Ritter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ritter Observatory clear sky chart from 2005-11-06 to 2024-09-14.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 33%	100721
	Night	15% 11% 4 8% 5% 4 4 3 5% 7% 35%	97157
Transparency	Day	47% 7% 12% 20% 12% 1	100523
	Night	48% 7% 12% 20% 12% 1	97026
Seeing	Day	19% 14% 29% 22% 12% 5%	15396
	Night	20% 11% 29% 27% 12% 1	25179

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	18% 19% 7% 11% 6% 5% 4 3 5% 4 19%	2527
	11th to 20th	Day	16% 19% 6% 12% 6% 6% 9% 5% 4 4 12%	2542
	21st to end	Day	26% 21% 9% 12% 4 3 3 3 3 4 12%	3124
February	1st to 10th	Day	14% 16% 4 11% 8% 5% 6% 4 5% 5% 21%	1710
	11th to 20th	Day	14% 12% 4 13% 7% 6% 5% 4 5% 5% 25%	1827
	21st to end	Day	17% 14% 4 9% 5% 5% 4 3 6% 6% 27%	1570
March	1st to 10th	Day	19% 16% 4 10% 5% 4 4 3 4 5% 25%	3184
	11th to 20th	Day	13% 13% 5% 9% 5% 4 5% 3 5% 6% 33%	3480
	21st to end	Day	19% 12% 5% 9% 6% 5% 4 3 5% 5% 26%	3815
April	1st to 10th	Day	15% 12% 3 8% 6% 5% 6% 5% 5% 6% 30%	2212
	11th to 20th	Day	18% 8% 3 7% 5% 4 5% 3 6% 8% 33%	2385
	21st to end	Day	18% 9% 3 7% 4 4 4 4 5% 7% 34%	2470
May	1st to 10th	Day	17% 9% 2 8% 5% 5% 5% 4 7% 7% 32%	4082
	11th to 20th	Day	17% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4081
	21st to end	Day	10% 6% 3 7% 5% 4 5% 5% 6% 7% 43%	4476
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 8% 40%	2598
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 9% 42%	2660
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 39%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 6% 10% 39%	4440
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 8% 11% 45%	4440
	21st to end	Day	6% 5% 2 7% 6% 6% 6% 5% 8% 9% 41%	4476
August	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	4104
	11th to 20th	Day	9% 6% 2 6% 5% 6% 7% 5% 8% 10% 37%	4044
	21st to end	Day	8% 5% 2 7% 4 5% 5% 5% 7% 11% 41%	4420
September	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	2147
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 4 7% 9% 44%	2014
	21st to end	Day	15% 6% 2 5% 4 3 5% 5% 6% 8% 41%	1980
October	1st to 10th	Day	11% 7% 3 8% 4 5% 4 4 6% 7% 42%	1947
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 3 6% 6% 35%	1800
	21st to end	Day	20% 9% 3 8% 4 5% 4 4 6% 6% 30%	1841
November	1st to 10th	Day	11% 8% 3 7% 5% 5% 4 4 6% 7% 40%	1672
	11th to 20th	Day	16% 14% 4 8% 6% 4 3 4 4 5% 32%	1710
	21st to end	Day	19% 12% 4 8% 5% 4 4 4 6% 7% 27%	1710
December	1st to 10th	Day	15% 17% 7% 13% 6% 5% 4 3 4 6% 20%	1710
	11th to 20th	Day	14% 16% 6% 10% 6% 6% 4 4 5% 6% 23%	2080
	21st to end	Day	23% 21% 7% 13% 5% 4 3 3 4 5% 11%	2783
January	1st to 10th	Night	16% 18% 6% 10% 5% 5% 4 3 4 5% 23%	4428
	11th to 20th	Night	15% 19% 7% 15% 6% 4 5% 5% 4 5% 15%	4411
	21st to end	Night	26% 19% 7% 11% 5% 4 3 2 3 4 15%	4532
February	1st to 10th	Night	16% 16% 5% 10% 7% 5% 5% 3 5% 5% 24%	2470
