Eagle Eye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Eye Observatory clear sky chart from 2005-11-05 to 2009-12-29.

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	11% 5% 5% 7% 46%	16490
	Night	10% 7% 54%	16471
Cloud Cover	Day	12% 5% 5% 7% 47%	16484
	Night	10% 7% 54%	16479
Transparency	Day	12% 22% 24% 13%	13439
	Night	14% 21% 24% 16%	13896
Seeing	Day	7% 18% 37% 27%	877
	Night	7% 29% 38% 17%	5123

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	17% 53%	1129
	Night	17% 5% 50%	1571
February	Day	14% 5% 57%	1089
	Night	9% 5% 59%	1306
March	Day	19% 6% 44%	1350
	Night	14% 6% 6% 49%	1372
April	Day	11% 6% 5% 6% 5% 46%	1379
	Night	12% 7% 49%	1222
May	Day	10% 6% 5% 8% 6% 5% 7% 39%	1600
	Night	10% 5% 6% 10% 47%	1099
June	Day	11% 6% 6% 5% 9% 43%	1551
	Night	5% 5% 7% 57%	1079
July	Day	10% 8% 5% 7% 10% 35%	1596
	Night	5% 6% 15% 48%	1095
August	Day	5% 5% 7% 7% 8% 11% 37%	1505
	Night	6% 6% 5% 11% 50%	1212
September	Day	10% 5% 6% 5% 6% 6% 10% 40%	1302
	Night	10% 5% 5% 5% 5% 7% 47%	1300
October	Day	10% 57%	1273
	Night	9% 5% 62%	1415
November	Day	8% 5% 57%	1347
	Night	7% 5% 65%	1823
December	Day	11% 5% 5% 55%	1369
	Night	11% 5% 6% 53%	1977

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	17% 53%	1128
	Night	18% 5% 51%	1573
February	Day	15% 5% 57%	1089
	Night	10% 5% 60%	1306
March	Day	20% 5% 5% 45%	1351
	Night	15% 5% 6% 49%	1374
April	Day	11% 6% 5% 5% 47%	1379
	Night	13% 7% 50%	1223
May	Day	12% 6% 5% 7% 5% 5% 7% 40%	1599
	Night	11% 5% 5% 11% 48%	1099
June	Day	12% 6% 5% 5% 8% 45%	1551
	Night	5% 7% 58%	1079
July	Day	11% 7% 6% 7% 10% 37%	1596
	Night	5% 6% 16% 48%	1096
August	Day	7% 7% 7% 7% 11% 40%	1499
	Night	6% 6% 10% 51%	1213
September	Day	11% 5% 6% 5% 6% 9% 41%	1304
	Night	10% 5% 5% 5% 7% 49%	1300
October	Day	11% 5% 58%	1275
	Night	10% 62%	1415
November	Day	9% 5% 58%	1344
	Night	7% 5% 65%	1823
December	Day	12% 5% 55%	1369
	Night	12% 5% 5% 54%	1978

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	6% 15% 31% 25%	888
	Night	7% 15% 26% 28%	1249
February	Day	6% 20% 29% 27%	890
	Night	6% 15% 28% 33%	1101
March	Day	14% 17% 22% 16%	1027
	Night	13% 21% 24% 16%	1076
April	Day	11% 19% 23% 21%	1038
	Night	13% 18% 22% 24%	949
May	Day	5% 16% 22% 26% 5%	1217
	Night	6% 21% 28% 22% 7%	887
June	Day	5% 14% 28% 30% 7%	1161
	Night	7% 17% 25% 36% 5%	840
July	Day	7% 23% 22% 20%	1058
	Night	6% 27% 26% 21%	786
August	Day	6% 20% 30% 12%	1372
	Night	6% 29% 31% 10%	1139
September	Day	13% 23% 18% 7%	1185
	Night	17% 25% 18% 7%	1163
October	Day	6% 18% 28% 20%	1173
	Night	9% 18% 23% 26%	1299
November	Day	7% 26% 23% 19%	1210
	Night	8% 26% 25% 20%	1670
December	Day	11% 19% 32% 11%	1220
	Night	10% 14% 34% 14%	1737

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	10% 41% 32% 7%	528
February	Night	13% 50% 27%	412
March	Night	13% 42% 31%	358
April	Day	15% 51% 19% 6%	78
	Night	9% 47% 32%	334
May	Day	8% 29% 39% 14%	231
	Night	32% 40% 16%	343
June	Day	6% 14% 48% 25%	218
	Night	19% 56% 19%	336
July	Day	6% 6% 35% 41% 7%	207
	Night	5% 48% 36% 5%	325
August	Day	6% 33% 44% 9%	143
	Night	39% 47%	359
September	Night	9% 40% 35%	337
October	Night	5% 24% 40% 20%	415
November	Night	6% 23% 42% 19%	654
December	Night	10% 35% 33% 8%	722

Page generated at 2009-12-30 04:20:37. Version ab11