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Mack Duncan's picture

Any suggestions?

Shot with a Nikon d3200

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8 Comments

Joe Svelnys's picture

You can upload the image to the following site and they will overlay what you caught in the field of view. It's fairly nice and fun to explore what was captured. ( http://nova.astrometry.net/upload )

I shoot with a d5500, very similar camera.

Chris Jablonski's picture

Hi Mack! One overriding impression is that your watermark totally overpowers the image itself.

I'm not an astro expert, but one suggestion: you used f/11, a needlessly small aperture, depriving you of light when levels are so low already. You were at the wide end of your zoom, so stopping down just a little to say f/4.5 or 5.6 would give you at least four times as much light. This wouild enable you to use a shorter shutter speed, or lower ISO, which would lower noise levels..

I suspect this is a crop from the top right corner of the original. Is that so?

Joe Svelnys's picture

I didn't notice that, good call Chris.

If this is the kit lens 18-55mm lens, at 18mm it opens up to f3.5.Going from f11 to f3.5 will bring your shutter down to 2 or 3 seconds.

Mack, also keep in mind crop factor is critical in astro. so a 18mm is really 27mm, but if you are using a 12mm, then a 12mm will be a 18mm. With these cameras I'd stay 1600 iso or lower.

Also look into the software Sequator, it is completely free and allows you to stack several shots together to add detail and help with noise further. So ten 3 second shots is about equal to a single 30 second exposure. Good stuff.

Chris Jablonski's picture

EXIF indicates that this lens opens up to f/3.5, Joe. I definitely wouldn't shoot wide open with astro if I could possibly help it, as resolution would suffer significantly, and there would be light fallof. There is no need for such a short shutter speed. I'd drop ISO instead to reduce noise.

Your Sequator approach is an alternative path but will only help noise. I keep things simple.

A general-purpose, moderately-priced zoom will struggle wide open, especially in the corners. Astro images are optically demanding. I think there is already coma and/or astigmatism in this f/11 image, especially at top right, whereas the bottom left is sharper, which made me think it's a crop from the top right of the original. If it's not there is slight decentring of the elements, which is common.

Joe Svelnys's picture

It's all a balancing act for sure. My kit lens at 18mm and f3.5 dose good, my sharpest image to date was with my 85mm at f1.8... Though 85mm (+crop factor) is really better for nebula (like Orions) then large star fields; and of course very short shutter times.

The shorter shutter I suggested above was to help counter even more star trailing. I couldn't quite tell if this was trailing or coma (most likely a combination of both).

Chris Jablonski's picture

Don't think it's star movement (esp. if it IS a 6 sec exposure), Joe. Look bottom left. No streaks. And all the streaks are curved. Think it's all aberration.

Mack Duncan's picture

Everything was automated by the camera except that I set it to 18 mm and a 6 sec exposure

Chris Jablonski's picture

Your EXIF data suggests it was 30 sec, Mack. Maybe that's incorrect.