Haggart Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Haggart Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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	19% 8% 3 7% 5% 4 4 3 5% 6% 37%	105593
	Night	22% 9% 3 7% 4 4 4 3 4 5% 34%	102564
Transparency	Day	47% 7% 12% 17% 13% 5%	105336
	Night	50% 7% 12% 17% 11% 3	102410
Seeing	Day	22% 10% 21% 27% 16% 4	14682
	Night	26% 7% 15% 30% 19% 2	23654

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	38% 14% 4 11% 6% 5% 4 3 4 3 8%	2539
	11th to 20th	Day	39% 14% 4 7% 4 4 3 2 3 3 17%	2540
	21st to end	Day	36% 11% 4 9% 6% 4 5% 3 4 4 15%	3050
February	1st to 10th	Day	30% 13% 4 7% 5% 4 5% 4 5% 6% 16%	1710
	11th to 20th	Day	29% 13% 3 10% 6% 5% 4 3 4 4 19%	1665
	21st to end	Day	30% 14% 4 8% 6% 4 4 2 3 4 20%	1498
March	1st to 10th	Day	19% 12% 4 10% 7% 7% 6% 4 6% 6% 19%	3279
	11th to 20th	Day	20% 9% 3 8% 5% 4 4 3 4 5% 36%	3490
	21st to end	Day	24% 14% 5% 11% 6% 5% 5% 4 5% 5% 15%	3914
April	1st to 10th	Day	29% 12% 3 8% 7% 5% 4 3 4 5% 19%	2280
	11th to 20th	Day	24% 13% 4 8% 5% 5% 4 3 5% 5% 24%	2249
	21st to end	Day	24% 10% 4 9% 5% 5% 4 4 5% 6% 24%	2451
May	1st to 10th	Day	22% 8% 3 7% 5% 5% 5% 3 5% 5% 32%	4358
	11th to 20th	Day	13% 6% 3 7% 5% 4 4 4 5% 7% 42%	4377
	21st to end	Day	23% 8% 3 8% 7% 6% 6% 4 5% 6% 24%	4813
June	1st to 10th	Day	22% 9% 3 7% 6% 4 4 3 5% 6% 31%	2660
	11th to 20th	Day	21% 9% 3 7% 6% 5% 5% 4 6% 7% 26%	2660
	21st to end	Day	9% 6% 2 6% 4 4 4 3 4 6% 51%	2660
July	1st to 10th	Day	4 3 1 3 2 3 3 3 4 5% 69%	4420
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 4 75%	4420
	21st to end	Day	6% 3 1 3 3 2 2 2 3 5% 70%	4790
August	1st to 10th	Day	3 3 1 4 3 3 4 3 5% 6% 65%	4135
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 7% 55%	4026
	21st to end	Day	9% 5% 2 4 3 3 4 3 5% 6% 54%	4283
September	1st to 10th	Day	8% 4 2 3 2 3 4 3 5% 7% 60%	2280
	11th to 20th	Day	11% 8% 3 8% 4 4 4 4 5% 7% 42%	2280
	21st to end	Day	15% 5% 2 6% 4 4 5% 3 4 7% 44%	2001
October	1st to 10th	Day	16% 6% 2 5% 4 3 4 3 5% 6% 46%	3180
	11th to 20th	Day	18% 7% 3 8% 5% 5% 5% 4 6% 7% 32%	3161
	21st to end	Day	28% 9% 2 8% 5% 4 5% 4 6% 8% 22%	3361
November	1st to 10th	Day	30% 10% 4 10% 4 5% 5% 4 5% 5% 18%	1669
	11th to 20th	Day	32% 9% 4 8% 6% 4 3 3 6% 5% 19%	1600
	21st to end	Day	27% 11% 4 7% 6% 6% 5% 3 4 5% 22%	1552
December	1st to 10th	Day	28% 12% 4 8% 5% 4 3 3 4 4 24%	1520
	11th to 20th	Day	29% 11% 3 10% 5% 5% 5% 3 6% 7% 15%	1928
	21st to end	Day	31% 15% 5% 11% 6% 4 4 4 5% 4 11%	2794
January	1st to 10th	Night	35% 16% 4 11% 6% 5% 4 3 3 3 11%	4406
	11th to 20th	Night	39% 14% 4 7% 5% 3 3 2 3 3 17%	4420
	21st to end	Night	38% 12% 3 9% 5% 4 3 3 3 4 16%	4611
February	1st to 10th	Night	29% 13% 3 8% 7% 5% 5% 3 5% 5% 18%	2470
	11th to 20th	Night	32% 11% 3 7% 5% 3 3 2 4 5% 24%	2402
	21st to end	Night	29% 15% 4 9% 4 4 3 3 4 5% 21%	1956
