How to shoot stars applying the 500 Rule and other tips
Keywords: landscape, night, sky, photography, shutter, speed, stars, astrophotography, jrp
THE 500 RULE
Getting the maximum shutter speed duration gets tricky because everything is moving, even if we don’t feel it.
The Earth rotates, our solar system moves, the constellations move, the galaxy moves. The numbers are very high. So I went very seriously (unnecessarily complicating things) to work on how fast were the visible stars in relation to my camera on earth. Although irrelevant, I even took into account my distance from the equator to find my relative rotational speed around earth’s axis. However I had to face two major issues: not having even remotely the privileged mind of Srinivasa Ramanujan (The Man Who Knew Infinity) to solve the equations, and the limitations of film speed at that time. I discovered that shorter focal lengths were better for this, but all my images of stars had trails, even when using night surveillance film.
It was not until the advent of digital SLRs and high ISO image quality that shooting into a starry night sky with round stars became possible for us, without a motorized computer controlled telescope. By the time I got interested and had a DSLR, all about vector theory was completely forgotten so I just went to our local planetarium and asked how they photographed stars. The answer was: “Amateur astronomers developed empirically a simple yet effective rule: The 600 Rule, where 600 is mm-seconds. When you divide 600 mm-secs over the focal length of your lens in mm, you get the maximum seconds time length to have well-rounded stars, without trails.” Ah!
Later it was found out that 600 was too large a number for prints above 8x10 inches and so the 600 Rule became the 500 Rule.
Below a shutter speeds table:
And you may want be more conservative and make your own 450 Rule, provided you have a good very high ISO performance camera.
How forgiving is this 500 Rule? Not much. My own image at Death Valley still looks acceptable on an 8X10 print, but not so hot on an 11x14 or larger.
A section of my Death Valley image at 100% magnification
As the table shows, the mistake was exceeding the 500 Rule shooting at 30 seconds with 24mm focal length. For that focal length I should have used 20 seconds, or zoom back to 16mm focal length.
ACTUAL SHOOTING
Just remember that your only variable for exposure will be ISO. Aperture is the widest open and the shutter speed is fixed, governed by the 500 Rule.
In closing, I would like to show you the stunning photographs made by two of my dearest friends and mentors, Ernesto Santos (esantos) and Larry Anderson (mnbuilder49). These images they made while traveling together to Needles, Custer State Park, in the Black Hills, South Dakota.
Enjoy.
Milky Way over Needles by Ernesto Santos (esantos)
Nikon D4, 14-24 mm f/2.8 @ 20 mm, f/2.8, 25s, ISO 1600
On a Gitzo series 3 tripod, Kirk BH-1 ball head
Painted with the tail lights of the car.
Click for an enlargement
Milky Way over the Eye of the Needle by Larry Anderson (mnbuilder69)
D4s, 14-24mm lens f/2.8 @24mm, f/2.8, 20 seconds, ISO 3200
Gitzo Series 3 tripod with Markins M20 ball head
Click for an enlargement
Got a Astrophotography question?
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Originally written on September 21, 2016
Last updated on January 24, 2021
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41 comments
J. Ramon Palacios (jrp) on November 30, 2017
Jim, go to page 2
Jim Donelson (jcdonelson) on November 30, 2017
You title the article "The 500 Rule and other tips" then you neither explain nor state the 500 rule.
Gary Worrall (glxman) on November 30, 2017
Great Article JRP It is amiss of mw that I haven't tried this already ........Gary
Paul OLeary (madpogue) on October 29, 2017
@Michael Hurder, maybe your camera manual has a cross-reference for actual color temperatures of its named WB settings. Did you check there?
J. Ramon Palacios (jrp) on October 13, 2017
Michael, article about night photography ... no, we don't have one for film or for digital here. On white balance, I only remember Direct Sunlight, 5000K degrees.
Michael Hurder (MKHurder) on October 13, 2017
Also, I keep forgetting to ask. I have WB settings with names, not kelvin values. Is there a chart that converts such?
