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BYN and Sesto Senso autofocus


SailmmIV
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Good morning,

I am trying to get my Sesto Senso focuser to work with BYN.   I previously had it working (manually only) with my Moonlite focuser.   I installed the 64bit ASCOM driver for the focuser (SS) and it worked in my initial installation using my laptop and their software.   When I tried to install it on my observatory desktop PC, BYN required a 32bit version of the driver.   I uninstalled the 64bit and installed the 32bit driver.   BYN connected to the focuser and offered me the option to set up the autofocus (which is what I wanted).   However, that night when I connected the whole set of observatory software programs, the focuser crashed out of BYN when I tried to connect to it.   I was running the 64bit versions of The SkyX Professional,  PHD2 and the 32bit version of BYN.   Is that my problem?  Do I have to downsize to 32bits on the TSX and PHD2 to use the SS focuser in BYN?   Thanks for any help you can provide.

Regards,

John Harris

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John,

Microsoft enforces so many restrictions in Windows that have nothing to do with BYN or ASCOM that the idea of matching ASCOM drivers and applications is made pretty complicated. I will try to explain.

Windows comes in two flavors...32-bit and 64-bit. Most newer PCs are 64-bit and would typically run the 64-bit version of Windows. The 64-bit version of Windows can run both 32-bit and 64-bit applications, but a 64-bit version of Windows would typically require low-level drivers that are 64-bit compatible. These low-level drivers are typically for hardware control, as opposed to ASCOM drivers which sit between the low-level hardware drivers and applications.

I downloaded the SESTO-SENSO-2-software-package-1-3.zip from the PrimaLuceLab web site. I can see that it has a low-level driver that needs to be installed. It includes both 32-bit and 64-bit installers for a Virtual COM Port driver. I would suggest that if you are running 64-bit Windows 10 that you need to install the x64 version of the VCP driver.

You also need to install the ASCOM driver for your focuser. Fortunately, there is no decision to make. There is only one installer and it installs two instances of the driver. They are labelled A and B. These allow you to focus both an imaging focuser and a guidescope focuser by using the "A" driver for one and the "B" driver for the other.

There are two flavors of ASCOM drivers. Simply, they are either provided by the developer as a DLL file, or as an EXE file. When an application connects to a DLL ASCOM driver, that driver temporarily becomes part of application. In order for this to work the driver must support the same bitness as the application. If a driver is provided as an EXE file, the driver runs in a separate executable process that does not need to be the same bitness as the application.

DLL-based ASCOM drivers are created to be either 32-bit only, 64-bit only, or they can be compatible with both 32-bit and 64-bit applications (for AnyCPU).

The Sesto Senso driver is a DLL-based driver that is built for AnyCPU which means that you can use the driver with either 32-bit BYN or 64-bit TSX. However, there is another limitation. The driver uses a serial COM port (that is created by the low-level VCP driver that was also installed). Typically the COM port is opened when the application connects the driver to the device (focuser) and the COM port is closed when the application disconnects from the device. Further it can only be actively in use by one application at a time. This means that if BYN is connected to the focuser then TSX will not be able to connect and vice versa. This is because there would be two instances of the driver one in use by BYN and the other by TSX and they cannot both be connected at the same time. The two driver instances do not know about each other and so cannot "share" the COM port. 

If your eyes have not glazed over yet, please read on. There is a solution.

ASCOM 6.5 SP1 (the current release) includes an application called the ASCOM Device Hub. Full disclosure...I am the author of Device Hub.

Device Hub is both an application and a driver for telescope, dome, and focuser. It appears that you do not need the telescope or dome functionality. The Device Hub Focuser runs as an EXE-based driver so it does not need to be the same bitness as the application. It also allows multiple applications to be connected to the Sesto Senso Focuser at the same time. 

To do this you can configure BYN and TSX to connect to the Device Hub Focuser and configure Device Hub to connect to Sesto Senso Focuser A. Then you can control the focuser from either BYN or TSX even though BYN is a 32-bit app and TSX is a 64-bit app. The only caution is that you should not try to adjust the focuser position from both applications at the same time. If you do, the results may not be what you expect.

You will notice that almost none of my explanation has to do with BYN. It all has to do with the ASCOM architecture, ASCOM drivers, and Windows. So...if you have questions about any part of my post, please ask them on the ASCOM-Talk forum here --> https://ascomtalk.groups.io/g/Help/messages. Please create a new topic to ask your questions...Thanks!

