Gina's DIY All Sky Camera - Mark 4 - with ZWO ASI185MC

[Gina]

Exposure now at 60s.  Video capture started.

[Gina]

The image on the laptop that is capturing the images shows far better resolution than shown here as uploaded images are limited to 1200 pixels wide whereas the camera is 1944 pixels.  Also, in making a screenshot the image is JPEG and loses more detail.  The raw images are showing hot pixels as well as much sharper stars.  I would like to stop the hot pixels which could be done in several ways :-

1. Take a dark and subtract it (AMCap has this facility)
2. Cool the camera.  Better cooling to ambient should help or I could add Peltier TEC cooling.
3. Use a mono camera rather than colour which will have much greater sensitivity and could use shorter exposures. 

Peltier cooling would mean I could cool to a set point and just use one dark if there was still noise or hot pixels.

[Gina]

Latest screenshot.

[ChrisLX200]

You're doing better than me, I just packed everything away after a wasted evening.

ChrisH

[Gina]

Bad luck Chris    If I'd taken notice of the weather forecast I probably wouldn't have bothered!  Still clear here.

[ChrisLX200]

I've taken a punt on buying a 1.8mm Fish-eye lens I spotted on Ebay. It might well be rubbish but Fujinon is a capable lens maker and it was cheap enough to make it worth the risk: http://www.ebay.co.uk/itm/152184576112 

Only problem is that I can't see details of the mount, it says CCTV lens but it could be anything - I'm hoping either C or CS mount but it could be proprietry.

ChrisH

[Gina]

It might be M12 - that's a common mount for CCTV cameras and many webcams also use that thread for their lenses.  Pretty sure you can get adapters.  Only problem might be that some CCTV lenses have a 6mm back focus.

[ChrisLX200]

Yes, I nearly added 12mm as a possible option. I have a 12x0.5mm tap lying around somewhere to make a suitable adapter if needed, or I could even cut the thread in the lathe if I get really desperate  

ChrisH

[Gina]

After a lot of cloud the sky seems to be clearing.  I have oriented the camera with east at the top so that I can get all the Milky Way in if the sky continues to clear.  ie. North is to the right of the image.

[Gina]

Clouded over again now   Oh well... I could do with an early night - this last week has been very busy.

[Gina]

Set video capture last night and left it running until about 4am when I woke up.  By then it was misty and starting to get light.  Running the video this morning shows some clear periods but a lot of cloud.

[Gina]

As promised earlier, here is a screenshot of an image in full sun.  Auto exposure at 32µs and gain down from the standard 240 to 17.

[Gina]

I have at last finished turning the aluminium mast fitting - many new printed keys for the drive pulley later   The problem has been that with turning seemingly proceeding slowly and smoothly the tool suddenly digs into the aluminium and the sudden load breaks the drive key.  However, much care I take I can't seem to stop this happening

[Gina]

Here's a rather poor photo.  I have yet to drill holes for the camera fixing bolts.

[Gina]

Drilled the fixing holes and counterbored to take the heads of cap-head screws.  Decided to attach the case separately and not with the camera attachment screws.  If I add a Peltier TEC between camera and masthead fitting I plan to use nylon screws.

[Gina]

Thick cloud tonight so no imaging.

[Gina]

Been looking into a case for the ASC to accommodate the larger 100mm dome with focussing motor and gears plus the control electronics - maybe the Raspberry PI 3 both for control and to connect to the camera to capture images, connecting to LAN by WiFi.  While looking for a Peltier Tec for camera cooling I found a project box that seems just the right size.  I was going to design and 3D print a casing but this seems a quicker alternative.  Not only is it just wide enough to take the dome but it's also long enough to include the RPi and the right depth to fit onto the masthead turned aluminium fitting.

The top will need a hole a bit bigger than the lens plus stepper motor shaft hole and mounting holes.  The bottom will need a 33mm hole for the mast and some fixing holes plus power cable.  The space above the box in the dome can be heated to stop condensation with the dew heater from an earlier ASC version. 

Quite amazing - I have never been able to find a suitable size project box in the past for my projects and have had to be content with something far too big.  That was one reason for getting a 3D printer - so that I could make custom cases.

[Gina]

Here's a scale model showing the masthead fitting, camera and lens with the box shown as translucent.

[Gina]

Hole for lens cut and camera/lens assembly inserted, focus gear added and dome placed on top.

[Gina]

Focus stepper motor fitted.

[Gina]

Hole cut in bottom.  Also photo of inside showing stepper motor.

[Gina]

Drilled holes for attaching the case to the masthead fitting and tapped the holes in the fitting to take M4 domed cap-head screws.  Fastened camera back onto mast fitting and attached box bottom plate.

[ChrisLX200]

OK stupid question time Gina   I lost the original thread on the 178 cooler mod but my Peltier turned up today and I have to ask... which side gets cold? LOL!  Let's start with the fact that one side has the power cables attached..

ChrisH

[Gina]

Can't remember but I'll see if I can find the info anywhere.  Or you could do what I did and connect it to power for a short time and see.  Disconnect as soon as one side gets hot to the touch.  Probably best to try it on low voltage - say 5v.  You'll soon tell

[Gina]

Have some more funds now and have ordered ASI178MM from FLO and Peltier TEC from Amazon