Hector J. Robinson Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hector J. Robinson Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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	14% 9% 4 7% 6% 4 5% 5% 6% 7% 32%	78345
	Night	16% 10% 4 7% 6% 3 5% 4 5% 6% 34%	81157
Transparency	Day	50% 6% 12% 20% 11% 1	78057
	Night	51% 5% 11% 20% 11% 1	80966
Seeing	Day	18% 12% 28% 24% 13% 5%	14378
	Night	19% 10% 28% 30% 12% 1	24368

By Month

Percentage Cloud Cover SE (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	16% 16% 7% 10% 8% 4 6% 4 4 5% 20%	2527
	11th to 20th	Day	15% 17% 7% 11% 9% 5% 8% 6% 5% 6% 11%	2557
	21st to end	Day	28% 17% 9% 11% 6% 2 4 3 4 4 12%	3124
February	1st to 10th	Day	15% 13% 6% 10% 9% 4 6% 5% 5% 5% 21%	1710
	11th to 20th	Day	14% 12% 5% 10% 8% 5% 6% 5% 5% 6% 24%	1787
	21st to end	Day	17% 11% 5% 10% 6% 3 4 5% 6% 6% 27%	1570
March	1st to 10th	Day	16% 11% 5% 7% 7% 4 5% 5% 5% 7% 29%	1899
	11th to 20th	Day	15% 12% 4 7% 6% 3 4 4 5% 6% 34%	1980
	21st to end	Day	19% 12% 5% 8% 7% 4 4 4 4 7% 26%	2178
April	1st to 10th	Day	16% 12% 3 6% 5% 3 5% 6% 5% 7% 31%	2074
	11th to 20th	Day	18% 9% 3 6% 6% 3 5% 5% 5% 8% 32%	2284
	21st to end	Day	19% 8% 3 6% 6% 4 4 5% 4 6% 34%	2340
May	1st to 10th	Day	16% 9% 4 6% 6% 4 5% 6% 5% 7% 32%	2340
	11th to 20th	Day	18% 9% 3 6% 5% 4 4 5% 5% 7% 33%	2301
	21st to end	Day	11% 6% 2 5% 5% 4 5% 5% 6% 9% 42%	2531
June	1st to 10th	Day	11% 6% 2 5% 7% 3 5% 6% 6% 9% 40%	2497
	11th to 20th	Day	11% 6% 2 5% 5% 3 6% 6% 6% 9% 40%	2694
	21st to end	Day	9% 6% 3 5% 6% 4 6% 5% 7% 10% 38%	2520
July	1st to 10th	Day	7% 5% 2 5% 5% 4 5% 6% 6% 9% 45%	2520
	11th to 20th	Day	9% 4 2 5% 5% 3 6% 5% 7% 10% 42%	2520
	21st to end	Day	8% 5% 3 5% 6% 4 5% 6% 7% 10% 41%	2557
August	1st to 10th	Day	8% 4 2 5% 7% 3 6% 7% 7% 10% 41%	2327
	11th to 20th	Day	10% 5% 2 5% 7% 4 7% 7% 8% 10% 36%	2303
	21st to end	Day	9% 5% 2 5% 5% 4 6% 5% 7% 9% 42%	2561
September	1st to 10th	Day	10% 7% 2 6% 6% 4 5% 5% 7% 8% 40%	2024
	11th to 20th	Day	9% 4 2 4 5% 3 6% 6% 6% 9% 45%	1980
	21st to end	Day	14% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	1980
October	1st to 10th	Day	12% 6% 3 6% 6% 3 4 4 5% 9% 41%	1923
	11th to 20th	Day	17% 8% 3 7% 7% 4 5% 5% 5% 8% 33%	1800
	21st to end	Day	19% 10% 3 6% 7% 4 5% 4 5% 6% 31%	1854
November	1st to 10th	Day	12% 6% 3 8% 6% 3 5% 5% 6% 7% 41%	1672
	11th to 20th	Day	14% 12% 3 6% 6% 4 5% 4 5% 8% 32%	1710
	21st to end	Day	19% 11% 5% 7% 5% 4 5% 4 5% 6% 29%	1612
December	1st to 10th	Day	16% 13% 8% 10% 6% 5% 6% 6% 5% 6% 21%	1520
	11th to 20th	Day	17% 14% 6% 9% 6% 3 5% 5% 6% 7% 23%	1818
	21st to end	Day	27% 18% 7% 12% 7% 3 4 3 4 5% 10%	2751
January	1st to 10th	Night	16% 16% 6% 9% 6% 3 5% 5% 4 5% 25%	4428
	11th to 20th	Night	16% 18% 8% 11% 7% 4 5% 5% 6% 5% 15%	4408
	21st to end	Night	25% 17% 8% 10% 6% 3 4 3 3 4 17%	4532
February	1st to 10th	Night	18% 14% 5% 9% 8% 4 5% 5% 5% 4 24%	2470
