Texas Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Texas Star Party 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	5% 6% 5% 5% 7% 52%	16439
	Night	5% 5% 7% 57%	16523
Cloud Cover	Day	5% 6% 5% 5% 8% 51%	16432
	Night	5% 7% 56%	16530
Transparency	Day	6% 10% 18% 26% 20%	14179
	Night	6% 10% 18% 27% 22%	14453
Seeing	Day	9% 24% 34% 23%	858
	Night	6% 24% 37% 24%	5251

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	6% 5% 5% 7% 54%	1226
	Night	6% 5% 6% 56%	1471
February	Day	5% 5% 6% 67%	1089
	Night	5% 7% 64%	1306
March	Day	6% 5% 6% 55%	1346
	Night	5% 5% 6% 58%	1375
April	Day	6% 67%	1415
	Night	5% 63%	1188
May	Day	6% 5% 5% 5% 8% 54%	1513
	Night	7% 7% 5% 5% 7% 49%	1185
June	Day	5% 5% 7% 7% 8% 49%	1551
	Night	7% 6% 7% 8% 7% 47%	1079
July	Day	8% 5% 5% 5% 10% 8% 7% 11% 29%	1477
	Night	5% 5% 5% 7% 8% 14% 37%	1213
August	Day	11% 5% 7% 7% 10% 7% 7% 10% 24%	1480
	Night	8% 5% 6% 6% 9% 14% 35%	1239
September	Day	12% 5% 7% 7% 6% 8% 7% 34%	1359
	Night	7% 7% 8% 8% 9% 43%	1243
October	Day	6% 66%	1271
	Night	5% 66%	1421
November	Day	73%	1330
	Night	75%	1837
December	Day	7% 61%	1382
	Night	66%	1966

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	5% 5% 5% 7% 54%	1225
	Night	6% 5% 6% 56%	1473
February	Day	5% 6% 67%	1089
	Night	8% 64%	1306
March	Day	6% 5% 7% 54%	1347
	Night	5% 7% 57%	1377
April	Day	5% 67%	1415
	Night	5% 63%	1188
May	Day	5% 6% 6% 8% 53%	1512
	Night	6% 7% 5% 8% 49%	1185
June	Day	6% 6% 7% 9% 48%	1551
	Night	6% 6% 6% 8% 8% 46%	1079
July	Day	7% 5% 5% 5% 5% 9% 9% 7% 11% 28%	1477
	Night	5% 6% 7% 8% 14% 37%	1214
August	Day	10% 5% 6% 7% 5% 8% 8% 8% 10% 22%	1474
	Night	8% 5% 6% 6% 9% 14% 35%	1240
September	Day	11% 5% 6% 7% 5% 9% 8% 33%	1361
	Night	7% 7% 7% 8% 9% 42%	1243
October	Day	6% 65%	1272
	Night	6% 65%	1421
November	Day	5% 72%	1327
	Night	5% 75%	1837
December	Day	8% 61%	1382
	Night	5% 66%	1967

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	9% 14% 28% 30%	998
	Night	7% 16% 30% 28%	1223
February	Day	5% 12% 36% 33%	986
	Night	6% 8% 31% 39%	1202
March	Day	9% 14% 35% 23%	1150
	Night	7% 14% 33% 25%	1210
April	Day	7% 8% 32% 41%	1236
	Night	7% 11% 24% 43%	993
May	Day	5% 10% 15% 28% 24%	1302
	Night	9% 10% 17% 20% 26%	972
June	Day	8% 15% 18% 26% 18%	1308
	Night	8% 15% 23% 21% 14%	915
July	Day	11% 14% 26% 16%	984
	Night	11% 19% 26% 20%	846
August	Day	15% 18% 19% 8%	1234
	Night	11% 20% 28% 13%	1076
September	Day	11% 17% 21% 13%	1244
	Night	14% 21% 23% 14%	1122
October	Day	5% 8% 20% 24% 29%	1195
	Night	11% 16% 22% 31%	1314
November	Day	5% 22% 33% 25%	1284
	Night	17% 35% 30%	1778
December	Day	7% 22% 34% 20%	1258
	Night	5% 20% 39% 17%	1802

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	11% 39% 34% 11%	473
February	Night	10% 39% 34% 13%	422
March	Day	16% 57% 23%	68
	Night	10% 37% 33% 14%	451
April	Day	33% 44% 20%	117
	Night	10% 39% 40% 8%	349
May	Day	10% 31% 32% 18%	158
	Night	6% 28% 40% 20%	360
June	Day	13% 43% 36%	229
	Night	12% 53% 27%	334
July	Day	13% 39% 34% 5%	112
	Night	5% 43% 43%	330
August	Day	5% 10% 27% 33% 16%	118
	Night	29% 56% 5%	351
September	Day	7% 10% 44% 16% 5%	56
	Night	7% 35% 42% 7%	340
October	Night	20% 37% 27% 6%	430
November	Night	19% 34% 32% 7%	679
December	Night	10% 31% 40% 12%	732

Page generated at 2009-12-30 04:20:46. Version ab11