RedShift Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the RedShift Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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% 11% 4 9% 5% 4 4 3 5% 6% 34%	101639
	Night	15% 14% 5% 11% 6% 4 4 3 4 5% 29%	98040
Transparency	Day	50% 4 11% 22% 11% 1	105171
	Night	57% 4 11% 19% 9% 1	102636
Seeing	Day	21% 13% 31% 23% 10% 3	16023
	Night	23% 11% 28% 27% 11% 1	25912

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	12% 28% 15% 20% 7% 5% 2 1 2 2 5%	2527
	11th to 20th	Day	14% 20% 9% 23% 12% 10% 3 2 2 2 4	2530
	21st to end	Day	17% 23% 13% 16% 8% 5% 4 2 2 2 7%	2783
February	1st to 10th	Day	9% 19% 7% 18% 15% 6% 3 3 2 3 14%	1638
	11th to 20th	Day	12% 16% 8% 16% 13% 6% 4 3 3 4 15%	1848
	21st to end	Day	12% 18% 7% 14% 11% 4 4 2 3 5% 19%	1570
March	1st to 10th	Day	12% 14% 5% 9% 5% 4 4 4 5% 6% 32%	3120
	11th to 20th	Day	11% 10% 8% 14% 5% 4 3 3 5% 7% 30%	3340
	21st to end	Day	19% 13% 6% 14% 5% 4 4 3 4 5% 24%	4030
April	1st to 10th	Day	18% 14% 4 8% 4 4 4 3 5% 6% 30%	2280
	11th to 20th	Day	21% 12% 2 6% 4 4 3 3 5% 6% 34%	2311
	21st to end	Day	16% 10% 3 7% 4 5% 4 4 5% 7% 34%	2470
May	1st to 10th	Day	14% 8% 2 6% 5% 3 4 3 5% 6% 43%	4082
	11th to 20th	Day	11% 8% 2 6% 4 4 4 3 5% 6% 49%	4289
	21st to end	Day	12% 6% 2 5% 4 4 5% 4 6% 8% 44%	4824
June	1st to 10th	Day	12% 5% 2 5% 5% 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 6% 9% 44%	2660
	21st to end	Day	13% 5% 2 6% 3 3 4 4 7% 9% 43%	2660
July	1st to 10th	Day	16% 7% 2 6% 3 3 4 4 5% 9% 41%	4440
	11th to 20th	Day	7% 4 1 3 3 4 3 3 6% 8% 57%	4440
	21st to end	Day	9% 5% 2 5% 4 3 4 4 5% 9% 51%	4813
August	1st to 10th	Day	9% 6% 2 6% 4 5% 5% 4 7% 9% 43%	4300
	11th to 20th	Day	14% 5% 2 5% 3 3 3 3 5% 6% 51%	4044
	21st to end	Day	12% 6% 2 6% 4 4 4 3 5% 7% 46%	4246
September	1st to 10th	Day	14% 5% 2 6% 5% 4 4 3 5% 7% 44%	2280
	11th to 20th	Day	13% 5% 2 5% 4 3 4 4 5% 9% 47%	2093
	21st to end	Day	16% 6% 3 7% 4 4 4 3 7% 8% 39%	2090
October	1st to 10th	Day	16% 8% 3 7% 4 4 4 4 5% 6% 39%	2090
	11th to 20th	Day	23% 17% 4 8% 5% 4 5% 3 5% 5% 21%	1795
	21st to end	Day	25% 16% 4 9% 5% 4 4 4 5% 5% 20%	1881
November	1st to 10th	Day	19% 19% 3 7% 3 4 4 3 4 6% 28%	1762
	11th to 20th	Day	16% 24% 7% 12% 6% 3 4 3 4 5% 16%	1800
	21st to end	Day	20% 25% 9% 12% 4 3 3 2 3 4 15%	1722
December	1st to 10th	Day	14% 28% 13% 16% 5% 3 4 2 3 3 9%	1520
	11th to 20th	Day	15% 25% 10% 18% 7% 4 4 2 4 4 8%	1918
	21st to end	Day	19% 23% 10% 14% 8% 4 4 3 3 4 9%	2783
