geekinthesticks
Posts: 97
Joined: Fri Feb 08, 2013 7:22 pm

Star Trails

Wed Sep 11, 2013 2:54 pm

I have had great fun using my Canon DSLR to take a series of still photos of the night sky, then either stacking them, or creating a time lapse video. I want to do something similar with my Pi i.e. take a series of stills of the night sky over several hours. Has anyone tried doing this? I see there are are "night" and "verylong" exposure options. Any suggestions as to which I should try?

I have just setup my Pi in a weather proof box. I can control the camera via WiFi and have an external power source, so I can move away from sources of light pollution. Of course as soon as I had got it setup up the weather closed in and it looks as thought there won't be any clear skies for a few nights :|

Ian.

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Hove
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Location: Cotswolds, UK
Contact: Website

Re: Star Trails

Wed Sep 11, 2013 5:12 pm

www.pistuffing.co.uk - Raspberry Pi and other stuffing!

Johnny5C
Posts: 82
Joined: Thu Apr 18, 2013 3:32 pm

Re: Star Trails

Thu Sep 12, 2013 11:19 am

Hove, I’m not sure that what the OP was hoping for.

I too have boxed up my camera and power source to make a deployable time lapse rig, and after a few goes my eyes have turned upwards. I have been looking (admittedly not too hard) for someone who has posted examples of exposure settings for photographing the night sky.

My plan now is to just get out there and have a play with various camera modes and see what works best.

I was hoping to have an exposure setting that would let me open the shutter for hours to capture star trails, but I don’t think this is possible with a digital sensor. Making a time lapse should work, but the exposure needs to be set correctly to actually see the stars.

I’m not a camera or pi expert, so was hoping that someone might have a command example for setting the exposure?

Niall101
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Joined: Fri May 10, 2013 2:24 pm
Location: Clinterty Observatories, Aberdeen

Re: Star Trails

Thu Sep 12, 2013 11:53 am

Hi Johnny5C,

From my past experience creating an "AllSkyCam" using a dedicated AstroImager (Meade DSI camera and 175-degree FOV lens), I found that the best (or, at least, most 'pleasing') results were obtained using 10-second exposures, and then post-processing to turm the sequence of images into a time-lapse video ( a frame rate of 10fps then giving 36 seconds of video per hour of time-lapse captured).

However, the biggest problem I think you will face (and I hope to stand corrected) is that there is no (easy) way to request 10-second exposures from the PiCam. You can ask for one exposure every ten seconds, but that is not the same!

There are webcams out there that can provide ten-second exposures - and some can be fairly easy to modify to be able to provide longer exposre times than that. But - you then need both the necessary drivers for the camera (typically connected over the USB interface), and you then need the high-level commands to control the image acquisition in the first place.

You are also going to have to think about the PiCam lens itself - it is not going to give you a 'wide' field of view, and it is not easy to remove and/or replace. You could try some of the smartphone lens 'adapters' that can be found on the likes of eBay - but I have no experience with these, and so cannot comment on final image quality.

I can't help you much further - I have barely been able to use my Pi since I bought it - specifically with astro-imaging in mind - because I have spent the whole summer carrying out long overdue repairs and modifications to the rolling roof of my observatory ahead of the dark skies of winter that lie ahead of us (bringing with them the promise of a very bright comet, expected to be easily visible throughout November/December).

Hopefully there are others who have tried this, and who will pass on their experiences and suggestions . . . . . .

Cheers,
Niall
Clinterty Observatories
Aberdeen, SCOTLAND
Scatch-built BBC B in 82: blank PCB+scavenged plastics& PSU. Sinclair Calc & ZX81 kits in 74&82. PONG (AY-3-8500) in 77. 1st PC in 89: 386/25+387&10MbHDD. Have previewed pictures with my PiCam. I'll maybe save one next week (new to Linux)!

geekinthesticks
Posts: 97
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Re: Star Trails

Thu Sep 12, 2013 12:27 pm

Thanks for the feedback. With my Canon I use exposures if something like 20secs (data not to hand at the moment), which gives good single image results. Like you said there is no timed exposure mode with the Pi camera. I as just wondering if anyone had any experience of trying this sort of thing with the Pi camera. I guess I'll just have to wait for a clear night to try it myself.

Ravenous
Posts: 1956
Joined: Fri Feb 24, 2012 1:01 pm
Location: UK

Re: Star Trails

Thu Sep 12, 2013 12:35 pm

I wonder if you could shoot video instead and process the frames in "avistack" (a free product known to amateur astrophotographers). I am guessing there will be a lot of sensor noise, so stacking software will be needed anyway...

Also - you could shoot some night-time stree or countryside scenes on a cloudy night just to test the low-light behaviour. Just a thought.

Johnny5C
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Re: Star Trails

Thu Sep 12, 2013 3:45 pm

Thanks Niall et al.

