SharpCap Forums

Posted: **Sat Nov 19, 2022 11:11 pm**

Greetings,

I've been having great times with Sharpcap so I suspect my problem is my terrible literature search skills. Caveats aside I cannot seem to find a way to set/reset/ change the position limits of +/-5000 for my focuser. They should be closer to +/- 100000 for this 5VDC motor using a FCUSB controller. Its a relative (no encoder) rig and Sharpcap loves it, but the thing seems to use 10X the steps of most systems. 10K steps limit (minus +/- 1500 for backlash) leaves almost no scanning range. The 8 " EdgeHD it's on has a huge range and since the motor is friction coupled it really doesn't need any limits at all. The driver has nothing regarding limits or postion so I hoping Sharpcap can save the night.

Shoestring Astronomy (FCUSB) and JMI (PCUSB) both offer this system for 5-12VDC motors.

How do I change Sharpcaps' (default) Focuser Max. Position limits?

Thanks, N29ST

Focuser Max Position in Manual.jpg

: FCUSB Controls.jpg (75.79 KiB) Viewed 668 times

Posted: **Sun Nov 20, 2022 3:17 pm**

Hi,

the limit for the maximum position is something that SharpCap gets from the ASCOM driver for the focuser - the ASCOM driver should implement a MaxStep property which SharpCap can read that specifies the maximum position (zero is the defined minimum, negative should not be allowed). It sounds like your ASCOM driver may be hard-wired with a low value for this property and no way to change it. (See https://ascom-standards.org/Help/Develo ... axStep.htm for more details of how this should work).

Unfortunately there isn't any way to override this in SharpCap at the moment. In theory a properly written ASCOM driver would reject requests to move beyond the max step limit anyway, but you could certainly imagine that a badly written one might be not do that and therefore that in theory SharpCap may be able to override things.

To check this is the real cause, you could try running the ASCOM 'Conformance' check on the FCUSB ASCOM dirver - really this is designed to check that drivers obey the standards properly, but one thing it does is to print out the values of the various properties of the driver - ie (for the ASCOM Simulator Driver)

Code: Select all

Properties 
15:13:41.044 Absolute                          OK       True
15:13:41.053 IsMoving                          OK       False
15:13:41.063 MaxStep                           OK       50000
15:13:41.070 MaxIncrement                      OK       50000
15:13:41.077 Position                          OK       25000
15:13:41.084 StepSize                          OK       20
15:13:41.092 TempCompAvailable                 OK       False
15:13:41.099 TempComp Read                     OK       False
15:13:41.126 TempComp Write                    OK       Temperature compensation is not available and a PropertyNotImplementedException exception was generated as expected
15:13:41.139 Temperature                       OK       5.21

You have probably got Conform.exe installed with the ASCOM platform - just click on the Windows button and search for 'Conform'. Choose 'Options'->Check Focuser, then 'Options'->Select Driver, then 'File'->Check Conformance

If it turns out that the low value is coming from the ASCOM driver then the first port of call is really the ASCOM driver authors to see if they have an update or can fix this issue. That's the right way to fix this as it keeps everything working as it should. If they drag their feet then we can try an override in SharpCap, but as noted above it may not work.

cheers,

Robin

SharpCap Forums

Focuser Limits

Focuser Limits

Re: Focuser Limits