Gina

Introduction. This talk is about Astronomy Photography or more commonly called astro-photography or astro imaging but before going into the main subject I shall describe how I got into it and also a few general principles that govern the whole process. I have been interested in astronomy from a young age having been introduced to it by my grandfather. Over the years I have looked at the night sky with binoculars and indeed, this is a good way to start observing. Most of my life I haven't had very good night skies for astronomy due to light pollution but when we moved here, away from towns and cities the night sky appeared awesome with thousands of stars visible. (All sky camera image of night sky with the Milky Way.) With such skies I felt I had to take more advantage of them than I had to date and bought a relatively cheap telescope from Amazon. (Picture of the Celestron whatever it's called.) I used this to get a more detailed view of the night sky using various eyepieces that allowed various angles of view. But having been interested and practicing photography since I was a child with a Box Brownie. it was inevitable that I would want to go on to astro-photography. I started with a webcam but moved on through an ordinary DSLR as used for standard photography to much better and more expensive dedicated astro cameras. After a few months I discovered a very active astronomy forum online called Stargazers Lounge, from which I have learnt a lot.

Done ?

If there's anything with a sharp corner around I'm bound to crash into it sooner or later!

INDI is running on the RPi which is running Linux. I think KStars/Ekos has a Windows version but not sure. I'm using Linux Mint which is very similar to Windows 7 from the user point of view.

I would indeed be very interested Carole, thank you very much.

I broke it! Or to be more precise whilst I was testing, the mast fell down and the top of the lens caught the corner of a concrete paving stone. The top lens element has completely disappeared though I suspect it or the fragments ended up in the pond. I tried feeling around in the bottom of the freezing cold pond for a few minutes but found nothing.

Replacement lens for my all sky camera.

Here it is through an open window. Those aren't starts in the sky, they'r hot pixels. 20s exposure with gain at 0, camera temperature 26C with no cooling.

Been trying to use a fixed focus with the new Fujinon 1.4mm lens. I cut some thin card to put in between the size adapter and the camera body. That wasn't enough so tried two layers which was too much so cut a piece of paper to replace the second card and that seems about right. I can get very fine adjustment by how tight I have the adapter. Here are some photos with the rig pointing out of the window towards the village. Firstly full frame then zoomed right in to the highest magnification in the KStars FITS Viewer. The final image is with the 3" dome over the lens.

I'm thinking of 3D printing the outer casing in PMMA filament (acrylic) so that I can see the state of the bags of colour-changing desiccant beads (orange dry - green wet) without opening the casing. This won't be glass clear but translucent though still showing the colour of what's inside.

I have two clear acrylic domes I could use (more if you count damaged ones). The one I've been using is 3" (75mm) and an ideal size but it has slight damage near the edge on one side. I also have a 4" (100mm) brand new, unused one so the question is whether to put up with some smearing of the image (it could be oriented towards the NW where the trees prevent a horizontal view of the sky) or go for the pristine big one that is a lot bigger than needed. A third alternative would be to buy another 3" dome but that's more money and I've already spent too much! I guess smeary trees are no real problem, as long as the good part covers most of the visible sky, it's good enough.

Unfortunately I'm not an observer so can really only cover imaging but that will be the title of the talk viz. "Astronomy Photography". OTOH, I can certainly touch on observing and how you need a very much bigger telescope to see anything directly.

Mount control is already covered by standard INDI drivers. I do indeed control mounts - I have an NEQ6 and EQ8 both of which I have controlled with INDI drivers from KStras/Ekos indoors, with INDI on the RPi.

The (used) Fujinon 1.4mm lens arrived in the post this morning. It's supposed to be used but looks brand new ? Hooray!! I really didn't want to mess about with the Fujinon zoom lens, I've played about with that in the past and didn't like it. Controlling those little levers was very difficult and never really worked well. I have checked my funds again and realised I had money in a saver account so transferred some of that to my current account and now have sufficient funds for the ASI 178MC camera which I've ordered from FLO. I guess I knew I was going to take that route eventually as I've done nothing towards designing controls for the zoom lens. Only trouble is the camera is not in stock and will take a week or so to arrive. Meanwhile I can use the ASI 178MM and get everything working with that.