	11th to 20th	Night	14% 15% 4 10% 6% 5% 4 4 5% 6% 28%	2237
	21st to end	Night	19% 13% 4 9% 5% 4 5% 3 5% 5% 27%	1884
March	1st to 10th	Night	18% 14% 4 7% 4 4 3 2 4 5% 35%	3669
	11th to 20th	Night	11% 8% 2 6% 4 5% 3 4 5% 7% 43%	3480
	21st to end	Night	16% 10% 4 9% 5% 5% 4 3 5% 7% 34%	3817
April	1st to 10th	Night	15% 12% 3 7% 4 4 4 3 6% 7% 36%	1985
	11th to 20th	Night	18% 7% 3 7% 5% 5% 5% 3 6% 6% 37%	1742
	21st to end	Night	16% 10% 2 6% 5% 4 4 3 6% 7% 37%	1710
May	1st to 10th	Night	18% 8% 3 7% 6% 5% 6% 3 6% 7% 32%	2813
	11th to 20th	Night	17% 8% 2 7% 4 4 4 3 6% 6% 39%	2812
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	3079
June	1st to 10th	Night	10% 5% 2 5% 5% 5% 4 4 7% 7% 44%	1576
	11th to 20th	Night	10% 6% 3 7% 4 4 4 4 7% 8% 44%	1520
	21st to end	Night	10% 5% 1 5% 4 4 4 5% 8% 10% 43%	1520
July	1st to 10th	Night	10% 3 2 5% 3 4 4 3 6% 10% 50%	2530
	11th to 20th	Night	8% 4 2 5% 4 3 4 5% 6% 9% 50%	2530
	21st to end	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 10% 45%	3075
August	1st to 10th	Night	13% 7% 2 6% 4 4 4 3 5% 9% 43%	2825
	11th to 20th	Night	9% 5% 1 5% 3 5% 4 4 6% 8% 49%	2785
	21st to end	Night	8% 5% 3 6% 4 4 5% 3 5% 8% 49%	3219
September	1st to 10th	Night	9% 6% 2 5% 5% 5% 4 4 5% 7% 49%	2012
	11th to 20th	Night	9% 6% 2 6% 4 4 3 3 5% 7% 52%	2024
	21st to end	Night	12% 6% 3 7% 4 4 4 3 6% 6% 46%	1980
October	1st to 10th	Night	13% 6% 2 6% 5% 5% 3 3 6% 7% 44%	2011
	11th to 20th	Night	17% 10% 3 7% 4 5% 4 3 5% 6% 37%	2160
	21st to end	Night	21% 9% 2 6% 5% 4 4 4 4 5% 34%	2511
November	1st to 10th	Night	13% 9% 3 6% 4 4 4 3 5% 6% 43%	2406
	11th to 20th	Night	15% 11% 3 8% 5% 5% 4 4 6% 7% 33%	2470
	21st to end	Night	19% 13% 4 9% 6% 4 4 3 5% 6% 27%	2470
December	1st to 10th	Night	17% 15% 6% 11% 5% 5% 4 3 5% 6% 24%	2470
	11th to 20th	Night	17% 15% 4 10% 6% 5% 4 4 5% 6% 26%	3110
	21st to end	Night	27% 20% 6% 10% 4 4 4 3 4 5% 12%	4884

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	68% 7% 10% 12% 4	2528
	11th to 20th	Day	74% 6% 10% 7% 3	2542
	21st to end	Day	78% 5% 6% 7% 3	3124
February	1st to 10th	Day	64% 7% 11% 13% 6%	1710
	11th to 20th	Day	60% 6% 10% 16% 8%	1837
	21st to end	Day	56% 6% 14% 16% 6% 2	1570
March	1st to 10th	Day	60% 7% 10% 17% 5%	3184
	11th to 20th	Day	47% 7% 16% 21% 8% 1	3480
	21st to end	Day	57% 7% 13% 15% 7%	3815
April	1st to 10th	Day	52% 7% 11% 17% 13%	2212
	11th to 20th	Day	48% 7% 12% 20% 12% 2	2385
	21st to end	Day	48% 6% 12% 21% 11% 2	2470
May	1st to 10th	Day	47% 9% 12% 22% 10% 1	4120
	11th to 20th	Day	45% 9% 13% 22% 10% 1	4085
	21st to end	Day	36% 9% 11% 19% 20% 5%	4489
June	1st to 10th	Day	39% 9% 11% 25% 13% 3	2598
	11th to 20th	Day	37% 8% 13% 23% 16% 3	2660
	21st to end	Day	39% 8% 14% 20% 16% 4	2660
July	1st to 10th	Day	40% 6% 12% 23% 17% 2	4371
	11th to 20th	Day	29% 8% 13% 31% 17% 2	4365
	21st to end	Day	36% 8% 14% 18% 21% 3	4334