What happens if you stack a moving star field image? Would the trails appear?

If (for instance) i could set my cam exposure to see the stars correctly, and did a couple of hours of time-lapse, but stacked the images rather than making a movie, would the trails appear?

I’m hoping that the exposure can eventually be manually set. I have no idea if this is actually possible though.

I have a nice little time lapse cam in a box, but I’m struggling to think of where to deploy it!

Ravenous
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Location: UK

Re: Star Trails

Thu Sep 12, 2013 3:50 pm

Johnny5C wrote: What happens if you stack a moving star field image? Would the trails appear?
On the one time I've tried this it worked fine. You lose a bit of the frame at the sides, but the bit that's common to all frames gets stacked and it helps to smooth the noise. (This was a DSLR on a fixed tripod and 100mm lens, so a fairly narrow view.) As long as the software identifies the stars and matches tehm up in all frames, it should work.

I guess for the raspi, if there are no manual settings, just let it snap away at stills (or try video) and see what happens... you might be able to tweak the exposure of the resulting image later...

jemtaylor
Posts: 20
Joined: Sat May 25, 2013 1:37 pm

Re: Star Trails

Thu Sep 12, 2013 4:48 pm

I think you've missed the point a bit there.... you can't stack the images and align on the stars because the object of the exercise is to photograph star trails. So if anything alignment is *not* what you want.

cheers

J

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jbeale
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Re: Star Trails

Thu Sep 12, 2013 6:14 pm

My experience with the R-Pi camera at night is that the frame is simply black. If you crank up the gain, then it's noisy black. But maybe with enough frames averaged, and some dark frame subtraction, you can get somewhere.

The RPi camera currently does not take exposures longer than about 1/20 second. The '-ex verylong' exposure setting does not and never has worked. Oddly enough, '-ex night' did at one time allow longer exposures (up to 1/4 second), but with some update about a month ago it seems to have become disabled. See also: http://www.raspberrypi.org/phpBB3/viewt ... 43&t=52546

geekinthesticks
Posts: 97
Joined: Fri Feb 08, 2013 7:22 pm

Re: Star Trails

Sun Sep 15, 2013 12:54 pm

Thanks for all the feedback. I tried last night, which was the first clear night for a few days. The result was that I got a load of black frames:) So, back to lugging around the DSLR. I wasn't too surprised, as I didn't really expect the camera to work well at night time. However, it's still going to be very useful for time lapses in daylight, or dusk.

I have almost finished the web server part of my project. I can connect to the Pi, which is acting as a WiFi hotspot. I then open a web page, which allows me to take a picture and preview it, so I can get the framing correct. Finally another button on the web page allows me to start and stop the time lapse script. I can get around 7hrs of uptime using a 7000mAh battery.

Johnny5C
Posts: 82
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Re: Star Trails

Mon Sep 16, 2013 4:24 pm

Good work geekinthesticks.

I have a pi/cam and a 7inch 12v LCD coupled up to a 12AH SLA.

One of my shell scripts calls up a 6 hour TL with 10s interval, and I turn the screen off once its running.

Im thinking about changing to one of Texy's small touch screens, as the mouse takes me over the power budget of the small 12V to USB adaptor i have. It boots fine, but when i start up the cam it reboots.

The texy screen will also free up the room for a small charge controller, so i can plug in a solar panel for longer runs.....

Its all wrapped up in a small PELI case to be deployed... Just in time for the weather to take a turn for the worst...

ranagazoo
Posts: 6
Joined: Sat Mar 23, 2013 1:43 pm
Location: Devon
Contact: Website

Re: Star Trails

Mon Oct 14, 2013 8:14 pm

After a couple of months of purchase the PiCam I have just got round to installing it and taking a picture and video. Uber excited!

I was wondering if you might be able to post some of your samples of the what you have done? I was hoping to get some star trails with the Pi but read it is not the best option, it would be great to learn more about the web interface to see the pi camp. I hope to do a time lapse work.

Cheers

Steve

Johnny5C
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Joined: Thu Apr 18, 2013 3:32 pm

Re: Star Trails

Tue Oct 15, 2013 11:49 am

Steve,

Not star trails, but my first real time lapse. Its a view of south dartmoor from my parents house.

(I see you're in Devon)

https://www.youtube.com/watch?v=V3iwHSzVpVo

Still working on night time lapse. ISS is over head this week. I will see if my pi cam can "see" it....

John.

radiator
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Re: Star Trails

Thu Apr 10, 2014 1:41 pm

Sorry if it's uncool to reopen a long-dormant thread, but I was wondering whether there has been any progress on this topic. For example, I understand that there have been recent firmware updates that may affect certain camera modes, and wonder whether the new firmware may make capture of star trails any better.

I have done only limited experimentation based on other threads about "long exposures", but my results were disappointing at best.

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