Advanced - Stars' traces around the circumpolar.

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EDIT: I've created the chatroom #Phototalks (chat.deviantart.com/chat/Photo…) to talk about photography tips, tricks, doubts, and all these things. Also some general talking is allowed.  I'll probably be there if you join.
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Okay so, this complicates a little bit. Because of the Earth's rotation, when we put a long exposure time all the stars appear moving, excepting one: the Polaris (the circumpolar star), and, in the picture, the traces of the rest of the stars will turn around this Polaris star. The objective,then, will be getting results like these: marioguti.deviantart.com/art/L…

You'll need a tripod, a DSLR camera and a remote control or delay trigger.

I'll post the different steps I follow when I make these kinds of pictures:

1 - I find the Polaris (okay, I'm not an astronomer, so my mobile phone does so for me, there are Apps for iPhone and Android like Google Sky Map, with which it's easy to find it).

2 - I compose the picture having in count where the Polaris is.

3 - I focus, most times using hyperfocal rules (I'll talk about it soon, don't worry, but you can have a look at this if you're impatient to try it: www.cambridgeincolour.com/tuto…). It's strongly reccomended to use them because we must get the infinite focused, if not the star traces won't look too good. There are Apps which calculate the hyperfocal distance (basically, at this calculated distance you must put yourself with a lantern and focus)

4 - I calculate the right exposure time, for that, I use the reciprocity rule (I'll also talk about this). There are also Apps which calculate this. Basically, you calculate the right exposure time for high ISO levels and then the App calculates, according to these results you got for high ISO, the right exposure time for ISO 100, or ISO 200 or whatever ISO you want to use (ISO 100 reccomended, since you'll use long exposure times and it's not neccesary to turn it higher).

5 - I turn off the noise reduction so that it doesn't take long processing. Why so? Because I'll make 2 or more pictures and then I'll merge them, so, if we don't want the traces to be divised by 2 or more parts, the time between shots must be the lowest possible.

6 - I make 2 or more pictures with the same settings. (you can also make only one but more noise because of long exposure will appear. Plus some cameras have time limitations.

7 - I merge them using a software called Starstax, which unites lights but doesn't double the exposure or anything. It detects the highlights (in this case, the traces) and unites them. To enter the pictures into this programme, they have to be in .TIFF format, so you can change the raw files into .TIFF when you export them through Lightroom, or with other softwares like Photoshop.

8 - I touch the last things in Photoshop, and that's all!

EXIF data and other details for this photo (marioguti.deviantart.com/art/L…):

2 pictures of 1182 seconds and ISO 100, and another one of 30 seconds and ISO 800 to get the man with the lantern. The 3 pictures at f/4 and a focal lenght of 10mm. Merged with Starstax.

Okay, this can get complicated at first, but once you make it once or twice this gets easier ;) If you try it, tell me about the results you got, problems, or others, please! I want to know :)
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barracudawarlock's avatar
Nunca lo lei mejor explicado!
Felicitaciones!
Vere si en estas vacaciones puedo hacer algo parecido.
No entiendo bien que es lo que tengo que buscar cuando te referis a Polaris. Es una estrella? Funciona esto en el hemisferio sur? tengo que buscar otra estrella? Aaarg! jajaja