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Add GoTo Capability

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#1 JohnMeggers

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Posted 25 March 2019 - 03:39 PM

Is there a relatively easy way to add GoTo capability to an older Losmandy G11, such as software running on a laptop, or is the best way (or only way) really to upgrade to the Gemini 2 system? I initially assumed something like PHD would accomplish what I'm asking, but now I'm not so sure. From what I'm reading, it sounds like PHD is more designed to control guiding, and so far I haven't found what look like any good alternatives. I was hoping for an approach that would be less expensive than the $1,600 Gemini 2 upgrade. Using my G11 as a non-GoTo mount, my star-hopping skills have improved greatly, which is good, but I want to start doing some AP, and don't want to spend most of my time hunting for a DSO to shoot. Pretty much everyone I've talked to about finding objects for AP says they use a GoTo system to locate them. Thanks for any information or suggestions.

 

John Meggers

Naples, FL

 



#2 Rustler46

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Posted 25 March 2019 - 03:59 PM

I did a quick search online for "Encoder Kit for Losmandy G-11" and found this source:

 

Losmandy GM8/GM11 Encoder Kit

 

This is just one of the search results high up on the list. So there may be other solutions that better fit your requirements. Ebay has some listings for Losmandy G-11 accessories.

 

In any case this hardware is considerably less expensive than the Gemini-2 solution at $1600. You would still need the software to work with the hardware. The push-to versus go-to functionality might be useful for what you want to accomplish. I hope this gives some food for thought. Losmandy products are indeed quite speedy, but of high quality. Your G-11 gives you a good basic GEM mount. The addition of object location capability would be a major upgrade. I really like my Gemini-1 setup.


Edited by Rustler46, 25 March 2019 - 04:06 PM.


#3 DuncanM

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Posted 25 March 2019 - 04:22 PM

The geared stepper motors on the Losmandy can be converted to goto via the Onstep controller system for about a $100. However goto speeds will be very slow (~.33d/sec).

 

You can replace the stock motors with larger stepper motors for more cost and some tinkering and get 1 to 3d/sec slew rates and you would control the mount via Onstep or via something like this:

 

 

https://www.cloudyni...-mount-gm8-g11/

 

which is a complete bolt-on kit for $240... It doesn't get easier or cheaper than that.


Edited by DuncanM, 25 March 2019 - 04:27 PM.

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#4 photoracer18

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Posted 25 March 2019 - 04:26 PM

The original stepper motors don't have enough power to do go-to. Pretty much everything that was advanced to go-to used servo motors originally because of the power output and because higher voltage also made servo motors run faster. Was not till later that go-to systems could be made to work on steppers but they have to be able to sustain a faster rate of stepping.

Why do you think you can't do AP with a non-goto G11. Plenty of imaging has been done with non-go-to mounts. Go-to mounts are good if you want to image things that don't travel at the sidereal rate. But as long as you can stick an auto-guider on a mount you can image with it. Later this year I plan on adding an ST-4 guider port on my gigantic Schaefer AT-9 mount. Thinking I might put my 16" Dob on it as the project is doable.
Be nice if I could add DSCs to it but not needed. I have a G11 Gemini 1 I am thinking I might return to non-go-to status. Already have the parts and it has DSCs on it so I can find anything I don't know where its located by memory. Go-to has made people lazy. I picked up a camera about the same time I did my first AP in the early 60's. Long exposure and no auto-guiders. It was all self guiding thru a cross-hair eyepiece. I added manual slow motion controls and a 60mm guidescope to my Criterion RV-6 so I could image in HS. Were no drive correctors then either (at least ones I could afford). No plate solving to align the mount, You had to drift align it yourself once I found someone who could describe how to do it. No taking short exposures and stacking.
OK, enough on that as I step down off my soapbox.

