New Higher Res Camera for the Raspberry Pi

[Dr_Ju_ju]

FYI, if nobody has yet seen it, there's a newer camera for the Raspberry Pi, that has a higher Res, using a Sony IMX477 chip, and best of all it uses interchangeable lenses as it has a C-CS mount. More details here https://thepihut.com/products/raspberry-pi-high-quality-camera-module 

Its double the price of the existing camera, but it may well make a reasonable all sky system with the appropriate lens...

[discardedastro]

Ooh, that's interesting.

The main issue with using the old camera boards - apart from the sensor - was lack of long exposure support. I hope this has been addressed in the latest release or it'll still be no use for all-sky applications.

[festoon]

I saw this too this morning looks very interesting given that you can interchange the lens with the C/CS mount

Looking at the spec of the IMX477 sensor https://www.sony-semicon.co.jp/products/common/pdf/IMX477-AACK_Flyer.pdf

The units of sensitivity are LSB at F2.8 with 1/120s integration. For all the other IMX sensors that I've compared this is usualy expressed in mV at F5.6 and 1/30s integration. Does anyone know a conversion factor between the two?

I would be very interested in this if it compared well to an IMX385 or IMX224

[Gina]

It didn't occur to me that it might not support long exposures!  I guess there must be a reason this camera is £50 and a "proper" astro camera 6 times as much!!

Edited April 30, 2020 by Gina

[Gina]

Reading the spec, it does say this sensor is for use in camcorders only and not specified for any other use which implies short exposures only such as 1/25th or 1/50th sec (or 1/30 1/60 in USA).  I imagine the full-well depth would be much less than an astro sensor.

[WimH]

3 hours ago, festoon said:

I saw this too this morning looks very interesting given that you can interchange the lens with the C/CS mount

Looking at the spec of the IMX477 sensor https://www.sony-semicon.co.jp/products/common/pdf/IMX477-AACK_Flyer.pdf

The units of sensitivity are LSB at F2.8 with 1/120s integration. For all the other IMX sensors that I've compared this is usualy expressed in mV at F5.6 and 1/30s integration. Does anyone know a conversion factor between the two?

I would be very interested in this if it compared well to an IMX385 or IMX224

Wouldn't that be exactly the same? Delta between F2.8 and F5.6 is 2 stops, delta between 1/120 and 1/30 shutterspeed is also 2 stops so in both test conditions, you have the same amount of light hitting the sensor during the time the shutter was open.

[WimH]

4 hours ago, discardedastro said:

Ooh, that's interesting.

The main issue with using the old camera boards - apart from the sensor - was lack of long exposure support. I hope this has been addressed in the latest release or it'll still be no use for all-sky applications.

Long exposure support is also what held me off buying the RPi v2 camera.

However, what I've been able to find back for the HQ camera so far (see the camera guide, p. 110: https://magazines-static.raspberrypi.org/books/full_pdfs/000/000/036/original/Camera-Guide.pdf?1588180275) is that there are 4 capture modes. Mode 3 (12MP) supports frame rates between 0.005fps to 10fps, i.e. shutter speeds of 0.1s to 200s. This could be more interesting.

EDIT: and this is confirmed elsewhere in the document in the CLI description (p.115):

Shutter speed
--shutter or -ss
Sets the shutter speed to the specified value (in microseconds). The upper limit is around
6000000 μs (6 s) for CM v1; 10000000 μs (10 s) for CM v2; 200000000 μs (200s) for HQ Camera.

Edited April 30, 2020 by WimH
Additional info

[Gina]

Very interesting.  (Or yes, more interesting!)

Edited April 30, 2020 by Gina

[Gina]

There's got to be some reason other cameras are many times more expensive! 

[festoon]

2 hours ago, WimH said:

Wouldn't that be exactly the same? Delta between F2.8 and F5.6 is 2 stops, delta between 1/120 and 1/30 shutterspeed is also 2 stops so in both test conditions, you have the same amount of light hitting the sensor during the time the shutter was open.

Thanks @WimH. This makes sense, but do you know the difference between the quoted unit of LSB and mV? The IMX385 spec for instance is a sensitivity of 2350mV (F5.6 1/30s) and the spec of the IMX is 250 LSB (F2.8 1/120s)

I never know why manufactures like Sony randomly change units with little or no explanation!

[Gina]

OK, so who's got £50 spare to buy one of these and test in an all-sky application?

[festoon]

One of the big down sides to this not being a dedicated asto cam is the lack of ASCOM or INDI support. FOr instance if I was to use this for a all sky camera, I'd want it to be compatible with INDI so I could use it with my Pi and the run AllSkEye from my laptop,

[Gina]

Another question...  Anyone used the Pi camera with INDI?

OH SNAP!!

[festoon]

PS this is what I built at the weekend for a project with my kids as an all sky camera (I know its terrible...but the kids loved the project). If I could replace my QHY5L-ii (with 2.5mm FL IR 1:1.2 (F1.2) lens) with this new Pi camera it would be fantastic. The Pi is running indigosky this has the drivers for the QHY5. The pi is connected to the house wifi whilst in the garden so I can connect to it from indoors. But I doubt INDI it would have the drivers for a new Pi camera...so I guess I have to stick to astro cameras

 

Edited April 30, 2020 by festoon

[Gina]

Any thoughts of using the Pi camera with INDI @RadekK?