	11th to 20th	Night	15% 12% 5% 9% 7% 3 5% 5% 5% 6% 27%	2274
	21st to end	Night	19% 11% 4 9% 6% 3 5% 4 4 5% 30%	1884
March	1st to 10th	Night	15% 9% 5% 7% 6% 4 5% 4 6% 5% 34%	2176
	11th to 20th	Night	14% 9% 4 5% 4 3 5% 5% 5% 7% 38%	1980
	21st to end	Night	20% 8% 4 6% 6% 4 5% 4 4 5% 35%	2178
April	1st to 10th	Night	15% 10% 3 6% 6% 4 3 5% 5% 7% 37%	1900
	11th to 20th	Night	17% 8% 3 5% 5% 3 4 5% 6% 7% 37%	1624
	21st to end	Night	17% 8% 3 5% 4 3 4 5% 5% 6% 38%	1620
May	1st to 10th	Night	17% 8% 3 7% 6% 4 5% 5% 5% 7% 34%	1620
	11th to 20th	Night	18% 6% 3 5% 6% 3 5% 4 4 7% 39%	1592
	21st to end	Night	9% 5% 3 5% 5% 3 4 4 6% 9% 46%	1744
June	1st to 10th	Night	12% 4 3 3 4 2 5% 5% 5% 9% 46%	1446
	11th to 20th	Night	9% 5% 3 6% 5% 3 5% 5% 6% 9% 44%	1260
	21st to end	Night	10% 5% 2 5% 4 3 5% 5% 5% 9% 47%	1432
July	1st to 10th	Night	7% 4 2 4 4 2 5% 5% 5% 8% 54%	1440
	11th to 20th	Night	8% 4 3 4 5% 3 4 4 6% 8% 52%	1440
	21st to end	Night	5% 3 2 4 5% 4 4 5% 7% 9% 51%	1760
August	1st to 10th	Night	7% 5% 2 4 5% 3 5% 4 6% 9% 50%	1611
	11th to 20th	Night	7% 4 2 4 5% 3 5% 5% 5% 9% 50%	1598
	21st to end	Night	8% 4 2 4 4 3 4 5% 6% 8% 51%	1792
September	1st to 10th	Night	10% 5% 2 5% 6% 3 6% 5% 5% 6% 47%	1917
	11th to 20th	Night	10% 4 2 4 4 2 4 4 6% 7% 53%	1980
	21st to end	Night	13% 6% 3 5% 5% 2 4 6% 5% 6% 44%	1980
October	1st to 10th	Night	13% 7% 2 5% 5% 3 4 3 5% 7% 44%	2035
	11th to 20th	Night	17% 9% 3 7% 5% 3 4 4 4 7% 36%	2160
	21st to end	Night	21% 8% 3 6% 6% 4 4 5% 5% 5% 33%	2501
November	1st to 10th	Night	14% 6% 3 5% 4 3 5% 4 5% 7% 43%	2406
	11th to 20th	Night	17% 10% 3 7% 6% 3 5% 4 7% 7% 31%	2470
	21st to end	Night	21% 13% 5% 6% 5% 3 4 4 5% 7% 29%	2564
December	1st to 10th	Night	18% 14% 6% 9% 7% 4 5% 4 5% 6% 22%	2660
	11th to 20th	Night	15% 13% 5% 9% 7% 4 6% 5% 5% 7% 24%	3363
	21st to end	Night	28% 20% 6% 9% 6% 3 4 4 4 4 12%	4912

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	65% 4 12% 12% 6%	2528
	11th to 20th	Day	73% 5% 10% 8% 3	2557
	21st to end	Day	77% 3 8% 8% 3 1	3124
February	1st to 10th	Day	62% 6% 10% 14% 7%	1710
	11th to 20th	Day	60% 6% 8% 17% 7% 1	1797
	21st to end	Day	59% 4 12% 17% 7% 1	1570
March	1st to 10th	Day	56% 5% 12% 20% 7% 1	1899
	11th to 20th	Day	52% 5% 11% 20% 11% 2	1980
	21st to end	Day	59% 4 8% 21% 7% 1	2178
April	1st to 10th	Day	52% 6% 11% 18% 13%	2074
	11th to 20th	Day	49% 5% 11% 20% 13% 2	2284
	21st to end	Day	50% 5% 13% 17% 13% 1	2340
May	1st to 10th	Day	50% 6% 10% 20% 11% 2	2340
	11th to 20th	Day	50% 6% 10% 19% 13% 2	2305
	21st to end	Day	39% 5% 15% 25% 15% 2	2531
June	1st to 10th	Day	40% 6% 11% 27% 14% 3	2497
	11th to 20th	Day	39% 6% 14% 22% 17% 3	2694
	21st to end	Day	39% 7% 13% 22% 17% 2	2520
July	1st to 10th	Day	35% 7% 9% 26% 19% 4	2451
	11th to 20th	Day	34% 7% 13% 26% 18% 2	2445
	21st to end	Day	35% 7% 13% 25% 18% 2	2415
