What is the purpose of EQMOD, Stellarium & APT Align/Sync?

[GuySt]

I'm unclear on the purpose for the various align and sync options in the control chain between mount and software and, unsurprisingly, I can find no clear explanation. Thus my questions below.

What I have:

Sky-Watcher HEQ5 <--> EQMOD <--> Stellarium <--> APT
                      EQMOD <--> APT

It's all talking to each other. I can Connect Stellarium to EQMOD/HEQ5, select a target, select Slew, and EQMOD moves the HEQ5. I can Connect APT to EQMOD/HEQ5, select an Object, and select GoTo, and EQMOD will move the HEQ5. Now I'm trying to get a handle on making sure that EQMOD, Stellarium, and APT all look at the same thing. Off to Google, YouTube and this Forum for ideas.

I discovered that EQMOD has an Alignment/Sync section and I found a YouTube vid (apparently by an EQMOD dev!) explaining how it works using Stellarium. He calls this GoTo alignment so that when Stellarium issues a Slew comment to EQMOD, EQMOD knows how much error correction it must apply in communicating with the mount. This process requires a scope with an eyepiece (to center the object using EQMOD's controls) and it uses the Stellarium Sync command. A problem here is that I do not have a scope, I have a Williams Optics RedCat 51 with a Nikon D7500 attached.

Q1: I suppose I could attempt to use the D7500's Live View to do this; has anyone done this kind of Alignment/Sync either with a Nikon or Canon or Sony product using the camera's Live View?

I turned my attention to APT and its PlateSolving options. I understand that the reason for use of PlateSolving is to get APT and Stellarium "synced" such that the RA/DEC for what one sees when one takes an image using the camera connected in APT is precisely the same in Stellarium. To do this, APT's PlateSolving tools also uses a Sync command.

Q2: What's the difference in doing the EQMOD <--> Stellarium Alignment/Sync steps versus the APT <--> Stellarium PlateSolving steps?

Q3: Are they related or do they interact? Does APT's Sync talk to BOTH Stellarium and EQMOD or just to Stellarium?

Q4: Should I be doing both?

Q5: If yes to doing both, which comes first?

I confess I spent many hours today trying to get a simulation working to see if doing APT's PlateSolving and its use of Sync gets all the way to EQMOD, but I could never get any of the three PlateSolving apps installed in APT to successfully complete a Solving run on multiple images--not one of the three (very frustrating), and thus I turn to you.

Regards.

Edited September 28, 2020 by GuySt

[tomato]

I use SGP and CDC and this is how it works for me.

Assuming you are accurately polar aligned, If you have your scope pointing at a known point in the sky, i.e. a known star is right in the middle of the FOV, or you have taken an image of a star field which has been successfully platesolved, then when you sync the scope your mount, planetarium software and integrated imaging software will all know where the scope is pointing, assuming they are all connected and communicating. You will see the cursor in the planetarium software move to the sync location, and then Gotos should be accurate. If using live view on your camera to manually sync you will need some form of target on the screen to show you the centre, but that would work fine.

Sorry I haven’t answered your questions in order, but the key point is yes, a single sync operation should work for everything connected.

[Synchronicity]

I've been trying to do this with APT. As an example, with accurate PA I then select M31 from the APT Objects list and tell it to move the scope there. Typically I've got the centre of the galaxy in frame but not in the centre. The image preview and platesolving confirms this.

Using the Aim and Goto++ buttons I tell APT where I want to centre on the image, it does its stuff and I end up farther away.

Reading the manual for APT I'm supposed to select Aim, click on the point I want centred, four concentric circles show the selected point, then I click GoTo++.   It never works so I'm sure I'm missing something obvious but don't know what.

I can platesolve in APT then select Show to send Stellarium to that point but I don't have it set up that Stellarium can send goto requests to the mount.

Michael

[raf2020]

Interesting topic for me as well as soon I am (hopefully) going to buy 80ED + HEQ5. I have very newbie question which could be a bit related. Is manual polar alignment of mount necessary always, even when finderscope with cam is controlled by PHD and ASCOM drivers alongside with some planetarium software (not sure which)?

Asking as my backyard is located to south and probably I will have very limited view on Polar star.

[GuySt]

raf2020 - yes, a proper Polar Alignment must always be done (or so I've read in multiple threads/blogs and heard in multiple videos). A leveled, balanced mount properly aligned is essential for correct, precise tracking.

I distinctly remember watching a YouTube video that specifically talks about Polar Alignment when the North Celestial Pole is not visible, so I believe there are some guides for you situation (google "polar alignment without polaris").

