Grasslands National Park (West)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grasslands National Park (West) clear sky chart from 2005-11-06 to 2024-11-28.

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% 7% 3 7% 5% 4 5% 4 6% 8% 43%	105702
	Night	6% 7% 3 8% 5% 5% 5% 4 6% 8% 43%	102492
Transparency	Day	38% 6% 15% 26% 13% 2	105432
	Night	37% 6% 15% 26% 13% 2	102352
Seeing	Day	12% 9% 29% 30% 16% 4	15855
	Night	10% 8% 32% 36% 13% 1	25270

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	5% 12% 5% 12% 6% 6% 7% 5% 6% 8% 29%	2219
	11th to 20th	Day	2 8% 4 12% 9% 7% 8% 5% 7% 8% 30%	2225
	21st to end	Day	4 10% 4 8% 6% 6% 5% 5% 5% 7% 40%	2835
February	1st to 10th	Day	8% 13% 5% 12% 7% 6% 6% 4 7% 6% 26%	1710
	11th to 20th	Day	6% 11% 5% 14% 8% 6% 5% 5% 8% 8% 24%	1665
	21st to end	Day	4 12% 4 11% 9% 6% 7% 6% 6% 7% 26%	1439
March	1st to 10th	Day	4 11% 5% 12% 8% 6% 5% 5% 5% 7% 34%	3216
	11th to 20th	Day	6% 8% 3 8% 5% 5% 5% 4 6% 10% 40%	3490
	21st to end	Day	7% 17% 7% 17% 7% 5% 5% 4 4 6% 20%	3938
April	1st to 10th	Day	8% 9% 3 9% 6% 6% 5% 5% 6% 8% 34%	2280
	11th to 20th	Day	12% 14% 4 8% 6% 5% 5% 5% 6% 6% 30%	2329
	21st to end	Day	13% 10% 3 7% 6% 4 5% 4 6% 8% 36%	2536
May	1st to 10th	Day	17% 12% 3 8% 5% 4 4 4 5% 6% 32%	4430
	11th to 20th	Day	9% 6% 2 7% 6% 6% 5% 5% 7% 9% 38%	4388
	21st to end	Day	14% 7% 3 8% 5% 6% 5% 5% 7% 8% 32%	4878
June	1st to 10th	Day	13% 6% 3 6% 5% 5% 6% 5% 6% 9% 37%	2850
	11th to 20th	Day	14% 6% 2 6% 6% 5% 6% 4 7% 8% 38%	2850
	21st to end	Day	6% 4 2 5% 4 4 5% 4 8% 8% 49%	2850
July	1st to 10th	Day	3 3 1 6% 5% 5% 6% 5% 7% 9% 50%	4740
	11th to 20th	Day	3 2 1 4 3 3 3 3 6% 8% 64%	4740
	21st to end	Day	3 2 1 3 2 2 3 2 4 7% 70%	4846
August	1st to 10th	Day	6% 4 1 5% 3 3 4 4 5% 7% 56%	4393
	11th to 20th	Day	4 3 1 5% 3 4 4 4 6% 9% 57%	4028
	21st to end	Day	7% 3 1 4 3 3 4 3 5% 7% 60%	4402
September	1st to 10th	Day	9% 6% 2 5% 4 4 4 3 6% 6% 52%	2280
	11th to 20th	Day	11% 6% 2 6% 4 4 3 3 6% 7% 49%	2280
	21st to end	Day	11% 7% 2 5% 3 3 3 3 5% 6% 51%	2004
October	1st to 10th	Day	7% 6% 2 5% 4 3 4 2 6% 7% 54%	3170
	11th to 20th	Day	5% 5% 2 5% 3 3 4 3 5% 11% 53%	3150
	21st to end	Day	4 7% 2 5% 4 4 5% 4 7% 8% 49%	3145
November	1st to 10th	Day	10% 13% 4 7% 5% 4 4 4 5% 7% 37%	1568
	11th to 20th	Day	5% 8% 4 9% 6% 5% 5% 5% 6% 7% 39%	1600
	21st to end	Day	6% 12% 4 8% 6% 5% 5% 4 6% 8% 35%	1576
December	1st to 10th	Day	6% 9% 6% 11% 10% 7% 6% 5% 6% 6% 29%	1520
	11th to 20th	Day	4 10% 5% 12% 7% 6% 5% 4 6% 7% 34%	1690
	21st to end	Day	5% 8% 3 8% 5% 4 4 5% 6% 8% 45%	2442
January	1st to 10th	Night	3 7% 4 10% 6% 7% 7% 6% 8% 9% 33%	4726
	11th to 20th	Night	3 7% 5% 13% 8% 6% 6% 6% 9% 7% 29%	4732
	21st to end	Night	3 8% 5% 10% 6% 5% 5% 4 6% 8% 40%	4860
February	1st to 10th	Night	5% 10% 4 11% 7% 6% 6% 4 6% 7% 34%	2470
	11th to 20th	Night	4 10% 4 11% 7% 7% 6% 4 6% 9% 32%	2402