I need to be sure the data I'm getting is really what I think it is though the only way to be sure will be to wait for a clear night sky and cool the camera until the noise disappears or until it's as cold as it will go. One thing is certain, I can get to a lower temperature with water cooling than even with a fan blowing air through cooler fins.

I'm getting some anomalous results from viewing the FITS images with KStars. I think it's normalising them - not a lot of variation between +20°C and -4°C. I'll find another FITS viewer.

Temperatures didn't quite wok out as above, turned out to be 20°C, 8°C, 4°C, 0°C and -4°C which was as far down as it would go without lagging the camera casing. I'll post the darks shortly.

Starting at ambient temperature of 20°C with no cooling and then 10°C, 5°C and 0°C - 60s exposures, gain 300, gamma 50. ASI 178MM. Water cooling system but no camera thermal lagging.

When I was using the ASI 185MC camera with Fujinon f1.8 lens I used 60s exposures mostly but I don't know how the ASI 178MC compares with the ASI 185MC for sensitivity except that the 185 has bigger pixels, in fact the same size as the 120. I'm thinking 60s exposures may be more appropriate for 178MM darks.

Decided I'd take some darks at various temperatures with the ASI 178MM camera. A direct comparison is difficult as the pixels of the ASI 120MC-S are 2.4x those of the 178MM though the 120MC has the Bayer layer to reduce sensitivity. What I think can be said is that the 178MC should be affected in sensitivity much the same as the 120MC. I think dark noise would be the same for MC as MM given the same sensor otherwise. So I reckon 30-40s exposures will be wanted for the 178MC for nighttime images and hence I propose taking 30s darks with the 178MM.

Yes, I have used the Fujinon 1.4mm lens with the ASI 178MM and did get full coverage. When funds permit, I'm planning to buy an ASI 178MC camera.

These are the connectors I have in mind for the ASC - they seem to be sealed - I already have 4 pin and 2 pin types. Multi Contact Multi-Pin Connector Chassis Socket or Plug Microphone Aviation x1

Commercial ASCs do not have remote focus from what I can find and I think the focus should remain good once set up. If I can do away with remote focussing I can save 4 wires from the controller to the ASC. If I want to use the ASI 120MC-S and Fujinon zoom lens for daytime imaging it will need the aperture control. This can also be used to take darks as the aperture completely closes. The disadvantage is the need to include a servo motor within the ASC casing. Connections required assuming no remote focussing :- USB cable. Peltier TEC - 2 wires. Dew heater - 2 wires. Servo motor - 3 wires. No. of wires required is not 7 as some may be combined - a common ground for instance. The servo motor needs ground, +6v and signal, TEC & dew heater need the +12v line as the electronics is ATM but I could change it. If I keep the +12v line that makes 6 wires otherwise 5. I could use a 6 way round cable or a sealed plug and socket.

I think the next design decision is whether to put all the electronics in the ASC housing. The advantage of having it inside the ASC casing is that it reduces the number of wires going into the sealed ASC casing plus the heat generated can help with dew heating (that's dew on the outside of the dome - the air inside is desiccated). The disadvantage is that the ASC would want shielding from the summer sun to stop it overheating and also it would make the housing a lot bigger. Silicone sealant can be used for sealing the wires where they go through the casing so I don't think that would be a problem. Overall, I think I would prefer to have the temperature inside the ASC controllable rather than leaving it up to "the elements". I think that's another decision made ?

I shall concentrate on the "Economy" version for the moment - I've no idea of how long delivery of the big Fujinon fixed focus lens will take, only that they say it's been sent. OTOH most of the design ideas I'm working on will apply to both versions. From testing the ASI 120MC-S camera and darks I've concluded that the passive cooler is inadequate as the camera temperature needs to be well below freezing to reduce noise sufficiently and I shall be going for water cooling (not as complicated as it sounds - just think of the flexible tubing for the water as cable carrying water rather than electricity). Having decided on the cooling system, the next question is the mounting. Whilst there are advantages in mounting the ASC on the apex of the roof such as just needing to be screwed to the barge boards there are serious problems with where the water cooling reservoir is mounted. Also, with the rolling roof the power cable has to loop down, with a possibility of catching on something and is subject to flexing every time the roof is opened or closed. The alternative is a mast (1¾" OD aluminium tube - very stiff and strong) attached to the observatory main framework with a strong bracket to bring it out clear of the rolling roof. The bottom can go in the ground. I think the mast mounting wins.