Skip to main content

Why a GEM for astrophotography?

*The GEM*

During a past on air hangout I spoke a bit about photographing Deep Space Objects and the equipment that I use to take those photos.  One of the things that was mentioned is that I use a GEM (German Equatorial Mount) on a very heavy tripod.  The GEM or Equatorial Mount is a really fancy way of saying it’s a tripod head that aligns the camera lens (either regular lens or telescope) with the earth’s axis.  I didn’t really explain in great detail why this is a must when you are trying to do very long exposures or “Stack” several shorter exposures.
Below is a photograph I took from the back deck of my house.  I had my camera mounted on a “Regular” camera tripod.  The region of the night sky may be recognizable by many people, it is the Orion Constellation area.  This photograph was achieved by taking several 13 second exposures (@24mm) and “Stacking” them using a free program called Deep Sky Stacker.  The total exposure on the image is just under 6 mins.
Since the earth moves, I had to move the camera to keep the Orion Constellation in the center of the viewfinder.  You will notice in the photograph that the in center of the photograph the stars are nice and round, as you move out from the center the stars start to take on an “Egg” shape, and at the very edges of the photograph, you can actually see what appears to be “Star Trails” and the image also gets a fuzzy look to it.  The reason for this is quite simply stated because a regular tripod mount does not rotate on the same axis as earth.  Each time I took another photo the Earth had moved and since my tripod head doesn’t move relative to the Earth’s axis the stars moved in the frame.
If you don’t mind this look, you can actually take shots with the equipment you probably already own.  If you’re looking to have an image like this where ALL the stars are nice and round you will need to purchase a GEM or something like Astrotrac, both of which move your camera with the axis of the Earth.


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&…