	21st to end	Night	4 10% 4 11% 7% 6% 6% 5% 6% 7% 34%	2014
March	1st to 10th	Night	5% 9% 4 11% 8% 6% 6% 4 7% 9% 31%	3647
	11th to 20th	Night	5% 6% 3 7% 4 4 4 4 7% 12% 43%	3490
	21st to end	Night	9% 15% 7% 16% 8% 5% 5% 5% 5% 6% 19%	3710
April	1st to 10th	Night	7% 8% 3 7% 6% 6% 5% 4 7% 7% 39%	1900
	11th to 20th	Night	12% 11% 4 8% 5% 5% 4 5% 7% 7% 34%	1797
	21st to end	Night	10% 8% 3 8% 6% 5% 6% 4 6% 7% 37%	1644
May	1st to 10th	Night	16% 10% 3 7% 5% 4 4 3 5% 6% 36%	2540
	11th to 20th	Night	10% 5% 1 5% 5% 5% 6% 6% 7% 10% 40%	2517
	21st to end	Night	13% 7% 2 6% 4 4 4 4 7% 9% 40%	2703
June	1st to 10th	Night	12% 6% 2 5% 5% 4 5% 3 7% 9% 43%	1330
	11th to 20th	Night	13% 4 2 5% 3 4 5% 5% 7% 8% 45%	1330
	21st to end	Night	5% 4 1 4 5% 3 4 4 5% 8% 56%	1330
July	1st to 10th	Night	4 2 1 3 3 3 4 5% 6% 10% 59%	2220
	11th to 20th	Night	3 3 1 4 3 3 3 4 5% 7% 63%	2220
	21st to end	Night	3 2 1 4 3 3 4 4 6% 8% 63%	2713
August	1st to 10th	Night	8% 4 2 4 3 3 3 3 6% 7% 59%	2545
	11th to 20th	Night	4 3 1 4 3 3 4 4 7% 9% 57%	2811
	21st to end	Night	8% 4 2 5% 3 3 4 3 5% 6% 56%	3264
September	1st to 10th	Night	9% 3 2 4 3 3 3 3 5% 7% 58%	1900
	11th to 20th	Night	9% 7% 2 5% 4 3 4 3 5% 7% 52%	1900
	21st to end	Night	9% 5% 1 5% 3 3 3 3 6% 9% 53%	2174
October	1st to 10th	Night	7% 5% 2 5% 3 3 3 3 5% 8% 54%	3800
	11th to 20th	Night	5% 5% 2 5% 3 3 4 3 5% 9% 56%	3778
	21st to end	Night	6% 6% 2 6% 4 4 5% 4 7% 8% 48%	4366
November	1st to 10th	Night	10% 11% 4 8% 6% 4 5% 3 5% 7% 38%	2730
	11th to 20th	Night	4 9% 4 9% 7% 5% 5% 5% 6% 7% 40%	2800
	21st to end	Night	5% 10% 4 11% 5% 5% 4 4 6% 8% 37%	2759
December	1st to 10th	Night	5% 10% 4 11% 10% 7% 6% 4 6% 8% 29%	2660
	11th to 20th	Night	4 9% 4 11% 5% 5% 5% 5% 6% 8% 35%	3496
	21st to end	Night	4 6% 3 6% 4 4 4 3 5% 7% 53%	5214

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	50% 10% 18% 17% 5%	2219
	11th to 20th	Day	50% 7% 16% 14% 12% 1	2225
	21st to end	Day	42% 8% 21% 23% 6%	2835
February	1st to 10th	Day	56% 7% 13% 16% 8%	1710
	11th to 20th	Day	55% 6% 16% 13% 9% 1	1674
	21st to end	Day	54% 8% 16% 13% 8%	1439
March	1st to 10th	Day	49% 7% 16% 23% 5%	3216
	11th to 20th	Day	39% 7% 23% 25% 6%	3490
	21st to end	Day	64% 9% 13% 11% 3	3938
April	1st to 10th	Day	46% 8% 15% 21% 9%	2280
	11th to 20th	Day	52% 6% 14% 20% 7% 1	2332
	21st to end	Day	45% 6% 14% 25% 8% 1	2536
May	1st to 10th	Day	51% 6% 13% 21% 8% 1	4430
	11th to 20th	Day	37% 8% 15% 27% 13%	4392
	21st to end	Day	43% 10% 16% 23% 8%	4878
June	1st to 10th	Day	42% 9% 17% 22% 10% 1	2850
	11th to 20th	Day	42% 7% 15% 23% 12% 1	2850
	21st to end	Day	30% 7% 16% 34% 13% 1	2850
July	1st to 10th	Day	27% 8% 18% 24% 18% 4	4666
	11th to 20th	Day	18% 5% 13% 34% 23% 6%	4659
	21st to end	Day	15% 3 8% 30% 30% 13%	4693
August	1st to 10th	Day	27% 5% 10% 33% 22% 3	4378
	11th to 20th	Day	23% 5% 17% 35% 17% 2	4067
