McDonald Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McDonald Park clear sky chart from 2005-11-06 to 2024-11-04.

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	23% 10% 3 7% 4 4 4 3 4 5% 32%	105506
	Night	27% 11% 3 7% 4 4 4 3 4 5% 30%	102105
Transparency	Day	28% 46% 8% 11% 6% 1	105259
	Night	31% 46% 8% 9% 5% 1	101998
Seeing	Day	29% 11% 24% 23% 11% 3	15215
	Night	35% 6% 16% 24% 17% 2	23457

By Month

Percentage Cloud Cover NW (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	39% 17% 4 9% 4 3 3 2 3 3 11%	2219
	11th to 20th	Day	27% 13% 4 8% 4 4 3 2 3 4 26%	2299
	21st to end	Day	44% 16% 4 7% 4 3 3 2 3 3 12%	2794
February	1st to 10th	Day	34% 12% 5% 8% 4 5% 4 3 4 4 17%	1697
	11th to 20th	Day	30% 15% 4 7% 5% 4 3 3 4 4 22%	1665
	21st to end	Day	26% 19% 3 8% 6% 6% 3 3 3 3 20%	1462
March	1st to 10th	Day	22% 18% 5% 10% 6% 4 4 3 4 6% 18%	3186
	11th to 20th	Day	21% 12% 3 8% 4 4 4 2 4 4 33%	3490
	21st to end	Day	25% 15% 4 9% 5% 5% 5% 3 5% 4 20%	3972
April	1st to 10th	Day	28% 13% 4 10% 5% 4 5% 4 5% 5% 16%	2280
	11th to 20th	Day	24% 12% 4 10% 6% 5% 5% 3 5% 5% 21%	2299
	21st to end	Day	27% 11% 4 9% 6% 5% 4 3 5% 5% 20%	2558
May	1st to 10th	Day	19% 11% 3 8% 5% 4 4 3 4 4 36%	4420
	11th to 20th	Day	17% 8% 3 7% 5% 4 5% 5% 7% 8% 33%	4377
	21st to end	Day	33% 12% 3 8% 5% 4 4 3 4 5% 18%	4813
June	1st to 10th	Day	27% 10% 4 7% 5% 5% 4 3 5% 6% 25%	2831
	11th to 20th	Day	29% 12% 4 8% 6% 4 4 4 4 5% 20%	2850
	21st to end	Day	17% 9% 3 8% 5% 5% 6% 3 6% 6% 34%	2850
July	1st to 10th	Day	9% 5% 2 4 3 3 3 3 4 5% 61%	4740
	11th to 20th	Day	7% 4 1 3 3 2 2 2 4 5% 68%	4714
	21st to end	Day	15% 5% 2 4 3 3 3 3 4 6% 53%	4790
August	1st to 10th	Day	7% 3 1 4 3 3 3 3 5% 6% 63%	4401
	11th to 20th	Day	13% 8% 4 6% 4 4 4 4 5% 7% 42%	4057
	21st to end	Day	17% 8% 3 8% 5% 4 4 3 4 6% 39%	4366
September	1st to 10th	Day	14% 7% 3 6% 4 3 3 3 4 6% 47%	2280
	11th to 20th	Day	18% 8% 3 8% 5% 5% 4 3 5% 4 38%	2280
	21st to end	Day	25% 6% 3 7% 4 4 4 3 4 4 36%	2012
October	1st to 10th	Day	23% 7% 3 6% 5% 4 5% 4 6% 7% 30%	3180
	11th to 20th	Day	37% 8% 3 7% 4 3 4 3 4 5% 23%	3161
	21st to end	Day	31% 12% 4 9% 5% 5% 5% 3 5% 6% 16%	3195
November	1st to 10th	Day	38% 11% 3 8% 5% 4 4 2 4 4 17%	1519
	11th to 20th	Day	38% 13% 3 7% 4 2 3 2 3 3 22%	1520
	21st to end	Day	37% 12% 4 7% 4 4 3 3 4 3 19%	1520
December	1st to 10th	Day	31% 14% 4 8% 4 2 4 2 3 3 26%	1520
	11th to 20th	Day	33% 14% 3 9% 4 4 4 3 3 3 19%	1747
	21st to end	Day	34% 17% 4 10% 5% 4 4 3 3 4 12%	2442
January	1st to 10th	Night	39% 17% 5% 8% 5% 3 3 2 3 2 13%	4726
	11th to 20th	Night	31% 12% 2 5% 2 3 3 2 4 6% 29%	4596
	21st to end	Night	42% 16% 4 8% 3 3 2 2 2 3 14%	4862
February	1st to 10th	Night	36% 12% 3 7% 5% 4 4 3 3 4 19%	2480
	11th to 20th	Night	30% 16% 3 7% 5% 4 3 2 3 4 21%	2402