Michael Hurder (MKHurder) on October 13, 2017
jrp: Is there an article about night photography with a film cameras?
J. Ramon Palacios (jrp) on October 5, 2017
Wade, thanks for your comment. 500 is a number derived empirically, i.e. by actual practice after shooting at given focal length at various seconds of exposure until they consistently found round stars. For the formula to make sense, i.e. yielding a result in seconds, the 500 (in this case) needs to be stated as mmXsecs (also expressed as mm-secs). mmXsecs/mm = secs. For any other focal length not in the table, you just divide 500 over that focal length. So yo really don't need a table. I'll email you a complete chart from 10 to 35mm.
Wade Ramsey (WKR) on October 5, 2017
Thanks for the very informative article. But I don't understand the formula you use for the 500 rule, divide 500 mm-secs over the focal length of your lens in mm to get the maximum exposure time. What are "mm-seconds?" And how do you divide them "over" the FL in mm? Does that mean divide them "into" or divide them "by" the FL? The chart is very helpful, but I have a DX camera and an 11-16 f/2.8 lens and the chart only goes down to 15mm for DX.
J. Ramon Palacios (jrp) on October 2, 2017
John, at low ISO you will either not get the stars or burn some pixels in the sensor. under a dark sky only horrible noise seems to be detected. If you have made some images of stars at that low ISO, please post them. I would love to see them.
John McDonnell (jmcdonnell) on October 2, 2017
I would recommend keeping the ISO in the 400 to 800 range if possible to help reduce noise.
J. Ramon Palacios (jrp) on January 26, 2017
Thank you, Michael Don't forget to show us your results in the Landscape forum
Michael A. Folger (MikeD750) on January 26, 2017
Great article JRP. You hit all of the areas with succinct information. I'll heading to Utah later this year and am looking forward to putting your tips into practice.
J. Ramon Palacios (jrp) on November 22, 2016
Jay, You are most welcome.
Jay Newmark (drbrog) on November 21, 2016
Great article JRP. Wish I saw this before a recent visit to Haleakla. Thanks for sharing.
J. Ramon Palacios (jrp) on October 10, 2016
Keith (kmox2163). You just need to get acquainted with the publishing format for our articles. At the the right hand side of the bottom of a page (before author and comments) you will have the option of clicking on for a previous page (if any), the next page, or show all pages at once. The 500 Rule is explained here on page 2.
J. Ramon Palacios (jrp) on October 10, 2016
Jim (Loncevac), maybe they discovered their mistake and decided to be too detrimental to have your article side by side with theirs ;-) Good trick that of the gafer tape.
J. Ramon Palacios (jrp) on October 10, 2016
(Edited by jrp Monday, 10 October 2016 ) Hi, Tom I feel more comfortable -for composing- using the 24mm focal length, but that is very personal. I have seen remarkable images at 20mm. Using lenses with shorter focal lengths introduce the problem of distortion in the foreground.
Ben Ransom (Ben___) on October 9, 2016
I've only done a little bit of astro shooting (love it!), and don't yet know whether to use in-camera Long Exposure Noise Reduction. First of all, does it do NR on Raw, or just JPG? (I only shoot raw.) I've shut it off for time-lapse to save battery power for longer sequences, and turned it on for static stills, when battery is not a concern. --Thanks! (Nikon D750)
Keith Moxham (kmox2163) on October 8, 2016
Apologies for being a bit slow, but what is the 500 rule - Keith
James Keenan (Lomcevak) on October 6, 2016
Nicely done, particularly the table accounting for FX and DX cameras mounting the same lens - effective focal length is the key to making use of the 500 Rule. I wrote to Sky & Telescope magazine about a night sky article they did that did not account for effective focal length, and got a highly technical response that essentially said lens focal length was focal length, crop factor was not an issue. They proposed using my letter and their rebuttal in the magazine as a teaching point for the readership - at which point I made my case again for effective focal length in more basic terms and said if they still felt they were right to go ahead. Never heard from them after that, and they did not use my original. For night sky I focus on infinity during daylight using camera AF and the most distant object I can see, the switch camera and lens to MF and use gaffer's tape to hold the lens focus ring in place - it can stay on for days and leaves no residue when you remove it.
