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Sky Commander on Orion XT classic

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#1 Jason D

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Posted 22 March 2015 - 10:34 PM

Once in a while, an inquiry is posted about installing DSC computer and encoders on Orion XT classic reflectors. I recently installed a Sky Commander on my XT10 classic and I wanted to share my experience. I considered Nexus DSC which looked interesting but I decided to go with the Sky Commander. I purchased the Sky Commander with 10K encoders and the XT classic installation kit from Astrosystems.
But first let me preemptively answer the following question: Why would an Orion XT10 classic owner invest in a Sky Commander + installation kit when it is cheaper to purchase a used XT10i – a whole 2nd scope with DSC? Furthermore, the same owner can sell the XT10 classic to recuperate a good portion of the XT10i purchase cost. It is a good question and I do not have a good answer. I just love my XT10 classic scope. I owned it for almost 10 years and I put enough customization in it to make it special. I decided to keep it and continue improving it.
As far as why did I finally decide to install DSC, well I got tired from star hopping especially form my light polluted backyard. Besides, it was time to complete another custom scope project for fun
Back to my installation experience. As I mentioned, I purchased the complete kit from Astrosystems. Randy from Astrosystems provided a great customer service.
Installing the Azimuth encoder was relatively easy. Randy provided all needed parts and detailed written installation steps with photos. I built a protective bracket and placed it on the top of the azimuth encoder to shield it from accidental falling objects as shown below. I used a straight metal fastener to build the protective bracket. It is easy to make.

 

skycommander33.jpg

 

skycommander8.jpg

 

As far as the ALT encoder, Astrosystem's solution involves two timing gears and a timing belt. Installing the first timing gear on the ALT bearing is straightforward using parts from the kit. The second timing gear is attached to the ALT encoder. The encoder is mounted on a plastic bracket with two slits. I requested an upgrade from Randy to include thumb screws to make it easier to loosen the encoder bracket for the timing belt removal/reattachment. I also built a protective bracket that is identical to the one I built for the azimuth encoder. The protective bracket also acts as a slide "guide" for the encoder bracket. I like Astrosystem's timing gears and belt setup. The ALT encoder is safe from any damage when the OTA is mounted and dismounted.

 

skycommander2.jpg

 

skycommander1.jpg

 

skycommander5.jpg

 

skycommander6.jpg

 

 

After I installed the system, I devised the following method to test the setup. I used my GLP to point at a paper taped to a wall at a distance of 33 feet. I marked the point where the green laser struck the paper. I then performed a 2 star alignment by pressing the Sky Commander “enter" button twice. Polaris was the default selection for both stars. Polaris now has a relative position of zero for both AZ and ALT.

 

skycommander7.jpg

 

 

Then I randomly moved the scope around its AZ and ALT axes. I completed several full AZ rotations and several full ALT swings. I searched for Polaris again then marked where the GLP laser struck the paper. I repeated the same experiment few times. See below:

 

skycommander4.jpg

 

Interestingly, dividing the circumference of a circle with a radius of 33 feet by the encoder resolution of 10,000, you get ((2*PI*33*12)/10000) = ~0.25". I drew a circle with a diameter of 0.5" and sure enough I was able to fit all marked dots within that circle. For reference, (360 degrees / 10000 steps) = 1 arcminute. That tells me that the Sky Commander did not miss any step.
Note: If you do not have a GLP installed on your scope, the above experiment can also be performed by inserting a laser collimator in the focuser then miscollimate the secondary mirror until the laser beam misses the secondary mirror. Do not expect the laser beam to be pinpoint when it strikes the wall 10s of feet away.

I had a chance to test the setup under the sky for one night. I carefully completed 2 star alignment using Regulus and Aldebaran. Looking for targets at the 4 corners of the sky brought the objects were easy within a plossl FOV at 70X -- or within 20 arc minutes. I will work on improving accuracy and consistency.
Jason


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#2 Jason D

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Posted 23 May 2015 - 06:48 PM

Another round of improvements:

 

Here is what I wanted to do:

 

1- Communicate with Sky Commander via my laptop remotely (wirelessly)

 

2- Use Stellarium to select a target then download its coordinates to Sky Commnander with few easy clicks

 

3- Have Stellarium track where my scope is pointing displaying two FOV circles: 5.5 degree for my RACI and 0.7 for my 17mm EP which I use as a finder.

 

I looked around the web and the only commercially available remote modules for astronomy are in the $150 to $200 range. That is way too much money for such a module.