	21st to end	Night	29% 15% 4 7% 5% 3 3 2 3 5% 24%	1991
March	1st to 10th	Night	23% 16% 4 9% 5% 4 4 3 4 6% 22%	3688
	11th to 20th	Night	23% 11% 3 7% 3 3 3 2 4 5% 35%	3489
	21st to end	Night	30% 14% 4 9% 6% 4 4 3 3 4 20%	3680
April	1st to 10th	Night	27% 14% 4 8% 5% 5% 5% 3 5% 5% 20%	1900
	11th to 20th	Night	23% 11% 3 9% 6% 6% 5% 4 4 5% 25%	1829
	21st to end	Night	30% 12% 3 8% 5% 4 4 4 5% 5% 20%	1621
May	1st to 10th	Night	18% 10% 3 7% 3 3 3 3 3 5% 42%	2540
	11th to 20th	Night	14% 8% 3 7% 5% 4 5% 4 5% 5% 42%	2516
	21st to end	Night	25% 14% 4 9% 5% 4 5% 3 4 5% 24%	2762
June	1st to 10th	Night	20% 10% 3 9% 6% 5% 5% 3 5% 5% 29%	1346
	11th to 20th	Night	23% 10% 4 7% 6% 6% 4 4 6% 7% 23%	1330
	21st to end	Night	16% 8% 1 6% 4 4 4 3 5% 7% 42%	1330
July	1st to 10th	Night	7% 4 1 3 3 2 3 3 3 5% 65%	2220
	11th to 20th	Night	5% 3 1 2 2 2 2 1 3 4 74%	2242
	21st to end	Night	11% 4 1 3 3 3 3 2 4 5% 60%	2762
August	1st to 10th	Night	6% 2 1 3 2 1 3 3 5% 7% 66%	2529
	11th to 20th	Night	10% 6% 2 6% 3 4 4 3 5% 7% 49%	2777
	21st to end	Night	18% 6% 2 7% 4 4 4 3 5% 8% 40%	3305
September	1st to 10th	Night	12% 5% 1 4 3 3 4 3 5% 7% 51%	1900
	11th to 20th	Night	19% 6% 3 7% 4 4 4 3 4 6% 41%	1900
	21st to end	Night	21% 8% 2 7% 4 3 4 3 4 5% 39%	2164
October	1st to 10th	Night	24% 10% 3 8% 5% 5% 5% 3 5% 5% 28%	3800
	11th to 20th	Night	37% 8% 2 5% 3 3 3 2 4 6% 28%	3777
	21st to end	Night	31% 12% 4 9% 4 4 4 3 4 4 22%	4366
November	1st to 10th	Night	38% 12% 3 6% 4 3 4 3 4 4 17%	2628
	11th to 20th	Night	39% 10% 3 6% 5% 4 2 3 3 4 21%	2660
	21st to end	Night	38% 12% 3 7% 4 4 3 3 3 4 20%	2660
December	1st to 10th	Night	31% 12% 3 6% 4 3 4 3 4 4 27%	2660
	11th to 20th	Night	39% 15% 3 9% 4 4 3 3 3 3 14%	3453
	21st to end	Night	38% 16% 4 8% 5% 4 3 3 3 3 13%	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% 35% 6% 6% 2	2219
	11th to 20th	Day	38% 36% 9% 10% 3 4	2320
	21st to end	Day	52% 38% 6% 3 1	2794
February	1st to 10th	Day	27% 63% 2 2 4 1	1697
	11th to 20th	Day	25% 64% 4 5% 2 1	1674
	21st to end	Day	23% 65% 4 4 3 1	1462
March	1st to 10th	Day	38% 39% 8% 11% 4	3186
	11th to 20th	Day	29% 40% 9% 20% 2	3490
	21st to end	Day	40% 39% 10% 7% 5%	3972
April	1st to 10th	Day	25% 65% 4 6%	2280
	11th to 20th	Day	22% 65% 4 5% 2 1	2299
	21st to end	Day	24% 64% 4 5% 3	2558
May	1st to 10th	Day	28% 40% 7% 17% 8%	4420
	11th to 20th	Day	28% 41% 18% 12% 1	4380
	21st to end	Day	45% 39% 11% 5%	4814
June	1st to 10th	Day	20% 65% 6% 7% 3	2831
	11th to 20th	Day	20% 65% 6% 7% 2	2850
	21st to end	Day	17% 64% 8% 9% 2	2850
July	1st to 10th	Day	11% 36% 6% 17% 19% 10%	4666
	11th to 20th	Day	9% 35% 6% 27% 21% 3	4633
	21st to end	Day	20% 38% 16% 18% 7% 1	4639
August	1st to 10th	Day	9% 38% 8% 28% 16% 1	4384
	11th to 20th	Day	26% 44% 15% 10% 4 1	4097