March	1st to 10th	Night	18% 14% 5% 11% 7% 5% 5% 4 5% 6% 21%	3591
	11th to 20th	Night	17% 8% 3 6% 3 4 4 3 6% 5% 41%	3490
	21st to end	Night	25% 14% 4 11% 7% 6% 5% 4 5% 5% 15%	3738
April	1st to 10th	Night	26% 14% 4 9% 6% 4 4 3 5% 5% 21%	1900
	11th to 20th	Night	22% 11% 3 8% 5% 3 4 4 5% 7% 29%	1879
	21st to end	Night	25% 10% 4 7% 4 5% 4 3 5% 5% 28%	1727
May	1st to 10th	Night	24% 10% 3 7% 3 3 3 2 4 4 37%	2590
	11th to 20th	Night	13% 6% 2 5% 4 4 4 3 5% 7% 48%	2516
	21st to end	Night	20% 9% 4 8% 6% 4 4 4 6% 7% 28%	2762
June	1st to 10th	Night	19% 9% 3 6% 5% 4 4 3 4 6% 36%	1520
	11th to 20th	Night	19% 11% 4 7% 5% 4 4 3 4 5% 33%	1520
	21st to end	Night	10% 5% 2 5% 3 2 4 3 4 5% 55%	1520
July	1st to 10th	Night	5% 2 1 3 2 2 2 1 2 3 76%	2540
	11th to 20th	Night	4 2 1 3 2 2 2 2 3 3 76%	2540
	21st to end	Night	5% 3 1 2 2 2 1 2 3 4 75%	2761
August	1st to 10th	Night	3 2 1 3 2 2 2 2 4 7% 72%	2801
	11th to 20th	Night	9% 6% 2 6% 3 3 4 3 4 6% 55%	2812
	21st to end	Night	11% 5% 2 4 3 3 3 2 3 5% 59%	3392
September	1st to 10th	Night	7% 3 2 4 2 2 3 2 4 5% 65%	1900
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 4 6% 48%	1900
	21st to end	Night	13% 6% 2 3 4 4 4 3 5% 7% 50%	2173
October	1st to 10th	Night	15% 5% 2 5% 3 3 4 3 5% 7% 49%	3800
	11th to 20th	Night	17% 6% 3 6% 5% 4 4 4 6% 8% 37%	3777
	21st to end	Night	27% 10% 3 9% 5% 4 4 3 5% 5% 25%	4203
November	1st to 10th	Night	32% 9% 3 7% 5% 5% 5% 3 5% 5% 21%	2627
	11th to 20th	Night	37% 9% 3 8% 4 4 4 3 4 4 21%	2800
	21st to end	Night	28% 10% 3 7% 5% 4 5% 3 5% 4 27%	2722
December	1st to 10th	Night	30% 10% 3 6% 4 4 4 3 4 6% 25%	2660
	11th to 20th	Night	30% 12% 3 9% 5% 4 4 3 5% 6% 18%	3276
	21st to end	Night	28% 14% 4 12% 7% 6% 4 3 5% 4 13%	4862

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	77% 9% 6% 4 2 1	2539
	11th to 20th	Day	74% 4 6% 10% 4 2	2540
	21st to end	Day	70% 8% 7% 8% 6%	3050
February	1st to 10th	Day	65% 8% 11% 10% 6%	1710
	11th to 20th	Day	67% 8% 9% 10% 4 2	1674
	21st to end	Day	69% 5% 10% 8% 6% 2	1498
March	1st to 10th	Day	60% 6% 16% 14% 3	3279
	11th to 20th	Day	49% 8% 9% 21% 13% 1	3490
	21st to end	Day	66% 11% 12% 8% 4	3914
April	1st to 10th	Day	66% 7% 12% 11% 3	2280
	11th to 20th	Day	61% 7% 10% 11% 8% 3	2252
	21st to end	Day	60% 8% 11% 12% 7% 1	2451
May	1st to 10th	Day	49% 9% 12% 18% 11%	4358
	11th to 20th	Day	36% 9% 19% 24% 12% 1	4380
	21st to end	Day	57% 12% 15% 14% 2	4814
June	1st to 10th	Day	53% 7% 16% 17% 6%	2660
	11th to 20th	Day	55% 8% 17% 14% 6%	2660
	21st to end	Day	34% 6% 18% 28% 11% 4	2660
July	1st to 10th	Day	17% 4 10% 17% 22% 29%	4351
	11th to 20th	Day	14% 4 7% 18% 37% 20%	4345
	21st to end	Day	16% 3 11% 27% 35% 7%	4639
August	1st to 10th	Day	19% 5% 10% 27% 27% 12%	4119
	11th to 20th	Day	26% 7% 18% 32% 13% 4	4065
	21st to end	Day	29% 6% 12% 25% 21% 8%	4282
