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Astro Projects

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All Sky Camera Mark 7

Gina

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This is my latest generation of all sky cameras and based on the ASI178MM followed by ASI185MC CMOS astro camera and a Fujinon fish-eye lens of 1.4mm focal length.  Although rated at f1.8, this lens lets a lot more light through than this would imply.  Image capture is provided by a Raspberry Pi 3 in conjunction with INDI software.  This is used with KStars/Ekos client software running on a Linux Mint desktop indoors.  Communication is via Wi-Fi.  The Mark 6 ASC has proved inadequate after being in use for some time. 

This blog will describe the problems of the Mark 6 and report my progress in developing this new version.

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Here are a couple of photos with the cover attached to the lens and the RPi placed beside the camera.

59f0b043c5a19_CoverCog02.thumb.png.19b2f2af0f9c2acf5da23fbf2de6a3ba.png59f0b03db2561_CoverCog03.thumb.png.9b245408884fb573d9f5d9cb486779a0.png

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This shows the probable position of a drive gear.  This can be on a shaft coming out of the side of the main casing.

59f0c4f4eedfd_CoverCogs01.png.59ba8c0a3fcf57e12e06731f37498782.png

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Not enough room in that one so here's another design :D  This should be the whole middle section housing all the electronics.  The dome shaped section holds the stepper motor.  There is an opening to take the cable from the driver module to the motor.

59f24b7d0a8f9_Middle3.png.a6bedc86eadda27d90eed0939176c90c.png59f24b770cf1d_Middle4.png.75b6c4cb23ce9cb9d09288d249142078.png

Edited by Gina

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New design and now printing ETA 2:15h.  That's ABS with 0.6mm nozzle and layer height of 0.5mm and printing speed of 60mm/s.

59f31b0d668a1_Middle5.png.09f97499a197244c1a128adc035d7c8d.png59f31bc65844e_Middle6.png.ddc7b4134580469b2196384e5bfc9bba.png

Edited by Gina

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There's a nice clear half moon up there to the south that I can focus on :)  If I can find the buck converter to run the RPi.  Otherwise I shall have to wire direct to the RPi and supply it with 5.1v from my bench supply.  Doubt I'll be able to capture any stars with the moon out but it will be set by midnight if I can stay up that late :D

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Found the buck converter and everything connected up with standard 13.8v power supply.  RPi is working as before but there's a problem - camera isn't working.  INDI driver recognises the camera alright but the camera is not showing up in KStars (only the Astroberry Board).

Quote

pi@ASCmono:~ $ indiserver -m 100 -vv indi_asi_ccd indi_rpibrd
2017-10-27T18:51:47: startup: indiserver -m 100 -vv indi_asi_ccd indi_rpibrd
2017-10-27T18:51:47: Driver indi_asi_ccd: pid=1021 rfd=3 wfd=6 efd=7
2017-10-27T18:51:47: Driver indi_rpibrd: pid=1022 rfd=4 wfd=9 efd=10
2017-10-27T18:51:47: listening to port 7624 on fd 5
2017-10-27T18:51:47: Driver indi_rpibrd: sending <getProperties version='1.7'/>

2017-10-27T18:51:47: Driver indi_asi_ccd: sending <getProperties version='1.7'/>

2017-10-27T18:51:47: Driver indi_rpibrd: read <defSwitchVector device='Astroberry Board' name='CONNECTION'>
2017-10-27T18:51:47: Driver indi_rpibrd: read <defTextVector device='Astroberry Board' name='DRIVER_INFO'>
2017-10-27T18:51:47: Driver indi_rpibrd: read <defSwitchVector device='Astroberry Board' name='CONFIG_PROCESS'>

59f384a3e8d01_INDIControlPenel-KStars01.png.479d5d1ef872635eaa115e14a1b5f69a.png

Edited by Gina

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Can't think what the problem can be or how to cure it so I guess that's it for the testing tonight.  Probably won't do any more on this project tonight - I'm tired now.

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Decided to try changing the USB cable and that fixed it :)  Now have camera out of the window though nearly horizontal.  Set up a small area of the sensor to speed up downloading and then adjusted the focus to make the moon as small as possible.  The best I could do was about 6-8 pixels wide and it still didn't show the phase - came out round with jagged edges.   Maybe still too bright.  Here is a screenshot of the KStars FITS Viewer back at full size.

59f396f070e41_Screenshotfrom2017-10-2721-23-30.thumb.png.feeaee12264a002e9cd0d95ad346b65a.png

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Made a bracket to attach pole to the guttering outside the living room window and tried to get an all round view but with the power wires just hanging, one of them broke.  So further sky testing will have to wait for the next clear night sky but meanwhile I have plenty to do on it. 

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Here's a couple of photos of the casing.  Two parts which fit together to allow access to the "works".

59f44cc26e7c7_Casing01.thumb.png.9bffec31b981ccd8135c595438049aa4.png59f44cbdaa5ac_Casing02.thumb.png.5e4b23c55040d66296063940f48c6dde.png

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For focus at infinity the lens to camera distance needs increasing by about 2mm (measured as 1.94mm) so either the lens or camera plus supplied adapter is not complying with the C/CS standard.  The C to CS adapter which is 5mm really needs to be about 6.9mm.  I've getting round this by using a 3D printed washer between camera casing and T2 to CS adapter to stop the adapter going right in.  The thread is about 7mm so there's still 5mm of thread to hold the lens which should be quite adequate.