Consider adding digital setting circles to your mount. Depending on your mounts era you may be limited to only Losmandy encoder mounts or you could possibly use JMI ones if its old enough. As for a DSC computer the gamut is pretty wide. I use an Argo Navis which in my estimation is the best except for the Nexus II system. But you can just as easily use something like an old JMI NGC mini-MAX. It has all the Messier and 7K of the NGC objects and fits in your hand pretty well. I recently sold one for only $35 because it was included with a set of encoders to fit my 16" Dob and I didn't need it. You can likely find everything you need to add them for $500 or even less. If the axis's of your mount have flat spots machined in them with a couple of threaded holes you can use the JMI encoder package which is cheaper than the Losmandy one.

#5 bridgman

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Posted 25 March 2019 - 05:20 PM

My recollection is that the G11 has pretty good mechanical setting circles, which should be able to get you into the ballpark. The big change over the last few years AFAICS is the emergence of plate solving tools, which can work with your imaging camera to figure out exactly where the scope *is* pointing.

 

I'm hoping that those two in combination should be sufficient to find AP targets fairly quickly without a full GOTO system, but I'm probably a few weeks away from knowing if that is actually the case.

 

I was looking through all the upgrades available from Losmandy, but my conclusion was that if I'm going to do anything more than upgrade the worms it would probably make more sense to sell the current mount and buy a new one with Gemini2, tucked motors, spring-loaded worms and all the other goodies.

 

Ignoring everything I just said, that EQStar package looks pretty darned interesting. Only caution would be that it may need an additional device if you want to do guiding as well as GOTO but it still seems like great value.



#6 JohnMeggers

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Posted 25 March 2019 - 10:00 PM

Why do you think you can't do AP with a non-goto G11. Plenty of imaging has been done with non-go-to mounts.

It's not that I don't think I can do AP without a GoTo, it's just that I don't want to spend all my time locating objects, and not have much time to image them. 



#7 JohnMeggers

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Posted 25 March 2019 - 10:03 PM

My recollection is that the G11 has pretty good mechanical setting circles, which should be able to get you into the ballpark. The big change over the last few years AFAICS is the emergence of plate solving tools, which can work with your imaging camera to figure out exactly where the scope *is* pointing.

 

I'm hoping that those two in combination should be sufficient to find AP targets fairly quickly without a full GOTO system, but I'm probably a few weeks away from knowing if that is actually the case.

 

I was looking through all the upgrades available from Losmandy, but my conclusion was that if I'm going to do anything more than upgrade the worms it would probably make more sense to sell the current mount and buy a new one with Gemini2, tucked motors, spring-loaded worms and all the other goodies.

 

Ignoring everything I just said, that EQStar package looks pretty darned interesting. Only caution would be that it may need an additional device if you want to do guiding as well as GOTO but it still seems like great value.

I'll be interested to hear what your experience is with the plate solving tools. I don't yet understand enough about how those work to make a guess. I would tend to agree with you on the upgrade path, but at this point, even paying full price for the Gemini 2 upgrade, I still have less into the mount than had I bought the full package new. Please let me know how things go with your finding targets.



#8 hcf

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Posted 25 March 2019 - 11:17 PM

I recently did a DIY platesolving pushto for visual using an action cam.  It might illustrate to you how pushto works with platesolving.

 

https://www.cloudyni...sual-astronomy/

 

For AP you would not need the  action cam, but be able to use your imaging camera instead (if it is compatible with the popular tools).

 

You need to find out if your mount motors are controllable by a computer. You won't need it for a platesolving pushto but will need it for guiding. This is where something like ONSTEP would come in handy.  


Edited by hcf, 25 March 2019 - 11:19 PM.


#9 bridgman

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Posted 26 March 2019 - 01:00 AM

AFAIK even the oldest G11s supported ST-4 autoguiding inputs, but I don't know that for fact.

 

The older G11 drives (and I guess newer ones as well) require relay/opto isolated drive for the ST-4 inputs. I'm guessing that newer cameras all include optoisolators since the opto prices have come down so much, but I have not yet confirmed that and need to do so before I plug the ASI290MC into the 492 drive of the G11. My understanding is that plugging the ST-237 into a G11 without a relay box is not recommended, although it may work if the G11 and ST-237 are on different power supplies, ie at least one is fed via AC adapter, so you can see why I'm hoping newer cameras do include the optoisolator stage.

