star trails

[bucketman]

I dont know how to say thank you enough. You guys are brill
Right I have got GIMP on my pc also down lowding a link a mate sent DeepskyStacker
I have never really used pp before (I know am a pain)but would love to do a star trail pic so please help
will use a D90 tripod and a remote if any one should be so kind as to take me step by step from shooting to after pp I would be buzzinig
may be some one could do a tutorial??? please help
rob

[Colin Southern]

Just a quick note for Photoshop users (CS5, not sure how many previous versions) ...

If you want to stack a number of images just open them all up and then go to FILE -> SCRIPTS -> LOAD FILES INTO STACK.

[bucketman]

After all your help done my first star trail last night the light pollution round here sucks. But i wanted to try and get the basics right before i try for real. also shoot in jpeg not raw if its clear tonight will have another go but in raw. No laughing will try and post the result
thank rob

[Donald]

Rob
Certainly the light pollution didn't help you. But you definitely need to go RAW so that you can do work on it once you get it out of the camera.

Can you get yourself to a more rural setting where you might, at least, get less of an impact from the urban light?

You certainly got the north star located. 10 1/2 minutes. Good on you.

[Donald]

For noise reduction purposes a camera can take a dark frame (of the same exposure) and subtract what's in common between the two, but it's a feature that can be turned off (called long-exposure noise reduction on Canons) so that there's no delay between frames.
...................
I'm planning to do some shortly, so I'll let you see how I got on. With long exposures I've done in the past there can be a lot of noise - but - it's shadow noise (for the most part) and you can simply raise the black clipping point until it goes away, and then lower the highlight clipping point to increase the contrast - it actually works surprisingly (or perhaps not so surprisingly) well.

Colin
Are you saying, therefore, that you don't have long exposure noise reduction at 'On'? That you attend to any noise issues in PP and let the camera do what it wishes? I might be on the fringe of learning something here! This could be one of those 'ah-hah' moments.

[Colin Southern]

Colin
Are you saying, therefore, that you don't have long exposure noise reduction at 'On'? That you attend to any noise issues in PP and let the camera do what it wishes? I might be on the fringe of learning something here! This could be one of those 'ah-hah' moments.

Hi Donald,

It kinda depends on how you're approaching the shot. If you're doing just the one shot - and don't mind waiting - then by all means leave it on, but if you're shooting multiple consecutive frames and intending to stack them then if long-exposure noise reduction is on then you're kinda sunk.

I'm finding that if you're only exposing for a few minutes then you shouldn't really need it so long as you get enough exposure into your highlights - and - I've had it do some weird stuff with long exposures too (like canceling out 3/4 of the stuff I actually wanted!).

Personally I don't use it very often - in part because I seem to get OK results without it, and also because I'm too impatient to wait (it can add 20 minutes or more to each exposure).

[bucketman]

my pic is 6x10 mins expousure then pped with GIMP (am learning)
rob

[Colin Southern]

I've been fine-tuning a few parameters ... this one is a by-product of something I have planned

5x 12 minute exposures ...

[revi]

Nice trails.

Funny how (only) some of them seem to have markers in them: bright points, cutting the trail in 5 parts... (most clearly the 2 bright trails on the left)
How did you combine the 5 exposistions?

Remco

[Colin Southern]

Nice trails.

Funny how (only) some of them seem to have markers in them: bright points, cutting the trail in 5 parts... (most clearly the 2 bright trails on the left)
How did you combine the 5 exposistions?

Remco

Hi Remco,

Thanks for the kind words

I was a bit puzzled by the "markers" too - I'm guessing it's an artifact from the sharpening.

To combine them I simply stacked them in Photoshop and (I think) just varied the layer opacity. I was also fooling around with blending modes, and I might have used lighter instead or as well - sorry, can't remember!

[PopsPhotos]

Have any of you experimented with a grad filter, upside down, to reduce light polution?

Pops

[Dave Humphries]

I was a bit puzzled by the "markers" too - I'm guessing it's an artifact from the sharpening.

I think they're easy to explain; it's where you started the second, and subsequent, exposures and the stars hadn't moved much since the end of the previous one - so that bit of star trak gets a 'double exposure' when the image layers are stacked.

Each image is a different segment of star trail, supposedly in different places, stacking should join them into a continuous arc, except if you start before they have moved enough, they overlap in the merged image. I guess sharpening may make it more noticeable, but it isn't the cause.

Cheers,

[Colin Southern]

I think they're easy to explain; it's where you started the second, and subsequent, exposures and the stars hadn't moved much since the end of the previous one - so that bit of star trak gets a 'double exposure' when the image layers are stacked.

Each image is a different segment of star trail, supposedly in different places, stacking should join them into a continuous arc, except if you start before they have moved enough, they overlap in the merged image. I guess sharpening may make it more noticeable, but it isn't the cause.

Cheers,

Hi Dave,

I think I here what you're saying, but that then begs the question of why all the segments don't suffer the same fate?

There was literally 1 second between ending one exposure and starting the next.

[Peter Ryan]

Is there any reason why you are taking multiple shots and stacking them rather one continuous shot for 1 hour? Is there a difference between time lapse photography with digital verses film?

[Colin Southern]

Is there any reason why you are taking multiple shots and stacking them rather one continuous shot for 1 hour? Is there a difference between time lapse photography with digital verses film?

A digital capture gets noisier the longer the exposure, and multiple captures helps to average out the random stuff.

[Peter Ryan]

Thanks Colin,

I thought that might have something to do with it. I have only done them on film. It might be easier to do them on film and then scan them.

[bucketman]

Ive read in a book ( making every photon count) to use a special type of camera or get your camera modified to do away with noise. But I also think it makes your camera useless except for long exposures. Its a book for astro photo's

[JonathanC]

I dont know how to say thank you enough. You guys are brill
Right I have got GIMP on my pc also down lowding a link a mate sent DeepskyStacker
I have never really used pp before (I know am a pain)but would love to do a star trail pic so please help
will use a D90 tripod and a remote if any one should be so kind as to take me step by step from shooting to after pp I would be buzzinig
may be some one could do a tutorial??? please help
rob

Sorry I'm late to the party, I missed this.
Check out Stargazerslounge.com especially in the Imaging, tips and techniques. This is an excellent forum for astrophotography, and they're a very friendly bunch of people.

[Nass]

Hello Bucketman,

You don't need a special camera to do startrails. This is a tutorial (ish) I put up on Flickr some time ago, hope it helps.

[JonathanC]

Rob, I hope you don't mind but I took out the light pollution from yor image.


Hope you can see this.