Gina's DIY All Sky Camera - Mark3 - with QHY5L-II-C

[Gina]

With cash flow problems out of the way (at least for now) I have bought a QHY5L-II-C planetary/guide camera to replace my old QHY5.  This is a far better camera and suitable for both day and night imaging in this application.  My results and assessment/conclusion for this camera can be seen in the best camera for all sky use thread from post #231.

Now comes the construction of a new casing for this new camera.  The whole thing will be much simpler as this will not need active cooling.  I shall be using remote aperture control for taking darks and to cater for very bright daytime skies and probably remote fine focus.  All the drive components and circuitry are already done for the Mark2 version.  See Gina's DIY All Sky Cam - Complete Redesign

[DrRobin]

Colour does make it easier to see the cloud/clear sky by day/evening, but is less sensitive at night.

I much prefer my colour camera over my olser composite video B&W one.

Robin

[Gina]

Yes, undoubtedly the mono version of the camera would be better at night but I think the colour one will be adequate and it seems to be more sensitive than the old QHY5.  Looks like I can get away without active cooling too.

[Horwig]

Looking good on the other thread Gina, the hot lines in the last image are not present on mine, wonder why the difference.

Huw

[Horwig]

Not sure why you are worried about not being suitable for daytime use, this with gain and exposure at minimum.

such a change, bright sun, blue sky

Huw

[Gina]

We start with these

[Gina]

This photo shows the mechanisms used for the remote focus and aperture as used with the old QHY5.  The stepper and servo motors will need a new mounting plate for use with the new camera.  Of course, a new casing will also be required which I'm thinking may be cylindrical.  With the much smaller size and lighter weight of the new version I think I could go back to the pole mounting rather than on the apex of the rolling roof.

With pole mounting (actually aluminium tube) it occurs to me that I might improve the cooling of the camera by thermally connecting it to the aluminium pole.  If simply enclosed in plastic the camera would warm up reducing the dark performance.

[Horwig]

A thought regarding the nonsense backfocal distance on the lens I found. I wonder if they were measuring from the back of the lens not the mounting surface, that might make a lot of sense.

Huw

[Gina]

Ah yes, could be - I've come across that sort of thing before

[Gina]

Been checking the sizes of the aluminium pipes I bought years ago for my weather station - why I bought so many I can't remember.  But there are various sizes and I bought two of each.  Anyway, that's by the way, I've found one with an ID just about the same as the OD of the camera - just a few thou smaller.  So I could either sand a bit off the inside of the pipe or slot it to open it up very slightly and secure the camera with a Jubilee clip or one printed from ABS plastic.  A dollop of thermal grease will ensure a good thermal connection.  The pipe will also provide good electrical screening.

I was going to reduce the size down to the pipe I used before which is about 24mm OD but as I haven't got any particular use for this pipe I might as well ues it to go from the camera to the ground with plastic brackets onto the obsy corner post.  It's currently 5m long but I don't think I want the ASC 5m above ground level   Have hacksaw - will cut shorter

[Gina]

Models of motor mounting plate and new, shorter focus pinion.  The stepper motor for focussing attaches to the small round holes and the servo for the aperture is a close fit in the rectangular hole.  The round hole in the middle takes the camera housing.

[Horwig]

I'm running an avi tonight again, I've not taken darks, it takes a step ladder to get to the camera. But I can tell the hot pixels from stars, the hot pixels are sharp and colourful. 

[Gina]

Yes, the difference is very clear, isn't it   Good luck

[Gina]

First go at the motor mounting plate turned out slightly wrong so this is a second try.

[Gina]

Here's a photo of the unit with motors mounted.  Here's a quiz - what's missing from the Arduino Nano on the circuit board to the left?

An the new circuit diagram.

[Horwig]

the usb socket?

[Gina]

Correct! - Well done   One minute it was there then suddenly it wasn't - not that I saw it go.  It's not on the USB cable and must have come off while I've been playing about with the motors or maybe when I put the IRLZ44N MOSFET on the board.  Can't find it - searched the table and the floor   Doubt I could refit it anyway so I've managed to unsolder the Nano ready to put a new one on.  Never had that happen before.

[Gina]

Apart from removing all the cooling parts from the circuit diagram I've also decided to feed the dew heater from the 12v supply and cycle it on and off every few seconds to maintain temperature.  Three benefits :-

1. I can boost the heating to clear raindrops.
2. Save a power wire.  (No 5v needed)
3. Run this off the 13.8v battery backed observatory main supply.

Item 3. will also help if I decide to include the cloud and rain sensor in the same unit.

[Gina]

I've been working on the mounting pipe.  Cut the 5m length to about 2.6m and cleaned up.  Cut slots in the end and sanded out the end of the pipe to take the camera.  I used coarse emery cloth wrapped round the handle of a screwdriver and held with a rubber band.  Then the working end of the screwdriver put in the chuck of my electric drill.  Here are some photos.

The DIY internal sanding tool.

End of the pipe, slotted and sanded.

The camera body slid into the pipe.  Nice snug fit

[Gina]

Next job on the pipe will be two holes, one at the top just below the camera to take the power and USB cable for the Arduino  (the camera USB is already inside the pipe). and the other just below the ROR rail level to bring all three cables out and into the warm room.  The outer casing of the ASC will come down below the top hole to keep the weather out.

[Gina]

Cable holes in ali pipe with mounting bracket just above bottom hole and parts of the unit and cable hole at the top.  I'm now looking at the outer housing and how to attach it.  I haven't put the new Nano on the circuit board yet.

[Gina]

Cable holes in ali pipe with mounting bracket just above bottom hole and parts of the unit and cable hole at the top.  I'm now looking at the outer housing and how to.

[Gina]

I've added the dew point code to the sketch - copied from my DSLR camera cooling sketch.  This saves the temperatures in tenths of a degree C as integer rather than real.  The idea is to calculate the dewpoint and set the dome temperature to a couple of degrees above.

//boolean readDHT22(){  double celsius, hum, a, b, temp, Td;  int chk = DHT.read22(DHT22_PIN);  switch (chk)  {  case DHTLIB_OK:    celsius = DHT.temperature;     hum = DHT.humidity;    a = 17.271;    b = 237.7;    temp = (a * celsius) / (b + celsius) + log(hum/100);    Td = (b * temp) / (a - temp);    ambientTemp = celsius * 10;    humidity = hum * 10;    dewPoint = Td * 10;    return true;    break;  case DHTLIB_ERROR_CHECKSUM:     Serial.println(" ***** DHT22 Checksum Error *****");    return false;    break;  case DHTLIB_ERROR_TIMEOUT:     Serial.println("  ***** DHT22 Timeout Error *****");     return false;    break;  default:     Serial.println("  ***** DHT22 Error *****");     return false;    break;  }}

[Gina]

Nano soldered onto circuit board, bracket added to motor flange to hold circuit board and USB cable connected. 

Here are two views of the unit to work out shape of casing.  Top of casing takes dome and bottom fits onto pipe.  I think the casing will need to be in two or more parts.

Front view.

Top view, indicating that an oval shape would be most efficient.

[Gina]

The replacement Nano has given up the ghost   "USB Device Not Recognised"   It's got the FTDI USB-Serial chip and these are know for failing.  Have to see if I've got any Nano left with the other type of chip.

Work on the case design is progressing