My first attempt at star trails

This is a good effiort. You are lucky to have a north-facing opportunity and clear skies. Why no EXIF data?

As to improvement, it depends upon what you want to end up with. Complete circles take 24 hours! I think less is more: why not try a three minute exposure on its own and work from there. If you use a neutral density filter, you can reduce the number of stars seen and get something more interesting, which would enable you to identify individual stars.

I wonder if the streak on the bottom LEFT was the ISS. You can look up its coordinates on the internet. Polaris is about 53° from your horizon, and the streak was about 45° N of the celestial equator in your last exposure -- I think: check my maths!

David

Sorry! I dont seem to be helping; but I‘ll try again.

The last photo seems not to be in focus (assuming it is on the same tripod as the others). Apart from that, I should have thought that the thing to do is to turn up the highlights (the stars), and turn down the darker areas, for more contrast. (But I may have misunderstood you.)

The original composite that you posted does the job of showing that the starts are circumpolar, but little else. A shorter exposure should show shorter trails, from which it should be possible to identify at least the plough, or cassiopeia, depending on the time of night. In the evening, the plough should currently be at the bottom of the sky.

What happens if you combine half or a quarter of the 122 images you already have?

David

If you meant the straight line at bottom left, I's say it was an airplane judging by the length of exposure. The length of each line tells you the angular velocity** of objects relative to your stationary camera - and an airplane would have a much higher angular velocity than any of the stars. A meteor would have an even higher angular velocity than anything in that scene which means that it would probably not even register in a 30 sec exposure (think ghost images like people walking across a night street shot).

** the term velocity includes direction which is why the star lines are circular but the airplane line is straight. The term 'speed' does not include velocity and therefore does not include direction.

Alan,

You have just made me realize why I have never spent time out in the cold photographing star trails! By their very nature they are always bound to be parts of concentric circles, and there is nothing much you can do to make the patterns rectangular or anything else. That may not be a profound statement, but it is not shallow and has the advantage of being truthful!

I wasnt sure about the focus, but it occurred to me a) because the trails looked wider and fuzziier than the other photos, and b) because the horizon on mother earth looked out of focus, and (at f/8 and 20mm focal length) I would have thought that it was pretty much at oo, as the stars are.

I am, however, certain that you must have covered the distinction between speed and velocity at school, as I did, and I am not sure why it came up above! 😁

David

Couldn't help but notice the exclamation point.
So how may I help?

Perhaps with star trails being the intended subject it is permissible to go much further than the above, for example:

Now I see why Astro guys seek high values of DR as fainter stars appeared in mine but almost buried in noise.

Noise reduction software can do wonders with star trails and general night sky images. This may or may not be acceptable. If the image is taken for scientific purposes, you wouldn't want to use the AI noise reduction software most of us use.

Alan,

I googled "star trails" and, apart from several articles on how to do them which might be worth following up, among the images was this one, which enables the identification of the stars involved. It might be interesting to see if you can do something similar it from your posiiton. There is no chance from here!

David

Thanks for the interesting link, especially the spiral look versus the more normal circular look. I think that Alan might be interested in that ...