[GuySt]

10 hours ago, Synchronicity said:

I've been trying to do this with APT. As an example, with accurate PA I then select M31 from the APT Objects list and tell it to move the scope there. Typically I've got the centre of the galaxy in frame but not in the centre. The image preview and platesolving confirms this.

Using the Aim and Goto++ buttons I tell APT where I want to centre on the image, it does its stuff and I end up farther away.

Reading the manual for APT I'm supposed to select Aim, click on the point I want centred, four concentric circles show the selected point, then I click GoTo++.   It never works so I'm sure I'm missing something obvious but don't know what.

I can platesolve in APT then select Show to send Stellarium to that point but I don't have it set up that Stellarium can send goto requests to the mount.

Michael

Synchronicity - If I remember rightly, the use of Aim in APT is for framing not syncing APT and EQMOD. That is, one uses PlateSolving to get an object in the center of the FOV such that it's RA/DEC is precise, these precise coordinates are synced with one's planetarium application (e.g., CdC) and mount driver (e.g, EQMOD). And thus the RA/DEC APT uses is the same as the RA/DEC CdC uses. Then when you select an object with either APT or CdC they're using the same RA/DEC.

APT's PointCraft tool always center's the object, though, which may not be aesthetically pleasing. The Aim option allows you to modify the FOV (which you can then save for future imaging/viewing sessions). I was just looking at a member's images of two galaxies which this seems relevant for: they are on left/right sides of the image. PointCraft would have put one of them in the center. So the photographer has to modify the FOV to get both galaxies where they were. The video I watched that made most sense is this one: 

 

Edited September 28, 2020 by GuySt

[tomato]

Once you have platesolved you need to sync the mount to this location, it doesn’t matter if the object is not perfectly centred, the software knows precisely where the scope is pointing from the successful platesolve. 
 

I’m not familiar with APT, but SGP has a module called Scope Centering, and if you press the button called ‘Solve and Sync’ it does exactly that.

[Paul M]

EQMod is a mount control system within the ASCOM "internet of things". APT or other such imaging software can be used to photographically identify where the telescope is pointing and send those coordinates to EQMod via"Sync" so it knows how to control the mount. Plate Solving is a method of precisely identifying the field displayed in an image and negates the need for star alignment with the mount handset. The handset is replaced by EQMod. In APT the various plate solving tools are found in the "Point craft" panel.

APT has a limited database of objects to choose from and knows nothing of the solar system objects. Stellarium can connect to APT (and others) to give the user a graphical interface that works 2 ways. If you take an image with APT, solve it and send it to Stellarium via the "show" button it will display a box round that field in Stellarium showing actual size and orientation of your image frame. Similarly you can find an object you'd like to image in Stellarium click on it and via the scope control window, tell it to sent the scope to that object. You can then take an image and plate solve in APT.  The Aim function is used for centering some part of the field in the image you just plate solved. Anytime you have a successful plate solve you can press "sync" even if the wanted object isn't centered. Every "sync" from a successful plate solve improves EQmod's sky model so improving GO-TO accuracy.

If you want to image a particular planet, comet or DSO you can use Stellarium to locate it and direct the scope to it. If you then take an image and your object is present but not central, use Aim to center it. If your object isn't present in that image plate solve it "sync" and send the coord's to Stellarium via "show". Look at Stellarium to see how far off it was and tell it again to GoTo your chosen object. This should be just a minor correction and the next image will hopefully contain your target. This is exactly how I found Stephan's Quintet with APT a couple of nights ago. However I used Cartes Du Ciel connected to APT because it's much less resource hungry on the little old notebook I was using.

Did I answer the right question?

[GuySt]

3 hours ago, Paul M said:

Every "sync" from a successful plate solve improves EQmod's sky model so improving GO-TO accuracy.

If you want to image a particular planet, comet or DSO you can use Stellarium to locate it and direct the scope to it. If you then take an image and your object is present but not central, use Aim to center it. If your object isn't present in that image plate solve it "sync" and send the coord's to Stellarium via "show".

Paul M - so ... I read you saying that using the Sync button in APT's PointCraft communicates with BOTH EQMOD (first sentence) and Stellarium (last sentence).

This was the gist of my overlong post - both Stellarium and APT have Sync options and both connect to EQMOD. At least one video shows syncing between Stellarium and EQMOD and another shows syncing between APT and Stellarium yet I could find no information anywhere that APT's Sync communicates with BOTH EQMOD and Stellarium (and I still cannot get a simulator to successfully platesolve an image to actually try it and see what happens in the EQMOD Alignment/Sync section when I do that 😡 ).

I may (very iffy) get a change to try it tonight. I think I'll take the gear out and not plan on taking any real images, just futz with the mount (polar align) then get the software all talking to each other and pointing to the same place. Baby steps.