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Astroman133, 

My eyes not only glazed over but my hair parted when all this went over my head.   😀  I’m sorry.   I’m a retired aerial photographer and pilot, but not much of a Windows technician.    I did get the focused to work manually one time from within BYN last night.   So I was able to focus on a star, but when I made a test image of the star (with Bahtinov mask), the focuser disconnected from the dialog box.   I was able to reconnect it but once again when I made an image (preview), the focuser disconnected again.  Do I need the hub ascom you mentioned and where would I find it? I appreciate your comments and explanation, and I’ll try to figure out how to make this work.   Do I have to create an account on the ascomtalk group forum as well?  

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Disconnections are usually a communications issue, like cabling or connections.

If BYN is the only application connected to your focuser then you do not need to use the ASCOM Device Hub. If you want to connect multiple applications to the focuser at the same time then you need some kind of hub. Device Hub can do the job. Launch DH from the Windows Start Menu per the following screen shot. First connect Device Hub to the Sesto Senso focuser and then connect the applications to the Device Hub Focuser. Then connecting BYN to the Device Hub Focuser will automatically connect DH to the focuser. Disconnection BYN will automatically shut DH down.

image.png.66dc64a55a2a67c1f81db20d25201573.png

Yes, if you want to post on the ASCOM-Talk forum, you need a free account.

 

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Astroman133,

Thank you for all your help.   I still have a lot to learn about this amazing hobby.   It has been help from individuals such as you who have helped me in so many ways to get where I am.  

Nothing disturbs me more than when something that wasn't working, starts working for no apparent reason.   I suspect the reason had something to do with operator error!  :)   

Anyway, the Sesto Senso focuser has started working in manual mode or whenever I press one of the direction arrows in BYN.   If it continues to work (I've only had one clear sky night to test), I will then try to figure out what the settings should be to make it autofocus.

Do you have any suggestions as to how to calculate the steps and how many steps per degree of temperature change?   These are fields in the BYN interface that need to be filled in the focuser configuration.   I'm not sure if it's a BYN function or an ASCOM function.

Regards,

John

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John,

I am glad that you are making progress.

You will be disappointed if you expect BYN to continually adjust the focuser to keep the image in focus throughout the night. It does not do that. It does, however, allow you to use the computer to manually adjust the focuser position. So, while other software, such as Maxim DL or FocusMax, can do autofocusing BYE/BYN cannot.

The ASCOM focuser specification provides properties that a client program can use to determine if a focuser and its driver support temperature compensation and if temperature compensation is on or off. It cal also support turning temperature compensation on or off, if this is supported. However, how temperature compensation is implemented by a driver or focuser are not dictated by the ASCOM standard and must be implemented totally by the driver and/or the focuser.

I only have experience with Moonlite focusers which support temperature comp (TC) and allow you to enter an adjustment factor of steps per degree in the driver's Setup dialog. However, a drawback of this approach is that the driver assumes that this factor is stable over whatever range of temperatures your imaging may encounter. I doubt that a single value is adequate over a wide range of temperatures, so I don't use it.

My technique varies depending on my camera. When I use BYE with my Canon T5i, I periodically abort the capture plan, switch to Frame & Focus to re-focus. Then I return to Imaging edit the capture plan to reduce the number of images and restart image capture. When I use my QSI monochrome camera I use an imaging program that I wrote.That program can track the size of a selected star in the captured image. When I see that the size has increased significantly, I will manually intervene to pause capture, refocus, and resume capture.

If you are using some other software that does true autofocus, then I would guess that temperature compensation would be less necessary.

Even if the steps/degree is stable over the range of temperatures that you encounter, it is likely to be different for different people due to the expansion characteristics of different optical trains and the sensitivity of different focusers. You are going to have to figure out what value(s) are appropriate for your setup for different temperatures. I would suggest keeping a log of values in a text file or spreadsheet on your imaging laptop. Then you can refer to that log to select an appropriate value for each imaging session depending on the expected temperatures and your equipment profile.

I hope this helps.

 

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Astroman133,

I can't thank you enough for your patience and the effort you've gone to in explaining to me how the focuser will or will not work with BYN. I reinstalled the Sesto on Seqence Generator Pro and used the ASCOM Device Hub you wrote (I admire anyone who can do something like that) to connect the Celestron CGEM DX mount which was causing the conflict.   Now everyone is happen, the mount is on the Device Hub, the focuser is on COM5 and all is well with SGP and BYN (which I am focusing manually every hour with the Sesto).  That is much easier than using the focuser on the Esprit 120mm.   Thank you again for all the help.   I have a much better understanding of what is going on now, thanks to you.   Regards, John.

 

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