	21st to end	Day	30% 40% 8% 14% 8%	4365
September	1st to 10th	Day	19% 60% 6% 9% 5% 1	2280
	11th to 20th	Day	22% 60% 5% 6% 7% 1	2280
	21st to end	Day	21% 59% 7% 8% 5%	2012
October	1st to 10th	Day	33% 41% 11% 13% 3	3180
	11th to 20th	Day	42% 38% 8% 6% 6%	3161
	21st to end	Day	41% 42% 7% 7% 4	3195
November	1st to 10th	Day	29% 58% 6% 6% 1	1519
	11th to 20th	Day	26% 59% 3 6% 3 2	1520
	21st to end	Day	25% 59% 3 8% 4 1	1520
December	1st to 10th	Day	27% 59% 3 5% 5% 1	1520
	11th to 20th	Day	36% 47% 7% 7% 2	1750
	21st to end	Day	48% 36% 10% 5% 1	2442
January	1st to 10th	Night	50% 36% 4 8% 2	4726
	11th to 20th	Night	33% 37% 11% 10% 5% 4	4637
	21st to end	Night	52% 39% 6% 3	4862
February	1st to 10th	Night	24% 64% 3 3 3 2	2480
	11th to 20th	Night	26% 63% 3 5% 3	2404
	21st to end	Night	20% 64% 5% 6% 3 1	1991
March	1st to 10th	Night	38% 39% 7% 9% 7%	3688
	11th to 20th	Night	26% 41% 11% 20% 2	3490
	21st to end	Night	41% 39% 12% 7% 2	3680
April	1st to 10th	Night	24% 65% 4 6% 1	1900
	11th to 20th	Night	22% 65% 5% 4 2 1	1829
	21st to end	Night	23% 65% 4 6% 2	1621
May	1st to 10th	Night	26% 39% 7% 21% 7% 1	2540
	11th to 20th	Night	26% 41% 18% 13% 2	2516
	21st to end	Night	43% 39% 12% 6% 1	2762
June	1st to 10th	Night	18% 65% 8% 7% 2	1346
	11th to 20th	Night	19% 66% 7% 6% 2	1330
	21st to end	Night	15% 63% 9% 10% 2	1330
July	1st to 10th	Night	9% 35% 6% 23% 19% 9%	2185
	11th to 20th	Night	8% 34% 5% 25% 27% 2	2200
	21st to end	Night	21% 36% 11% 17% 15% 1	2674
August	1st to 10th	Night	6% 38% 12% 27% 16% 1	2521
	11th to 20th	Night	21% 44% 20% 11% 3 1	2803
	21st to end	Night	28% 41% 12% 11% 7%	3305
September	1st to 10th	Night	18% 60% 7% 8% 6% 1	1900
	11th to 20th	Night	21% 60% 6% 6% 5% 2	1900
	21st to end	Night	20% 60% 6% 9% 4	2164
October	1st to 10th	Night	37% 42% 12% 7% 2	3800
	11th to 20th	Night	39% 39% 7% 11% 5%	3777
	21st to end	Night	39% 42% 7% 8% 3	4366
November	1st to 10th	Night	31% 57% 6% 5% 2	2628
	11th to 20th	Night	26% 59% 4 5% 4 2	2660
	21st to end	Night	27% 59% 3 4 5% 1	2660
December	1st to 10th	Night	24% 60% 5% 5% 5%	2660
	11th to 20th	Night	41% 48% 6% 3 2 1	3449
	21st to end	Night	50% 36% 6% 5% 2	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	43% 16% 16% 13% 7% 4	180
	11th to 20th	Day	44% 13% 14% 16% 11% 1	180
	21st to end	Day	45% 9% 21% 16% 8% 1	198
February	1st to 10th	Day	47% 13% 19% 13% 6% 2	357
	11th to 20th	Day	42% 11% 24% 18% 4 1	365
	21st to end	Day	39% 13% 27% 14% 6% 1	332
March	1st to 10th	Day	37% 14% 24% 16% 8% 1	460
	11th to 20th	Day	36% 11% 22% 18% 12% 1	460
	21st to end	Day	38% 15% 20% 18% 8%	506
April	1st to 10th	Day	37% 14% 23% 17% 7% 1	460
	11th to 20th	Day	29% 15% 27% 17% 10% 1	452
	21st to end	Day	31% 17% 26% 16% 9% 2	460
May	1st to 10th	Day	22% 12% 31% 26% 8% 2	463
	11th to 20th	Day	24% 10% 24% 26% 12% 4	488
