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Indianapolis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indianapolis clear sky chart from 2003-08-01 to 2005-11-07.

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	20% 5% 5% 6% 5% 7% 31%	8730
	Night	21% 5% 5% 6% 6% 34%	8440
Transparency	Day	21% 15% 41% 19%	4256
	Night	17% 14% 41% 24%	4332
Seeing	Day	6% 22% 28% 29% 13%	554
	Night	10% 27% 36% 22%	2473

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	31% 9% 9% 8% 5% 18%	497
	Night	33% 7% 6% 5% 6% 5% 22%	854
February	Day	26% 10% 8% 5% 7% 21%	570
	Night	26% 9% 7% 6% 7% 27%	684
March	Day	29% 7% 6% 5% 5% 5% 8% 22%	664
	Night	23% 7% 7% 5% 6% 5% 28%	700
April	Day	25% 5% 6% 35%	738
	Night	18% 7% 5% 6% 5% 39%	582
May	Day	17% 6% 7% 5% 8% 34%	808
	Night	14% 5% 7% 5% 5% 10% 36%	545
June	Day	12% 5% 7% 7% 7% 10% 34%	840
	Night	14% 7% 5% 7% 11% 36%	476
July	Day	13% 6% 5% 6% 8% 5% 6% 10% 30%	856
	Night	12% 5% 5% 6% 8% 5% 5% 8% 35%	505
August	Day	12% 5% 8% 5% 7% 8% 33%	1158
	Night	10% 7% 6% 6% 8% 40%	883
September	Day	12% 6% 6% 6% 45%	996
	Night	14% 6% 53%	946
October	Day	23% 6% 6% 5% 5% 6% 5% 5% 29%	620
	Night	20% 5% 5% 6% 8% 34%	742
November	Day	37% 6% 5% 6% 22%	473
	Night	39% 6% 5% 24%	694
December	Day	32% 8% 7% 24%	510
	Night	26% 8% 5% 5% 5% 5% 27%	829

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	37% 18% 36% 8%	133
	Night	32% 16% 37% 13%	261
February	Day	27% 16% 42% 11%	195
	Night	21% 12% 42% 21%	275
March	Day	28% 17% 49%	246
	Night	23% 19% 44% 12%	290
April	Day	18% 12% 48% 15%	343
	Night	16% 5% 48% 26%	295
May	Day	25% 17% 42% 13%	407
	Night	22% 16% 42% 17%	296
June	Day	21% 13% 42% 21%	451
	Night	19% 11% 46% 19%	266
July	Day	23% 14% 36% 24%	433
	Night	22% 12% 29% 32%	262
August	Day	20% 24% 40% 15%	590
	Night	14% 21% 42% 20%	520
September	Day	9% 12% 43% 29% 5%	632
	Night	7% 10% 34% 40% 7%	652
October	Day	17% 17% 41% 22%	439
	Night	13% 16% 38% 27%	587
November	Day	23% 11% 40% 23%	213
	Night	18% 16% 43% 21%	314
December	Day	34% 6% 39% 19%	174
	Night	19% 17% 49% 12%	314

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	19% 49% 24% 6%	201
February	Night	12% 40% 40% 6%	171
March	Day	12% 36% 36% 16%	25
	Night	23% 38% 33%	193
April	Day	15% 24% 35% 20%	45
	Night	13% 30% 38% 18%	150
May	Day	41% 25% 25% 5%	58
	Night	7% 28% 41% 21%	163
June	Day	8% 26% 31% 22% 10%	114
	Night	15% 52% 26%	163
July	Day	6% 19% 33% 26% 13%	106
	Night	15% 46% 33%	169
August	Day	9% 25% 33% 28%	83
	Night	13% 29% 46% 7%	265
September	Day	5% 8% 21% 44% 20%	79
	Night	13% 32% 41% 8%	297
October	Day	29% 18% 36% 13%	44
	Night	8% 23% 35% 28%	315
November	Night	17% 35% 39% 6%	173
December	Night	14% 43% 34% 7%	213

Page generated at 2008-09-02 02:07:14. Version ab11