Star Trails Software and Imaging

[Grimmeister (Anthony)]

Hi Everyone,

A bit of a general question; I was taking some images on the Canon 600D with the 18-55 mm Lens for some star trails. While I got "a" result for my test I was wondering if anyone could chime in with some advice? as I have seen some killer star trail shots and would liek to work towards this level.

I took the exposures and saved them as RAW on the camera, by the time I converted these to TIFs for processing in Star Trails each frame was 100Mb in size and took ages to process. Would I see any real difference if I just take the images as Large JPegs on the camera and process direct into Star Trails without any conversion??? I know I lose some quality with JPeg compression but would be alot easier to process.

Also when I took the images there were some tree's in the foreground, once these were layered together I found the tree's had a type of gradient to them despite them not moving much during exposure is this normal for objects in the foregroud to do this when processed??? as it makes it look really rubbish? I suspect I may need to overlay one frames exposure back over the final star trails output to remove this but there may be an easier way???

Lastly I found the star trails looked more like dotted lines rather than a streak. I suspect again this is due to the pause between frames can anyone confirm and suggest a good setting?

Thanks in advance.

Anthony

[iceman (Mike)]

Post the images!

[JB80 (Jarrod)]

The Star Trails software definitely works better using jpegs, assuming you are using startrails.de that is. I'm not certain how much difference you would see to be honest, it might just give you a bit more in processing later?
Still there is no harm in trying both to compare, most people just use jpegs though.

Can you post a pic to show what you mean about the trees?
It is normal for them to slightly blur, I suppose there are a few ways to deal with it like you said you could add a single frame after or you could take a single frame at the start with the trees lit up and add that to the stack.

And yep I would say that the dotted line is from the pause between shots and is another good reason not to use RAWs with startrails as the camera takes time to process each image and that time is long enough for the gaps to be created. It could be down to your memory card and the time it takes to write the image to it using RAWs.
Also it could be that you have some settings like "Auto noise reduction" still turned on in your camera, all these settings should be off as again it takes time for the image to process.
Normally I just set my camera to jpegs and leave the remote shutter on continuous and go do something else.

Once you have it sorted then you can go back and try with RAWs but to get the hang of it it is easier at least to use jpegs.

[Octane (Humayun)]

Stick with RAW. You have far greater exposure latitude and flexibility with fixing the files if they're under-/over-exposed. Not to mention fixing white balance -- white balance can potentially set the tone of your image from being cold and stark to warm and inviting.

If all the image(s) are ever going to be used for are web resolution (i.e., not for printing), then, downsize them to 1280x on the longest edge (or, whatever you prefer) and then output as 16-bit TIFFs.

I don't see there being any other way around the gradient in the trees, than to blend in your trails image with a static image of the foreground.

Try not to leave more than a 2 second gap between exposures. The length of your exposure is going to be dependant upon how bright the sky is, the phase of the Moon and local light pollution. Ideally, you want an image that peaks somewhere between 1/3rd to 1/2-way across the x-axis of the histogram when reviewing the image on your camera's LCD.

Hope that helps.

H

[Grimmeister (Anthony)]

Hi Everyone,

Thanks for the responses, I will have a play with JPEG and TIF's (at a smaller size) and see if I can see any differences.

Attached is the image I took as a test and I have circled the parts that go a bit weird.

For the Camera speed I suspect the timer setting was too long between frames (I had 5 seconds after looking at it again), the SD card in the camera is one of the fastest I could buy at the time so I don't think this was the problem But thanks for the idea as it always helps to rule these things out.

Anyway, red circles aside this was my first star trails from my backyard.

Cheers

Anthony

[Octane (Humayun)]

The smearing in the trees is a result of them moving about between exposures. It's combined the pixels using a median or lighten combine algorithm. What's happening is that you're getting 50% tree and 50% sky (or, movement) summed together.

It's a pain in the butt -- it helps to have trees further off in the distance when you compose so that their movement is minimised.

But, yes, combining an exposure where the trees didn't move, with the trails image should be a very simple exercise to do.

H

[Hakka (Lincoln)]

Originally Posted by Grimmeister

For the Camera speed I suspect the timer setting was too long between frames (I had 5 seconds after looking at it again),

Use 1 second intervals, 5 is way too long. SD card speed wont be an issue with startrails.

Do you have a version of photoshop CS? It will stack RAW images, and you have a lot more control over the stacking process. For example you could use masks to minimise the issues with the trees, you'd pick one shot with no tree movement and mask out the rest.

[Grimmeister (Anthony)]

Hi H and Lincoln,

Thanks for your guidance on this , now I understand what is happening I will have a play and see what I can do to tidy it up a bit .

Now for a nice place to spend an evening taking pictures without clouds.

Cheers

Anthony