Tom Egel (tegel) on September 28, 2016
Thanks for the excellent article and inspirational photos! Besides the 14-24, are there any other lenses you can recommend? I have the 20 and 24mm f/2.8 AIS primes along with the 16/2.8D fisheye. My main body is a Df. I've dabbled with the 20mm a few times, but the results have been just okay. I'll definitely try again using your suggestions here, but I'm interested in your opinion on what to expect with my existing gear. Thanks, Tom
J. Ramon Palacios (jrp) on September 25, 2016
Richard, Brian, Billy, Tom, thank you for your comments
Tom Jacob (sevendayimages) on September 24, 2016
Very nice write-up JRP, thanks for posting this because it made some things clearer and with sense now :) Will try it out, but it will be difficult to match the excellent pictures included in your article. Thanks for taking the time. Cheers
Billy Close (Bclose) on September 24, 2016
Great Info, Texas has some state parks that are designated as being Dark Sky parks. Great for this and they have extremely low to no light interference from outside sources. I am sure most states have something similar to this.
Brian Sullivan (BrianS) on September 23, 2016
Incredible set of images! Thanks for sharing this info! While night time shooting has always interested me I have actually never done it. Perhaps someday... Cheers! Brian
Richard Luse (DaddySS) on September 23, 2016
Excellent! Thanks Ramon for the clear information and the 500 rule chart.
J. Ramon Palacios (jrp) on September 23, 2016
Dave, please show us your work when you get a chance to practice this type of photography. And there is so much that can be done with foregrounds!
J. Ramon Palacios (jrp) on September 23, 2016
Donna, Thank you. I know you will do superb stars images.
J. Ramon Palacios (jrp) on September 23, 2016
Very kind of you, Geoff. I'll check on the photopills app that Jordy recommend.
David Summers (dm1dave) on September 23, 2016
Great article! I am looking for some star shooting opportunities.
Donna Knodle (dgknodle) on September 22, 2016
A very informative article which will give me the push to try this type of photography. You really explained the how's and why's that need to be done to obtain shots like yours.
Geoff Baylis (GBaylis) on September 22, 2016
Great article, thanks. I was planning to undertake my first attempt at photographing the stars next month, so this info is just what I needed to get me underway. I already use TPE, but thanks also to Jordi for the tip about photopills. Geoff
J. Ramon Palacios (jrp) on September 22, 2016
Thank you, Susan. We might get a chance to use the rule ;-)
Susan DiCriscio (Scout330) on September 22, 2016
What a great article! Thank you, hope to be able employ these rules in the upcoming ANPAT
J. Ramon Palacios (jrp) on September 22, 2016
Marsha, glad you liked it.
J. Ramon Palacios (jrp) on September 22, 2016
(Edited by jrp Thursday, 22 September 2016 ) Joe, thank you. Yes. I've seen those stars color differences, even under ugly light pollution like in my shot here. I would rather make the sky darker than altering WB temperature.
J. Ramon Palacios (jrp) on September 22, 2016
Jordi, thank you for commenting. I've seen what phopilld does and is great but I am an Android guy.
Marsha Edmunds (meadowlark2) on September 21, 2016
Good information, Ramon. I'm looking forward to capturing some Milky Way and Northern Light shots and will enjoy referring back to this.
Joe Zamudio (cocavaak) on September 21, 2016
Nice! I think too many photographers use a cooler white balance that makes the sky blue - that is not real. Also, a common mistake is to crank up the ISO or process so that all the stars are white. The stars are various colors and when you zoom in to your photo you can see that!
Jordi Viñas Bascompte (jordivb) on September 21, 2016
Good article! I also use TPE, but I'd recommend one more app called photopills (only iOS though)