All Sky Camera for Daytime Use

[Gina]

Having completed my ASC Mk 5 night sky camera I'm now thinking about a colour camera for daytime use.  Colour will allow seeing the difference between clear blue sky and grey cloud.  To start with, the field is wide open for the camera and lens.

Ideas for camera :-

1. ZWO ASI185MC
2. Raspberry Pi Camera
3. Webcam
4. CCTV Camera

Ideas for lens - must be a fish-eye lens to give sufficient FOV :-

1. 2.5mm f1.2 lens supplied with ASI185MC
2. Fujinon Zoom Lens - 1.4mm to 3.1mm at f 1.4
3. Other CCTV lens
4. RPi combined camera and lens                                                                                                                                                                 

[Gina]

Combinations I have considered so far are :-

1. The ASI185MC plus 2.5mm f1.2 lens fails the FOV criterion - the sensor doesn't fully cover the circular image produced by the lens - there are gaps top and bottom.
2. The ASI185MC plus Fujinon zoom lens passes the FOV criterion with shorter focal lengths   The downside is the awkward controls on the lens.
3. The RPi camera has a pretty good resolution of 8Mpx but it is tiny and unless the built-in lens is adequate, which I doubt, it would need a different (fish-eye) lens.

None of the above fill me with joy and I'm open to suggestions and very much welcome them

[ChrisLX200]

The ASI185MC is rather expensive to dedicate to this job, and it has capabilities (sensitivity and frame rate) that are really OTT for the purpose? I would go for a webcam if you can find one with a wide enough FOV - good ones auto-focus without any extra work

ChrisH

 

edit: something like this?  https://www.amazon.co.uk/170degree-camera-Fisheye-Resolution-module/dp/B015PCAVZG/ref=sr_1_4?ie=UTF8&qid=1477577771&sr=8-4&keywords=Webcam+fisheye

[Gina]

Yes, I agree and not my original intention for the ASI185MC which was for planetary imaging.  For daytime use I would not need the high resolution I like for Milky Way imaging - clouds do not exactly have a sharp outline   I think a webcam should be quite adequate.  I have a few around so I'll collect them up and see which still work.  The problem is going to be finding a fish-eye lens with a short enough focal length and small enough image circle.

[tekkydave]

There are some relatively cheap fisheye lenses for the raspi camera like this 

[Gina]

Thanks Dave   I have a wide angle CCTV lens that looks like that one but not sure just how wide angle until I test it.  Do you know what size the raspi camera sensor is?  I can't seem to find the answer to that.  I have a camera but not sure how to remove the lens without damaging the rest of it.

[tekkydave]

I'm not sure you can easily remove the lens on the standard camera board. You would still need to fit a 12mm mount for the fisheye lens anyway. I cheated and bought a raspi noir camera board with the 12mm lens mount already fitted.

The technical specs for the camera are here

[Gina]

Thank you for the link Dave - very useful   I have a raspi noir v2 camera with the 8Mpx sensor but it has the standard lens which is tiny.  Where did you get the camera with the M12 mount?

[tekkydave]

The original seller in China doesn't sell them anymore but this one is the same I think.

[Gina]

The LS-30180 Fisheye IP65 Lens 1.58mm Focal Length M12 for Camera Board arrived in the post today   I'd forgotten I'd ordered it

I was thinking of using it with the Raspberry Pi v2 camera but I thing the sensor may be too small.  This lens does 180 degrees with a 1/3" sensor whereas the RPi camera has a 1/4" sensor.  I reckon I would want about 1mm FL for full sky view.

Actually I have a whole dose of cameras I could use - QHY5, QHY5L-II-C and ASI185MC and I think a couple of others.  As for lenses, I have the Fujinon zoom lens and ZWO 2.5mm lens which has too long a focal length to give an all sky view.  Apart from the awkward controls the Fujinon zoom is a great lens, slight distortion around the edges but overall pretty good

[Gina]

Overall I think an arrangement I had before for 24hr viewing would be fine for daytime use viz. Fujinon zoom lens on QHY5L-II-C camera.  I would probably team this up with an RPi 3.  I shall have to have a good think about what I do for the focussing.  The RPi running indiserver is not really suitable for motorised focussing in this application so I'll be looking into some sort of manual arrangement.

