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  #241  
Old 25-02-2019, 12:08 PM
Stefan Buda
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I will second what John said. Stefan is a all round nice guy with an designer's eye for detail and an engineer's demand for precision.
I've been following this thread and it's an impressive piece of work!
Thanks Bo for the kind words.

I left the scope set up last night and woke up early this morning so I snapped some lo-res moon images.

The attached image is a single 8ms capture with the old QHY8 OSC.
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  #242  
Old 25-02-2019, 09:43 PM
Stefan Buda
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I tested my improvised OAG last night and it works, but I will need to fiddle with the PHD settings to get it better. Even as it is now, I get better guiding than with the guide scope.
By the time I sorted some camera problems, it got late and even the moon was up, so I just grabbed 10x60sec subs of Eta Car and some darks to match.
Should be good from a dark site with more subs and calibration frames.
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  #243  
Old 03-03-2019, 04:05 PM
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Went to the Messier star party last night and I wanted to do a 3 panel mosaic of Eta Car, but unfortunately I was not able to solve my guiding problems. One of the axes misbehaved all night. Tomorrow I will perform autopsy on the old EQ6. I bought it second hand many years ago and I always used it with short focal length instruments until now.
The attached image is a roughly processed bunch of 59 minutes of not very good subs - due to poor guiding. Full frame of QHY8 resized to 40%.
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  #244  
Old 03-03-2019, 04:21 PM
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Remarkable work Stef, my hat is off to you.
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  #245  
Old 04-03-2019, 09:25 AM
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Very promising results Stefan,
Any chance of you coming to Snake Valley this weekend for some fine tuning of your CDK?
Bo
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  #246  
Old 04-03-2019, 04:07 PM
Stefan Buda
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Remarkable work Stef, my hat is off to you.
Thanks Dave.
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Originally Posted by traveller View Post
Very promising results Stefan,
Any chance of you coming to Snake Valley this weekend for some fine tuning of your CDK?
Bo
Hi Bo,
I ripped apart my mount this morning and made some improvements to the mechanism. The DEC axis idler gear was able to move sideways because the shaft was smaller than the hole in the gear. I wanted to make a better fitting shaft but I discovered that the hole in the motor plate, for the shaft, was not drilled squarely. I ended up drilling a larger hole, making a new shaft, and increasing the hole in the idler gear. To get to the point, if I can get the mount working satisfactorily, I will zip up to Heathcote again to have a go at producing an image. At this stage it looks like it will be Wednesday, if the forecast holds. Unfortunately Snake valley is a bit uncertain weather-wise and I don't want to risk wasting time at this stage. One day I would like to make it to Snake Valley though.
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  #247  
Old 04-03-2019, 05:29 PM
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Guiding issues aside it looks like an excellent performer Stefan
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  #248  
Old 12-03-2019, 08:16 AM
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Guiding issues aside it looks like an excellent performer Stefan
I'm very happy with its optical and mechanical performance, but with my present camera I won't be able to get the max resolution out of it. For that I would need a mono camera with smaller pixels and probably a better mount.

Meanwhile I made another CF tube and managed to avoid some of the cosmetic issues I had with the first one.
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  #249  
Old 21-03-2019, 12:50 PM
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I should have posted a 100% crop from the last image to better show the resolution. With a well matched pixel size mono camera and good tracking/guiding it should have no problem exploiting the full resolution that seeing allows.

At the moment I'm in the process of selecting and ordering components for the controller box so that I can start designing the PCB.

There will be no updates for a while as I'm also taking two weeks off for a late holiday.
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  #250  
Old 21-03-2019, 10:28 PM
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Enjoy yourselves.
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  #251  
Old 26-04-2019, 03:40 PM
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I've been struggling with the problem of how to separate the control box from the back plate of the OTA in order to mount it on the pier in a fixed position. The main difficulty is that at least 13 wires are required to do it properly.
In the end I settled on a 15 pin D-Sub connector as the required cable is available from Jaycar.
Next I designed a small PCB with 3 connectors that will live inside a small junction box attached to the back plate. This box will also contain the ambient temperature sensor and a status LED.

