startrails

[george013]

I know it's not a wonderful picture. It's my first and probably last one I made.
The power of this kind of pictures for me is it shows what people 1000's of years ago saw and started thinking of what they saw. Trying to explain the rythm of it. And I'm just pointing the camera on it. Now we can explain a lot of what we see.

My intention was startrails, so I used about 92 shots of 25 sec, f5 and 17mm. First time playing with layers in Gimp. I coulld load all the picturese at once as individual layers. I only had to change the properties individual. There might be a way to to that easier.
As you can see I included the test picture also. That black plain on the left is the roof of the house.
What I can't explain is that the circular lines left under are changing to rather straight lines right top.



George

[Stagecoach]

What I can't explain is that the circular lines left under are changing to rather straight lines right top.
George

I'm confused George, are you referring to the axis lower left which I suspect was North for you. As you used such a wide angle I suspect that will cause the lines farther out to appear straighter than if taken with say a 30mm.

[Wavelength]

I liked the result; those trees so close and those stars far away....

[Shadowman]

Nice effect.

[xpatUSA]

What I can't explain is that the circular lines left under are changing to rather straight lines right top.

George

I didn't know either, but it seems to be a common effect:



even reversing curvature:



Source: http://earthsky.org/astronomy-essent...re-star-trails

There's a clue here

https://en.wikipedia.org/wiki/Star_trail#Rotation_of_the_Earth

I'll guess that where the lines go straight is true West or East . .

[lovelife65]

Like it quite a bit

[george013]

I took these picture on my holidays on Sardina, Italy. I live in a city so this is a one time try.

When looking for startrails in Google I can find most complex trails. I wonder how they did it. And I still wonder why those, mine, trails are not really concentric. I don't believe it's the lens. There must be another explanation. Who is standing up?

George

[xpatUSA]

I took these picture on my holidays on Sardina, Italy. I live in a city so this is a one time try.

When looking for star trails in Google I can find most complex trails. I wonder how they did it. And I still wonder why those, mine, trails are not really concentric. I don't believe it's the lens. There must be another explanation. Who is standing up?

George

I'll stand up again. You obviously missed my post or did not understand it.

Take a camera with a 180 degree angle of view lens. Point it due West or East. The northern stars will trace an arc. The southern stars will trace an opposite arc. The stars between those two will trace straighter lines.

That effect is clearly shown in the second image here:

startrails

As was said before, your lens angle of view had quite a lot to do with it, no need for "another explanation".

[Stagecoach]

George,

Here's roughly what you would have seen from Rome (Sardinia was not on the pick list unfortunately) on the day and time you took the star trail if that was north in the left lower.



I had only input my 28 mm lens FOV into Stellarium but your post reminded me to enter the wider FOVs I now have.

[selig1656]

I have zero experience in this , so , I shall enjoy your work in awe .

[george013]

George,

Here's roughly what you would have seen from Rome (Sardinia was not on the pick list unfortunately) on the day and time you took the star trail if that was north in the left lower.



I had only input my 28 mm lens FOV into Stellarium but your post reminded me to enter the wider FOVs I now have.

It's not about the single picture. It's about the trails. Why are they not concentric. Ted showed some examples and described it but didn't explain it. If it was the lens single, the focal length, why not in all my pictures?
Here is a picture I shot at 15mm.


George

[Stagecoach]

It's not about the single picture. It's about the trails. Why are they not concentric. Ted showed some examples and described it but didn't explain it.

George

Here's a basic explanation, you were pointing roughly NE or the opposites.

http://kathyadamsclark.blogspot.com/...es-matter.html

and less basic..........

https://www.photopills.com/articles/...r-trails#step4

And I forgot to say, it is about the picture because it's the picture that shows where the 'axis' roughly is determining the direction you were pointing at the time and what will be in the FoV.

[george013]

Here's a basic explanation, you were pointing roughly NE or the opposites.

http://kathyadamsclark.blogspot.com/...es-matter.html

and less basic..........

https://www.photopills.com/articles/...r-trails#step4

And I forgot to say, it is about the picture because it's the picture that shows where the 'axis' roughly is determining the direction you were pointing at the time and what will be in the FoV.

I start to see the light.

It's not said in these words but it's about the relation between the optical ax of the camera and the rotation ax of the earth. If they're pointing in the same direction, you get circles. I've a start.

George

[JBW]

I start to see the light.

It's not said in these words but it's about the relation between the optical ax of the camera and the rotation ax of the earth. If they're pointing in the same direction, you get circles. I've a start.

George

Remember George AP is perhaps the most complex photography genre. It's going to take a while.