Star trails

I've been meaning to try this for a while and got around to my first try this evening.
Not a great location in our garden due to light pollution but I've proved it works.

(f13 @ISO400 14minutes with lens at 17mm)

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I've found that too Woo when I tried to get shots of the ISS, but I was pleasantly surprised tonight as the time it took to save the image was only a few seconds with the new camera with a fast memory card.

 

Also been meaning to try this for a few years too..even bought a little plugin timer to do it with last year. Had a quick go the night before last and now waiting for clear skies to get out and have a "real" go at it.



Mine looks like interupted lines because I was manually pressing the shutter and the gap between each was too long. This is 5 by 30 secs exposures.

Steve...

 

It's worked pretty well Steve and you've actually got some added data in the image as it's possible to time the passage of the stars using the breaks.[hr]

Just had a thought Woo (and probably my only one of the day!:-/). If you turn off any in-camera processing such as long exposure noise reduction it should reduce the time it takes to save. And I think (though I'm not certain) that shooting RAW rather than jpg will reduce save time as he camera isn't having to convert the image from RAW to jpg.

 

I think for the longer exposures your using, you'll probably need the noise reduction. Filesize should not be an issue here when saving, the camera is designed to save at its megapixel size, jpeg or RAW it can only capture those alotted pixels...and no more.

My shot above was taken in jpeg as it was just a test, next attempt willl be in RAW and then converted to 16bit tiffs, combined and saved out as jpeg. Which method are you using for combining?

Steve...

 

Interesting thread guys.
Someting to try some time
Thanks

 

Yes it does take longer than a jpeg, but all cameras have a built in buffer to account for that, thats why many cameras can allow you to shoot in "burst mode", for example the Canon 550d, boasts 3.7 frames per seconds ( I believe the buffer is around 200mb - but dont quote me on that).

Anyway, all I am saynng is that taking one shot (jpeg) at however long it is should be no longer that a shot taken at 1/4000. Which is what I assumed you and woo where talking about at the start of the topic...unless I have got hold of the wrong end of the tripod.

Steve...

 

I think I've now got the answer to Woo's original "complaint" that he found long exposures took a long time to save. It brings me back to what I first said about turning off noise reduction.
There are two forms of noise reduction with Canon cameras, the first - high ISO noise reduction, appears to be performed by the sensor and is instant, and in any case is not needed for star trails as high ISO isn't really required. This second form, and the one most likely to be employed in astro photography is - long exposure noise reduction. LEN as far as I can discover is performed in-camera (if selected in the menu) and is done by taking a 'black frame' of equal duration to the shot. Thus after the shutter closes after a 15 minute star trail shot, the camera records another 15 minute shot and it's this second 'black' shot that appears to be lengthening the image save time. (But it's not in fact saving an image it's taking an image)
The purpose of the 'black frame' is to provide a reference 'clean frame' that the in-camera software uses to subtract noise from the primary shot.

Simples?:-/

 

I have neither of those two NR on my canon, so settle for short 30 sec exposure and combining either in dedicated astro software or simply in photoshop...and I also use a black frame too.

I was looking into another tutorial the other day and it was talking about averaged blacks and flats and/or bias shots...it was about then that I fell asleep...lol

Steve...