DSO - Upham
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DSO - Upham 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	7% 5% 5% 6% 56%	8655
	Night	8% 6% 5% 6% 54%	8514
Transparency	Day	5% 7% 23% 30% 31%	6555
	Night	6% 8% 24% 30% 29%	6243
Seeing	Day	11% 25% 36% 24%	443
	Night	5% 17% 43% 31%	2765

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	10% 5% 7% 50%	549
	Night	11% 6% 7% 49%	804
February	Day	17% 7% 8% 40%	549
	Night	17% 5% 5% 47%	695
March	Day	10% 5% 56%	683
	Night	10% 5% 62%	679
April	Day	7% 5% 62%	720
	Night	8% 6% 6% 58%	600
May	Day	5% 66%	766
	Night	5% 5% 5% 6% 60%	598
June	Day	5% 5% 68%	780
	Night	6% 5% 7% 6% 55%	537
July	Day	10% 5% 6% 9% 45%	795
	Night	7% 5% 5% 5% 8% 6% 6% 7% 40%	558
August	Day	7% 9% 6% 8% 9% 42%	1129
	Night	8% 5% 8% 5% 8% 11% 38%	914
September	Day	6% 5% 6% 57%	1020
	Night	6% 5% 5% 7% 7% 52%	926
October	Day	5% 5% 7% 62%	620
	Night	5% 6% 6% 59%	744
November	Day	10% 6% 62%	509
	Night	11% 57%	654
December	Day	6% 71%	535
	Night	69%	805

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	9% 10% 42% 33%	356
	Night	11% 10% 38% 31% 7%	517
February	Day	11% 17% 31% 35%	335
	Night	8% 9% 33% 36% 12%	394
March	Day	34% 36% 20%	466
	Night	6% 28% 37% 23%	486
April	Day	19% 30% 45%	533
	Night	17% 35% 41%	435
May	Day	6% 10% 24% 58%	600
	Night	7% 13% 28% 47%	445
June	Day	7% 23% 65%	632
	Night	5% 11% 16% 61%	381
July	Day	8% 11% 18% 18% 42%	487
	Night	10% 10% 21% 22% 35%	316
August	Day	16% 12% 37% 24% 9%	722
	Night	14% 21% 35% 13% 15%	565
September	Day	5% 6% 20% 33% 33%	759
	Night	7% 7% 23% 37% 25%	671
October	Day	10% 28% 35% 22%	722
	Night	11% 22% 35% 27%	815
November	Day	5% 21% 37% 31%	483
	Night	5% 22% 30% 38%	561
December	Day	5% 7% 24% 41% 21%	460
	Night	5% 21% 35% 33%	657

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	7% 19% 44% 28%	224
February	Day	50% 50%	4
	Night	8% 31% 50% 10%	197
March	Day	29% 18% 27% 24%	54
	Night	10% 21% 42% 24%	227
April	Day	24% 45% 22% 7%	53
	Night	10% 35% 44% 10%	170
May	Day	11% 36% 27% 22%	61
	Night	23% 53% 19%	178
June	Day	6% 35% 43% 11%	60
	Night	19% 52% 26%	176
July	Day	10% 17% 51% 20%	58
	Night	7% 48% 40%	177
August	Day	11% 42% 40%	87
	Night	6% 28% 53% 7%	267
September	Day	24% 39% 34%	66
	Night	6% 38% 48%	278
October	Night	14% 43% 35%	362
November	Night	6% 17% 45% 26%	247
December	Night	18% 40% 31% 6%	262

Page generated at 2008-09-30 03:41:15. Version ab11