There appears to be a computational error in the display of the total lunar eclipse, for example as seen from Newport Beach California on January 31 at 5:31 AM PST. Specifically, the percent obscuration of the moon varies in proportion to the selected zoom. It should be constant regardless of zoom.
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6 comments
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Bill Tschumy Dan,
We are aware of this problem but it is particularly difficult to solve. It arises because we artificially magnify the Moon when you are zoomed out. Most planetarium apps do this to make the Moon more visible at wide fields of view.
For right now, just know that the correct view of the eclipse is shown when zoomed into a less than 25º FOV. This corresponds to when we switch from drawing a stylized view of the Moon to a more realistic one.
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Dan Carlock Thanks Bill for your explanation. Attached are two illustrative screen snaps. When you cite the FOV limit, that applies to the smaller of the two dimensions?
Another "bug" is that when time is set to "now" and the Moon's Object Info > Visibility > Next Lunar Eclipse is selected, the displayed time is not constant but fluctuates over a range of approximately seven seconds, straddling the minute boundary. When it falls back to the previous minute, an invisible line feed character is inserted. Can this be resolved?
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Bill Tschumy The FOV label shows width x height. It is the width that matters.
I do see the occasional text wrapping to a blanks line. I can try to look at his but it seems pretty minor. I don't think it is an extra line feed but rather just the way the text is wrapping in that entry. Occasionally it thinks the text wraps to another line when it doesn't quite. This doesn't happen for all eclipses and the next one just happens to have the amount of text to cause this. I can try to look into this at some point, but I consider it a pretty minor issue.
As far as the exact time dithering, this is just the result of how the eclipse timing is calculated. Depending on the starting conditions (the time now) the calculation can vary by a few seconds.
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Dan Carlock May I suggest that not all calculations need be continuously updated; why not just buffer the value once (when the page is loaded) and then refresh it only after dismissing and reloading it? Or, when tugging the page down to trigger a refresh?
Another example is the displayed az/alt bearings in the upper left hand corner during real-time observations when the iPhone's compass and GPS are engaged. I notice that the values are fluctuating many times per second. This is important and essential when using the app to guide a telescope, not so much for hand-held observation. Perhaps logic could be added to either update the display at a slower rate, or suppress the display of arc minutes and seconds, when the app is not guiding a telescope. If the compass is disengaged, then the complete frozen value can be displayed.
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Steenkh Bill, you write "It arises because we artificially magnify the Moon when you are zoomed out." Does this mean that you also artificially magnify the Moon when Moon Magnification is set at 1x? I have this setting, but I still need to zoom in in order to see the correct position of the shadow.
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Bill Tschumy Yes, we have magnified the Moon when zoomed out for years (I think since SkySafari 1.0). Almost all planetarium programs do this. Otherwise the Moon is barely visible in the chart when displayed at (say) 90º. This magnification is independent of the "Moon Magnification" settings.
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