el-cheapo sky camera

[DaveL59]

ahh looks like the sun has found a way past the edge of the lens as it sets 🙂

 

[Gina]

Yes, I get that too.  Well, similar.

[MarsG76]

Great project.. my Skycam is also a budget el-cheapo solution.. I use my rarely used IS DMK41 with a $9 CS and a $8 4" security camera dome on top of my Obsy.... It doesn't deliver quite as a wide field of view as your project but still allows me to keep an eye on the sky when I'm imaging when away from home or inside watching tv through VNC.

[DaveL59]

yep is just the flare on the large front lens element from the sun hitting at a low angle and bouncing internally, looked pretty neat tho, sun setting but outside the actual image area of the lens or was that burning its way thru anodised ally casing to reach the sensor, transparent aluminium is here at last 

A couple months back I was out for a smoke and there was the crescent moon, but it started as a single at the top and had a double at the bottom. Wasn't able to get a decent pic but I was seriously wondering what was up with my eyes when I first saw it after playing with aligning binos earlier in the day but was the same effect with one or two eyes...

@Mars - what's the CS lens you are using tho? I just switched up from 2.8mm to 1.7mm so FoV went fro 100 to 185 degree, tho I'm probably only getting 170 of that since the lens sits just below the edge of the inner module mounting. I did think about going CS for the 5MP module I have coming, for the larger optics, but then there's a jump in price from £7-12 for M12 to £25+ for the equivalent CS and the v small dome case wouldn't have handled the physical size of the CS unit. Oh and they tend to be for larger sensors so hard to get the full view on a smaller 1/2.8 one. Might consider it further down the road if I can sort a housing that would handle it as it'd only be a case of swapping the board lens mount and screwing in the new lens.

Edited May 21, 2019 by DaveL59

[skybadger]

Take an existing one and paint it  in layers of latex ?

 

[DaveL59]

ok so while the day view with the new 1.7mm lens was great, the step down from f1.8 to f2 is costly and that loss of light pass means pretty much nothing showing (well, one star low left of centre) where the previous lens showed the tree outlines against the sky as well as some brighter stars, oh well  Even the aircraft lights are dimmer than with the faster 2.8mm lens. Will see later how the moon shows but at the mo it does look like a big hurdle, trade off  FoV vs faster lens.

Also looks like a street light on the far side is reflecting off the lens onto the dome and causing a double "star" pattern, don't think it is the neighbours light in the window but I guess when they turn it off that'll confirm things. 

A little disappointing then, but of course the stars will be "smaller dots" now that the FoV has expanded so much and that maybe isn't helping either. One option might be to use 2 cameras with 2.8mm lens alongside each other to give a half-half overhead and use a larger dome to house them, hmmmm. Lets see how the 5MP IMX335 starvis+1.7mm plays out then can decide next steps... which could well be tomorrow it seems as its already cleared customs

 

Edited May 21, 2019 by DaveL59

[Gina]

Strange, there shouldn't be much difference between f1.8 and f2.  OTOH I found the Fujinon fish-eye lens 1.4mm and f1.8 let in a lot more light than the 1.55mm f2 lens which is considerably smaller.  I suspect focal ratios on fish-eye lenses mean something different from "normal" lenses and telescopes.

[DaveL59]

yeah I think it may be an insurmountable issue tbh. Thinking back to photography days, losing 1/4 up to 1/2 of a stop is reducing the light entering the sensor plane and in such low light, while you might compensate by increasing exposure time or pushing the ISO (sensitivity) you also gain noise. Also each point of light is now much smaller at the exit pupil (went from FoV 110-180) so per pixel on the sensor there's less light and more dark hitting it, hence you may get brighter stars but not so much the dimer or further stars. I was a little surprised the sky was so dark compared to the 2.8mm lens tho, I'd have expected the background luminescence to have still showed the trees for example.

Even switching to CS lenses there's few in the f1.x range and they are mega pricey (350 ish) vs the more available F2.x ones in the £45 bracket. So even with the larger glass you still have the issue of not enough aperture so back to the same situation I expect. In fact the F2.x CS lens isn't that much bigger at the objective than the M12 version, around 30mm so not really much gain for 5x cost.

I did have a fiddle with brightness etc and turning on WDR and it lightened things up a little but noise made the image less useful. You could make out a couple stars but pretty much not a very usable image.

Still, we'll see with the new board module, one difference with the 5MP sensor that's coming in today is it'll have smaller pixels and similar sensitivity. Not expecting a step back to the earlier setup but it might help a little. Wonder how possible it'd be to hack the on-chip OS to push the shutter speed slower as 1/25 is a lot optimistic for night sky, beyond my skillset tho I'd say, am way too rusty on coding these days and these modules can be easy to brick.