 

I also found a old thread in CN that describe how to link Sky Commander to Stellurim to have it track OTA movement.
http://www.cloudynig...-commander-xp4/
I followed the instructions and it worked; however, there was no mention on how to download targets. In addition, I did not like the continuous tracking since it will drain my Sky Commander battery quicker.

 

I wanted to stick with Sellarium as opposed to using other astronomy software options. Sellarium is simple and easy to use. Besides, it is free. Interestingly, I read somewhere here on CN that even if I purchased SkySafari Pro, I still will not be able to download targets to Sky Commnander.

 

So, I decided to start my own DIY project to get what I want. First, I wanted to build a wireless module for much less cost than the $150-$200 modules. I researched and found an RS232 bluetooth module called BLK-MD-BC04-B by Bolutek which seems to fit the bill. The cost was around $12 from Ebay. 10s of vendors carry it. You should not have a problem locating a vendor on Ebay that sells it. To complete the setup, I also purchased an RJ12 to RS232 adaptor, USB cable power switch, a project box, a rechargeable battery, and few USB cable connections. My total cost was $30.

 

sky1.jpg

 

I put it all together. It was easy. I just connected different components together. There was no soldering or any special electronic components needed such as resisters or capacitors. The only effort I put into it was drilling holes in the project box then epoxy the different components inside the box. The result was a "professionally" looking module ;)

 

sky2.jpg

 

sky3.jpg

 

IMPORTANT: Even tough building the module was easy, getting it to work was a different story. There are lots of details that I am skipping in this post. The DIY module did not work initially. I could not figure out what was wrong until I borrowed an analog oscilloscope from a friend to figure out what was going on.

 

So far, I solved the hardware problem to enable my laptop to talk to my Sky Commander remotely via bluetooth. I still needed to solve the software problem of getting Stellarium to talk to my Sky Commander. Since I could not find any software solution to allow me to download selected Stellarium targets to Sky Commander, I decided to develop my own software solution. I studied Stellarium API which enables Stellarium to control telescopes then developed a Python script from scratch that works as a mediatory between Stellarium and my Sky Commander.

 

sky4.png

 

sky1.png

 

Bingo!!!! I have a working solution that meets my requirements for ~$30

 

Here is how it works:

1- I power-on the Sky Commander, my DIY bluetooth module, and I start up my custom python which also auto-start Stellarium. Bluetooth connection is established automatically.
2- I complete a typical two star alignment using only my Sky Commander
3- I walk to my laptop then select any target. I have a touch screen which makes it easy to pan Stellarium display, resize, and select targets.
4- I press Cntrl-1 to download the coordinates of the selected target to my Sky Commander. I can also press Alt-1 to download the coordinates of the center on current Stellarium display.
5- Then I move to my scope. Here is the catch: I do not touch any keys on my Sky Commander. The arrows and relative position are already on my Sky Commander display. I just move my OTA until the relative ALT/AZ deltas are zeros. I can continue to do that all night without touching my Sky Commander.

 

Since the Python script is under my control, I added several enhancements:

1- If the script does not detect any RA/DEC changes within 1 minute, it stops polling sync locations from Sky Commander, hence, saving battery life. Once I select the next target, it will wake up again and start polling coordinates.
2- I can use the script in offline mode (without Sky Commander) to select targets and save them in an observing list file. I can create several observing list files. Then I will have the option to replay any of these files during my observing session. That is, I do not need to select targets. The targets and their sequence will be replayed from the selected observing list file. Stellarium can still be used to track the OTA coordinates.
3- I added the option to send any of the observing lists to Sky Commander flash memory. In this case, I will not need the bluetooth or my laptop during the observing session. Personally, I do not like this option too much. I prefer to select targets off Stellarium.

 

Jason


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#3 Jason D

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Posted 23 May 2015 - 06:55 PM

In this post I will describe how I mounted my Sky Commander XP4 on my XT10. I found a sturdy gooseneck mounting holder with a 360 holder clip meant for smart-phones. I found it on Ebay for ~$15. I added few simple improvements to make it even sturdier. It works nicely. The gooseneck and the swivel clip allows me to position my Sky Commander XP4 exactly where I want it to be. I mounted it on the far side of the base to ensure it does not get in my way at night. It is easy to mount/dismount using its sturdy clip. I just clip it on, then connect the RJ11 cable to my DIY bluetooth module and the RJ45 cable to my encoders via an RJ45 coupler. 

