Plate Solve in Sequence Loop

[admin]

Hi,

yes, that makes sense. I have a Celestron SE mount, and even when using it in AltAz mode, the backlash is pretty horrible

cheers,

Robin

[StarFlea]

Hello Robin,

I found this older thread by accident and I'm wondering if there's already a solution to the problem, because I'm currently struggling with it too.

I also do a PlateSolving in the sequencer with subsequent Re-GOTO within a loop. My target object is slowly moving away from the center.

I have now stacked all the images of a session (without alignment) to illustrate this drift, you can also see that the target position jumps back and forth several times:

Drift.jpg (710.95 KiB) Viewed 3898 times

and the drift-graph:

DriftGraph.jpg (24.68 KiB) Viewed 3898 times

The "MOUNT SOLVEANDSYNC" step is elementary in the sequencer. Is there a way to check if the re-GOTO has already finished or to insert a PAUSE?

In beta 4.1 you mention "Option to recenter live stacking periodically (using plate solving) once the drift reaches a threshold level" under the new features.
How does that work, or would that be a solution for the sequencer?

BTW: Here is my sequence for frame capturing:

DeepSkyLiveStacking_100x10_(PS)_v1.scs

(414 Bytes) Downloaded 93 times

Best regards!
StarFlea

[admin]

Hi,

well, the theory is that when SharpCap sends the slew command to the mount ASCOM driver, it should wait until the slew is complete before allowing SharpCap to continue. However, it wouldn't suprise me at all if some ASCOM drivers just start the movement off and let SharpCap carry on straight away. There is also the possibility that even if the ASCOM driver thinks the movement is done, the mount itself may still be finishing the movement or settling.

I can see that the code for the resync does not handle these possibilities quite as well as some other parts of SharpCap, so I will tweak that for the next update of SharpCap 4.1. Additionally in 4.1 there is an option to specify the mount settling time (for instance 5s) - this will cause SharpCap to wait 5s after mount movements when automatic steps are happening - I will make sure the resync also obeys this setting.

For SharpCap 4.0, the best thing to do is to add a delay into your sequence after each resync step. There is a delay step ('Wait for XX seconds') that you can use for this purpose.

As for the recenter feature coming up in SharpCap 4.1, that's part of live stacking, so if you set it up and enable it in a manual stack then it will remain enabled for stacks started under sequencer control.

cheers,

Robin

[StarFlea]

Hi Robin,

first of all thank you for your comments. I've modified my sequence but am unable to test it at the moment as I've had bad weather here for the past 3 months (except for a few nights).

But maybe you can decide if this sequence is better than the previous one and maybe able to avoid the drifting.

1. The initial position of the mount is saved once.
2. Within the loop, live stacking and explicitly capturing are stopped.
3. Then platesolving and synchronizing
4. The mount will slew back to the previously saved coordinates
5. Wait 10 seconds
6. Restart capturing and live stacking
7. LiveStack of 10 frames in a row

Code: Select all

SEQUENCE
    LIVE STACKING START
    SAVE MOUNT COORDINATES
    LOOP 100 TIMES
        LIVE STACKING PAUSE
        CAPTURE STOP
        RETRY ERRORS UP TO 5 TIMES
            MOUNT SOLVESYNCONLY
        END RETRY ERRORS
        GOTO SAVED COORDINATES
        DELAY 10
        CAPTURE START
        LIVE STACKING RESUME
        LIVE STACK FOR 10 MORE FRAMES THEN PAUSE
    END LOOP
    BEFORE SEQUENCE FINISH DO
        LIVE STACKING SAVE AllFormats
        LIVE STACKING STOP
        CAPTURE STOP
    END DO
END SEQUENCE

Does it make sense to stop capturing explicitly? Should I also add a pause after SOLVESYNCONLY? Actually, the mount doesn't move there.

Best regards,
StarFlea

[admin]

Hi,

The Capture Stop and Capture Start steps are not needed, and may cause issues. Those steps are to start/stop saving images to individual files (like the 'Start Capture' button on the toolbar), and should not be used in conjunction with live stacking or plate solving (even when the camera is in still mode).

I would also put the 'Before Finish' at the start of the sequence - that's where it is supposed to go and I'm not sure if it will apply if there is an error in the sequence steps that preceed it.

cheers,

Robin

[StarFlea]

OK, thanks, that was valuable information!
I reworked the sequence...

Code: Select all

SEQUENCE
    LIVE STACKING START
    BEFORE SEQUENCE FINISH DO
        LIVE STACKING SAVE AllFormats
        LIVE STACKING STOP
    END DO
    SAVE MOUNT COORDINATES
    LOOP 25 TIMES
        LIVE STACKING PAUSE
        RETRY ERRORS UP TO 5 TIMES
            MOUNT SOLVESYNCONLY
        END RETRY ERRORS
        GOTO SAVED COORDINATES
        DELAY 10
        LIVE STACKING RESUME
        LIVE STACK FOR 10 MORE FRAMES THEN PAUSE
    END LOOP
END SEQUENCE

Best regards!
StarFlea

[admin]

Hi,

yes, that looks about right (although hard to be 100% sure without running it for real!). Good luck!

Robin