All Sky Camera Revisited

[CedricTheBrave]

2 minutes ago, Gina said:

Are you satisfied with your sky coverage?

no I think the ZWO 170mm lens that came with the cam is not right.

 

[Gina]

This is the lens I'm using :- All Sky Lens for QHY5-II and 1/2 Inch Cameras  with ASI178 camera.  Covers a full 180 degrees of sky (or trees etc.).

[CedricTheBrave]

definitely need to look at one of those. the spec on this one says 'nearly' 170 degrees but it does look less

 

[Gina]

I think the 170 degrees applies to the diagonal.  The minimum dimension is the height and even the width is less than the diagonal.  With a circular image it's the smallest dimension that matters.  Of course, you may not want all the image due to buildings and trees.

Edited October 16, 2019 by Gina

[CedricTheBrave]

Like the look of your lens but I am going to complete the build with this lens for now, just cant afford to add another cost at the moment.

once its mounted up in the correct place etc then i will get a better idea of what its covering and where i need to go.

 

[Gina]

Designed a printed thermal jacket for the camera with space for the USB plug and cable.  This is either part of the casing or the outer casing could be separate, probably the former.  I have not modelled the USB cable & plug but made space for it from measurements.

[Gina]

Printing the thermal jacket in PLA using honeycomb infill with a solid layer every 10 layers to form closed air cells for thermal insulation.  When this is finished I can rune the cooling test with this camera jacket and see how much better it is than the earlier version.  This may not be as efficient as polystyrene foam but much easier to implement.

[Gina]

Print has gone wrong   A couple of layers past the solid infill the layer adhesion failed and the honeycomb became straight lines.  I'll try again with higher extrusion temperature and rate and see if that fixes it or I might have to go over to PETG with it's better inter layer adhesion.

[Gina]

Increased temperature, increased extrusion for infill and reduced speed.  OK so far.  Total time looks like being about 6 hours so it will be running overnight unless it goes wrong before I go to bed.  If it fails during the night sobeit.  Using 2.85mm PLA of which I have plenty.

Edited October 17, 2019 by Gina

[Gina]

All went well.  Greeted by a nice clean print when I got up this morning 😀  I'll be testing it shortly.

Edited October 18, 2019 by Gina

[Gina]

Cooling test with new 3D printed thermal jacket.  Starting at 22.5°C.

[Gina]

-4°C so far.  A degree lower than before.

Edited October 18, 2019 by Gina

[Gina]

Now down to -7°C and that's with an ambient of 17°C.  Still going down I think.

[Gina]

Seems to have settled at -8°C.

[Gina]

The new thermal jacket certainly works better than the previous camera casing.  The top of the jacket is a bit thin and there was slight condensation but worse is condensation on the top of the lens.  However, I plan to have it all in a sealed outer casing with desiccant bags to absorb moisture and also the lens will be in the warm zone slightly above the level of the dew heater.  Also, with all these rail showers the RH indoors is over 50%.

[Gina]

With the extra sensitivity of the mono camera, it won't need as much cooling so I might be overdoing it - depends on the cooling and I won't know how good that is until I get the Nofan.  No!!  It isn't here yet.  Should have arrived yesterday.

[Gina]

Latest!!  Grrr...

[Gina]

Wonders upon wonders!!!  In spite of that it's arrived - yippee   I've unpacked it and it looks beautiful but looks are not paramount - I now need to see how I'm going to use it and then arrange a test rig to see how well it performs for my application.  I know full well it was a gamble but a gamble worth taking, I believe.

[Gina]

The Nofan comes with a number of mounting plates that provide 3 different arrangements of attachment points to the motherboard (this is a CPU cooler).  In my case it is a matter of seeing which arrangement best suits the ASC.

[Gina]

The first try on a square didn't work because one screw would have gone through the USB plug.  Of the other two, one was a bit wider than the other and next best to a square so I've modelled that.  One screw would currently go through the USB cable but I can move that.  A new design would be needed anyway to allow for the fixing screws.

Edited October 19, 2019 by Gina

[Gina]

New model.

[Gina]

Printing new thermal jacket.  Meanwhile, I've placed Nofan on the table, TEC on top and camera plus jacket etc. on top.  This would be ideal as the airflow will be limited by the table and the small exposed parts of the camera casing are not covered.  Anyway, I'll just see what happens.

Starting temperature 27.5°C.

[Gina]

Well, the temperature has come down to 14°C so far.  Think it's still going down.  Not surprised the cooling isn't brilliant as I'm not really giving the cooler much of a chance.  Ambient is 21°C.

[Gina]

Not going down much more - just 13°C now.  So that's about it.  Total cooling 15°C.  That may be enough for a cold night and will be better with free airflow.

Edited October 19, 2019 by Gina

[Gina]

The new print has finished and I'm now running a test to see if there's any difference from the previous one under the same test conditions.  The difference with this print, apart from the mounting holes and the rerouted USB cable is that this uses ordinary rectilinear infill rather than the honeycomb I used previously.  This gives a more open cell structure with a lot less filament.  Also less printing time.

Again starting with the camera running and starting at 28°C.

Edited October 19, 2019 by Gina