August	1st to 10th	Day	34% 9% 13% 31% 13% 1	2314
	11th to 20th	Day	40% 8% 12% 25% 13% 2	2303
	21st to end	Day	37% 7% 11% 26% 18% 2	2561
September	1st to 10th	Day	41% 7% 15% 22% 14% 2	2024
	11th to 20th	Day	34% 6% 12% 33% 14% 1	1980
	21st to end	Day	41% 6% 13% 25% 14%	1980
October	1st to 10th	Day	40% 6% 11% 27% 14% 2	1923
	11th to 20th	Day	49% 6% 11% 22% 11%	1800
	21st to end	Day	53% 5% 13% 19% 10% 1	1854
November	1st to 10th	Day	43% 7% 12% 24% 13% 1	1672
	11th to 20th	Day	52% 5% 14% 20% 9% 1	1710
	21st to end	Day	55% 5% 13% 19% 7%	1612
December	1st to 10th	Day	63% 6% 12% 15% 4	1520
	11th to 20th	Day	61% 5% 13% 16% 5%	1814
	21st to end	Day	79% 4 8% 6% 3	2751
January	1st to 10th	Night	62% 4 12% 16% 6% 1	4428
	11th to 20th	Night	70% 5% 11% 11% 4	4408
	21st to end	Night	72% 4 9% 11% 3	4532
February	1st to 10th	Night	63% 6% 10% 15% 6% 1	2470
	11th to 20th	Night	58% 4 9% 19% 9% 1	2275
	21st to end	Night	56% 4 12% 18% 8% 1	1884
March	1st to 10th	Night	51% 4 11% 23% 10% 1	2176
	11th to 20th	Night	44% 5% 12% 21% 15% 2	1980
	21st to end	Night	52% 4 9% 22% 11% 1	2178
April	1st to 10th	Night	47% 5% 10% 23% 14% 2	1900
	11th to 20th	Night	45% 5% 10% 20% 19% 2	1624
	21st to end	Night	46% 4 11% 20% 16% 3	1620
May	1st to 10th	Night	50% 6% 11% 19% 13% 2	1620
	11th to 20th	Night	46% 5% 8% 21% 17% 2	1593
	21st to end	Night	34% 6% 15% 26% 16% 3	1745
June	1st to 10th	Night	35% 5% 13% 27% 17% 3	1446
	11th to 20th	Night	36% 6% 13% 26% 17% 2	1260
	21st to end	Night	34% 6% 12% 26% 21% 1	1432
July	1st to 10th	Night	30% 6% 11% 29% 21% 3	1400
	11th to 20th	Night	29% 6% 12% 31% 19% 2	1392
	21st to end	Night	28% 6% 17% 24% 21% 4	1662
August	1st to 10th	Night	30% 6% 15% 31% 17% 2	1600
	11th to 20th	Night	31% 6% 15% 31% 14% 3	1598
	21st to end	Night	30% 6% 14% 28% 20% 3	1792
September	1st to 10th	Night	34% 6% 12% 27% 17% 2	1917
	11th to 20th	Night	31% 6% 10% 32% 21% 2	1980
	21st to end	Night	39% 5% 13% 28% 14% 1	1980
October	1st to 10th	Night	39% 5% 11% 25% 19% 1	2035
	11th to 20th	Night	49% 5% 11% 20% 14% 1	2160
	21st to end	Night	51% 5% 10% 23% 10% 1	2501
November	1st to 10th	Night	40% 6% 11% 27% 16% 1	2406
	11th to 20th	Night	50% 4 13% 22% 10% 1	2470
	21st to end	Night	56% 4 14% 20% 7%	2564
December	1st to 10th	Night	63% 6% 11% 14% 6%	2660
	11th to 20th	Night	59% 6% 13% 15% 6% 1	3366
	21st to end	Night	76% 4 10% 8% 2	4912

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	23% 19% 35% 16% 7% 1	270
	11th to 20th	Day	24% 15% 40% 17% 3 1	270
	21st to end	Day	30% 16% 32% 17% 5%	297
February	1st to 10th	Day	25% 19% 38% 14% 4	270
	11th to 20th	Day	24% 20% 34% 18% 3	270
	21st to end	Day	24% 28% 36% 8% 4	225
March	1st to 10th	Day	26% 19% 32% 17% 5%	304
	11th to 20th	Day	23% 13% 31% 24% 7% 1	420
	21st to end	Day	26% 15% 30% 22% 6% 2	462
April	1st to 10th	Day	19% 16% 31% 24% 9% 1	420
	11th to 20th	Day	26% 17% 28% 17% 7% 4	412