	21st to end	Day	23% 4 12% 38% 19% 3	4401
September	1st to 10th	Day	32% 5% 11% 29% 17% 6%	2280
	11th to 20th	Day	34% 6% 16% 28% 13% 3	2280
	21st to end	Day	34% 4 13% 30% 17% 3	2004
October	1st to 10th	Day	31% 3 11% 35% 16% 3	3170
	11th to 20th	Day	28% 4 14% 40% 12% 3	3150
	21st to end	Day	31% 5% 16% 37% 11%	3145
November	1st to 10th	Day	46% 5% 16% 24% 8% 1	1568
	11th to 20th	Day	42% 8% 18% 24% 8% 1	1600
	21st to end	Day	46% 7% 20% 20% 6% 1	1576
December	1st to 10th	Day	53% 8% 14% 19% 5% 1	1520
	11th to 20th	Day	47% 7% 22% 20% 3	1689
	21st to end	Day	36% 6% 15% 22% 14% 7%	2442
January	1st to 10th	Night	41% 11% 21% 20% 7% 1	4726
	11th to 20th	Night	48% 6% 15% 17% 13% 1	4732
	21st to end	Night	41% 6% 21% 26% 5%	4860
February	1st to 10th	Night	48% 6% 16% 19% 10% 1	2470
	11th to 20th	Night	47% 8% 17% 17% 10% 1	2403
	21st to end	Night	46% 7% 13% 22% 11% 1	2014
March	1st to 10th	Night	46% 8% 17% 21% 9%	3647
	11th to 20th	Night	33% 6% 27% 26% 8%	3490
	21st to end	Night	64% 8% 11% 12% 4	3710
April	1st to 10th	Night	42% 7% 15% 25% 11% 1	1900
	11th to 20th	Night	47% 7% 11% 22% 10% 2	1797
	21st to end	Night	45% 6% 13% 24% 12%	1644
May	1st to 10th	Night	45% 7% 11% 26% 10% 1	2540
	11th to 20th	Night	34% 9% 16% 27% 13%	2518
	21st to end	Night	37% 10% 17% 28% 8%	2703
June	1st to 10th	Night	38% 7% 16% 24% 13% 1	1330
	11th to 20th	Night	35% 6% 15% 26% 16% 2	1330
	21st to end	Night	26% 6% 18% 31% 17% 2	1330
July	1st to 10th	Night	19% 7% 22% 31% 18% 3	2185
	11th to 20th	Night	21% 4 13% 32% 21% 8%	2178
	21st to end	Night	18% 3 11% 28% 31% 9%	2628
August	1st to 10th	Night	25% 3 10% 33% 25% 4	2537
	11th to 20th	Night	23% 5% 16% 35% 19% 2	2838
	21st to end	Night	28% 5% 11% 34% 18% 4	3264
September	1st to 10th	Night	27% 4 10% 30% 20% 9%	1900
	11th to 20th	Night	33% 5% 12% 28% 18% 5%	1900
	21st to end	Night	29% 5% 12% 32% 21% 3	2174
October	1st to 10th	Night	29% 5% 10% 34% 21% 1	3800
	11th to 20th	Night	25% 4 13% 41% 16% 1	3778
	21st to end	Night	33% 6% 12% 37% 13% 1	4366
November	1st to 10th	Night	46% 6% 15% 21% 10% 2	2730
	11th to 20th	Night	41% 6% 18% 24% 10% 1	2800
	21st to end	Night	45% 6% 21% 20% 7%	2759
December	1st to 10th	Night	51% 7% 17% 16% 8% 1	2660
	11th to 20th	Night	44% 8% 21% 22% 4 1	3497
	21st to end	Night	31% 5% 13% 28% 17% 6%	5214

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 9% 31% 29% 14% 7%	180
	11th to 20th	Day	7% 11% 32% 27% 20% 3	183
	21st to end	Day	11% 10% 32% 31% 15% 1	297
February	1st to 10th	Day	15% 10% 39% 27% 7% 1	270
	11th to 20th	Day	9% 9% 37% 31% 12% 2	270
	21st to end	Day	10% 6% 34% 35% 10% 5%	225
March	1st to 10th	Day	10% 10% 34% 30% 15% 1	317
	11th to 20th	Day	9% 10% 38% 26% 13% 3	460
	21st to end	Day	12% 10% 30% 26% 17% 3	506
April	1st to 10th	Day	12% 14% 37% 29% 8%	460
	11th to 20th	Day	15% 16% 32% 25% 9% 2	452
	21st to end	Day	19% 12% 28% 29% 10% 2	526
