Switching to a German Equatorial Mount – A whole new world!

I ran up the limit on my alt-az quite soon, simply because I was limited to the 10s exposures and even with a lot of stacking, I could get only about 10-15 minutes of meaningful data on any given night.

Here is a cool video by Junk Pile that shows the basic difference between Altazimuth mounts and equatorial mounts.

Alt az mounts are good to keep an object in the general area so work great for planetary astrophotography and perhaps some bright Deep Sky objects at best.

Equatorial mounts on the other hand let you get longer exposures, since they follow the earth’s rotation (reasonably well). This makes them a great fit for any kind of galaxy, nebula, star cluster or other deep sky objects that require really long exposures.

I picked up an old used GEQ mount on cloudynights.com and instantly saw great results. While It took me some time to figure out polar alignment and get accurate tracking, once I got the hang of it, the difference was cloudynights and clearskies (See what I did there? :D)

Even simple short 30s exposures gave me tremendous improvements in image quality.

Here is a quick comparison of images I was able to capture of the Dumbbell nebula with my Alt-Az mount (20 minutes of data) vs my EQ mount (40 minutes of data). Both objects were captured with the same Nikon D3200 unmodified DSLR with the same Nexstar 5SE SCT scope. They were both processed with Pixinsight and Photoshop so I didnt really change any other parameter other than the mount itself.

The dumbbell nebula, m27 is one of the easier targets for a beginner astrophotographer given its brightness and relative closeness at 1360 light years. This comparison shows the same image taken with an Alt-Az mount and a GEQ mount.

This of course, is still a basic image since I havent done any autoguiding with my GEQ. With the GEQ mount, you can get good 30s exposures (60s if youre lucky) without seeing star trials (or your object shaking in the final image). Beyond this time frame, you are bound to run into atmospheric abberations, tiny imperfections in the gears of your mount and similar factors that dont let you take longer exposures.

This is where Autoguiding comes into the picture.

Autoguiding is a technique that helps you pick a “guide” object, like a star and track its movement, thereby sending feedback to your mount on small corrections that need to be made to keep the object well focused.

My next attempt at capturing DSOs will be with my autoguider camera and guidescope which I am yet to give a spin. I’ll be sure to share my learnings once I stumble upon a millions errors šŸ™‚

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