August	1st to 10th	Day	36% 8% 14% 27% 15% 1	4091
	11th to 20th	Day	36% 9% 13% 30% 12% 1	4083
	21st to end	Day	34% 8% 12% 32% 12% 2	4419
September	1st to 10th	Day	38% 8% 14% 21% 18% 2	2147
	11th to 20th	Day	34% 7% 12% 29% 17% 1	2014
	21st to end	Day	38% 8% 14% 24% 16% 1	1980
October	1st to 10th	Day	40% 7% 11% 26% 15% 2	1947
	11th to 20th	Day	47% 5% 13% 21% 13% 1	1800
	21st to end	Day	52% 6% 13% 19% 10% 1	1841
November	1st to 10th	Day	41% 7% 12% 23% 16% 1	1672
	11th to 20th	Day	54% 5% 11% 18% 11% 1	1710
	21st to end	Day	55% 6% 14% 17% 7%	1710
December	1st to 10th	Day	66% 6% 11% 13% 4	1710
	11th to 20th	Day	60% 7% 12% 16% 4	2077
	21st to end	Day	76% 6% 8% 7% 3	2783
January	1st to 10th	Night	62% 7% 10% 14% 6%	4428
	11th to 20th	Night	71% 6% 10% 10% 3	4411
	21st to end	Night	73% 5% 10% 9% 3	4532
February	1st to 10th	Night	60% 7% 11% 15% 5% 1	2470
	11th to 20th	Night	56% 6% 10% 19% 8% 1	2238
	21st to end	Night	57% 6% 11% 17% 8% 2	1884
March	1st to 10th	Night	51% 6% 10% 24% 8% 1	3669
	11th to 20th	Night	37% 8% 16% 22% 16% 1	3480
	21st to end	Night	48% 6% 13% 24% 8% 1	3817
April	1st to 10th	Night	47% 8% 11% 18% 14% 2	1985
	11th to 20th	Night	46% 6% 11% 19% 16% 2	1742
	21st to end	Night	45% 7% 11% 20% 15% 3	1710
May	1st to 10th	Night	50% 8% 9% 19% 12% 2	2840
	11th to 20th	Night	42% 9% 11% 25% 12% 1	2813
	21st to end	Night	32% 9% 11% 26% 20% 2	3087
June	1st to 10th	Night	35% 9% 11% 26% 18% 2	1576
	11th to 20th	Night	35% 8% 12% 26% 16% 3	1520
	21st to end	Night	32% 9% 14% 24% 19% 1	1520
July	1st to 10th	Night	30% 7% 11% 28% 17% 6%	2490
	11th to 20th	Night	29% 8% 15% 28% 18% 2	2482
	21st to end	Night	31% 9% 17% 20% 20% 4	2977
August	1st to 10th	Night	38% 8% 13% 25% 15% 2	2814
	11th to 20th	Night	31% 8% 12% 30% 18% 1	2812
	21st to end	Night	33% 7% 12% 29% 17% 2	3219
September	1st to 10th	Night	35% 7% 12% 24% 19% 4	2012
	11th to 20th	Night	32% 6% 11% 28% 24% 1	2024
	21st to end	Night	38% 7% 12% 24% 17% 2	1980
October	1st to 10th	Night	38% 6% 13% 22% 20% 1	2011
	11th to 20th	Night	47% 6% 11% 20% 15% 1	2160
	21st to end	Night	50% 6% 11% 22% 10% 1	2511
November	1st to 10th	Night	42% 5% 12% 24% 17% 1	2406
	11th to 20th	Night	48% 7% 13% 20% 10% 1	2470
	21st to end	Night	57% 6% 11% 19% 6%	2470
December	1st to 10th	Night	61% 6% 12% 15% 7%	2470
	11th to 20th	Night	57% 8% 14% 14% 7% 1	3112
	21st to end	Night	73% 6% 11% 7% 2	4884

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	27% 21% 31% 18% 2 1	270
	11th to 20th	Day	30% 20% 37% 9% 4	270
	21st to end	Day	31% 18% 30% 18% 3	297
February	1st to 10th	Day	30% 19% 37% 11% 3	270
	11th to 20th	Day	29% 20% 36% 13% 1	270
	21st to end	Day	29% 27% 33% 9% 1	225
March	1st to 10th	Day	25% 24% 34% 13% 4	308
	11th to 20th	Day	26% 15% 36% 17% 5% 1	460
	21st to end	Day	33% 16% 30% 15% 6%	506
April	1st to 10th	Day	22% 17% 34% 18% 7% 1	460
	11th to 20th	Day	26% 19% 28% 16% 8% 2	452