[ChrisLX200]

I've just ordered a 1/2" format 1.55mm f/l (f/2.0) lens which I expect to work OK with the ASI178MM for ASC use. http://www.modernastronomy.com/shop/accessories/qhy-accessories/all-sky-lens-qhy5-ii-half-inch-cameras/ Not exactly cheap but megapixel IR fish-eye lenses such as this one are very hard to come by. There is also a smaller format (1/3") lens which I currently use with the QHY5L-II (http://www.modernastronomy.com/shop/accessories/qhy-accessories/all-sky-lens-for-qhy5l-ii-cameras/) and it performs well - very sharp image with little edge distortion (1.25mm f/l, f/2.0) but if used with the larger sensor of the ASI178MM it would result in a small image circle and a lot of wasted pixels. Anyway, I'll let you know how well it works and of course post an image or two.

 

[Gina]

Thanks Chris   I shall be very interested in seeing the results of the 1.55mm lens with the ASI178MM.  I would like to get full sky cover with the ASI178MM.  I don't mind losing a few pixels as this camera has plenty of them   Slower than the 2.5mm f 1.2 I'm using ATM but I think I could increase the exposure to 2m.

[Gina]

Actually, a slower lens might mean I could do daylight imaging with the Raspberry Pi KStars/Ekos/INDI system which currently only goes down to 1ms which is too long an exposure.  I don't know why it doesn't go down to the minimum exposure of the camera.

It might be possible to use the same ASC for 24hrs which would be good.  I've decided to just use the night viewing for cloud watching.  High resolution Milky Way imaging is pushing things just a bit too much with an ASC - I reckon and I'll use my main rig for that with a wide angle lens covering the 4/3" sensor of the ASI1600MM-Cool, which is a more suitable camera for proper imaging.

[Gina]

Re-focused the ASC as it was a fair way out last night, and put it back outside the living room window.

[Gina]

The re-focussing wasn't all that successful!  But doesn't matter all that much for cloud watching

[ChrisLX200]

Cloudy here too. I've been playing with another lens I've had for some time, the problem I had with it was that it doesn't focus (by that I mean it is fixed focus with no mechanism for adjusting it). Basically it's a C/CS thread mount (so will screw into either) and the distance appears to be set for C-Mount (so you need the 5mm spacer if fitting to a CS-Mount camera). I think the idea in the original application was that it's simply screwed all the way in and it was in focus. Sadly not so on any camera I have! I found on any of the C-Mount cameras correct focus is a couple of turns out - but in this postition the lens was unstable and flopped about. So in the end I never tested it properly and just put it in a draw. The lens itself is (as far as I can tell) C-Mount fish-eye, 1/2" format, f/1.8, 1.4mm focal length. It's made by Fujinon.

So today curiosity got the better of me as to how well it could really perform given the chance, and I made a little adapter from Delrin rod which allowed me to use the CS thread itself to focus, the adapter holds the lens on-axis and locks to the camera with 4 grubscrews, the lens body is a push fit and has a locking thumbscrew to hold it in place when focus has been achieved:

As you can see, the lens is large - about 2" diameter (as it needs to be to achieve f/1.8 in this focal length!) but it comes with nice lens cap which neatly covers the bulbous end element. The lens is currently attached to a GPCAM mono - only 1/3" format sensor so I could expect some overlap of the FOV. It would be better suited to 1/2" or perhaps larger sensor (no knowing what the original application was and no such info printed on lens or box).

I focussed the camera (an easy job now!) and took this quick cap outside - 5sec with the GPCAM. No stars - it's cloudy of course.

Well the resolution is excellent - and apparently sharp across the whole FOV. The house bottom-left is pretty near to the edge of field. To be honest I did not expect it to be this good but the real win is it only cost £22 + postage A gem of a lens and such a bargain I ordered another one LOL! I would try this lens on the hi-res ASI178MM but I would need to think just how to make an adapter which would work the same way and allow it to focus.

Anyway, I thought I'd let you know - and there are a couple left for sale I think.. http://www.ebay.co.uk/itm/152328982118

 

[Gina]

Ended   A couple of hours ago!!!  Pity - looks like a good lens.

[Gina]

Using the thread for focussing is something I thought of for the Fujinon zoom lens.

[ChrisLX200]

Oh poo. That was quick - there were 4 last time I looked (those couple of hours ago I guess..)

[ChrisLX200]

I should have PM'd you instead of posting here I guess.

Got some stars now.

[Gina]

And have some cloud here after a couple of hours of clear sky.  Supposed to clear again later though.  Whether I stay up remains to be seen

[ChrisLX200]

That's why I was staying up, and the cloud has finally gone 15 mins after I came in - at 2:30am! I just don't have any enthusiasm for setting up at this time in the morning though..

[Gina]

I know what you mean.  It got to 1am and was still cloudy so I set the kit to take a couple of hundred 2m subs and went to bed leaving it running.  I'll see if I've caught anything useful shortly.

[ChrisLX200]

My ASC struggles in daylight, this is the minimum possible exposure and gain (on a sunny day)...