Problem with startrails on the edges. EOS 700D.

[S_Liebert]

Hi! 

I've been having some problems with stars turning into small trails, using my 700D. I've been searching all over to try to get an answer, but all just say the same thing. Shorter exposure, remove band to avoid wind, use remote, shoot in RAW etc. But this is not really my problem. It actually look like the firmware is enhaching the problem, when I zoom on stars on the LCD the stars would be round, and when there is two close stars they are seperated, but when I let my finger go they turn into lines and two close stars turns into one line. After I started using Walimex Pro 16/2,0 wide angel lens it seems like the stars in center looks fine, but in the corners/edges I still get trails. I've been playing around with all kinds off settings, tonight I would try with a bit higher aperture. But after that I'm all out of options. Is there anyone who has struggled with this kind off problems and know something that might help it would be very appreciated.

[Ray-uk]

Sounds to me that you are suffering with coma, this is a lens defect and always more noticeable at the edges of a shot particularly with wide angle lenses.

[S_Liebert]

I have to lenses and the mistake occurs with both. The other one is a standard (Canon Ef-S 18-55MM F/3.5-5.6) - the problem is even worse when I take pictures with this lens. 

[ebiggs1]

Your problem is lens aberrations, coma in particular.  All  lenses suffer form this some more some less.  Sorry but the two lenses you have are not the best for this either.  When you shoot landscapes, etc, this isn't a problem most of the time. However when you shoot pin points of light, stars, it is a big problem.

Your only solution is to get better lenses. An example of a very reasonably priced lens for astro work is the Rokinon 14mm f/2.8 IF ED UMC Lens.

[S_Liebert]

Thank you! Didn't think about this problem when I got the Walimex lens, as I was a bit focused on aperture as it's northern lights season here now. Thanks for the advise.

[ebiggs1]

Keep in mind pretty decent lenses for astro work like the Rokinon 14mm f/2.8 IF ED UMC Lens still suffer from some coma.  It is just less in this lens.  Also there are variations between exact same copies of the Rokinon 14mm f/2.8 IF ED UMC Lens.  If you get a good one, you get a very good astro lens.

[Waddizzle]

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ote:

Keep in mind pretty decent lenses for astro work like the Rokinon 14mm f/2.8 IF ED UMC Lens still suffer from some coma.  It is just less in this lens.  Also there are variations between exact same copies of the Rokinon 14mm f/2.8 IF ED UMC Lens.  If you get a good one, you get a very good astro lens.

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I must be the luckiest user of Rokinon lenses around.  I have only bought the Cinema versions, and they are perfect.

This was the Rokinon 85mm T1.5, shot on a Rebel T5.

[Waddizzle]

Here was my first attempt at astrophotography, in a major urban area, no less. just outside of New York City. I didn't realize what I had until I looked at it on my PC in a dimly lit room.

Rokinon 14mm T3.1 Cinema lens, with 6D.

[ebiggs1]

"I must be the luckiest user of Rokinon lenses around. "

Perhaps but virtually any lens can do a bird shot like that.  The night sky needs work but you probably already realize that.

[TCampbell]

To be sure, I would need to see your actual image (preferably the RAW file ... untouched.)

Are your exposures longer than 20 seconds (with the 16mm lens)?

What sort of tripod are you using?

Do you use a remote to trigger the exposure -or- alternatively, are you using the delay timer?

All lenses have degraded quality as you get farther from the center of the image... and moreso at low focal ratios.  Some very high end lenses only degrade slightly... others degrade more severely.