Gina

The cover and its operating mechanism will need making in several parts which could either be made of ABS and glued together or made of PETG and fastened together with nuts and bolts.  Think I favour the former - my Titan printer is equipped with fume extraction so fine with ABS.  Fumes and nano-particles are blown into the loft.

Going for my smaller high resolution printer, "GinaRep Pilot", for these parts and I'll leave my bigger "GinaRep Titan" for the bigger casing parts.

A bit later :- Hmmm... Pilot printer is not working properly.  Oh well, have to put up with fast but coarser printing

As I thought the dome was rubbish.  It needs finer printing but that takes a lot longer.  The aesthetics are not important - it just needs to work!  The flat "roof" could have a slight slope on it.  I don't really want to spend too long on this project but I want an ASC working again.  I can be too fussy at times

I think there might be problem printing this unless I reduce the support spacing as the filament is drooping inbetween but I'll eave it printing and see if I have enough clearance from the lens tube.  Whilst a dome is esthetically nice a flat top is much easier to print.

Designed and now printing the main part of the domed cover.

Designed and now printing a test lens tube (to see if it fits).

Here's another diagram.  If I print the lens cover in black filament I can use it closed for taking darks and eliminate hot pixels.  I shall probably print the main casing in white ASA filament as that is UV safe and will stay cooler in bright sunshine.

Checking the materials used between camera and lens I find they are all black anodised aluminium but at least there would be less aluminium conducting the heat.  The only way round this would be to attach lens to camera with plastic but this has its own problems.  Maybe the anodising on the threads of the various adapters will help with thermal insulation.  Just have to suck it and see but it probably means the Peltier TEC cooling will be needed.  Maybe I could arrange a heat conducting copper strip from the hot side of the TEC to the lens   Copper conducts heat much better than aluminium.

The lens support being aluminium will conduct heat from the camera to the lens which might be useful if the camera was allowed to warm up as it would warm the lens and help prevent dew.  However, a warm camera produces more noise and this was the reason for adding the Peltier TEC cooling.  The cooling pad can be seen between the camera and the lower aluminium heat sink, which dissipates heat to the aluminium pipe that supports the whole unit. 

If cooling is off the camera can warm up when in use but if the camera were mounted directly to the aluminium block it would be cooled to near ambient.  In view of the sensitivity of the camera and good light throughput of the lens, this would probably be adequate cooling.  But if the lens were at ambient temperature in the winter there is a strong probability of dew settling on the lens.  I really think the lens could do with being heated.  The upshot of this is that the lens wants to be thermally insulated from the camera.  Then the camera can be cool to reduce noise and the lens can be heated to prevent misting up.  In other words the lens support is a nuisance.

I think I shall try the ASC without the lens support.  I'm not sure about the Peltier TEC cooling but the cooler pad is already there and powering it with control from the RPi is no problem.  Similarly heating the lens would be no problem - I just need to decide the best method of heating it.  Heating the air in a dome is easy - just a string of resistors.  For the lens it might be better to use Nichrome wire insulated with Kapton tape (high temperature thin insulation).

Coming now to the rest of the ASC, here are two photos of the insides.  With and without the lens support.

Skirt and lens tube extended and taper increased slightly to improve clearance.

If the pivot is further out the problem is lessened.

Here is a cross-section of the lens tube and cover together with a pivot about which the cover might move.  The problem with any cover with a long skirt is the cover catching on the tube as it opens or closes.  This is shown in the two diagrams below for a typical case - shown to scale with a 15mm skirt.

I don't think sealing would work well enough with a remote controlled cover so I shall concentrate on the skirted version.  The idea I have is to provide a tube to go round the lens and sealed to it and have the cover like a lid with curved top going over that.

After an overnight Windoze update I was able to install SketchUp and the extras I need and have it working.  So I think the W desktop can take a running jump

I've ordered a Pine64 processor board for this project.  It is similar to the Raspberry Pi but has a USB3 port I can use for the camera and the Ethernet port is gigabit, so downloading images will be much faster.  It also has a 64bit processor and 2GB RAM so like a Pi with go faster stripes   It has a Pi compatible GPIO port and another as well.  This should work like the RPi but faster and with more facilities.

Now then...  Motorised cover...  I guess 28BYJ-48 stepper motor and A4988 driver module to drive it.  That isn't a problem.  More of a problem is the cover itself and how the drive is arranged bearing in mind that the stepper motor wants keeping dry.  The cover either wants to seal to the lens or have a skirt that goes down over it sufficiently far that the horizontal rain we get here sometimes, can't blow up under.

Here's a photo of the Mark 6 ASC with lens.  The yellow bracket holds the RPi board and locates the unit within the casing.  This will require a redesign, as will the casing either to use no dome or to use a different dome.  I tend to favour no dome. 

These images show the reduction in quality and the lights reflected in the dome.  Discarding the dome would get rid of these but the lens would want protecting from bad weather and wind blown dust and therefore would want a cover over it when the ASC is not in use.

My Mark 6 ASC has been working for about 9 months but now the acrylic dome has yellowed and become less transparent in spite of being an expensive CCTV camera dome designed for outdoor use and guaranteed not to yellow..  This means either getting a replacement every year (or less), using a cheaper acrylic dome or dispensing with a dome altogether and adding a motorised cover for the lens which is only removed when the camera is in use.  I have not yet decided on which option to use or the design of this ASC.

These photos show the yellowing of the dome, a cheap smaller dome from one of my earlier ASC versions and the internal parts of the Mark 6.

Amp has arrived

Spoke too soon!  TeamViewer dropped connection to Win desktop and now won't reconnect.  Looks like I shall be using the laptop instead after all...

Seems I've fixed the Windows desktop   Left it running overnight and it's still working fine   And TeamViewer is still connected and working fine

Took the vacuum cleaner to the Win 7 desktop and sucked up pretty well all the dust including the heatsinks.  I took the graphics card out to clean it as I couldn't get at it properly in place.  The fan and cooling fins were well clogged up with dust!  The central processor heatsink and fan were also very dirty as were the PSU and case fans and grills. 

I have now connected the desktop up again and TeamViewer is now working again.  So I may have cured the problems.  Tomorrow I plan to take the Linux Mint desktop and give that a spring clean followed by adding the new 3TB HDD.  Unless the Windows desktop fails again I shall leave its Data HDD in it and copy the astro images off it and onto the 3TB drive in the Mint box via the 1Gb/s wired LAN.  That's a lot faster than USB.

I also want to set up my 6TB NAS drive in due course

Fireplace opening is a rectangle with dimensions of 16.25" wide x 23.5" high and I have several pieces of 48" x 24" OSB spare.  I had planned to fit the board inside the opening but I could just as easily put it on the surface of the fire surround and use battens to fit inside the opening.  That would save me cutting half an inch off one edge    I have power tools - a circular saw I can use for the outside and a jigsaw for the round speaker hole.