January	1st to 10th	Night	14% 28% 9% 20% 8% 4 2 1 2 3 10%	4428
	11th to 20th	Night	11% 19% 9% 22% 13% 10% 3 2 2 2 7%	4440
	21st to end	Night	15% 24% 11% 18% 9% 5% 4 2 2 3 7%	4884
February	1st to 10th	Night	11% 19% 8% 17% 13% 6% 4 2 3 4 14%	2537
	11th to 20th	Night	12% 16% 7% 18% 11% 5% 4 3 4 5% 16%	2218
	21st to end	Night	15% 17% 5% 15% 8% 5% 4 3 5% 5% 19%	1884
March	1st to 10th	Night	16% 11% 4 8% 5% 3 3 2 5% 7% 36%	3733
	11th to 20th	Night	9% 12% 4 11% 5% 4 4 3 5% 6% 35%	3619
	21st to end	Night	16% 12% 5% 13% 5% 4 4 3 5% 6% 26%	3631
April	1st to 10th	Night	18% 12% 4 8% 5% 4 4 4 5% 6% 30%	1900
	11th to 20th	Night	20% 10% 3 7% 4 4 4 2 4 6% 35%	1817
	21st to end	Night	18% 9% 3 7% 5% 4 4 3 4 6% 36%	1710
May	1st to 10th	Night	15% 7% 3 7% 5% 4 5% 4 5% 6% 40%	2813
	11th to 20th	Night	13% 8% 2 6% 5% 4 4 4 6% 7% 41%	2610
	21st to end	Night	18% 5% 3 5% 4 4 3 3 5% 7% 42%	2743
June	1st to 10th	Night	12% 8% 2 6% 5% 4 5% 4 5% 7% 41%	1520
	11th to 20th	Night	10% 6% 2 6% 5% 4 5% 4 6% 8% 42%	1520
	21st to end	Night	11% 7% 2 6% 4 4 5% 4 5% 7% 45%	1520
July	1st to 10th	Night	13% 9% 2 6% 4 4 5% 4 5% 8% 40%	2530
	11th to 20th	Night	7% 4 1 4 3 4 5% 4 5% 7% 57%	2530
	21st to end	Night	8% 5% 2 6% 4 5% 4 4 6% 8% 48%	2750
August	1st to 10th	Night	12% 5% 2 7% 4 5% 5% 4 6% 7% 43%	2635
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 4 7% 51%	2785
	21st to end	Night	9% 6% 2 7% 4 4 4 4 5% 7% 47%	3407
September	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 5% 7% 49%	1900
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 6% 7% 48%	2067
	21st to end	Night	16% 7% 2 7% 4 4 4 4 5% 7% 39%	2090
October	1st to 10th	Night	19% 7% 3 7% 4 3 4 3 4 5% 41%	2090
	11th to 20th	Night	24% 13% 4 9% 4 4 4 3 4 6% 26%	2380
	21st to end	Night	26% 14% 4 8% 5% 4 4 3 4 5% 24%	2717
November	1st to 10th	Night	17% 18% 4 8% 5% 3 3 3 4 6% 28%	2536
	11th to 20th	Night	16% 25% 7% 12% 4 4 4 3 3 3 19%	2600
	21st to end	Night	18% 25% 8% 11% 3 4 4 2 4 5% 15%	2673
December	1st to 10th	Night	15% 29% 10% 15% 5% 4 3 2 3 3 11%	2660
	11th to 20th	Night	15% 24% 9% 18% 8% 3 3 2 3 4 10%	3279
	21st to end	Night	23% 24% 10% 12% 5% 3 3 3 3 4 11%	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	90% 2 4 4 1	2528
	11th to 20th	Day	91% 2 3 3 1	2530
	21st to end	Day	86% 2 7% 4 1	2783
February	1st to 10th	Day	77% 3 7% 12% 1	1638
	11th to 20th	Day	74% 4 8% 10% 4	1858
	21st to end	Day	69% 4 9% 13% 4 1	1570
March	1st to 10th	Day	55% 3 11% 21% 10% 1	3120
	11th to 20th	Day	54% 3 13% 19% 8% 1	3340