Its almost tempting to try a hacked USB webcam, but I doubt the network-USB server would handle streaming video, its fine for scanner and small file transfers but doesn't cope well if you push large sustained transfers at it. Don't really want to put a PC out in the shed as it gets way too warm, plus am not sure about a new neighbour esp after the police have visited several times recently...

[DaveL59]

ack so a minor error on my part. New board module arrived, powers up and gives a nice image. BUT its slightly oversize for the mounting sphere in the mini dome... DOH!

So I guess plan-B then, leave this one up and re-fix this new one in the dud dummy dome housing to test and then acquire a new dome for its final fit. Got one on order that I purchased cheap as not working, that's of the larger type with an arm to wall mount it, so hopefully won't be a problem 🙂 So I guess a side-by-side test is on the cards after all lol

 

[DaveL59]

ok after a degree of faffing about, the 1B version is back in the small dome and now the 5MP is fitted up in the old dummy dome, side by side on the edge of the shed roof. Still to fiddle a bit with the settings on the new one but its certainly working 🙂 

old first and new below. The new one is showing more colour esp to the brickwork but I guess the acid test will be night sky assuming its clear enough.

 

[DaveL59]

so side by side, and a couple tweaks to the new 5MP AE and it sees a star

and so does the 1B version lol

Figured out that the "double star" effect in 1B was in fact my IR lighting, so worth considering if you are imaging even with IR filters. The 5MP setup isn't showing it in colour mode but switch to B&W and ugh, not so nice! I have a pair of 4 LED units 6 inc apart at roof level for movement sense on the camera covering the garden and garages, handy to track the kitties and the odd fox or hedgehog.

So here you go, piccies, 1B then 2 then 2 B&W and a bit earlier, sunset

 

[DaveL59]

so all in all, hmmmm a minor improvement on the v1B but I think the issue may still be not enough aperture at the lens that's now holding this back more than the sensor. Losing that 1/4-1/2 stop is enough to drop the stars too low perhaps. Min shutter on the 5MP is 1/50 tho you can adjust the max to 80ms (was 63ms) which I have done, no real improvement that I noticed.

Setting AGC up to 70 tho improved things a bit more

 

[DaveL59]

ok, after a little thinking and scanning the web, decided I'll experiment with the CS lens range. While the current setup does still show a couple stars, literally a couple, it was doing better with the older M12 2.8mm lens that's rated f1.4 or f1.8 in the IMX291 setup. So I have ordered a CS lens mount with IRcut and a CS 2.5mm F1.2 (FoV 130) and a CS 2.1mm F1.8 (FoV 133) which should help to determine what's going to be possible with these IMX291/335 sensors.

Assuming the IMX335 performs at F1.8 then I can consider a better CS lens for it later on down the road, IF and when I feel the huge step up on cost might be worth it that is. I notice that getting below 2.1mm in the CS range you get a cost jump to £30-£50 but also aperture drops to F2 unless you want to carry a huge cost step to get to F1.6 (>£200). For my skies and this sensor setup I doubt that expense would be worth it to be honest. Still I should get an idea how far it can be pushed in a week or so. Having 2 cameras set up I can always use one 180 view for total cover and the narrower FoV set up tuned for night sky 🙂

 

 

[Gina]

You can get the ZWO ASI 120MC-S camera plus fisheye lens from FLO for £146 plus carriage.  Not quite all sky but a good amount.  It all depends on how much you want to spend.

[DaveL59]

thanks Gina, that's pretty good and 150 deg would do here in many respects given houses are quite close, they don't give the F rating of the lens tho. Downside for my setup is that its USB and that'd mean locating a PC in the shed or perhaps try the USB2 server that I'm pretty sure will barf at the transfer rate or buy a high-end USB server so more expense. I think I will see how this goes with faster lenses and see where this experiment ends up. Gotta slow the spend too, starting the new job in a couple weeks will help there I expect, less time to mull ideas and then just go buying stuff 😉

 

[Gina]

As you probably know, I use the Raspberry Pi which costs about £30 from Amazon, with free (open source) software.  I have all the information for using this and have posted it on here in Blogs.

[DaveL59]

that's a possible option down the road, perhaps. Never tried the Pi so far as I've a fair few small HP mini desktops and servers cluttering the place and a couple full size desktops that are kicking their heels as spare doorstops. Thing is temps in the shed can get quite high and isn't the most secure so my pref is to not put anything of value out there even tho it is linked to the alarm. 