September	1st to 10th	Day	23% 5% 14% 27% 20% 12%	2280
	11th to 20th	Day	39% 7% 14% 19% 14% 7%	2280
	21st to end	Day	39% 6% 14% 20% 15% 6%	2001
October	1st to 10th	Day	38% 6% 8% 24% 21% 4	3180
	11th to 20th	Day	49% 7% 17% 16% 10% 2	3161
	21st to end	Day	58% 6% 9% 16% 9% 1	3361
November	1st to 10th	Day	67% 7% 10% 11% 4 1	1669
	11th to 20th	Day	66% 5% 12% 9% 6% 2	1600
	21st to end	Day	64% 5% 7% 10% 12% 1	1552
December	1st to 10th	Day	63% 5% 10% 10% 10% 2	1520
	11th to 20th	Day	66% 8% 11% 11% 4	1928
	21st to end	Day	74% 8% 9% 6% 3	2794
January	1st to 10th	Night	77% 7% 7% 5% 3 1	4406
	11th to 20th	Night	72% 5% 6% 11% 4 2	4420
	21st to end	Night	72% 4 7% 9% 6% 1	4611
February	1st to 10th	Night	67% 8% 10% 10% 5% 1	2470
	11th to 20th	Night	63% 6% 12% 10% 6% 2	2404
	21st to end	Night	65% 6% 10% 10% 6% 2	1956
March	1st to 10th	Night	60% 8% 14% 15% 4	3591
	11th to 20th	Night	42% 9% 14% 19% 15% 1	3490
	21st to end	Night	67% 10% 13% 10% 1	3738
April	1st to 10th	Night	64% 7% 13% 12% 5%	1900
	11th to 20th	Night	54% 8% 14% 14% 6% 3	1879
	21st to end	Night	57% 7% 14% 14% 6% 3	1727
May	1st to 10th	Night	48% 10% 12% 20% 9% 2	2590
	11th to 20th	Night	32% 12% 17% 30% 8% 2	2516
	21st to end	Night	48% 16% 23% 11% 3	2762
June	1st to 10th	Night	50% 7% 16% 21% 6%	1520
	11th to 20th	Night	52% 6% 17% 20% 5%	1520
	21st to end	Night	30% 7% 18% 29% 11% 5%	1520
July	1st to 10th	Night	16% 3 8% 20% 26% 27%	2500
	11th to 20th	Night	15% 3 7% 20% 36% 19%	2492
	21st to end	Night	13% 4 12% 28% 37% 6%	2674
August	1st to 10th	Night	13% 4 10% 36% 29% 8%	2793
	11th to 20th	Night	29% 8% 20% 28% 11% 4	2839
	21st to end	Night	29% 5% 13% 27% 19% 7%	3392
September	1st to 10th	Night	21% 6% 14% 28% 20% 12%	1900
	11th to 20th	Night	36% 7% 13% 23% 13% 9%	1900
	21st to end	Night	33% 6% 17% 21% 15% 8%	2173
October	1st to 10th	Night	34% 6% 10% 29% 20% 2	3800
	11th to 20th	Night	43% 7% 17% 19% 12% 2	3777
	21st to end	Night	58% 7% 9% 14% 10% 2	4203
November	1st to 10th	Night	62% 7% 9% 13% 8%	2627
	11th to 20th	Night	67% 6% 9% 9% 8% 2	2800
	21st to end	Night	59% 6% 9% 10% 13% 3	2722
December	1st to 10th	Night	60% 6% 11% 11% 10% 2	2660
	11th to 20th	Night	65% 7% 10% 10% 7%	3276
	21st to end	Night	68% 9% 12% 8% 2 1	4862

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	42% 13% 18% 15% 11% 1	180
	11th to 20th	Day	42% 8% 17% 21% 9% 2	180
	21st to end	Day	37% 11% 16% 20% 15% 1	350
February	1st to 10th	Day	37% 11% 19% 22% 8% 2	370
	11th to 20th	Day	35% 15% 24% 18% 8% 1	365
	21st to end	Day	38% 14% 22% 17% 9%	348
March	1st to 10th	Day	35% 13% 25% 20% 7% 1	460
	11th to 20th	Day	29% 12% 25% 21% 10% 3	460
	21st to end	Day	33% 15% 25% 19% 7%	506
April	1st to 10th	Day	34% 15% 20% 19% 8% 3	460
	11th to 20th	Day	28% 17% 27% 16% 8% 4	452
	21st to end	Day	27% 13% 26% 22% 10% 1	460
