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Smartphone instead of webcam?

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#1 AstroTripper

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Posted 27 January 2013 - 03:08 PM

Was wondering if it's possible to use an Android powered smartphone instead of webcam for some cheap and basic planetary imaging. And if this would even make any sense?

I'm new to this stuff so bare with me, please. First of all, I have not had any experience with webcams, so I'm not sure what their capabilities are.

That said, I'm thinking that two very important factors would be image quality and access to raw (or at least uncompressed) data. How does that look for those cheap webcams? Compressing video looses o lot of data, but I heard you can hack some of them to output raw data, is that common?

Do you think there might be any advantages to using a phone vs webcam? I'm thinking mounting might a bit tricky, but on the other hand, no need to carry a laptop.

What do you think about this idea?

#2 Tapio

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Posted 27 January 2013 - 03:21 PM

Add a fps (frames per second) number which is pretty important. Webcams are good in that department and can do raw imaging which I think smartphones can't.
And the 'lens' in smartphones is pretty useless in planetary imaging.
A small webcam without lenses and small (SSD)memory and screen (for focusing) would be nice to have ;).

#3 shrevestan

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Posted 27 January 2013 - 06:44 PM

I've seen presentable images made with iPhone video converted and stacked with Registax so it can be done.

#4 SteveRosenow

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Posted 27 January 2013 - 06:48 PM

If you have an Android smartphone with a high resolution output, I see no reason why it can't be done.

#5 Toxic Coolaid

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Posted 27 January 2013 - 07:13 PM

Here's a way to mount it.

http://www.telescope...escope-Photo...

#6 AstroTripper

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Posted 28 January 2013 - 05:09 AM

Ok, so mounting is not a problem, there's some work involved in both cases, but it's possible. Great.

Turns out I have a built-in webcam in laptop, completely forgot about it's existence. It's VGA only, but to my surprise, it can capture uncompressed video at 30fps. But can you do the same on cheap USB webcams at higher resolutions than VGA? I don't think 30 fps at FullHD would be possible, due to limited bandwidth of USB.

I did some testing for Android devices that I have, and here's what I can do besides shooting compressed photos and videos:
- capture uncompressed preview stream, resolutions vary greatly, my LG phone can only do 720x480, but my tablet can go up to FullHD, so we're talking about 1080p uncompressed image data at few fps
- automating process of shooting full resolution photos with maximum possible JPEG quality, but I'm not sure at what fps that would be possible

I'm curious how the quality comparison would end up. I'm thinking of setting up a small test scene and doing some tests.

Add a fps (frames per second) number which is pretty important. Webcams are good in that department and can do raw imaging which I think smartphones can't.


In terms of FPS alone, smartphones can have an upper hand. New ones can shoot FullHD videos at 30fps. But that's compressed. And you're right, smartphones can't normally save RAW or even uncompressed images or video.

And the 'lens' in smartphones is pretty useless in planetary imaging.


Is there any difference? Isn't it all the same *BLEEP* in webcams too? Actually, I would even expect that a 'lens' in smartphone to be of better quality than in webcam.

A small webcam without lenses and small (SSD)memory and screen (for focusing) would be nice to have ;).


I guess for someone with knowledge in electronics, that would be possible to do. There are off-the shelf cmos sensor modules vailable, that you could probably hook up to Rasperry Pi and do some cool stuff with it.

#7 Tonk

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Posted 28 January 2013 - 06:33 AM

When I use my webcam the lens is entirely removed (just unscrewed and removed) and the scope or eyepiece become the "lens" depending if prime focus or projection

#8 AstroTripper

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Posted 28 January 2013 - 07:37 AM

When I use my webcam the lens is entirely removed (just unscrewed and removed) and the scope or eyepiece become the "lens" depending if prime focus or projection


I see, that makes sense, one obstruction less in the path of light. +1 for webcams I guess.

What resolution (compressed, uncompressed?) and capture speed can you get with your cam?

#9 Tonk

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Posted 28 January 2013 - 09:25 AM

Its a web cam from 8 years ago - you don't want to know!

one obstruction less in the path of light.


This actually isn't the point - its to do with setting the focal point and the focal length of the optical system. You have the choice of eye piece projection, afocal and prime focus set ups.

If you can't remove the webcam lens then those choices are reduced to just eyepiece projection - which is OK most of the time for bright planets

#10 mmalik

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Posted 28 January 2013 - 09:29 AM

Was wondering if it's possible to use an Android powered smartphone instead of webcam for some cheap and basic planetary imaging. And if this would even make any sense?