	21st to end	Day	29% 12% 23% 22% 10% 3	529
June	1st to 10th	Day	26% 12% 30% 22% 8% 2	661
	11th to 20th	Day	30% 13% 27% 22% 7% 1	680
	21st to end	Day	21% 11% 26% 28% 13% 2	680
July	1st to 10th	Day	16% 8% 29% 35% 10% 2	671
	11th to 20th	Day	12% 9% 25% 36% 14% 3	655
	21st to end	Day	11% 7% 24% 37% 15% 6%	531
August	1st to 10th	Day	13% 6% 24% 31% 17% 9%	487
	11th to 20th	Day	10% 5% 25% 31% 21% 7%	477
	21st to end	Day	18% 11% 23% 28% 15% 5%	539
September	1st to 10th	Day	19% 11% 23% 29% 15% 3	490
	11th to 20th	Day	23% 9% 21% 27% 15% 4	490
	21st to end	Day	28% 10% 22% 25% 12% 3	490
October	1st to 10th	Day	30% 9% 21% 21% 17% 3	490
	11th to 20th	Day	36% 10% 18% 21% 13% 3	490
	21st to end	Day	38% 13% 20% 17% 9% 2	387
November	1st to 10th	Day	42% 13% 22% 18% 5% 1	189
	11th to 20th	Day	49% 7% 15% 13% 12% 3	180
	21st to end	Day	47% 8% 21% 9% 11% 3	180
December	1st to 10th	Day	46% 8% 19% 11% 9% 6%	180
	11th to 20th	Day	50% 7% 21% 15% 5% 2	180
	21st to end	Day	48% 12% 19% 16% 5% 1	198
January	1st to 10th	Night	50% 10% 16% 15% 8% 1	850
	11th to 20th	Night	45% 7% 16% 21% 11% 1	819
	21st to end	Night	43% 8% 18% 21% 9% 1	836
February	1st to 10th	Night	43% 9% 21% 21% 6% 1	760
	11th to 20th	Night	43% 7% 20% 22% 8%	744
	21st to end	Night	38% 10% 20% 22% 9% 1	628
March	1st to 10th	Night	34% 10% 18% 22% 15% 1	760
	11th to 20th	Night	40% 6% 19% 22% 13% 1	760
	21st to end	Night	40% 7% 18% 24% 9% 2	836
April	1st to 10th	Night	37% 7% 16% 27% 11% 1	760
	11th to 20th	Night	30% 7% 22% 25% 15% 1	701
	21st to end	Night	36% 5% 16% 29% 12% 2	481
May	1st to 10th	Night	23% 7% 15% 29% 24% 1	380
	11th to 20th	Night	22% 2 11% 29% 31% 5%	374
	21st to end	Night	27% 3 10% 31% 27% 3	411
June	1st to 10th	Night	24% 4 17% 32% 20% 4	380
	11th to 20th	Night	27% 6% 14% 27% 21% 5%	380
	21st to end	Night	20% 3 11% 31% 31% 4	380
July	1st to 10th	Night	15% 2 10% 30% 40% 4	370
	11th to 20th	Night	11% 4 8% 30% 40% 7%	368
	21st to end	Night	10% 3 3 29% 49% 7%	416
August	1st to 10th	Night	13% 1 4 22% 48% 11%	378
	11th to 20th	Night	10% 1 6% 25% 46% 12%	541
	21st to end	Night	16% 3 8% 30% 38% 5%	721
September	1st to 10th	Night	16% 2 11% 38% 28% 5%	760
	11th to 20th	Night	22% 4 14% 22% 32% 6%	760
	21st to end	Night	28% 5% 13% 28% 24% 3	760
October	1st to 10th	Night	29% 4 16% 26% 23% 2	760
	11th to 20th	Night	38% 5% 14% 24% 16% 3	760
	21st to end	Night	41% 8% 17% 23% 9% 2	836
November	1st to 10th	Night	47% 7% 19% 21% 5%	754
	11th to 20th	Night	50% 7% 17% 16% 9% 1	760
	21st to end	Night	47% 9% 17% 15% 10% 2	760
December	1st to 10th	Night	37% 7% 22% 23% 11% 1	760
	11th to 20th	Night	51% 6% 21% 17% 4 1	818
	21st to end	Night	52% 7% 21% 16% 4	935

Page generated at 2024-11-01 19:47:42. Version ac07

Copyright © 2024 Attilla Danko.