May	1st to 10th	Day	18% 9% 23% 28% 18% 4	653
	11th to 20th	Day	14% 7% 26% 29% 19% 5%	675
	21st to end	Day	16% 9% 24% 25% 19% 6%	734
June	1st to 10th	Day	15% 11% 24% 28% 19% 3	680
	11th to 20th	Day	16% 11% 34% 24% 12% 3	680
	21st to end	Day	10% 8% 26% 31% 21% 5%	680
July	1st to 10th	Day	6% 3 25% 39% 21% 6%	671
	11th to 20th	Day	4 6% 26% 37% 21% 5%	668
	21st to end	Day	4 4 26% 36% 25% 5%	739
August	1st to 10th	Day	8% 5% 22% 37% 21% 7%	671
	11th to 20th	Day	9% 6% 22% 33% 21% 10%	477
	21st to end	Day	8% 7% 24% 36% 19% 6%	539
September	1st to 10th	Day	11% 8% 29% 34% 14% 4	490
	11th to 20th	Day	14% 7% 26% 30% 21% 3	490
	21st to end	Day	14% 11% 28% 28% 15% 5%	390
October	1st to 10th	Day	23% 10% 20% 21% 22% 4	300
	11th to 20th	Day	8% 7% 39% 28% 15% 3	300
	21st to end	Day	12% 13% 39% 25% 9% 2	330
November	1st to 10th	Day	18% 12% 32% 27% 11%	300
	11th to 20th	Day	11% 16% 37% 27% 9% 1	300
	21st to end	Day	12% 10% 36% 28% 11% 3	291
December	1st to 10th	Day	10% 9% 38% 32% 10% 2	270
	11th to 20th	Day	10% 15% 34% 32% 7% 2	183
	21st to end	Day	10% 7% 33% 28% 19% 4	198
January	1st to 10th	Night	7% 10% 36% 34% 11% 2	950
	11th to 20th	Night	10% 11% 35% 33% 8% 2	950
	21st to end	Night	7% 12% 38% 31% 11% 1	1032
February	1st to 10th	Night	8% 7% 34% 34% 15% 1	760
	11th to 20th	Night	9% 6% 37% 37% 10% 1	744
	21st to end	Night	7% 8% 29% 36% 17% 3	628
March	1st to 10th	Night	10% 8% 35% 35% 12% 1	760
	11th to 20th	Night	10% 7% 36% 34% 11% 2	760
	21st to end	Night	12% 7% 31% 35% 12% 2	769
April	1st to 10th	Night	10% 6% 36% 38% 10% 1	570
	11th to 20th	Night	19% 7% 33% 31% 9%	563
	21st to end	Night	14% 9% 30% 38% 9%	570
May	1st to 10th	Night	15% 6% 25% 39% 13% 1	570
	11th to 20th	Night	12% 4 28% 39% 16% 1	561
	21st to end	Night	17% 7% 25% 31% 18% 2	584
June	1st to 10th	Night	16% 8% 22% 35% 17% 1	380
	11th to 20th	Night	16% 6% 30% 38% 11%	380
	21st to end	Night	7% 6% 24% 45% 18% 1	380
July	1st to 10th	Night	6% 4 21% 48% 20% 1	370
	11th to 20th	Night	5% 3 28% 48% 15% 1	368
	21st to end	Night	4 3 26% 48% 19% 1	589
August	1st to 10th	Night	7% 3 23% 46% 19% 2	567
	11th to 20th	Night	7% 3 21% 46% 22% 1	564
	21st to end	Night	9% 5% 24% 42% 19% 1	627
September	1st to 10th	Night	11% 3 26% 40% 20% 1	570
	11th to 20th	Night	12% 5% 28% 37% 18% 1	570
	21st to end	Night	11% 5% 31% 37% 15% 1	744
October	1st to 10th	Night	12% 7% 28% 35% 16% 1	760
	11th to 20th	Night	11% 9% 31% 34% 14% 1	760
	21st to end	Night	13% 10% 35% 34% 7% 1	964
November	1st to 10th	Night	16% 10% 35% 30% 9%	975
	11th to 20th	Night	8% 12% 39% 30% 10% 1	1000
	21st to end	Night	10% 11% 39% 31% 9%	986
December	1st to 10th	Night	9% 9% 35% 33% 14% 1	950
	11th to 20th	Night	9% 9% 37% 34% 10% 1	950
	21st to end	Night	13% 6% 35% 33% 12% 2	1045

Page generated at 2024-11-24 23:22:19. Version ac07

Copyright © 2024 Attilla Danko.