 

 

sky5.jpg

 

sky6.jpg

 

sky7.jpg

 

 

 



#4 Jason D

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Posted 23 May 2015 - 06:56 PM

More photos:

 

sky8.jpg

 

sky11.jpg

 

 



#5 Jason D

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Posted 23 May 2015 - 06:59 PM

More photos:

 

sky9.jpg

 

sky10.jpg

 

 



#6 Jason D

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Posted 23 May 2015 - 07:00 PM

sky13.jpg

 

sky14.jpg

 



#7 yonkrz

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Posted 25 May 2015 - 04:33 AM

Looks good Jason,I use the same setup on my 12" Z-dob,also from Randy.they work great.



#8 Jason D

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Posted 25 May 2015 - 03:40 PM

Looks good Jason,I use the same setup on my 12" Z-dob,also from Randy.they work great.

 

Hello Jeff, 

Can you upload photos of your setup?

Jason



#9 Jason D

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Posted 25 May 2015 - 04:23 PM

Does anyone use or know of any commercial astronomy software that allows users to select a target on their laptop/tablet/smart-phone then download the target coordinates to Sky Commander?

 

I did quite a bit of research on the web and I could not find any information to suggest such a software exists. All I found is the ability of many commercial astronomy software to track where the OTA is pointing via the Sky Commander.

 

Below are few photo shots from 2 nights ago. For illustration purposes, I selected M13 on my laptop touch screen then hit Cntrl-1. The coordinates were automatically and wirelessly downloaded to my Sky Commander  with AZ/ALT delta values and arrows ready for me.

 

sky20.jpg

 

After moving my OTA to zero out both AZ/ALT delta values, M13 was within the view of my 17mm EP. On my laptop screen, both my 17mm and RACI FOV circles are centered on M13.

 

sky21.jpg

 

Jason 


Edited by Jason D, 25 May 2015 - 08:08 PM.


#10 yonkrz

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Posted 25 May 2015 - 05:51 PM

092.JPG
095.JPG

 

 

Looks good Jason,I use the same setup on my 12" Z-dob,also from Randy.they work great.

 
Hello Jeff, 
Can you upload photos of your setup?
Jason

 

Heres a couple,i modified it myself,Randy makes a Z-dob setup,but I like the belt better.


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#11 Jason D

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Posted 25 May 2015 - 06:14 PM

I see you installed the ALT encoder on the far side -- that is what I did too.

I see only one thumb knob to secure the ALT encoder. Do you just loosen it and the whole encoder rotates around the other screw?

Jason



#12 yonkrz

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Posted 26 May 2015 - 06:01 AM

I see you installed the ALT encoder on the far side -- that is what I did too.

I see only one thumb knob to secure the ALT encoder. Do you just loosen it and the whole encoder rotates around the other screw?

Jason

Yes,that's what came in the kit,that way I just tilt it to the desired tension.



#13 BDS316

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Posted 26 May 2015 - 06:29 AM

Jason I can see from the pics that you've gone to putting the counterweight on the bottom of the tube rather than the top...Is it working better that way?



#14 Jason D

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Posted 26 May 2015 - 08:26 AM

 

Jason I can see from the pics that you've gone to putting the counterweight on the bottom of the tube rather than the top...Is it working better that way?

 

 

It works much better. 

With counter weight, the goal is to move the center of gravity as close as possible to the ALT axis. The only way to do it is by positioning the weight where you see it in the photo.

Here is the thought process: There is a significant weight at the front/top of the OTA (RACI finder + focuser + eyepiece). The weight of the primary mirror is not enough to offset the weight. To move the center of gravity to the ALT axis, draw an imaginary line from the front/top of the OTA though the ALT axis and extend that line. The extension of the line will move in the direction of the lower/bottom edge of the OTA. That is where the counter weight should be placed. 

In my case, I built a little counter weight consisting of ceramic magnets that follow the curvature of my OTA for maximum traction plus I glued fishing lead weights to the magnets and finally wrapped the whole thing with soft rubber padding,

Jason

 

3353680-counterweight4.PNG
3340122-counterweight.PNG


#15 BDS316

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Posted 26 May 2015 - 02:35 PM

Thanks....another question or two if I may (hope I'm not hijacking the thread but after all we're talking about modifying XT Classic Dobs)

 

I noticed that you have four altitude pads (Teflon or magic sliders?) on each side rather than the usual two.  Please explain...

 

Thanks



#16 Jason D

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Posted 26 May 2015 - 03:02 PM

This thread has been too quite. You are not hijacking it :)

 

These are magic sliders. The reason I went with 4 because:

1- I wanted to distribute the weight on several sliders

2- Since I am using FRP around the ALT hubs, more contact points meant smoother movement. That is, since FRP has a relatively rough bumps, more contact points will average out the bumps to give me a smoother movement.

 

I do not want to make it sound that I put too much science behind my mod. I just did it for what I believed to be good reasons (above) and never looked back.

