Author Topic: Greetings, and question  (Read 232 times)

Offline Jeff Raven

  • Mercury
  • *
  • Posts: 7
Greetings, and question
« on: May 30, 2020, 04:13:24 PM »
Hello all,

I've been a lurker on the board for quite some time, but finally decided to bite the bullet and post something. I've been amazed at how much information I've seen on this site, including the technical expertise and personal experience and resources that have been shared by many (too many to list, and I wouldn't want to miss someone). I've learned and gained so much, so I wanted to send a general thank you to one and all.

Now to the question: watching the SpaceX launch today (and wasn't that great to see!) I noticed that when they were heading to orbit after the second stage separation, from one camera angle the curve of the earth was very nicely convex, but from the other it looked ever-so-slight concave. Obviously the latter has to be due to some visual or lens effect I don't understand, and I was hoping someone could explain it to me? I have 'debates' with flerfers on some comment boards, and I'm sure that will come up (it has when I've sent links to clips of launch to orbit flights), and I just don't know or remember enough about optics to give an intelligent answer when it does.  Any help would be greatly appreciated.

Thank you in advance.

Offline JayUtah

  • Neptune
  • ****
  • Posts: 3363
    • Clavius
Re: Greetings, and question
« Reply #1 on: May 30, 2020, 08:18:43 PM »
Yes, it's a lens effect.  Wide-angle lenses exaggerate the curve of the Earth's surface as seen from a high altitude.
"Facts are stubborn things." --John Adams

Offline Jeff Raven

  • Mercury
  • *
  • Posts: 7
Re: Greetings, and question
« Reply #2 on: May 31, 2020, 11:09:53 AM »
Thank you, Jay.  I appreciate the quick answer. If I could ask a follow-up (I know how at least one of the people who I go back and forth with thinks)?  As I said, I can't remember my photography classes (been nearly 40 years), but is there a specific reason/effect that causes the curve to be exaggerated in one view (in the case of this launch, it was when the Earth was 'to the right' and space to the left) and then the opposite (that false concave look) when the camera view was the other way (Earth to the left, space to the right)?

For specifics (I'm sure you saw this live, but just in case you wanted a reference in the video: 


at 3:25:13 the horizon has that beautiful curve, and at 3:25:48 the horizon has that distortion (it also looks closer?)

Is it possible that there's a bit of zoom used on the distorted image, causing the pincushion effect, while the other lens either is wide-angle or is not zoomed? Or just something as simple as 2 different lenses?

Apologies if this has already been answered in other threads (I saw some mention of it for the lunar surface pictures, but not those from orbit).