	21st to end	Day	64% 3 9% 17% 6% 1	4030
April	1st to 10th	Day	55% 3 9% 21% 12%	2280
	11th to 20th	Day	52% 3 8% 21% 15% 2	2311
	21st to end	Day	49% 4 11% 19% 15% 2	2470
May	1st to 10th	Day	42% 3 9% 27% 17% 2	4120
	11th to 20th	Day	37% 3 10% 28% 19% 3	4293
	21st to end	Day	38% 5% 12% 24% 20% 2	4837
June	1st to 10th	Day	37% 4 12% 29% 16% 2	2660
	11th to 20th	Day	36% 4 14% 27% 18% 1	2660
	21st to end	Day	36% 5% 15% 28% 15% 1	2660
July	1st to 10th	Day	40% 5% 14% 26% 12% 2	4371
	11th to 20th	Day	24% 5% 16% 36% 16% 2	4365
	21st to end	Day	30% 6% 14% 29% 20% 1	4662
August	1st to 10th	Day	37% 5% 14% 31% 12% 1	4285
	11th to 20th	Day	34% 4 15% 30% 16% 1	4083
	21st to end	Day	37% 6% 14% 29% 12% 1	4245
September	1st to 10th	Day	40% 4 13% 29% 13% 1	2280
	11th to 20th	Day	34% 5% 16% 31% 13% 1	2093
	21st to end	Day	42% 4 16% 28% 10%	2090
October	1st to 10th	Day	31% 4 8% 37% 19% 1	3480
	11th to 20th	Day	53% 6% 11% 20% 10%	2946
	21st to end	Day	61% 5% 14% 16% 4	3081
November	1st to 10th	Day	58% 4 10% 20% 8%	1762
	11th to 20th	Day	70% 4 10% 11% 4	1800
	21st to end	Day	76% 3 11% 8% 2	1722
December	1st to 10th	Day	83% 2 6% 7% 1	1520
	11th to 20th	Day	82% 3 9% 5% 1	1915
	21st to end	Day	82% 3 8% 6% 1	2783
January	1st to 10th	Night	83% 2 6% 8% 1	4428
	11th to 20th	Night	87% 2 5% 5% 1	4440
	21st to end	Night	86% 2 7% 4	4884
February	1st to 10th	Night	76% 3 6% 11% 4	2537
	11th to 20th	Night	71% 4 8% 12% 4	2219
	21st to end	Night	68% 3 11% 14% 4	1884
March	1st to 10th	Night	49% 3 16% 23% 9%	3733
	11th to 20th	Night	49% 4 12% 25% 9% 1	3619
	21st to end	Night	59% 4 9% 20% 7% 1	3631
April	1st to 10th	Night	55% 4 8% 21% 11% 1	1900
	11th to 20th	Night	52% 3 8% 22% 13% 3	1817
	21st to end	Night	49% 4 9% 22% 14% 3	1710
May	1st to 10th	Night	44% 4 12% 20% 17% 3	2840
	11th to 20th	Night	42% 4 11% 26% 16% 2	2611
	21st to end	Night	42% 3 13% 20% 15% 6%	2751
June	1st to 10th	Night	41% 5% 10% 28% 15% 2	1520
	11th to 20th	Night	37% 5% 12% 25% 19% 2	1520
	21st to end	Night	37% 5% 13% 27% 16% 2	1520
July	1st to 10th	Night	43% 4 12% 23% 12% 6%	2490
	11th to 20th	Night	26% 5% 15% 34% 18% 2	2482
	21st to end	Night	34% 7% 11% 24% 21% 2	2662
August	1st to 10th	Night	39% 6% 13% 27% 13% 2	2626
	11th to 20th	Night	33% 4 13% 32% 18%	2812
	21st to end	Night	35% 6% 13% 24% 21% 1	3407
September	1st to 10th	Night	35% 4 13% 26% 21% 1	1900
	11th to 20th	Night	34% 4 14% 33% 14% 1	2067
	21st to end	Night	44% 3 15% 25% 11% 1	2090
October	1st to 10th	Night	39% 4 9% 36% 12%	3480
