this week's SharpCap 4.1 (4.1.10476) beta update brings a substantial new feature in prototype form - a moon mosaic planning tool.
The goal of this tool is to help capture mosiac images of the moon - in particular it will help plan the layout of mosaic panels needed to ensure that the whole moon (either just the illuminated area or the whole disk) is captured.
Currently the options of what you can do for each panel are fairly limited (you can specify how many frames to capture and whether to do autoexposure for each panel or just once), but those options will expand in future. This first version is very much about testing if the software can plan and execute the correct GOTO movements to capture all the required panels. Unfortunately over the last week or so, the weather hasn't been helpful here, and when it *has* been clear the moon has either been close to the sun in the daylight sky or in areas of the sky that are out of view from my observatory, so I have only tried this in simulation so far.
You will find the tool available in the Sequencer menu. It only becomes available if you have a camera open in live mode and a GOTO mount connected to SharpCap - both are necessary for the tool to work.
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Alignment
The real first step is to help SharpCap work out the orientation of the moon relative to the camera view and also the scale of the camera view. There are two ways to do this :
1) Plate solving - if you already have a plate solving application installed and set up to work with SharpCap **AND** it can work down to the small field of view that will be associated with capturing a mosaic, then select the 'Plate Solving' radio button. This will show a 'Plate Solve Nearby' button that will move the mount 3 degrees away from the moon, set a 4s exposure and then try to plate solve. If it succeeds then it will move back to the moon and the view of the moon will update to match the view in the telescope (orientation, etc).
2) If plate solving is not an option, then you need to use manual alignment, as follows
a) Check the focal length and the pixel size for the camera are correct. SharpCap will use the focal length from your ASCOM driver if possible and will also automatically set the pixel size if it is known for your camera. Settings these correctly means that the size of each panel of the mosaic can be worked out
b) Use the orientation dial to rotate the moon shown in SharpCap to match the orientation of the moon as seen through the telescope. For crescent/half/gibbous moons then the shape of the illuminated area will guide you. At the full moon you will need to rely on the features on the disk.
c) Use the 'Flip North/South' checkbox if the features of the moon appear the wrong way round after adjusting the rotation. I think this is likely to be necessary if you have a secondary mirror or diagonal mirror in the imaging system.
d) Click on the moon image in SharpCap in the location that matches the current center of the field of view of the camera. This helps SharpCap account for any errors in the mount pointing when planning and executing the mosaic. At this point a single red frame will appear over the moon, which should match your field-of-view, like this
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* You can adjust the focal length, rotation and placing of the field of view rectangle if it doesn't seem quite right
* Since the view is of an 'average moon', aim to base where you click on where it is relative to the illuminated area of the moon, not on surface features
* If you are unsure about whether you have the 'flip N/S' option right, aim for a point along the moon's equator for the center of view/click on point - that makes the N/S option redundant.
Once your alignment is correct, click the 'Done' button.
Panel Plan Options
Once you have completed either manual or plate solving based alignment, SharpCap will show an overlay on the image of all the planned mosaic panels, like this
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* Turn 'Whole Disk' on or off - when on, SharpCap will plan to photograph the whole disk rather than just the illuminated area
* Adjust the overlap between panels (measured in pixels). This is the minimum overlaps that SharpCap will allow between neighbouring panels - sometimes SharpCap will use a parger overlap if it does not increase the number of panels needed
* Adjust the 'safety margin' around the edge of the moon - increasing this makes SharpCap include a larger area in the mosaic to help guard against any missing areas. If you look closely you will see an halo around the edge of the illuminated area above - this indicates the area covred due to the margin of 50 pixels. If you increase the margin, this halo will become wider and the panels will be adjusted to cover it.
Note that the current way that the panels are planned is probably not always 'optimal' - I intend to do more work on this aspect later to try to ensure that the minimum number of panels are used, but wanted to put out something now that would allow the other parts of this tool to be tested and get feedback.
Mosaic Capture Settings
Once you are happy with the panel plan, you can move on to adjusting the mosaic capture settings. These are quite limited at the moment - just the ability to adjust
* The number of frames to capture for each panel and
* Whether to perform autoexposure once, for each panel or not at all.
Again, this is deliberate at this stage to try to get something simple but testable available - I would be interested to hear what other options might be desireable here. I should also point out that the current way that these options are available at the bottom of the planning window is not likely to continue - I am expecting to have a separate window to specify these in a manner similar to the deep sky sequence planner.
The only thing left at this point is to press the 'Run' button and see if the mosaic capture actually does what it is supposed to do!
Some final things to note:
* The inclusion of the 'Phase' adjustment to work through the moon's phases is incorrect - that was supposed to be something for me to test with and not available in the uploaded version. I will remove that for the next update.
* It's currently deliberate that you cannot adjust the camera controls or access the menus when using this tool. I would like to allow that in future, but it opens a lot of extra complexity (what if someone changes the ROI or binning while the planner is active? What if they close the camera?). All of that complexity would need more code to make sure it is dealt with in a sensible way, and for now I have decided that not allowing that to happen is the best way forward.
* In the future I plan to extend this to Solar mosaics too - that requires a new alignment approach, since neither plate solving or the manual alignment will work - I have a plan for that when we get that far.
* The current code does not optimize the order in which the mosaic panels are captured - I do want to do this in future to try to limit the effects of backlash in the mount movement (most movements should try to be in the same direction as the mount tracks, longer pauses should be included after RA movements that got 'backwards', etc)
* If anyone tests from the Southern hemisphere, let me know what I've got wrong from your point of view...
As always, feedback welcome. As this is the first version, there may be a lot of 'I got this far and then it didn't work', but that's valueable too
cheers,
Robin