I'll play a little further with the cctv setup and maybe revisit depending on the results with CS lenses, just gotta be sensible re £ I think and expectations both with the sensor and the stray light. That said, clear outside rates this location as bortle 5 so there may be limits on what can really be achieved but the earlier results were not bad for such a limited ability setup.

[skybadger]

Hi Dave

When does the starvis kick in ? Isn't that the point of using a Sony ixm91. 

M

[DaveL59]

ahh Starvis is more branding, just means the sensor is more capable in very low lighting, as in more sensitivity. From past equipment the sony exmoor IMX range are a step change from the OV sensors, low light with IR illumination shows well across a wider field where non-starlight sensors fall to dark/shadow earlier. It always helps to have good aperture also, most of my cctv are running with f1.4-2.0 lenses depending where they are covering and the faster lens means the camera can still be showing colour outside even when its quite dim after the sun has gone down.

So I thought why not give this a go and point one at the sky, just never quite got around to it until recently. First shot with the 2.8mm wide lens was surprisingly good, that lens is f1.8 or might be f1.4, I can't exactly recall. If it was 1.4 then the step down to f2 would explain a lot as that's a big drop in aperture. Hence I thought I'd swap to CS lenses and test a little further to see if I can improve the view at low cost.

The new 5MP IMX335 seems much sharper in image both day and dark night, less noise and better definition to shapes compared to the IMX290/291 so it might give me something workable with the right lens, we'll see. Shutter speed (exposure) is a limiting factor tho since these cctv units generally cannot do much slower than 1/30s since the firmware is more geared to low-blur motion capture than best low-light still image. That said these might be workable as an eyepiece camera with an M12 eyepiece adaptor and feed video clips into stacking software, esp the IMX291 that has larger pixels, a future project maybe.

[DaveL59]

well the "new" dome housing arrived, its a used PTZ unit that no longer functions hence a low price. Downside is its a black casing and tinted dome, was hoping the PT part might power and be useable over IP to steer but nada, totally dead. No prob, so I've stripped it down and removed the original boards and cabling, ready for retro-fit of the 5MP module which I'll use the old camera board as a staging mount to bolt the bracket onto. I left the PT motors and wiring in place to keep the camera mount stable, may find a way to use them later but not too important given the camera will be aimed directly upward. Also painted the main body white to try reduce absorbed heat a touch 🙂

So now the wait for a few parts:

• CS lenses and mounts
• Clear dome to replace the smoked one
• Rubber gasket for the dome ring to body seal as there isn't one, so that'd be a problem with this rig mounted inverted

I did pop the dome over the existing camera rigs last night just to see the impact, looks to lose 1/2+ stop given the smoked dome not too surprising, tho the 5MP still showed an OK image resolution suffered a little, all cloud so no ability to check against stars, tho aircraft lights showed fine. For sure a smoked dome is no use at all for night use in my intended application.

A wee test of my patience now, till all the bits arrive lol

 

[DaveL59]

oh well, the new CS lenses and IRcut fittings arrived today, took longer than the last order but they're here and now awaiting install. Of course being the UK, weather is against doing anything today, lots of rain. OK is only 12v DC but no way am I going to be messing about up a ladder opening the current casing to extract the electronics from the temp housing and in case folk aren't aware, 12V DC can be dangerous esp if you're wet.

So I guess it'll have to wait till the weekend if its dry. Am back to work again from Monday so was hoping to get that in place before but time will tell...

[Gina]

Good luck with the weather.  It's stopped raining here but there's more heavy rain forecast.  A yellow alert!

[DaveL59]

thanks Gina, yeah has eased but it can wait till things dry a bit more or tomorrow I think. Hope you don't get flooding, for sure the weather put paid to plans to go visit a country house with my daughter in my last week or so of freedom, whenever we've both been free its rained lol

[DaveL59]

ha and just after I typed that, the next deluge starts, think there's no chance to fiddle out there today.

Last year (?) we had torrential rain for several hours along with lightening, the lot. My desk phone died during one set of lightening but thankfully nothing else affected on the equipment front, only the nice 4ft box bush in the garden, which seems to have drowned as it went yellow in the days following and is now totally dead. Can't be certain why the phone was affected but there's a lot of overhead phone cables around here even tho mine's fed below ground.

For info I've now got suppressors on the phone, vdsl, satellite and TV feeds and the LAN cable out to the shed, hopefully will limit future damage, worth considering for external cabling if you've not already.

[pete_l]

If it's any consolation, here's a sample from my IMX291 + 1.7mm lens
The image is a stack of 10 shots taken at about 23:00 a few nights ago.
North is to the top. You can see Polaris, U.Maj and Bootes - Arturus is the bright star in the lower half

The red light on the right is my Wimax internet connection