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Mississauga
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mississauga clear sky chart from 2005-11-05 to 2008-11-27.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	17% 7% 6% 5% 6% 5% 5% 7% 31%	12227
	Night	19% 7% 5% 5% 5% 5% 5% 6% 31%	12164
Cloud Cover	Day	17% 7% 5% 5% 6% 5% 5% 7% 31%	12246
	Night	19% 7% 5% 5% 5% 5% 6% 31%	12187
Transparency	Day	5% 19% 27% 14%	8252
	Night	18% 27% 13%	8209
Seeing	Day	54% 7% 14% 11%	718
	Night	57% 10% 15% 6%	3768

By Month

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	22% 13% 5% 8% 8% 6% 6% 6% 15%	798
	Night	30% 10% 6% 7% 5% 5% 5% 17%	1242
February	Day	18% 12% 8% 7% 9% 5% 7% 16%	739
	Night	18% 8% 7% 10% 8% 7% 5% 7% 19%	1050
March	Day	17% 8% 6% 7% 5% 6% 5% 6% 27%	999
	Night	16% 7% 7% 6% 6% 5% 6% 32%	998
April	Day	21% 6% 5% 5% 38%	1114
	Night	18% 8% 6% 6% 36%	866
May	Day	14% 5% 5% 5% 7% 40%	1267
	Night	13% 6% 5% 7% 47%	779
June	Day	12% 5% 7% 6% 7% 10% 37%	1251
	Night	10% 5% 5% 5% 7% 10% 39%	718
July	Day	11% 10% 6% 9% 9% 35%	1269
	Night	10% 6% 5% 7% 9% 44%	771
August	Day	8% 6% 5% 5% 5% 10% 42%	1185
	Night	12% 5% 5% 47%	847
September	Day	19% 5% 5% 6% 6% 37%	1024
	Night	19% 5% 5% 44%	953
October	Day	21% 8% 6% 6% 5% 5% 6% 27%	923
	Night	16% 8% 6% 6% 5% 5% 35%	1111
November	Day	21% 11% 6% 7% 6% 8% 22%	914
	Night	24% 9% 5% 5% 5% 5% 5% 6% 24%	1532
December	Day	28% 11% 9% 8% 5% 5% 14%	744
	Night	25% 11% 9% 7% 6% 6% 5% 16%	1297

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	23% 13% 5% 8% 7% 6% 5% 6% 15%	797
	Night	30% 11% 6% 8% 5% 18%	1243
February	Day	18% 12% 8% 8% 8% 5% 7% 16%	737
	Night	17% 8% 8% 10% 7% 7% 7% 18%	1041
March	Day	18% 7% 7% 7% 5% 7% 5% 6% 26%	1022
	Night	17% 7% 8% 5% 6% 6% 32%	1020
April	Day	21% 7% 5% 38%	1113
	Night	19% 8% 6% 6% 36%	866
May	Day	14% 5% 5% 5% 7% 41%	1266
	Night	13% 5% 5% 6% 48%	779
June	Day	12% 5% 7% 6% 7% 10% 37%	1260
	Night	11% 5% 5% 5% 7% 9% 40%	720
July	Day	10% 5% 9% 6% 8% 10% 36%	1269
	Night	10% 6% 7% 9% 44%	772
August	Day	8% 5% 5% 5% 5% 9% 43%	1180
	Night	12% 5% 5% 5% 5% 47%	849
September	Day	19% 5% 5% 6% 5% 37%	1023
	Night	19% 5% 6% 44%	954
October	Day	20% 9% 6% 6% 5% 5% 5% 6% 27%	923
	Night	16% 8% 6% 5% 5% 5% 35%	1111
November	Day	21% 11% 6% 6% 5% 5% 8% 22%	912
	Night	24% 9% 5% 5% 5% 5% 5% 6% 24%	1531
December	Day	28% 11% 9% 7% 6% 15%	744
	Night	25% 11% 9% 6% 6% 6% 5% 16%	1301

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 25% 14% 6%	441
	Night	19% 23% 6%	673
February	Day	23% 21% 7%	416
	Night	6% 20% 24% 7%	629
March	Day	6% 19% 32% 9%	631
	Night	18% 33% 11%	677
April	Day	17% 30% 26%	667
	Night	21% 20% 25% 6%	547
May	Day	18% 31% 22%	919
	Night	15% 36% 19% 5%	603
June	Day	6% 26% 31% 14%	937
	Night	6% 27% 30% 14%	549
July	Day	6% 23% 28% 14%	707
	Night	25% 27% 17%	439
August	Day	15% 26% 22%	1017
	Night	15% 25% 24%	713
September	Day	6% 14% 28% 16%	784
	Night	13% 37% 15%	764
October	Day	5% 13% 27% 11%	721
	Night	10% 27% 18%	873
November	Day	7% 20% 22%	619
	Night	5% 19% 24% 7%	1045
December	Day	8% 24% 13%	393
	Night	7% 26% 18%	697

Seeing (when cloud cover <= 80%)
Color Meanings: Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month		Occurrence of each Forecast	Data Points
January	Night	70% 9% 6%	371
February	Day	100%	1
	Night	68% 6% 12%	318
March	Day	66% 9% 11%	93
	Night	67% 13% 7%	371
April	Day	66% 5% 11% 6%	90
	Night	67% 7% 12%	319
May	Day	68% 8% 10% 5%	93
	Night	67% 10% 13%	221
June	Day	64% 5% 11% 7%	84
	Night	64% 10% 17%	169
July	Day	61% 9% 12%	81
	Night	62% 20% 8%	193
August	Day	36% 22% 22% 8%	90
	Night	38% 6% 28% 16%	278
September	Day	34% 7% 13% 19% 11%	88
	Night	36% 8% 20% 21%	350
October	Day	36% 14% 20% 9%	91
	Night	37% 17% 25% 8%	367
November	Day	28% 14% 14% 42%	7
	Night	51% 13% 15%	442
December	Night	68% 12% 7%	369

Page generated at 2008-11-27 13:47:34. Version ab11