pulsating trail of ISS

[blucenturion]

Hi, name's John. I live in N California redwood country. My first post; I've been looking at the Imaging Gallery since joining. If the ISS is predicted to pass over and skies permit, I'll take my Canon 5D Mk II with Canon 16-35 f2.8 into the backyard and use a remote cord. This exposure was 2 min and for the first time my ISS trail has this funky pulsating aspect to it. I don't want any more of these, believe me. I was wondering if anyone could speculate the cause, perhaps? The aperture was 4.5, ISO 1600. TIA.

[davew]

That's weird ! It almost as if it was an interference pattern. The brighter stars have the same effect as well.

Was this on a fixed tripod and was there a filter screwed on the front of the lens ?

Dave.

[StuartJPP]

I know this may sound condescending (and by me saying that probably makes it sound worse) but are you 100% sure it was the ISS? I have seen other satellites do this (tumbling satellites) or perhaps above...a filter attached to the lens.

Another thought was if the camera was mounted on a tracking mount, I did notice this doing an Iridium flare once though that was more jaggered rather than this effect.

[Leveye]

Unless this was not the station and the light was pulsating on and off i don't see how this is possible with a single exposure. Aliens! ;-)

[IanL]

It is not unusual to get a pulsing-type of pattern with some satellites, either because they are rotating (regular pattern) or tumbling (irregular pattern - dead satellite or discarded rocket stages/fairings).  The light is reflected off different surfaces which changes the brightness rapidly.  I can't think that you would get that effect with the ISS since it doesn't rotate like that.  The stars do look a bit odd as well and seem to have similar aliasing effects.  Do you have a larger version of the image you could post as it is hard to see much in the small version you have attached?

[blucenturion]

I was on a tripod, no filters. How do I attach images to a reply?

[blucenturion]

2000 px

[davew]

I've down loaded the image and rotated it. Looks very much like aliasing effects. Don't know why, sorry.

It doesn't look like a rotating satellite to me.

Dave.

[Earl]

IIRC the 5DMKii does suffer from aliasing issues.

[blucenturion]

what does "IIRC" mean?

[davew]

If I remember correctly.

Dave.

[blucenturion]

thanks, I was speculating "In _ Rare Cases"

[blucenturion]

I'm convinced aliasing lies behind it, though my previous outings did not display it, perhaps the incredible brightness of this morning's overflight amplified the problem. I've turned down in-camera sharpness to nil. Thanks for the help, that was very quick, I do appreciate the effort.

[IanL]

It looks more like aliasing due to whatever process you are using to downsize the images.  The second larger image is much less jagged than the smaller one.  Are you capturing the original images as JPEG or RAW?  Always better to use RAW as you can do a lot more in post-processing.

[Astrosurf]

I didn't know about aliasing. That's very interesting. Here's a link for anyone interested: http://www.picturecorrect.com/tips/aliasing-in-digital-photography-explained/

Alexxx