Edited April 30, 2020 by Gina

[Gina]

I'm not sure there's any significant advantage of using KStars/Ekos/INDI for an all-sky camera for capturing the images.  This is a much simpler application than standard astro imaging.  As long as you can access the RPi and camera over WiFi it doesn't really matter what software you use.  I think Raspian as OS on the RPi covers this but I haven't investigated.  I'm using INDI to control cooling and dew heater on my present ASC with a ZWO astro camera (ASI178MM or ASI178MC).  All this works fine using modified a Astroberry Board INDI driver for cooling and dew heater control.  I would like to use INDI with the Pi camera as I'm familiar with INDI.  Any other software would need programming the GPIO lines for cooling and dew heater control.

Edited April 30, 2020 by Gina

[festoon]

9 minutes ago, Gina said:

I'm not sure there's any significant advantage of using KStars/Ekos/INDI for an all-sky camera for capturing the images.  This is a much simpler application than standard astro imaging.  As long as you can access the RPi and camera over WiFi it doesn't really matter what software you use.  I think Raspian as OS on the RPi covers this but I haven't investigated.  I'm using INDI to control cooling and dew heater on my present ASC with a ZWO astro camera (ASI178MM or ASI178MC).  All this works fine using modified a Astroberry Board INDI driver for cooling and dew heater control.  I would like to use INDI with the Pi camera as I'm familiar with INDI.  Any other software would need programming the GPIO lines for cooling and dew heater control.

Completely agree Rasbian would be fine just for connect to over network. However, the advantage I found is that using INDI allows you to work with AllSkEye across the network on another PC.

[WimH]

1 hour ago, festoon said:

Thanks @WimH. This makes sense, but do you know the difference between the quoted unit of LSB and mV? The IMX385 spec for instance is a sensitivity of 2350mV (F5.6 1/30s) and the spec of the IMX is 250 LSB (F2.8 1/120s)

I never know why manufactures like Sony randomly change units with little or no explanation!

Here's my attempt to link LSB and mV specs :-) Consider this as 1st-order approximation as it assumes e.g. ideal ADC being used etc.

Both mV and LSB quantify the luminosity response of a pixel under specific conditions, when expressed in mV the measurement is before the ADC (analog domain), when expressed in LSB the measurement is after the ADC (digital domain). There is no real way of comparing them unless we know for instance more about the ADC specs and settings used. IMX477 has for instance 8, 10 and 12-bit ADC settings. When looking at the IMX477 datasheet, it mentions 250LSB sensitivity and 1023LSB saturated signal. This means 10-bit ADC setting was used for the sensitivity measurement.

Furthermore, the datasheet mentions the sensor uses an analog supply voltage of 2.8V. Accepting that this is also the input signal range of the ADC (which is not 100% correct, but again, this is 1st order approximation), a 250LSB response at the output of the ADC would equate to 683mV on the input.

If Sony is really talking about mV per pixel and not mV per um2, this looks like an acceptable number, considering the difference in pixel area between both sensors (assuming both sensors have similar quantum efficiency and charge conversion rate).

 

[Gina]

I think if I could use the new Pi camera with INDI I might buy one to play with even though I would loose some sky coverage to the north (I wouldn't want to lose any to the south) but having to mess about with unfamiliar software tips the balance too far against.

[discardedastro]

Think I'll give it a punt. Need to work out how best to power it and keep it all dry, but I have some thoughts on that front, and can test easily enough on a dry night. Just going to get the "default" lens and I can go buy a C-mount fisheye later if the exposure settings etc work.

Edit: never mind, The Pi Hut are all sold out! Guess demand is high. Will watch the internet with interest. Also, I would've thought for basic use the indi_webcam driver would work for the Pi camera out of the gate - it's exposed as a v4l device.

Edited April 30, 2020 by discardedastro

[festoon]

13 minutes ago, discardedastro said:

Think I'll give it a punt. Need to work out how best to power it and keep it all dry, but I have some thoughts on that front, and can test easily enough on a dry night. Just going to get the "default" lens and I can go buy a C-mount fisheye later if the exposure settings etc work.

Edit: never mind, The Pi Hut are all sold out! Guess demand is high. Will watch the internet with interest. Also, I would've thought for basic use the indi_webcam driver would work for the Pi camera out of the gate - it's exposed as a v4l device.

If it works in indi, can do 30 secs exposure and sensitive then it will be a very cool gadget for all all sky cam

[Gina]

I just use a cheap buck converter to change my 13.8v main supply to 5v for the RPi.  And always add a fuse at the power input.

Edited April 30, 2020 by Gina
typos

[discardedastro]

2 hours ago, Gina said:

I just use a cheap buck converter to change my 13.8v main supply to 5v for the RPi.  And always add a fuse at the power input.

I thought the Pi has its own polyfuse internally? I use a DC-DC converter too, vandalised a USB-C cable to just supply it on the usual connector rather than soldering on etc.

For an all-sky I'd definitely be looking to use a PoE hat so I can drive it off my usual IP camera switches. For an enclosure, just planning to get a spare bit of flat plate glass from my mirrormaking stock and use that as a "lid" over a simple project box, epoxy to hold it in place on top. Glass means nice and easy to clean and simple enough to keep above dew point, and I think I could sink enough power over PoE for a dew heating circuit plus the Pi etc...

[Gina]

If you're planning an all-sky camera, a flat window is not suitable.  You will get gross distortion round the edge.  An acrylic hemispherical dome is used for all-sky applications.

[RadekK]

On 30/04/2020 at 15:48, Gina said:

Any thoughts of using the Pi camera with INDI @RadekK?

As far as it can be controlled by video4linux2 (V4L2) as a regular webcam, it can be handled by INDI with indi_v4l2_ccd driver. AFAIK the latest raspbian provides support for V4L2 for these cameras so it shouldn't be a problem. I have not tested it though, so it's just a guess