[Paul M]

1 hour ago, GuySt said:

Paul M - so ... I read you saying that using the Sync button in APT's PointCraft communicates with BOTH EQMOD (first sentence) and Stellarium (last sentence).

It seems that APT can solve an image and then it can be sent to Stellarium via "Show" but Sync in APT only updates the mount position with EQMod. You need to click on that object in Stellarium and hit "sync" to update Stellariums scope position and you can select an objects in Stellarium and "slew" will slew the scope to it. You don't need APT to control a telescope with Stellarium and vice versa. If you slew to an object via the scope control panel in Stellarium you would need to image and plate solve in APT to confirm the slew accuracy. I can't see that Stellarium can send position info to APT directly. I think APT reads the scope position from EQMod when Stellarium issues a GOTO. Both send position info to EQMod and Stellarium can receive it from APT directly (because EQMod isn't interested in frames size and orientation!).  

The thing is that all these applications were conceived independently and not necessarily with consideration for each other. ASCOM just allows them to communicate in certain ways. The link between Stellarium or any other planetarium and APT is very useful but can seem clunky. After some practice it becomes clear how best to use them together. Just be careful though, I've hit the wrong button in Stellarium more than once and sent the scope right back where it just came from!

I really only fire up Stellarium or Cartes Du Ciel if I'm wanting to locate something not in APT's limited data base. The ability to display your cameras field of view and orientation in Stellarium is extremely useful for planning an imaging session. You can set that up without APT connected but it wouldn't show the actual orientation of the camera frame.

I used to use both SkySafari and Stellarium to control my mount even before starting imaging but without plate solving it really needed the handset to do star alignments to get set up before using the planetarium for GoTo's.

KStars and Ekos work a bit more harmoniously together but, for me, are an order of magnitude more complicated than APT/Stellarium. I'm planning on going back to those in the near future.

If imaging ever gets easy for me I'll lose interest..

 

[Synchronicity]

I've watched the video posted by GuyST and think I have the answer to my specific issue.  When doing Aim and then GoTo++ I answered Yes to the dialogue box when it seems that I should have answered No.

Up til now I've just used the APT list to select targets and that has worked fine for the 2 nights I've been at this stage of refinement!!  I would solve and then send the data to Stellarium to show where I was but have not yet tried getting Stellarium to send the mount anywhere.

I think I understand what's been said here and have a better handle how each part interacts with the others - the next clear night will be the test of that!

As ever, thanks to those with knowledge that give their time passing it on...

Michael

[GuySt]

All - again, much thanks for your comments and help.

I'm happy to report that last night, to get more familiar with mount setup, polar aligning, etc. I took my gear out. PoleMaster worked (or so I think) for polar alignment (thank god - my old neck/back was very unhappy trying to use the HEQ5's built-in polar scope). 

I prepared the night by uninstalling and reinstalled the three plate solving apps that APT can use. Made sure that APT was configured correctly for my Williams Optics RedCat 51. And every time I use the PointCraft tool whichever plate solving app was used successfully solved the image I took for that purpose. Well, there was one that was VERY bad, but another plate solving run on a new image was fine. So, PointCraft worked and I can say that using the Sync button in APT **does** talk to EQMOD (and the counter in EQMOD's Alignment/Sync section increments with each use of the Sync button). So, that question is solved. Also, I did not perform an EQMOD/Stellarium Sync, so that doesn't seem to be necessary.

Confess it's a bit odd (though rewarding) to have the gear see things I cannot see. Last night here in Madison, Wisconsin, was not a good night with at 97% full moon, a Class 8 Bortle sky, and high clouds. But, for fun I did an image run on M31, thinking it might work. Here's what I got with only light frames (10 @ 30s, 800 ISO) and darks (no flat or bias frames). This is post-processed in GIMP to remove noise, reduce the size by 50% and save as JPEG at 90%. M31 was not visible in last night's sky through binoculars - at all, not even a hint of fuzziness. Yet, there it is with M110 and M32 as well. Holy moly!

[Paul M]

Well, done. Glad it's coming together for you. Right now I'm ok with the software and rather like APT but my images have grossly bloated stars. Need to spend time on resolving that before I concentrate on trying to make nice images.

[Altocumulus]

May I hijack this thread slightly for more on the sync issue. ( p.s. I found our yesterday that eqmod needs a check to save sync points, so they can be stored for the next session ).

Does a set of star syncs still work during the daytime, for Solar work? - logically it should, but I would appreciate confirmation. Is there any point in syncing the Sun, or indeed the Planets?

 

I use Sharpcap - the polar alignment procedure is brilliantly easy to use - and CDC.