	21st to end	Day	27% 14% 30% 19% 8% 3	420
May	1st to 10th	Day	23% 14% 30% 21% 7% 5%	423
	11th to 20th	Day	21% 10% 28% 23% 13% 4	447
	21st to end	Day	15% 6% 24% 29% 19% 7%	485
June	1st to 10th	Day	13% 7% 30% 32% 15% 3	576
	11th to 20th	Day	15% 7% 28% 33% 14% 3	630
	21st to end	Day	12% 8% 31% 29% 16% 4	630
July	1st to 10th	Day	8% 5% 24% 27% 26% 10%	621
	11th to 20th	Day	11% 6% 26% 30% 19% 8%	618
	21st to end	Day	9% 5% 24% 28% 26% 9%	498
August	1st to 10th	Day	8% 3 22% 30% 22% 15%	446
	11th to 20th	Day	12% 4 22% 28% 22% 12%	439
	21st to end	Day	11% 6% 19% 29% 24% 11%	495
September	1st to 10th	Day	12% 6% 22% 28% 21% 12%	450
	11th to 20th	Day	8% 5% 20% 27% 28% 12%	450
	21st to end	Day	16% 10% 24% 22% 18% 10%	450
October	1st to 10th	Day	14% 9% 26% 23% 20% 8%	450
	11th to 20th	Day	19% 17% 28% 26% 7% 2	450
	21st to end	Day	27% 14% 35% 19% 4 1	369
November	1st to 10th	Day	16% 19% 33% 20% 10% 2	270
	11th to 20th	Day	20% 22% 33% 18% 7% 1	270
	21st to end	Day	27% 14% 37% 16% 6%	223
December	1st to 10th	Day	23% 21% 34% 15% 5% 2	180
	11th to 20th	Day	24% 23% 36% 13% 3 1	180
	21st to end	Day	28% 22% 33% 14% 3	288
January	1st to 10th	Night	24% 15% 34% 21% 5% 1	950
	11th to 20th	Night	27% 13% 32% 22% 4 1	931
	21st to end	Night	20% 15% 33% 27% 5%	836
February	1st to 10th	Night	27% 11% 35% 23% 3	760
	11th to 20th	Night	24% 13% 32% 27% 4	743
	21st to end	Night	26% 16% 35% 21% 2	628
March	1st to 10th	Night	20% 12% 33% 29% 6%	743
	11th to 20th	Night	19% 14% 35% 26% 5% 1	720
	21st to end	Night	23% 11% 29% 28% 9%	792
April	1st to 10th	Night	20% 12% 34% 29% 5%	640
	11th to 20th	Night	21% 10% 34% 26% 8% 1	533
	21st to end	Night	21% 9% 30% 32% 8%	540
May	1st to 10th	Night	19% 9% 29% 31% 10% 1	540
	11th to 20th	Night	21% 4 27% 35% 13% 1	531
	21st to end	Night	11% 4 23% 40% 22% 2	584
June	1st to 10th	Night	14% 2 25% 45% 14%	496
	11th to 20th	Night	10% 4 23% 49% 14%	360
	21st to end	Night	10% 5% 22% 40% 21% 2	532
July	1st to 10th	Night	8% 4 16% 39% 30% 4	525
	11th to 20th	Night	9% 3 19% 42% 23% 4	522
	21st to end	Night	6% 2 17% 47% 26% 2	591
August	1st to 10th	Night	8% 3 16% 42% 28% 3	537
	11th to 20th	Night	10% 1 18% 37% 32% 3	534
	21st to end	Night	10% 2 15% 39% 31% 3	594
September	1st to 10th	Night	13% 6% 17% 34% 26% 5%	657
	11th to 20th	Night	10% 4 18% 34% 30% 4	720
	21st to end	Night	14% 7% 22% 31% 23% 3	720
October	1st to 10th	Night	17% 8% 23% 32% 18% 3	720
	11th to 20th	Night	22% 11% 30% 26% 10% 1	720
	21st to end	Night	24% 13% 30% 27% 5%	792
November	1st to 10th	Night	17% 12% 30% 28% 12% 1	740
	11th to 20th	Night	22% 15% 31% 23% 8% 1	760
	21st to end	Night	28% 11% 32% 22% 7%	760
December	1st to 10th	Night	27% 13% 35% 19% 7%	760
	11th to 20th	Night	24% 14% 35% 22% 4	812
	21st to end	Night	31% 12% 32% 22% 3	1045

Page generated at 2024-03-03 06:28:54. Version ac07

Copyright © 2024 Attilla Danko.