If the lens and camera with adapter complied with standards I would not need to adjust focus it should be correct with the lens simply screwed in!  I guess I could measure the back focus of the lens but it isn't easy - could do with an optical bench.  The lens has no method of focus adjustment other than unscrewing it.  TBH I can hardly believe that either lens or camera would be wrong - it's very puzzling!  :(

Had a thought...  @ChrisLX200 did you have this problem?  Am I right in thinking you have the Fujinon fish eye lens DF1.4HB-L1?

EDIT :- Going through my threads I found where you sold me the second of two identical Fujinon fish-eye lenses, Chris, as I thought but my memory plays up at times :D  And yes, you did say you had the focussing problem with this lens.

Edited by Gina

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A couple of photos of the casing fitted to the ASC insides and aluminium tube that forms the mast.

59f4b6f42320a_Casing03.thumb.png.93c2da7bc4855833e19f77e641b06c96.png59f4b6ee3a59f_Casing04.thumb.png.c391fff4901cb3659b4c6296a9074c06.png

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Looking through my old files and images from earlier versions of my ASC I have to say I much prefer the colour images.  I think the Fujinon fish-eye lens would work well enough with the colour version of the ASI178 but I really can't keep buying cameras and certainly not ATM with a big bill on the horizon for repair of my Rayburn (essential equipment).  I have an ASI185MC camera not doing anything at present but the sensor on that doesn't quite get all the sky image in.  It's close (but no cigar!)  The 178 sensor is 5mm high and the 185 is 4.6mm.

Here are the comparisons :-

                        ASI178                                      ASI185
Resolution      6.4 Mega Pixels 3096*2080    2.3 Mega Pixels 1944*1224
Pixel Size        2.4µm                                       3.75µm
Sensor Size    7.4mm*5mm                            7.3mm*4.6mm

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I think I may try the ASI185MC camera and see what it looks like.  The resolution is much less both because the camera pixel size is bigger and in going from mono to colour - but OTOH when I was focussing on the moon the lens only seemed to be able to do around 6 pixels of the ASI178MM when I zoomed right in so I might not be loosing anything.  If I ever get around to planetary imaging, the ASI178MM would be better than the ASI185MC.

This is an image taken back in June 2015 when I was using the Fujinon zoom lens with ASI185MC.  The Fujinon fish-eye lens is vastly superior in light transmission.

59f4cf799d971_Aurora01.thumb.jpg.f752f18c6324e689c65ebc1a8dc3de7a.jpg

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If I can persuade the lens and camera to line up optimally the sensor will very nearly cover the FOV as can be seen in this screenshot.  I have the ASI185MC attached to the Fujinon fish-eye lens and focused by unscrewing a bit.  OK so this is focused on the room and not further away on stars or moon or even distant trees.  I may try that tomorrow.  I would be quite satisfied with this coverage.  This image was obtained using SharpCap on my Win7 laptop.  I have yet to check it out with INDI and RPi.  I just used the quickest way to check the FOV as I haven't got the RPi wired up ATM.

59f4e01116714_ASI185MC01.png.a385b0afcbf4614ddeb6a4d0ef926579.png

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With the lens in its normal position I get this view.  So I think I need a lens support that permits adjustment in the Y direction as well as Z for focus and which holds the lens with its optical axis at right-angles to the sensor.

59f4e2dd37d0f_ASI185MC02.png.561dc9b5e05e44a58d95f57fad4d2afe.png

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This is the full frame of the ASI178MM which shows how the image circle is offset on the sensor.  All these cameras seem to have the sensor offset a bit from centre.  With the ASI178MM and the sensor covering more than the image circle it doesn't matter - just crop off the unwanted margin.  But for the smaller ASI185 it does matter.  I therefore propose to design a 3D printed adapter to carry the lens and be attached to the camera.  Being plastic this will also thermally isolate the lens from the camera body so that the lens can be heated and the camera cooled.  Hopefully small variations in temperature with resulting varying expansion will not result in the image going out of focus.

59f4e79192a18_Screenshotfrom2017-10-1122-47-00all.thumb.png.7e9560675b4cd27794455a04068be3ab.png

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I shall be interested in seeing how well the ASI85MC and Fujinon fish-eye lens combination work at night.  I plan to use it only for dusk to dawn imaging and make up a much cheaper combination for daytime - maybe RPi camera and CCTV fish-eye lens 12mm board camera mount - possibly for web streaming. 

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Here is the ASI178MM image from above cropped to represent the coverage of the ASI185MC when the image is shifted appropriately to fit it on the sensor.  This shows that the coverage should be quite adequate - I don't need to see the ground below the trees :D

59f5a89726c94_FOV01.thumb.png.a339f195864e518529f783a961bd2cad.png

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Here is a design for the lens support with the inside offset by 0.5mm from the rest.  This is the basic shape and I'll add holes I can tap for grub screws once I've checked this for sizes.  You need a keen eye (or a ruler) to see the offset as it's pretty small.  Side view, top view, bottom view and cross-section.

59f5c141650c4_LensSupport01.png.c41d956bf4b34ae39b7b4bcb9783b740.png59f5c140c3fb8_LensSupport02.png.40c76f0ca853a0307b68300c3b19f686.png59f5c13ff33c3_LensSupport03.png.69b48060ee07f1d5d6c0816c9a3272e9.png59f5c14267d3c_LensSupportSection01.thumb.png.06ca2834069b1bf9e955e97c123ae640.png

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Added a marker to show north (or south, depending on which way the sensor is out).

59f5c71bedf05_LensSupport05.png.b009e78beeef8b286b75f2450a6e0c35.png

 

Edited by Gina

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