Not exactly, at least not in 'proper' astrophotography sense. Yes you may take eye piece projection kind of videos but that's not what a somewhat serious astronomer will do. Astro web cams can take long exposures which makes them what they are, long exposure video devices (Edit: for DSOs). I am not recommending that you buy a proper astro web cam per se but you are not on the right track with this approach. Anything prime focus is what you need to look for. Some DSLRs have video crop mode that you could use to take prime focus videos of planets that you can later extract, stack, process, etc. Read appendix 'F' of this... doc if it helps. Thx

#11 Tapio

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Posted 28 January 2013 - 09:41 AM

(HD) resolution is not so important.
Jupiter and Saturn fit nicely in 800x600 or even 640x480.
Moon and Sun are bigger and benefit more resolution.
My ASI120MM can do the following:
1280X960@30FPS
640X480@70FPS
512X400@80FPS
480X320@100FPS
320X240@130FPS

#12 WayneJ

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Posted 28 January 2013 - 10:05 AM

Yes you may take eye piece projection kind of videos but that's not what a somewhat serious astronomer will do. Astro web cams can take long exposures which makes them what they are, long exposure video devices.


That's completely inaccurate with regard to planetary imaging (which is the point of the OP's question.) Planetary imaging uses high speed video capture, not long exposures.

Just as a note that "web cams" are no longer used by most planetary astrophotographers and the phrase "web cam" is looked upon nowadays with a great deal of disappointment. I use a $700 industrial machine-vision camera running on a Firewire 800 bus that captures full-frame (644x488) at up to 120 fps. Calling that a webcam is like calling a Canon 5D an "instamatic". Since "webcams", i.e., those things people use to see each other doing odd things on the internet, are no longer used by those in the planetary photography field (except for the occasional hold-out that's still using the original Neximage or Philips SPC900), the correct term is "planetary cam".

In response to the original question -- yes, you can use eyepiece projection to capture images you see through the eyepiece. I wouldn't bother disassembling my phone to use the camera in it for planetary photography -- the resulting image will never be very good, so there's no point in ruining an otherwise useful camera.

The problems with phone cameras and "web cams" is that 1) they use very, very small pixels and CMOS sensors; 2) they run at relatively low framerates and you cannot control image size (you don't want or need to capture in "HD" mode as most of the pixels will be wasted); and 3) they will almost always have a built-in IR filter that will significantly decrease the amount of light reaching the sensor, making for dim, noisy images.

Can you take a picture of a planet or the moon using a phone camera, through a telescope? Sure. It just won't compare those taken with planetary cams or images taken through large apertures with monochrome cameras and dichroic filters.

Also, a much better forum for this question is the Solar System and Planetary photography forum. The users there can provide you with many examples of images taken with a wide variety of equipment.

Finally, for planetary imaging, you want to collect many thousands of frames of video and then use sorting and stacking software to combine them for post-processing. Using a video stream from a webcam still leaves the problem of converting the captured video into a format that this software can use.

Here's an example of a Jupiter image from just past opposition in December. This was taken from my observatory designed and dedicated to planetary imaging and in good (although not great) seeing. The image is an RGB composite of about 5000 (of 10000) frames per color channel

http://exosky.net/ex...335ut_wjaesc...

Regards,

Wayne

#13 mmalik

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Posted 28 January 2013 - 10:17 AM

Yes you may take eye piece projection kind of videos but that's not what a somewhat serious astronomer will do. Astro web cams can take long exposures which makes them what they are, long exposure video devices.


That's completely inaccurate with regard to planetary imaging (which is the point of the OP's question.) Planetary imaging uses high speed video capture, not long exposures.


I was referring to DSOs there (NOT planetary). Thx

#14 WayneJ

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Posted 28 January 2013 - 10:41 AM

I was referring to DSOs there (NOT planetary). Thx


It's still incorrect. Most "webcams" or planet cams cannot take long exposures. Without monkeying around in firmware, most cannot take exposures longer than 1s. You might be thinking of the Malincams that are specifically designed for extended-exposure "electronic eyepiece" use.

#15 mmalik

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Posted 28 January 2013 - 11:02 AM

You might be thinking of the Malincams that are specifically designed for extended-exposure "electronic eyepiece" use.


Correct. Thx

#16 AstroTripper

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Posted 28 January 2013 - 12:53 PM

Just to be clear, I was in no way suggesting replacing dedicated astrophotography cam with a smartphone. I was just wondering if I could use a phone instead of a cheap webcam+laptop combo to get comparable results. You know, just to play around, without spending hundreds of dollars.

I did a quick and dirty test app for Android, and I can capture uncompressed image data in 720x480 at 3-4 fps with my phone. I could probably optimize it and maybe reach 8-10 fps. More powerful phones could probably do better. Still, a far cry from even basic 30fps some cheap webcams allow.