 

EDIT - after some poking around on the ZWO site I found a post from Sam confirming that all the ASI cameras had opto-isolated ST-4 outputs, so should just plug & go:

 

https://bbs.astronom...ilit=g11#p14869

 

Thanks for posting the info about plate-solving push-to... just going through it now.


Edited by bridgman, 26 March 2019 - 01:28 AM.


#10 JohnMeggers

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Posted 26 March 2019 - 11:49 AM

AFAIK even the oldest G11s supported ST-4 autoguiding inputs, but I don't know that for fact.

 

The older G11 drives (and I guess newer ones as well) require relay/opto isolated drive for the ST-4 inputs. I'm guessing that newer cameras all include optoisolators since the opto prices have come down so much, but I have not yet confirmed that and need to do so before I plug the ASI290MC into the 492 drive of the G11. My understanding is that plugging the ST-237 into a G11 without a relay box is not recommended, although it may work if the G11 and ST-237 are on different power supplies, ie at least one is fed via AC adapter, so you can see why I'm hoping newer cameras do include the optoisolator stage.

 

EDIT - after some poking around on the ZWO site I found a post from Sam confirming that all the ASI cameras had opto-isolated ST-4 outputs, so should just plug & go:

 

https://bbs.astronom...ilit=g11#p14869

 

Thanks for posting the info about plate-solving push-to... just going through it now.

Mine is an older G11, one of the Celestron-branded ones.



#11 JohnMeggers

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Posted 27 March 2019 - 01:04 PM

I was thinking about this last night when I had my scope out in my back yard. Could I use plate solving in the following way: Use my finder sight (Telrad, etc.) to get in the ballpark of where I think my target, capture an image, plate solve to figure out where I actually am (specifically in relation to my target object), and then use that to establish a vector (direction and distance) to reach my object? I understand this could perhaps need to be done more than once to find the target.

 

So am I on the right track? It seems a bit like this is a variation on star hopping, the difference being you're using a computer to analyze an image to identify a location, as opposed to starting from a known location. Plate solving would (theoretically) identify the current location regardless of having to use a visible star as an identifiable starting point. This wouldn't require GoTo, but would definitely be faster than visually star hopping from a known location.

 

Thanks for any comments or explanations.

 

John


Edited by JohnMeggers, 27 March 2019 - 01:06 PM.


#12 DuncanM

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Posted 27 March 2019 - 01:35 PM

I was thinking about this last night when I had my scope out in my back yard. Could I use plate solving in the following way: Use my finder sight (Telrad, etc.) to get in the ballpark of where I think my target, capture an image, plate solve to figure out where I actually am (specifically in relation to my target object), and then use that to establish a vector (direction and distance) to reach my object? I understand this could perhaps need to be done more than once to find the target.

 

So am I on the right track? It seems a bit like this is a variation on star hopping, the difference being you're using a computer to analyze an image to identify a location, as opposed to starting from a known location. Plate solving would (theoretically) identify the current location regardless of having to use a visible star as an identifiable starting point. This wouldn't require GoTo, but would definitely be faster than visually star hopping from a known location.

 

Thanks for any comments or explanations.

 

John

 

 

 

You want to image an object.

 

PA your mount.

 

Aim the OTA where you think the object is, and plate solve the image; it returns an RA and Dec. You adjust your setting circles to that RA and Dec and then using the high speed setting on your drive, slew the mount to the RA and Dec of the target and plate solve again and repeat the process.

 

 

You can use Onstep with your current motors to automate this process, where you would manually slew the mount to within a few degrees of the target, platesolve, sync the Onstep software to that position, then command it to slew to the target object. It will whir away at 40 to 80x sidereal (~.15 to .3d/sec) and in a minute or less it should be accurately centred on the target.

