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How do you tell if you have a bad lens? I have a Sony A7 II and am using a 50mm 1.8. I was just trying to take a shot of Orion, all manual settings and I tried multiple f stops from 1.8 - 3.5, ISO from 400 - 1600, exposure times no greater than 10" - 2", and using live view to focus on a bright star and get it as sharp as possible. All the stars in the picture look like they have wings. I am shooting from a tripod and it was a little windy last night so maybe that is what it is. I'm trying to get some pics uploaded but having trouble. Any tips or suggestions are helpful.

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Stars toward the edge will have wings if the lens suffers from astigmatism.  The size of the wings should decrease with increasing f-stop.  By f/8, they should be gone, though this might only be possible to test with an artificial star.

Stars on axis (in the central region) should be pinpoint or close to it with just about any decent lens.  I would try photographing a flashlight (torch) reflection off of a dark ball bearing about 30 feet away.  Try it centered and near the edge at varying f-stops while tripod mounted.  This should allow you to characterize the aberrations of your lens.

p.s., Is that a B-1 bomber in your avatar photo?

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1 hour ago, Louis D said:

Stars toward the edge will have wings if the lens suffers from astigmatism.  The size of the wings should decrease with increasing f-stop.  By f/8, they should be gone, though this might only be possible to test with an artificial star.

Stars on axis (in the central region) should be pinpoint or close to it with just about any decent lens.  I would try photographing a flashlight (torch) reflection off of a dark ball bearing about 30 feet away.  Try it centered and near the edge at varying f-stops while tripod mounted.  This should allow you to characterize the aberrations of your lens.

p.s., Is that a B-1 bomber in your avatar photo?

Thanks for the quick reply. The stars in the entire field were all jacked up but I'll try your recommendation. 

 

Yes they are, I used to work on them and they are one of my favorite aircraft.

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5 hours ago, pcardinal42 said:

stars in the entire field were all jacked up

Hi. If it's not the wind, try taking the exposure from your phone rather than touching the camera physically. It maybe vibration as you started the shot.

HTH

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1 hour ago, alacant said:

Hi. If it's not the wind, try taking the exposure from your phone rather than touching the camera physically. It maybe vibration as you started the shot.

HTH

Guess I should've mentioned that I use a 2" delay for the shutter. So whatever vibrations should have rested but I have set up the remote settings for my phone for the next time.

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1 hour ago, alacant said:

Hi. If it's not the wind, try taking the exposure from your phone rather than touching the camera physically. It maybe vibration as you started the shot.

HTH

Guess I should've mentioned that I use a 2" delay for the shutter. So whatever vibrations should have rested but I have set up the remote settings for my phone for the next time.

light house.jpg

orion.jpg

ruins.jpg

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The star shapes in the third image suggest camera movement. Next time try hanging something from the hook on the bottom of the tripod and not extending the centre rod. More weight and a lower centre of gravity will make it more stable, even if it's a cheap tripod. And a 10 second delay will be more than enough to allow any vibrations from pressing the shutter release to damp down. Using a remote release is even better. Another thing is to try not to move around too much while the image is being taken as vibrations through soil can sometimes affect it too

Once you've tried that, take images in different directions from the same spot and look at how the lines move. If they are reasonably consistant across the image, but vary from image to image then it's likely to be star trails

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1 hour ago, pcardinal42 said:

It is this one https://www.amazon.com/gp/product/B005KP473Q/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 I didn't splurge on it so maybe I need to do my usual buy once cry once 

Looks the same as my Hama tripod, but nearly twice the price - and still good value! Not as solid as would be ideal, but I've had good results for long exposure looking for meteors, but of course that's getting star trailing as part of the package.

I have found that it's best not to raise the centre pillar to get good results, also you can stick a carrier bag with a few kg of 'stuff' on the hook which will help stabilise it a lot.

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I thought about it after my star trails post and came up with a way to prove or disprove my theory.  Take exposures at 1s, 2s, 4s, and 8s and see if the star trails double in length with each doubling of exposure time.

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I had a night of no wind, weighed down the center of my tripod, and used the app on my phone to take the pictures. 28 lights and darks, F1.8, 10", ISO 400, and stacked in sequator. The raws were much more stable. I appreciate all the advice.

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