Gina Posted October 24, 2016 Author Share Posted October 24, 2016 I always prefer to make things if I can and enjoy the process. I could have stopped at various points in my ASC project but my projects tend to be never-ending As for costings, I'll tot up how much my present ASC incarnation would cost to make up from scratch sometime - I would be interested to know myself. A much cheaper ASC could be made using a lower resolution camera and would be quite adequate for watching out for clouds. My Mk 5 is for very wide field imaging as well as for cloud watching. Even when the Mk 5 is fully working it won't be the end of my all sky cameras - I plan to produce a complementary colour version for daytime use. Link to comment Share on other sites More sharing options...
Gina Posted October 24, 2016 Author Share Posted October 24, 2016 I've worked out a layout of components for the RPi HAT that allows for control of 2 dew heaters and the Peltier TEC. Or more correctly one dew heater and one raindrop "drier upper". Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Here's a screenshot of the Astroberry INDI driver library for the parts used in the ASC RPi control. I am using the first three lines of the Astroberry Board control driver to control the Peltier TEC (Line A) and the dew heaters (Lines B & C) using electronics parts rather than relays (as shown in posts above). The Astroberry Focuser driver is being used with a different stepper motor and driver module (as previously mentioned) viz. modified 28BYJ-48 5v and A4988 driver module. Only full stepping is used so only the DIR, STEP and SLEEP lines are used. The micro-stepping control lines and ENABLE are left unconnected leaving the stepper driver always enabled and in full stepping mode. The RESET line is connected to +3.3v to hold it at logic "1". To summarise, the following GPIO lines are used, with their functions. Focuser :- GPIO4 - DIR GPIO17 - STEP GPIO23 - SLEEP Board :- GPIO5 - Peltier TEC control - Line A GPIO6 - Dew Heater - Line B GPIO26 - Rain Evaporator - Line C The focuser is controlled by KStars/Ekos in either Manual or using Auto-focus modes. Currently the cooling and heater controls are simply called Line A, Line B and Line C in Ekos but I might edit the Astroberry Board INDI driver code to show more meaningful controls in Ekos. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Amended cooling and heater control circuits :- Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 This is interesting Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 I think the new HAT for the ASC is complete. Connected power to the HAT before connecting to RPi to set the output voltage of the buck converter to 5.1v as required by the RPi. Then turned off bench PSU power and plugged the HAT onto the GPIO pins and the RPi power plug into the power socket on the RPi. Next step was to power up again with the 13.8v (as per observatory supply) and connect with PuTTY and KStars/Ekos. Firstly, the cooling control which is working fine This was followed by connecting the present dew heater first to one heater line and then the other. Both are working fine. New HAT has passed all tests Next job is to construct a second heater so that rain drops may be dried off the dome. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Missed a test But it has passed that too. I didn't have a stepper driver module plugged in before but now have a new A4988 module and the stepper motor rotates both ways fine using Manual focussing Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Now have the ASC outdoors hung on the guttering as usual fro testing. When first put out the camera sensor temperature was 24.5°C. I've now switched the cooling on and watching the temperature falling Now down to 11°C and there's dew showing. So I'll now switch on the dew heater. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Hmm... I don't think the dew heater will help with the sky view - fog has moved in and the visibility is down to about 20m Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Here's a couple of photos of the new HAT and dew/raindrop heaters. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 With 2 or 3 faint stars showing through the fog I though I'd try auto-focus - and it worked Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 As a result of the auto-focus, there are more stars showing. This is a 30s exposure. The fog has got thicker - the weather station mast is no longer visible from the house (about 10m). Doesn't seem to be all that thick vertically though so I guess this is basically low cloud. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 With the cooler on the sensor temperature went down to 5°C but has risen to 6°C with the dew heater on. It rose to 6.5°C with both heaters on which quickly cleared the dew even in the fog and now with just the lower power heater on there is no dew showing and the camera sensor is slightly cooler. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 I think I have now pretty much finished the Mk.5 ASC. The new HAT and control circuitry appears to be working perfectly. The Peltier TEC external camera cooling is working well and making a significant reduction in thermal noise enabling exposures of 60s or more. The dew heater is working well even with virtually 100% RH (fog) and it only remains to test the full heating power against rain. No doubt that test will be available before too long The only thing left now is to take the ASC plus mast out to the observatory and screw the bracket to the framework just outside the warm room and feed the power cable inside. Oh and also to check the WiFi signal and fit the repeater if necessary. With the ASC virtually finished I am now concentrating on the control and power distribution box for my main imaging system and moving to the relevant thread. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 There just remains one thing left that I want to add to this thread - the total cost of parts involved. I am leaving that for another day... Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 The fog has thinned a bit and the stars are showing better so I have repeated the autofocus process and obtained a much better result with an HFR of only just over a pixel as can be seen in this screenshot. Link to comment Share on other sites More sharing options...
Gina Posted October 25, 2016 Author Share Posted October 25, 2016 Here's the latest 30s capture following autofocus. I'll make that it for tonight and post more images when the sky is clearer. Link to comment Share on other sites More sharing options...
hughgilhespie Posted October 26, 2016 Share Posted October 26, 2016 Hi Gina, Well done on finishing this project. Inspiring as always and well thought through. Regards, Hugh Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2016 Author Share Posted October 26, 2016 Thank you Hugh Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2016 Author Share Posted October 26, 2016 Clear sky tonight an I've been capturing ASC images and also improving the focus using the Ekos autofocus - getting down to an HFR of 1.4 pixels. Screenshot of focuser screen and 2 captures the second with histogram stretching. I can just about make out the NAN Link to comment Share on other sites More sharing options...
ChrisLX200 Posted October 26, 2016 Share Posted October 26, 2016 Hate to say it but.. that looks out of focus to me? We use the same camera and same lens Gina so I'm used to the images it produces Perhaps it's the dome? ChrisH Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2016 Author Share Posted October 26, 2016 I thought that but the autofocus system reported the star focussed on as having an HFR of 1.4 pixels. I agree, it doesn't look like it. Think I'll try manual focus another night. It did seem to choose a star near the centre of the field but... Link to comment Share on other sites More sharing options...
ChrisLX200 Posted October 26, 2016 Share Posted October 26, 2016 Pah! Computers - what do they know? This is a jpeggy image (so a bit fuzzy..) @ 10sec using similar kit ChrisH Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2016 Author Share Posted October 26, 2016 Yes, your image looks sharper than mine Chris - a lot sharper. Link to comment Share on other sites More sharing options...
ChrisLX200 Posted October 26, 2016 Share Posted October 26, 2016 Is there any backlash (or backlash compensation) in your focusing mechanism - such that it calculates the postion correctly but then doesn't manage to turn the lens all the way? ChrisH Link to comment Share on other sites More sharing options...
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