Skip to main content

The "Top Secret" "Rule of 600"

Ok, it's not secret at all, but is sure is asked about a ton!

One of the most important things when it comes to good looking landscape astrophotography shots is crisp round stars.  This is achieved by knowing how long you can keep your shutter open without having the stars move (trail) in the image.
I recently posted an image on G+ and a question was asked in the replies.  The question was regarding something called the “600 Rule” or the “Rule of 600”.

It isn’t some secret code among astrophotographers….. Oh wait…. Forget what I’ve said until now, there is no rule of 600, it doesn’t exist, enter the Men in Black…….

Seriously, there isn’t some great secret, there is however a bit of math, which some may find as scary as a visit from the “Men in Black”.

Ok, here is the meat and potatoes of the 600 rule.

600 / Real Focal Length = Maximum exposure before trailing occurs.
Confused yet?  I thought so……

Lets use a real world example.  I shoot with a Nikon D7000 which uses a 1.5 crop sensor (Canon uses 1.6).  We’ll use an 10mm lens to keep the numbers easy.
To figure out exposure length we take the lens focal length of 10mm and multiply it by the crop factor of our camera we are using mine so that will make it 10x1.5 = 15
The effective focal length is 15mm

600 / 15 = 40 (seconds)


Popular posts from this blog

How to Make the Stars POP!

If there is one thing I've learned about processing night shots.

There are as many opinions and as many ways to do things as there have been sunrises! With that being said, I thought I'd share another technique that I've employed a couple of times

This technique is very simple and very effective.  The nice thing about my tutorial is that I show you how to do it yourself.  I’m not a fan of “presets” that take the adjustment factor out of your hands.  I’d rather show someone how to do it for themselves.  That way you can actually expand your knowledge and learn to help yourself and others around you.

In this particular “How to” we will be increasing the size and brightness of the larger stars.  This technique can also be used to bring out the natural colour of the stars or any other adjustments you may want to use.

Like most of my tutorials, I take the approach that you have a basic knowledge of photoshop.  If you don’t and need some further assistance with this tutorial, please…

How to Reduce Star Trails

600/(18x1.5)= &%*@!*$

So, you either didn't follow the 600 rule, you're bad at math, or you made a mistake! Now you've got a shot that you absolutely love but the stars look like eggs, or worse yet, they are mini trails!
Don't scrap that photo without at least trying this little know trick of the trade.
In this tutorial I will teach you how to remove small trails to make your stars look crisper.
****  Does it always work??  Nope ****
But heck, why not at least give it a go before deleting that photo.
The Original Image
Here is my original image opened in Photoshop.  You will notice that the stars look like mini trails. This particular image was exposed for 43 seconds (23 seconds longer than I usually expose an image).

The Original Image Magnified
Here you will notice how the stars are trails and not as crisp as they should be. Normally most people would throw this image out.

Stars Layer Selection
Start off by selecting the sky.  I used the marquee tool but you can use an…

Make Stellarium More Realistic when planning for a night shot

**Article by Darryl Van Gaal
As both a landscape, and deep space astrophotographer I find myself using Stellarium ( on a weekly basis.  It's a great (free) program and in my opinion is one of the best out there competing with programs that cost hundreds of dollars.

I like it for the ease of use along with the reality of the night sky.  If you use the right settings, the sky you see in Stellarium is strikingly similar to the sky you'll see when you look out your door.

Like I said, I do believe that it is an easy program to learn the ins and outs of,  BUT, like anything, there is still a learning curve.

I've posted about Stellarium in the past ( ) teaching you how to simulate your cameras field of view with a particular lens on it.  Which is aid in planning photography outings.

This post is similar as it will teach you how you can use it to help you get a feeling as to what you&…