	21st to end	Day	27% 16% 32% 15% 8% 2	460
May	1st to 10th	Day	23% 19% 29% 18% 9% 3	463
	11th to 20th	Day	20% 13% 33% 17% 13% 4	487
	21st to end	Day	12% 10% 29% 24% 18% 7%	529
June	1st to 10th	Day	13% 10% 32% 31% 13% 3	618
	11th to 20th	Day	12% 10% 32% 31% 11% 4	680
	21st to end	Day	12% 11% 31% 28% 13% 4	680
July	1st to 10th	Day	10% 7% 25% 28% 19% 11%	671
	11th to 20th	Day	10% 7% 28% 28% 19% 8%	668
	21st to end	Day	8% 5% 29% 28% 21% 9%	542
August	1st to 10th	Day	10% 5% 22% 29% 21% 13%	486
	11th to 20th	Day	13% 5% 25% 28% 19% 10%	479
	21st to end	Day	10% 5% 23% 29% 23% 9%	539
September	1st to 10th	Day	15% 6% 22% 28% 19% 9%	490
	11th to 20th	Day	9% 6% 21% 26% 26% 11%	463
	21st to end	Day	19% 11% 24% 22% 17% 7%	450
October	1st to 10th	Day	15% 10% 27% 25% 16% 8%	450
	11th to 20th	Day	21% 20% 30% 20% 7% 1	450
	21st to end	Day	25% 22% 31% 17% 4 1	356
November	1st to 10th	Day	18% 19% 34% 19% 8% 3	270
	11th to 20th	Day	28% 23% 26% 18% 5%	270
	21st to end	Day	27% 24% 32% 16% 1	270
December	1st to 10th	Day	26% 27% 29% 11% 7%	270
	11th to 20th	Day	23% 27% 34% 13% 3	270
	21st to end	Day	30% 20% 35% 12% 3	297
January	1st to 10th	Night	25% 17% 33% 20% 5%	950
	11th to 20th	Night	28% 16% 34% 17% 5% 1	934
	21st to end	Night	23% 16% 35% 22% 4	836
February	1st to 10th	Night	27% 14% 33% 23% 3	760
	11th to 20th	Night	23% 14% 36% 23% 3	743
	21st to end	Night	28% 15% 36% 18% 3	628
March	1st to 10th	Night	21% 14% 31% 27% 6% 1	760
	11th to 20th	Night	19% 17% 35% 23% 6% 1	760
	21st to end	Night	24% 12% 31% 25% 8%	836
April	1st to 10th	Night	22% 14% 35% 25% 4 1	655
	11th to 20th	Night	22% 12% 33% 24% 7% 1	563
	21st to end	Night	21% 10% 35% 26% 8% 1	570
May	1st to 10th	Night	21% 9% 29% 30% 10% 1	570
	11th to 20th	Night	20% 6% 30% 29% 14% 1	561
	21st to end	Night	10% 5% 28% 35% 19% 3	617
June	1st to 10th	Night	12% 4 29% 38% 16%	570
	11th to 20th	Night	12% 5% 25% 40% 17% 1	570
	21st to end	Night	13% 5% 24% 35% 21% 2	570
July	1st to 10th	Night	10% 4 21% 36% 27% 3	555
	11th to 20th	Night	9% 4 22% 37% 23% 4	552
	21st to end	Night	7% 2 18% 43% 27% 3	624
August	1st to 10th	Night	8% 3 18% 41% 27% 3	567
	11th to 20th	Night	12% 2 17% 34% 30% 5%	564
	21st to end	Night	9% 3 16% 38% 30% 4	627
September	1st to 10th	Night	11% 6% 21% 33% 26% 4	682
	11th to 20th	Night	10% 5% 19% 33% 29% 4	736
	21st to end	Night	15% 7% 22% 30% 23% 3	720
October	1st to 10th	Night	16% 8% 25% 30% 19% 3	720
	11th to 20th	Night	21% 15% 29% 23% 9% 2	720
	21st to end	Night	25% 15% 30% 24% 7%	792
November	1st to 10th	Night	17% 15% 31% 26% 10% 2	740
	11th to 20th	Night	23% 16% 32% 21% 7% 1	760
	21st to end	Night	27% 13% 33% 21% 6%	760
December	1st to 10th	Night	26% 15% 34% 20% 5%	760
	11th to 20th	Night	26% 14% 35% 21% 4	802
	21st to end	Night	31% 14% 33% 18% 3	1045

Page generated at 2024-09-11 10:00:05. Version ac07

Copyright © 2024 Attilla Danko.