DIY all-sky cam?

[ixalon]

I've actually measured yesterday how much current the LX modded SPC900 draws. Here are the results:

http://stargazerslounge.com/diy-astronomer/148315-spc900-lxmod-yesyes-style-9.html#post2027811

Nice measurements! Interesting, draws more than I expected, but still leaves a some room to play with.

[yesyes]

At last a bit of a gap in the clouds. I can now confirm that the LX modified SPC900 with that not quite 180deg lens does pick up stars!

This is an 11 sec exposure. The circled dots appear to be dead pixels but the rest is stars.

[Gina]

How did you get the 11sec exposure frame from webcam to here, Chris?

[yesyes]

it's a SharpCap screenshot

[yesyes]

Jupiter moving into view (bottom right).

I just noticed what looks like scheduled captures in SharpCap. I think I need to explore the options a little more. Maybe it already does what I need to make these images available on a website.

[Gina]

it's a SharpCap screenshot

Ah right I'll give it a try sometime.

[Reggie]

nice shot Chris It's got me realllly thinking now, obviously a pan and tilt servo setup for an all sky cam = an alt/az mount in telescope world, I'm starting to think it should be relatively simple to build a miniature wedge to make it into an EQ mount and build the smallest goto mount ever.

[yesyes]

In that image Jupiter is just under 40 degrees up in the sky. So the camera goes down to about 35 degrees above horizon in the longer dimension of the sensor. That would make it a 110 degree viewing angle.

[yesyes]

Here is an image of clouds moving in.

I would say it is usable at night as a cheap solution but doesn't have a all-sky view. Success but not quite as good as expected.

Thanks for the idea, Michael:D

During the day I don't get good pictures though. It seems the sky is too bright. I only see the branches in the field of view, the rest is a featureless grey or white. It might be a focus problem. I focused the camera lens indoors. But it's hard to get to and try now that it's installed on my shed.

[Horwig]

Silly idea, why not mount the sky-cam on the telescope mount, and bias its view in the prevailing wind direction, and then at least it should give some prior warning of incoming cloud.

Huw

[Gina]

I don't think the focus can be out because it's showing stars alright. I think it's overloaded by the light.

[yesyes]

Good point .. ;-)

[RobertCL]

So I've been following this thread with some interest because I've had a modified Philips webcam for some time now and it's been sat around doing nothing much and I've always thought that some kind of all-sky camera would be nice to have.

So here's my effort made from what I had previously along with the embedded USB hub and USB <-> Serial convertor ideas from SPC900 mod yesyes' thread.

Last night I stood it out on the patio and ran a long USB cable back into the livingroom. You can see my rather subtle clingfilm round the plugs approach to protecting the USB connection from the weather.

I left SharpCap running overnight (from about 6pm -> 7am) capturing 30s exposures and here is the resulting video (creating using mencoder on linux [ mencoder "mf://*.png" -mf fps=30 -ovc lavc -lavcopts vhq:vbitrate=1500 -o movie.avi ]) :

And a single frame - roughly north is left, east is down, south is right. The bright sausage just over the trees on the right is Jupiter just coming into view.

So here's a list of issues:

- "Forgot" to take a dark frame so there are annoying blue spots on the image. Even if I had taken one, I'm not sure what software I could use to subtract it from all the .png files I ended up with before combining them into a video. Also, there must be some way to take the data I've got and infer a dark from it, it's really obvious which pixels need to go! I think I've managed to create a dark in Photoshop from the frames I took, but I can't think how to subtract it from all the images I've got - doing it in Photoshop leaves black holes in they sky (rather than blue holes!) because the sky background in the images isn't totally black.

- Exposure. I set it at 30s, 20 (or 30?) for the gain after some messing around. Really you need some software that allows the settings to change over time, then it could run during the day as well and get all those lovely clouds going over! However to do this, I think I'd need to flick the "long / normal" switch back to normal (which is a physical switch on mine) and switch the camera back to full auto mode - hence "better"(*) software required. (* - SharpCap is already superb but I also think that a sky camera needs some custom software)

- Moon. Spoiled it rather last night, but thats not too bad I guess.

- Light from the house was reflecting on the dome at the start, until I moved a planter around to block the light - you can see it appear near the start of the video. Could be solved by moving the camera away from the house, but they you need a longer USB lead at which point my camera stops working. So instead you need a computer "outside" (or in the shed), but I don't have power in the shed, so ....? Some kind of very low power PC running from a 12V battery maybe...

- The dome has misted up this morning, not sure if it did last night, maybe the camera running all night kept it sufficiently warm.

- The field of view isn't "all sky" - it's not bad, but it would be nice if it were more than I've got, but I'm using a (I think) 2.1mm lens that I got from ebay. I've not managed to find anything wider on the few attempts I've made to look.

- Water / weather proofing. I've not tested it, but hopefully the copious amounts of glue-gun glue will be enough. I'm not really planning on leaving it out at the minute anyway.

- Some of the frames are "spoiled" due to the exposure being incorrect - you can see a few of these in the video where it kind of flashes. I should really have removed them before creating it.

- Would be nice if I'd thought to orient the camera so north was up!

- Given it was fairly clear last night, as 30s exposure doens't seem to have picked up many stars - though maybe the moon is to blame for that?

