you shoot them as wide open as they go (small aperture numbers). Some of that can also be because the 500 rule and 400 rule is overly generic rule that doesn’t account for something like sensor resolution (the megapixels).

A more precise rule that accounts for megapixels is one called the NPF rule. N stands for aperture (it’s a weird science optics thing), P for pixel density (distance between pixels), and F for focal length. The formula is pretty complicated, but the good news is you don’t have to worry about it all if you have the PhotoPills app on your phone. Open up PhotoPills and scroll down to the Spot Stars pill and you can put in the camera and focal length to show you the NPF and 500 rule shutter speed.

UPDATE: Jeff was surprised at just how small Neowise is an astronomical element. It requires a much longer focal length that most astrophotography at more than 100mm. Therefor your shutter speeds are going to be considerably shorter than shooting something like the Milky Way. Jeff shot Neowise at 105mm on a Canon 80D crop sensor camera. The 500 rule then would be 500/(105*1.6) = 3 seconds and NPF rule says 1.86 seconds. As NPF sugggested, the stars were beginning a trail a bit.

NOTE: There are star tracking devices you can use with your camera that move you camera exactly in sync with the stars enabling you to use a shutter speed of several minutes. Check the doodad of the week below for one option.

ISO

You are going to shoot as wide open (smallest number) you can for the aperture and use as long a shutter speed as you can just short of getting star trails. That leaves ISO as the only variable of the exposure triangle you have much control over. Even then, it isn’t too much control.

Your choices are probably ISO 3,200, ISO 6,400, or ISO 12,800. Yep, that means your image is going to have quite a lot of noise in it. Good to just accept that in you head right now. It is the reality of all astrophotography shots.

There are things you can do to limit that noise. The obvious one is to increase your shutter by using one of those star trackers mentioned. That can be expensive though, so the next thing to mention is turning your camera off between shots.

As your shutter is open and that sensor is being powered on to measure the photos that hit it, the sensor starts to warm up. Heat is the enemy of all electronics, they don’t perform very well when they get hot, and in the case of camera sensors their ISO performance is impacted. So take a shot or two in a row, then turn the camera off for a minute or two before taking another shot.

Canon 80D / Tamron 70-200mm f/2.8 / Focal Length: 105mm / Aperture 2.8 / Shutter 2 seconds / ISO 1,000 / Shot at 10:10pm

Plan Your Comet Shoot

My favorite app for planning outdoor shoots of all types is PhotoPills. Takes a little bit of getting used to it so that you can understand how to use it, but really nothing better for planning to shoot the sun, moon, and Milky Way.

Unfortunately the app doesn’t have the Neowise comet as one of the things it can help you plan around, so it isn’t an option here. Instead you should check out https://stellarium-web.org/ Another app to look into is one called Sky Guide for iOS that was helpful for trying to locate Neowise when out in the field (it was tough given how small it is in the sky).

Also note that the new moon starts on 7/20/2020, which will make the most ideal conditions possible for shooting Neowise. From now through then you can get yourself out to an area with as little light pollution as possible and do some practice runs to figure out the best settings for your equipment. Then you should be ready to go on 7/20 and a few days after to see if you can create an image of the comet you are proud of.

Doodads

Jeff: Atomos Ninja V ($600).

Brent: Star Tracker: Sky-Watcher Star Adventurer Astro Pack ($330)

Reminders

Comments

  1. The 500 rule will smear your stars out beyond the resolution of today’s digital cameras. It is a hold over from high speed (large grain) film.
    A rule can be derived from first principles this way: The stars rotate a full circle in 24 hours. The worst case are the stars on the celestial equator which turn and angle of 2 pi / (24 hours) or 73*10*-6 radians per second. Most digital cameras have a pixel pitch of about .005 millimeters and an antialiasing filter that smears spots to cover .01 millimeters. The rule is then .01 millimeters/(73*10*-6 radians per second)= 140 millimeter-seconds. So use a rule of 140 if you have a camera with 5 micron pixels and an antialiasing filter. You can do longer exposures if you are pointed to objects closer to the celestial pole, since they don’t move as fast.

  2. Astronomical – relating to Astronomy, a branch of science that deals with celestial objects, and the physical universe as a whole
    Astrological – relating to a superstitious belief system where the position of the sun and planets have an influence on the affairs of people and the world around us.

  3. Pingback: How I Got The Shot - Details About The Creation Of 5 Landscape Photos - Master Photography Podcast

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