May	1st to 10th	Day	22% 14% 24% 25% 12% 4	463
	11th to 20th	Day	26% 11% 16% 27% 17% 2	488
	21st to end	Day	22% 8% 19% 30% 17% 3	529
June	1st to 10th	Day	23% 8% 19% 29% 17% 4	490
	11th to 20th	Day	21% 11% 26% 25% 15% 1	490
	21st to end	Day	10% 6% 23% 35% 21% 5%	490
July	1st to 10th	Day	7% 4 21% 40% 24% 4	486
	11th to 20th	Day	4 5% 19% 45% 21% 5%	484
	21st to end	Day	4 3 17% 44% 25% 7%	531
August	1st to 10th	Day	6% 3 14% 41% 28% 8%	487
	11th to 20th	Day	4 3 16% 37% 31% 10%	477
	21st to end	Day	7% 6% 23% 35% 21% 7%	539
September	1st to 10th	Day	9% 5% 23% 34% 24% 5%	490
	11th to 20th	Day	14% 7% 19% 29% 25% 5%	490
	21st to end	Day	16% 9% 23% 31% 17% 4	490
October	1st to 10th	Day	21% 8% 22% 24% 19% 5%	490
	11th to 20th	Day	21% 11% 19% 27% 18% 4	490
	21st to end	Day	31% 11% 22% 20% 11% 4	488
November	1st to 10th	Day	30% 17% 17% 21% 11% 3	253
	11th to 20th	Day	33% 12% 25% 15% 14% 3	200
	21st to end	Day	29% 11% 20% 21% 19% 1	188
December	1st to 10th	Day	37% 13% 16% 21% 10% 4	180
	11th to 20th	Day	42% 10% 22% 17% 8% 1	180
	21st to end	Day	45% 12% 17% 13% 12% 2	198
January	1st to 10th	Night	43% 9% 17% 19% 11% 1	760
	11th to 20th	Night	39% 10% 13% 24% 13% 1	760
	21st to end	Night	34% 8% 15% 29% 12% 2	836
February	1st to 10th	Night	34% 9% 17% 26% 13% 2	760
	11th to 20th	Night	37% 11% 15% 24% 13% 1	744
	21st to end	Night	37% 10% 17% 29% 8%	628
March	1st to 10th	Night	31% 10% 18% 27% 13% 1	760
	11th to 20th	Night	28% 9% 18% 31% 13% 1	760
	21st to end	Night	33% 11% 19% 25% 11% 1	836
April	1st to 10th	Night	32% 8% 18% 26% 16% 1	760
	11th to 20th	Night	26% 10% 19% 29% 14% 2	751
	21st to end	Night	31% 9% 16% 27% 15% 1	587
May	1st to 10th	Night	22% 8% 18% 34% 17% 1	417
	11th to 20th	Night	20% 7% 16% 30% 26% 1	374
	21st to end	Night	26% 5% 16% 33% 19% 1	411
June	1st to 10th	Night	22% 6% 16% 31% 24%	380
	11th to 20th	Night	22% 7% 19% 36% 15% 1	380
	21st to end	Night	11% 4 18% 44% 22% 1	380
July	1st to 10th	Night	7% 3 9% 51% 29%	370
	11th to 20th	Night	6% 3 14% 46% 30% 1	368
	21st to end	Night	3 2 7% 53% 33% 2	416
August	1st to 10th	Night	5% 1 8% 38% 43% 6%	533
	11th to 20th	Night	5% 2 6% 35% 45% 6%	564
	21st to end	Night	8% 3 13% 40% 32% 4	769
September	1st to 10th	Night	8% 3 14% 39% 33% 3	760
	11th to 20th	Night	13% 3 11% 33% 34% 6%	760
	21st to end	Night	16% 5% 12% 38% 26% 3	760
October	1st to 10th	Night	21% 4 15% 31% 25% 3	760
	11th to 20th	Night	22% 6% 12% 32% 24% 4	760
	21st to end	Night	28% 9% 18% 26% 16% 3	836
November	1st to 10th	Night	34% 8% 18% 28% 12% 1	780
	11th to 20th	Night	40% 10% 15% 24% 10% 1	800
	21st to end	Night	31% 8% 17% 29% 15% 1	778
December	1st to 10th	Night	34% 7% 17% 27% 13% 1	760
	11th to 20th	Night	40% 9% 16% 23% 11%	760
	21st to end	Night	41% 11% 18% 21% 8% 1	836

Page generated at 2024-11-22 05:02:27. Version ac07

Copyright © 2024 Attilla Danko.