All Sky Camera Revisited

[Gina]

Oh I don't intend to give in though I might have to cut back just a little.

[Gina]

There isn't really any more I can do to the ASC until I get the 1.55mm lens (or possibly a replacement Fujinon 1.4mm though that's no longer the preferred option), so I've put all the parts in an empty box, labelled it and put it to one side.  I need a rest from it anyway!

[Gina]

Looks like I shall need another Peltier TEC sometime.  The original came from Farnell Element 14 but I can't remember the type number, only that it was rated at about 15v and 2A (my observatory power supply is 13.8v).  Nearest seems to be APH-127-10-25-S  which is 15.4v and 1.9A.  Tried the cheap Chinese ones in the past and they are very inefficient and not worth bothering about.

[Gina]

1.55mm f2 fisheye lens arrived today and the ASI 178MC colour camera is due to arrive from FLO tomorrow so this project is back on. ?

[Gina]

Set up the ASC with 1.55mm lens on pole on guttering between showers.  This is the full image on the ASI 178MM.   The pole is at about a 10° angle so FOV is lower to the south.  It can be seen that the E-W view well covers the sky.  The roof and chimneys of the bungalow are at the top the frame.  This shows that this lens is an ideal complement to the ASI 178 astro camera sensor.

Edited March 12, 2019 by Gina

[Gina]

Here come the clouds again...

[Gina]

When I get the colour camera those solid mid grey areas will show as blue.

[Gina]

Crescent moon at pixel level - zoomed right in.  Seems I haven't got the focus that bad.  This is at almost minimum sensitivity - 32µs exposure and gain of 50.

Edited March 12, 2019 by Gina

[Gina]

Getting dark now - exposure increased to 0.3s and gain 100.

[Gina]

Some stars showing but so is next door's floodlight and the moon.  Exposure 1s, gain 100.

 

[Gina]

Exposure 10s, gain 100.

[Gina]

Same settings but next door have switched their flood light off.  That just leaves the moon producing internal reflections in the lens.  This is with bare lens and no dome.  Focus seems a little soft to the top left (NE - Ursa Major) but otherwise the lens seems fine.  The slight defocussing could be due to the focus fixing thumb screw.  Camera temperature is showing as 7.5°C - no cooling.

Edited March 12, 2019 by Gina

[Gina]

Exposure 20s, gain 100, gamma reduced from 50 to 40.

[happy-kat]

Nice and clean images.

[Gina]

Clouds driven by high winds.

[Dr_Ju_ju]

Well you keep them down your way, I'm trying to complete a Horsehead set (just need to finish some blues).... 

[Gina]

They come and go - I'm getting periods of clear sky.  Just hoping I can get these clear spells after midnight 30 when the moon is due to go below the horizon.  Also, no showers.

[Gina]

Big black rain clouds coming in so I've unhooked the rig and brought it indoors.  Never mind I've proved the lens is alright which is what I wanted to do.

[Gina]

ASI 178MC camera arrived this afternoon as expected and I've had it working.  The focal plane of the image sensor was nearer the front than the ASI 178MM but the lens focus adjustment easily accommodated the difference.  Weather forecast is dire for the foreseeable future so I'll concentrate on the casing. 

Edited March 13, 2019 by Gina

[Gina]

Wonder what chance there might be of any clear sky after dark

[Gina]

Moon at nearly 1st quarter.  Zoomed right in to pixel resolution.

[Gina]

Had to dash out and bring the rig in as it's started raining and no protection as yet - just bare camera and lens.  No star test then with the colour camera but it is looking promising.  I wanted to test the colour camera to be sufficiently sure that it would be alright before continuing with building the ASC and I am adequately satisfied, so I shall be designing and printing parts for the casing to use the new lens. 

Image just before the rain - 10s exposure - gain 0 - camera at around ambient temperature of 8°C. 

 

Edited March 13, 2019 by Gina

[Gina]

Been looking at the outer casing and the dome. 

There is an inner casing surrounding the camera which insulates the cooled camera body from the outer space which will probably need to be warmed to keep dew off the outside of the dome (the inside will have desiccant).  The other use of the camera casing is to exclude damp or wet in the event of a breech of the outer casing.  Last time this happened as the result of storm damage the astro camera inside was destroyed by wet (there being no internal camera protection from rainwater).  This sealed inner enclosure means the USB cable to the camera and the wires to the Peltier TEC need sealing where they go through the inner casing.  To reduce the size of the inner casing, a right angle USB plug is used but this still makes the casing bigger than would be desired.

This photo shows the situation.  Only the lower part of the camera casing is shown.

ATM the top part of the camera casing is simply extended to the top of the camera as shown below.  Previously, with the Fujinon fisheye lens the dome would have been about 40mm above the camera housing but with the smaller lens I'm now using, the dome would be level with the top of the camera casing.  This is shown below with the 3" dome.  Clearly, this won't work.  I could ease the problem by tapering the upper camera casing part but I'm not sure I can do enough to avoid a flat top around the dome, making sealing more difficult.  An alternative would be to use the 4" dome I have.  This needs more thought.

Edited March 13, 2019 by Gina

[Gina]

I've produced a new design for the upper part of the camera casing, reducing the size of the top whilst still avoiding support.

Edited March 14, 2019 by Gina

[Gina]

It looks like I may be able to use the 3" dome with this new design camera casing.