 

These are old photos. Ignore the weight position.

 

4958476-alt_mod.JPG
4874333-alt.jpg
5385766-3cb9.jpg

 

 


Edited by Jason D, 27 May 2015 - 12:48 AM.


#17 Jason D

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Posted 14 February 2016 - 03:03 PM

I have been exchanging PMs with a fellow member about the information I included in this 1 year old thread. When the fellow member asked for details I realized I could not recall many of them. I had to dig deep for old notes and I had to take apart what I built to get answers. So, while the regained knowledge is fresh in my mind, I decided to resurrect this old thread and document them for future reference.

.
If you decide to purchase an "RS232 Bluetooth Serial Adapter" (I just checked EBAY -- the cheapest is $9.01 from Hong Kong) to setup a bluetooth wireless connectivity between Sky Commander and your tablet/laptop then you need to:

 

skycommander13.jpg

1- Purchase a new "DB9 to RJ11 female" (I just checked EBAY -- the cheapest is $3.29) similar to the one you got from Sky Commander.

.
2- Purchase or look around your house for an extra RJ11 phone cable (RJ12 is OK). Do not use the Sky Commander provided RJ11 cable -- more about this later in this post.

.

3- Configure the DB9 to RJ11 adapter based on the following connectivity -- BE VERY CAREFUL AND DOUBLE CHECK. Once you insert the hollow end pins of the DB9 to RJ11 adapter, you can't pull them out without damaging them. Furthermore, I recommend cutting all remaining unused hollow pins to avoid electric circuit shorts.

 

skycommander15.jpg

skycommander11.jpg

That is it!!! Connect the off-the-shelf RJ11 cable between Sky Commander and the DB9 adapter then connect the DB9 adapter to the RS232 Bluetooth adapter. Make sure your baud rate is setup at 9600 -- the default for Sky Commander.

.

You can also purchase a battery (check mine earlier in this post).

.

I have been using my solution for around 1 year without issues. The battery lasts few observing sessions before a recharging it. 

.

Now all you need to do is setup your tablet/laptop to connect to the bluetooth adapter -- beyond the scope of this post.

.

About Sky Commander provided cable, Sky command RJ11 cable is connected differently (at least mine) from off-the-shelf RJ11 cables. That implies you can't just purchase another off-the-shelf RJ11 cable (phone line cable) and expect it to work. Apparently, the Sky Commander vendor has one  end-connector twisted compared to the other end-connector. The following photo will clarify what I meant:

 

skycommander10.jpg

.

If you really really really want to use the Sky Commander provided cable instead of off-the-shelf RJ11 cable then use the following connectivity; however, now you will be bound to the Sky Commander provided cable. To get a longer cable in the future, you will need to get it from Sky Commander at high cost or build your own cable. Again, you are better off using an off-the-shelf RJ11 cable with the connectivity I provided earlier

 

skycommander12.jpg

 

One more important piece of information: If you connect the RS232 bluetooth adapter to Sky Commander provided RJ11 and Sky Commander provided DB9 adapter, it will NOT work. You need to reverse TX and RX lines. To understand what I mean, compare the above illustration to the one included in Sky Commander vendor website  http://www.skyeng.com/cable.html (last diagram). Or you can refer to the one below:

 

skycommander14.jpg

 

Jason


Edited by Jason D, 14 February 2016 - 06:39 PM.

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#18 Jason D

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Posted 14 February 2016 - 03:10 PM

 

 

Jason I can see from the pics that you've gone to putting the counterweight on the bottom of the tube rather than the top...Is it working better that way?

 

 

It works much better. 

With counter weight, the goal is to move the center of gravity as close as possible to the ALT axis. The only way to do it is by positioning the weight where you see it in the photo.

Here is the thought process: There is a significant weight at the front/top of the OTA (RACI finder + focuser + eyepiece). The weight of the primary mirror is not enough to offset the weight. To move the center of gravity to the ALT axis, draw an imaginary line from the front/top of the OTA though the ALT axis and extend that line. The extension of the line will move in the direction of the lower/bottom edge of the OTA. That is where the counter weight should be placed. 

In my case, I built a little counter weight consisting of ceramic magnets that follow the curvature of my OTA for maximum traction plus I glued fishing lead weights to the magnets and finally wrapped the whole thing with soft rubber padding,

Jason

 

 

 

More recent thread and a post pertaining to my weight-balance solution:

 

 

http://www.cloudynig...llic-solid-ota/

 

http://www.cloudynig...-dob/?p=6930387

 

counterweights2.png
 
counterweights.jpg

 

Jason




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