Indianapolis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indianapolis 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	17% 8% 5% 5% 5% 7% 34%	16494
	Night	18% 7% 5% 5% 6% 35%	16437
Cloud Cover	Day	17% 8% 5% 5% 5% 6% 34%	16508
	Night	18% 8% 5% 6% 35%	16452
Transparency	Day	7% 14% 23% 14%	12528
	Night	6% 14% 23% 16%	12627
Seeing	Day	6% 21% 27% 23% 11%	1008
	Night	10% 29% 30% 14%	5090

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	24% 14% 6% 5% 25%	996
	Night	23% 12% 6% 7% 5% 25%	1702
February	Day	17% 11% 7% 7% 7% 7% 6% 23%	1091
	Night	19% 10% 7% 7% 5% 5% 5% 28%	1315
March	Day	21% 10% 5% 5% 5% 6% 6% 24%	1308
	Night	18% 7% 6% 5% 5% 7% 32%	1375
April	Day	18% 8% 5% 40%	1451
	Night	17% 7% 5% 7% 38%	1153
May	Day	18% 5% 5% 5% 5% 5% 5% 6% 35%	1614
	Night	18% 5% 5% 5% 5% 5% 8% 33%	1095
June	Day	10% 5% 6% 5% 7% 5% 8% 37%	1661
	Night	9% 5% 6% 6% 6% 8% 41%	958
July	Day	12% 5% 5% 6% 5% 9% 38%	1701
	Night	11% 5% 5% 8% 45%	991
August	Day	10% 5% 6% 6% 5% 5% 8% 40%	1537
	Night	7% 5% 5% 6% 8% 50%	1180
September	Day	12% 6% 5% 5% 5% 7% 42%	1337
	Night	11% 5% 6% 46%	1262
October	Day	18% 6% 8% 36%	1225
	Night	20% 5% 6% 40%	1467
November	Day	18% 8% 6% 6% 5% 35%	1299
	Night	18% 7% 5% 6% 38%	1872
December	Day	25% 15% 5% 8% 21%	1274
	Night	27% 12% 6% 8% 5% 20%	2067

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	24% 13% 5% 6% 5% 5% 5% 24%	995
	Night	23% 13% 6% 7% 5% 25%	1701
February	Day	18% 11% 7% 7% 6% 5% 5% 23%	1089
	Night	19% 10% 6% 6% 5% 5% 29%	1306
March	Day	23% 11% 5% 5% 5% 6% 6% 24%	1329
	Night	21% 6% 5% 5% 7% 31%	1399
April	Day	18% 9% 6% 40%	1450
	Night	17% 8% 5% 6% 38%	1153
May	Day	18% 6% 5% 5% 5% 6% 36%	1609
	Night	18% 6% 6% 6% 7% 33%	1088
June	Day	11% 5% 6% 7% 5% 5% 8% 37%	1671
	Night	9% 5% 6% 7% 8% 41%	959
July	Day	12% 5% 5% 5% 6% 5% 9% 38%	1701
	Night	11% 5% 5% 6% 46%	992
August	Day	9% 5% 5% 5% 6% 5% 6% 8% 41%	1532
	Night	8% 7% 7% 49%	1181
September	Day	12% 5% 5% 5% 6% 42%	1336
	Night	10% 5% 7% 47%	1263
October	Day	18% 7% 5% 5% 8% 36%	1225
	Night	20% 5% 5% 6% 40%	1467
November	Day	18% 9% 5% 7% 5% 34%	1297
	Night	18% 7% 5% 5% 6% 38%	1872
December	Day	25% 14% 5% 7% 5% 21%	1274
	Night	27% 12% 5% 8% 5% 21%	2071

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	16% 25% 7%	655
	Night	5% 13% 25% 9%	1125
February	Day	7% 18% 20% 5%	780
	Night	6% 22% 21%	976
March	Day	7% 19% 21% 6%	896
	Night	6% 20% 26% 11%	997
April	Day	16% 28% 15%	1134
	Night	5% 11% 24% 20% 6%	887
May	Day	7% 13% 22% 21%	1198
	Night	9% 14% 21% 17% 6%	811
June	Day	9% 16% 24% 17%	1271
	Night	11% 17% 26% 19%	756
July	Day	10% 15% 23% 15%	1120
	Night	6% 16% 22% 21%	674
August	Day	7% 11% 25% 19% 5%	1337
	Night	6% 13% 26% 26% 5%	1036
September	Day	6% 10% 19% 22% 7%	1148
	Night	6% 11% 20% 25% 9%	1098
October	Day	6% 12% 25% 16%	1072
	Night	11% 25% 18%	1274
November	Day	5% 14% 23% 15%	974
	Night	15% 25% 20%	1482
December	Day	7% 16% 16%	943
	Night	7% 12% 18% 5%	1511

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	20% 37% 26%	520
February	Night	11% 42% 25%	400
March	Day	12% 26% 28% 9%	64
	Night	14% 37% 29% 5%	439
April	Day	11% 27% 31% 10% 5%	111
	Night	11% 34% 31% 9%	343
May	Day	6% 21% 20% 28% 13%	125
	Night	6% 27% 32% 20%	349
June	Day	5% 25% 32% 20% 7%	225
	Night	23% 47% 18%	331
July	Day	5% 19% 28% 24% 13%	193
	Night	18% 39% 28%	320
August	Day	12% 26% 32% 20%	116
	Night	16% 36% 34% 5%	346
September	Day	16% 20% 32% 16%	112
	Night	5% 15% 30% 33% 6%	410
October	Day	24% 24% 25%	62
	Night	10% 27% 30% 12%	459
November	Night	14% 29% 30% 11%	544
December	Night	13% 34% 22%	629

Page generated at 2009-12-30 05:20:30. Version ab11