Probably some other stuff as well! I'll have to have another go with it when the moon isn't full because that spoils in a bit really.

Thats all for now!

Robert.

[msinclairinork]

Well done! I'm quite impressed by that!

Michael

[Gina]

Great stuff And very interesting - looks very promising I'll be having a go at it later - got an obsy to finish first

[theodore]

YesYes - I've had very similar results to yours. The camera works great, but the big problem for me is the hot pixels, they swap it a bit and there is not software for subtracting dark frames on the fly that I can find..

I have got a bit more FOV by using an old wide angle lens as the 'window' in front of the cam one - I did this because I don't have a dome.

Theo

[ixalon]

Looks great! Should have mine up and running next weekend. Fingers crossed!

Edit: I've ended up writing custom software. I'm using a QHY5 and bundled software doesn't cut the mustard. The plan is to use both dark frame subtraction and the dark pixels on the sensor to remove noise. Also hope to implement auto-gain control and meteor detection... This may take some time!

[RobertCL]

So I left it out again last night to capture the clouds and here is the result; a few glimpses of the moon and a few stars, but mainly clouds and hot pixels!

I started off with 30s exposures, but it wasn't capturing and details on the clouds, just uniform white, so I switched to 15s exposures about half an hour or so in (you'll notice the clouds slow down). Not sure why it's a bit green either.

Same timings as the previous video roughly, ran from about 5:30pm -> 7am until it I got complete white out.

Interestingly, I'd left the camera out all day but not running and when I first turned it back on at about 5pm the dome was obviously misted up because everything looked blurred and out of focus. However after about 5 mins it cleared, so I don't know if that means that it generates enough heat when running to keep itsself clear or whether it was just a coincidence. Though I've never seen my telescope optics clear themselves when they get dewed up, so I'd like to think the camera running generates enough heat to keep the dome clear.

Better go and check that rain didn't get into it now!

Edit: Oh, and I turned the camera round so north is now up, south is down, etc.

Robert.

[Gina]

Thanks for posting that I love time lapse

[msinclairinork]

^^DITTO^^

Well done!

Michael

[ixalon]

Finally got my first frame! Can just make out Orion at around 4-5 o'clock.

Some problems:

• Sensor noise - I'll have to take some darks
  
• Glare from bright light sources - I'm going to have to shield more of the dome from bright light sources around, they cause internal reflections in the perspex dome I've put some tape over the worse offenders, but could do with some more.
  
• Focus issues - I'm using a 1.4mm f/1.4 lens (Fujinon FE185C046HA). At f/1.4 it only takes a few degrees turn on the C or T threads to bring the image out of focus. I've not found a set of adapters that will let me tighten everything up whilst maintaining focus.
  

[RobertCL]

Nice

You've got a much better field of view than I have. I really like the way you get the whole horizon in the image.

Internal reflections in the dome do seem to be a problem. I get exactly the same.

I left mine out again last night and managed to take some darks, so all I need to do now is work out a nice way to subtract them from all the images it will have taken overnight.

It seems that the Philips web canes will generate enough heat to clear dew from the dome, which is handy. Mine cleared itsself again last night.

[Gina]

Finally got my first frame! Can just make out Orion at around 4-5 o'clock.

Some problems:

• Sensor noise - I'll have to take some darks
  
• Glare from bright light sources - I'm going to have to shield more of the dome from bright light sources around, they cause internal reflections in the perspex dome I've put some tape over the worse offenders, but could do with some more.
  
• Focus issues - I'm using a 1.4mm f/1.4 lens (Fujinon FE185C046HA). At f/1.4 it only takes a few degrees turn on the C or T threads to bring the image out of focus. I've not found a set of adapters that will let me tighten everything up whilst maintaining focus.
  

Nice one

Are you still using a QHY5 camera? Unfortunately, I can't really afford one of those, at least not for some time, AP is taking precedence.

Regarding reflections in the dome, maybe you could erect barriers further from the dome so that the whole dome is shaded from the lights.

[ixalon]

You've got a much better field of view than I have. I really like the way you get the whole horizon in the image.

It's a pretty mad lens, quite pricey, but doubt I'd ever need to change it. On a 1/2 inch sensor it gives 185 degree FOV!

It seems that the Philips web canes will generate enough heat to clear dew from the dome, which is handy. Mine cleared itsself again last night.

My dome frosted over last night - we did have quite a thick frost, so I'm not too surprised, but makes me think a heater might be a nice addition. The dome was completely cleared and dry though by the time I went out to look at it this morning.

Are you still using a QHY5 camera? Unfortunately, I can't really afford one of those, at least not for some time, AP is taking precedence.

Yep, still using the QHY5 though it's not ideal. It's absolutely useless in the daylight with this lens (no automatic iris control) and even at 0% gain, and 1ms exposures, the sensor is saturated.

Regarding reflections in the dome, maybe you could erect barriers further from the dome so that the whole dome is shaded from the lights.

Been wondering that too. I've left the lip of the dome attached (see pic), so maybe I could attach some vanes that shield it from the light.

Long term plan is to move house (T minus 1 year) to somewhere with no pesky lights (or overhead wires - I've got a pretty rubbish garden as far as stargazing goes!)

[ixalon]

Think I've got the focus nailed (by partially unscrewing the front of the QHY to bring the lens a little further from the CCD)... however it makes the reflections show badly!