BTW Wayne, very impressive Jupiter image. And 5000 frames per channel? I did not realize how much data goes into creating a single image.

Thank you for all the replies. To sum it up, it seems to me there's not much advantage to using a smartphone over a cheap webcam, except for maybe less junk to carry around. I'll probably try it anyway out of curiosity, just to see what's the quality like. That is, if I ever see a clear night sky here :mad:

#17 WayneJ

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Posted 28 January 2013 - 01:20 PM

I was just wondering if I could use a phone instead of a cheap webcam+laptop combo to get comparable results. You know, just to play around, without spending hundreds of dollars.


I think the answer you're looking for is YES! You can certainly try and snap shots with the phone's camera and you SHOULD do so before investing further. Take some pictures of planets, the moon, etc. See how far you can push it and what you enjoying taking pictures of... then decide if and/or when you want to plunge deeper.

I took my first "astrophotos" of the moon by putting a VHS-C camcorder up to the eyepiece of my old Criterion 6" newt and recording. From there I broke-open a Connectix "QuickCam" (around 1994?) and used the sensor in that to take monochrome, 7-bit images of Jupiter at 5 FPS and manually stacking them. Who knows what you'll do with your smartphone... but everyone starts somewhere and never hurts to try (just don't do anything to your phone that can't be "undone").

Regards,

Wayne

#18 Tapio

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Posted 29 January 2013 - 04:27 AM

I did a quick and dirty test app for Android, and I can capture uncompressed image data in 720x480 at 3-4 fps with my phone. I could probably optimize it and maybe reach 8-10 fps. More powerful phones could probably do better.


This sounds interesting if you could make app for uncompressed video.
What phone did you use ?

#19 AstroTripper

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Posted 29 January 2013 - 07:42 AM

Thanks Wayne, I will definitely by trying, just out of curiosity.

This sounds interesting if you could make app for uncompressed video.
What phone did you use ?



LG P920, also known as Swift 3D or Optimus 3D. I did a quick modification to my app today, and turns out that with just dumping the data to sd card, I get ~10fps, and I still believe I could improve that. Now, this is far from getting 'uncompressed video', it's just a bunch of image files encoded in YUV format. But it's not a problem, converting that data to whatever you need is pretty easy. I already did YUV->RGB conversion in the app, and with ImageMagick (on pc) you can pretty much output every imaginable format out there.

#20 AstroTripper

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Posted 14 February 2013 - 12:51 PM

Ok, I was finally able to test this idea. The results? Poor, very poor. Looks like it makes no sense with camera lens in place. Jupiter is just a tiny bright blip. Doesn't look like smartphone can replace eyepiece projecting the image directly at webcam's sensor after it's lens had been removed.

#21 merlin_four

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Posted 14 February 2013 - 01:01 PM

I got this shot of Jupiter through the eyepiece with my iPhone. Omni XLT 150, 2x barlow, 6mm Orion Expanse eyepiece, single exposure. Didn't even think of doing video, but I don't see why that wouldn't work. Just gotta have really steady hands :D

Posted Image

#22 AstroTripper

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Posted 14 February 2013 - 01:48 PM

Nice one. I tested with similar setup, only with 10mm eyepiece, which gives me x150 magnification, vs x250 of yours.

The thing is, when shooting video, the resolution is much smaller. So with 720p, this Jupiter would probably be just a few pixels in diameter. This is were modded webcam (with lens removed) has huge advantage. I guess I had no idea how much of an impact this has on the end result.

#23 Sean13

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Posted 14 February 2013 - 02:30 PM

I could be wrong, but I think that depends on the resolution of video you shoot. If you turn your video res down you may get better results. Maybe.

Also the video feature usually has a zoom. Crank it up as high as you can. This would kind of be similar to Backyard EOS capturing the 5x live view. The video will look *BLEEP*, but you might be surprised what kind of detail comes from stacking and sharpening it.

#24 Greg K.

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Posted 14 February 2013 - 07:49 PM

I could be wrong, but I think that depends on the resolution of video you shoot. If you turn your video res down you may get better results. Maybe.

Also the video feature usually has a zoom. Crank it up as high as you can. This would kind of be similar to Backyard EOS capturing the 5x live view. The video will look *BLEEP*, but you might be surprised what kind of detail comes from stacking and sharpening it.


Since all smartphones that I know of use digital zoom, you won't really gain anything by zooming.

#25 Sean13

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Posted 14 February 2013 - 09:05 PM

True, but the Canon live view 5x is also a digital zoom and still does a better job then full frame video capture for planetary. Technically you won't be gaining any detail, but you will get a larger scale image that you can actually look at.

This is just a guess as it seems to work on my Canon 450d, but I have no experience playing with an eyepeice and cell phone cam.






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