 

 . 



#13 hcf

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Posted 27 March 2019 - 02:57 PM

I was thinking about this last night when I had my scope out in my back yard. Could I use plate solving in the following way: Use my finder sight (Telrad, etc.) to get in the ballpark of where I think my target, capture an image, plate solve to figure out where I actually am (specifically in relation to my target object), and then use that to establish a vector (direction and distance) to reach my object? I understand this could perhaps need to be done more than once to find the target.

 

So am I on the right track? It seems a bit like this is a variation on star hopping, the difference being you're using a computer to analyze an image to identify a location, as opposed to starting from a known location. Plate solving would (theoretically) identify the current location regardless of having to use a visible star as an identifiable starting point. This wouldn't require GoTo, but would definitely be faster than visually star hopping from a known location.

 

Thanks for any comments or explanations.

 

John

Yes, you can do that. That is how I started, but then automated the procedure and connected the output of plate solving to Sky Safari so I could visually see where I was. It was not very difficult to do this on a linux computer/raspberry pi running the astrometry.net platesolver locally.



#14 bridgman

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Posted 27 March 2019 - 05:48 PM

So am I on the right track? It seems a bit like this is a variation on star hopping, the difference being you're using a computer to analyze an image to identify a location, as opposed to starting from a known location.

Yep... you either use setting circles or star-hopping to get close, then plate solving helps you get on target. Alternatively if you have a guidescope/camera you could do something even more like computer-assisted star hopping (where plate-solving catches you if you get lost).

 

I forgot to ask if your G11 has manual setting circles. I don't know if the Celestron-branded ones have them.


Edited by bridgman, 27 March 2019 - 05:51 PM.


#15 JohnMeggers

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Posted 28 March 2019 - 10:18 AM

Not certain about the setting circles. I believe so but I’ll have to check tonight.

#16 JohnMeggers

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Posted 28 March 2019 - 11:04 AM

Yes, you can do that. That is how I started, but then automated the procedure and connected the output of plate solving to Sky Safari so I could visually see where I was. It was not very difficult to do this on a linux computer/raspberry pi running the astrometry.net platesolver locally.

So are running astrometry.net software on the same RPi you're running Sky Safari on? I use SS on my iPad but wasn't aware until now (when I looked) it is also available for laptop platforms. Professionally, my work is on the network side, not the host side, so I can stumble my way around Linux but I'm far from competent at it. My laptop is a Mac.


Edited by JohnMeggers, 28 March 2019 - 11:04 AM.


#17 hcf

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Posted 28 March 2019 - 03:10 PM

So are running astrometry.net software on the same RPi you're running Sky Safari on? I use SS on my iPad but wasn't aware until now (when I looked) it is also available for laptop platforms. Professionally, my work is on the network side, not the host side, so I can stumble my way around Linux but I'm far from competent at it. My laptop is a Mac.

No, Sky Safari still runs on my tablet.  The pi just acts like a digital setting circle which provides location information got from platesolving, over wifi to Sky Safari. The IP address of the Pi and a port are set in sky safari. It uses a common protocol called the Basic Encoder System which is used by most DIY setting circles to talk to Sky Safari.  (encoder.py in the github repo below).

If you are familiar with linux/python you could look at my code for the plate solving pushto on github here

 

https://github.com/arhcf/pswai

 

The code above uses an action cam, but if you can figure out how to get a photo from your imaging camera into the pi, eg: use gphoto2 for DSLRs, you can replace the action cam part with a gphoto2 call. Are you planning to use a DSLR?

 

If you can get astrometry.net working locally on the Mac laptop (check on their google group), you should be able to run the code above on the mac laptop too instead of a pi (not 100% certain, but I can't think of any obvious problems).

 

You could first try to setup astrometry.net on the mac, connect it to the camera, and try to do platesolving manually. If that works, then try to connect it to SS using the code above.


Edited by hcf, 29 March 2019 - 12:47 PM.



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