I will be using an Arduino Uno for the controller as it has nice robust USB socket and voltage down converter.
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  #252  
Old 08-05-2019, 08:59 PM
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DHL contacted me today about the junction box PCBs being on their way from China.

Meanwhile I finished designing the PCB shield for the Arduino. It has 3 MOSFET switches for controlling the heaters and the fan - connected to PWM pins.
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  #253  
Old 11-05-2019, 10:49 AM
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It took DHL less than two days to deliver the PCBs, from the factory in China to my doorstep.
And the Chinese did a great job too.
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Last edited by Stefan Buda; 12-05-2019 at 08:20 AM.
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  #254  
Old 16-05-2019, 12:09 PM
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What would we do without the efficient Chinese manufacturing.
Took one week from uploading the Gerber files to receiving the finished PCBs for the Arduino shield.
The junction box is finished. I now have to 3D print a solder template for applying solder paste to the PCB - for the SMD components.
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  #255  
Old 29-05-2019, 08:29 PM
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All functionality tested, with bits of code, and working well.

I also designed and 3D printed an enclosure as I could not find anything off the shelf to suit. I'll post a picture when the cosmetic finish is done.
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  #256  
Old 29-05-2019, 09:02 PM
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Great to see the finer details coming together
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  #257  
Old 01-06-2019, 04:25 PM
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Thanks Colin. I really like your giga-mosaics, by the way.

I gave the box a textured paint finish to hide the 3D printing lines.

Also I discovered that I can't communicate with the temperature probes when the stepper motor driver is enabled, due to interference caused by PWM. Fortunately I designed the focuser to operate in full step mode so that the stepper can be powered down when not needed to move, without loosing position.
One LED is the 12V power indicator and the other two are for the heaters.
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  #258  
Old 22-06-2019, 10:16 PM
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I have been testing the controller code for almost a week now. The software is meant to remain powered up permanently, in an observatory setting.
On initial power up it starts monitoring the ambient temperature and the two mirrors temperature as well. Once it detects a change of 0.25 degrees C, it starts to make decisions about turning on heaters and fans. If the the ambient is dropping and the primary is lagging behind more than a preset value, then the fans come on. The secondary heater comes on when needed, to stop the secondary from over cooling during the night. The primary is less likely to over cool but there is a preset temperature for the primary heater to come on if needed. Every time there is a further drop in ambient, the software resets the minimum temperature reached and that becomes useful in the morning when the ambient starts to rise rapidly and the optics tend to fog up. Once the software detects the rise it switches on both heaters and the fans and keeps them going until the ambient gets to a preset value above the minimum reached. The hope is that by that time air humidity has dropped enough so that the heaters and the fans can be powered down to await the next cycle of dropping temperature.
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  #259  
Old 23-06-2019, 08:35 AM
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Quote:
Originally Posted by Stefan Buda View Post
I have been testing the controller code for almost a week now. The software is meant to remain powered up permanently, in an observatory setting.
On initial power up it starts monitoring the ambient temperature and the two mirrors temperature as well. Once it detects a change of 0.25 degrees C, it starts to make decisions about turning on heaters and fans. If the the ambient is dropping and the primary is lagging behind more than a preset value, then the fans come on. The secondary heater comes on when needed, to stop the secondary from over cooling during the night. The primary is less likely to over cool but there is a preset temperature for the primary heater to come on if needed. Every time there is a further drop in ambient, the software resets the minimum temperature reached and that becomes useful in the morning when the ambient starts to rise rapidly and the optics tend to fog up. Once the software detects the rise it switches on both heaters and the fans and keeps them going until the ambient gets to a preset value above the minimum reached. The hope is that by that time air humidity has dropped enough so that the heaters and the fans can be powered down to await the next cycle of dropping temperature.
Hi Stefan, good to see you again up and about.
You have a heating pad for the secondary and fans only for the primary, correct?
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  #260  
Old 23-06-2019, 10:14 AM
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I am curious. What does overcooling the secondary do? I thought the cooler the better when it came to mirrors or is it more the cooler the better so long as the secondary and primary are in sync with regards to ambient?

Does it make the secondary shift shape slightly compared to the primary?

Greg.
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