	11th to 20th	Night	50% 4 9% 25% 12%	3955
	21st to end	Night	53% 4 14% 22% 7%	4467
November	1st to 10th	Night	57% 4 11% 20% 7% 1	2536
	11th to 20th	Night	72% 3 10% 10% 5% 1	2600
	21st to end	Night	73% 3 12% 9% 2	2673
December	1st to 10th	Night	81% 3 7% 8% 1	2660
	11th to 20th	Night	80% 3 9% 6% 2	3281
	21st to end	Night	79% 4 10% 5% 1	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	24% 22% 31% 17% 6% 1	270
	11th to 20th	Day	29% 17% 37% 14% 3	270
	21st to end	Day	28% 15% 33% 20% 3 1	297
February	1st to 10th	Day	23% 28% 31% 12% 4 1	270
	11th to 20th	Day	24% 26% 37% 11% 1	270
	21st to end	Day	26% 32% 37% 4 1	225
March	1st to 10th	Day	26% 28% 34% 12% 1	270
	11th to 20th	Day	27% 14% 31% 19% 8%	372
	21st to end	Day	31% 15% 29% 18% 6% 1	506
April	1st to 10th	Day	29% 13% 37% 16% 4 1	460
	11th to 20th	Day	32% 16% 29% 13% 7% 3	452
	21st to end	Day	26% 15% 29% 22% 7% 2	460
May	1st to 10th	Day	23% 15% 36% 18% 6% 2	463
	11th to 20th	Day	17% 10% 37% 25% 8% 2	604
	21st to end	Day	14% 12% 32% 28% 11% 3	734
June	1st to 10th	Day	16% 11% 34% 26% 11% 3	680
	11th to 20th	Day	15% 10% 38% 27% 8% 3	680
	21st to end	Day	18% 9% 33% 27% 11% 3	680
July	1st to 10th	Day	10% 7% 30% 33% 15% 4	671
	11th to 20th	Day	11% 7% 29% 33% 14% 5%	668
	21st to end	Day	10% 5% 32% 34% 15% 4	739
August	1st to 10th	Day	12% 5% 26% 30% 20% 6%	605
	11th to 20th	Day	14% 5% 23% 31% 17% 10%	479
	21st to end	Day	17% 7% 25% 30% 17% 4	539
September	1st to 10th	Day	18% 8% 25% 26% 16% 6%	490
	11th to 20th	Day	12% 5% 28% 32% 18% 6%	490
	21st to end	Day	19% 12% 24% 28% 13% 5%	490
October	1st to 10th	Day	22% 14% 26% 21% 13% 3	490
	11th to 20th	Day	33% 14% 34% 16% 4	333
	21st to end	Day	38% 16% 29% 12% 5%	330
November	1st to 10th	Day	35% 14% 30% 16% 4	300
	11th to 20th	Day	29% 19% 37% 11% 3 1	300
	21st to end	Day	32% 23% 32% 11% 2	299
December	1st to 10th	Day	32% 21% 29% 13% 4 1	270
	11th to 20th	Day	31% 23% 31% 11% 3 1	270
	21st to end	Day	39% 18% 29% 10% 3	297
January	1st to 10th	Night	27% 17% 32% 19% 5% 1	950
	11th to 20th	Night	25% 17% 32% 20% 6% 1	950
	21st to end	Night	24% 12% 34% 24% 6%	1045
February	1st to 10th	Night	21% 16% 34% 24% 5%	877
	11th to 20th	Night	22% 20% 29% 23% 5%	743
	21st to end	Night	27% 16% 33% 21% 3	628
March	1st to 10th	Night	20% 14% 32% 26% 7% 1	760
	11th to 20th	Night	19% 14% 35% 26% 6% 1	760
	21st to end	Night	23% 12% 28% 27% 8% 1	727
April	1st to 10th	Night	26% 10% 33% 24% 6% 1	570
	11th to 20th	Night	26% 11% 31% 24% 7% 1	563
	21st to end	Night	23% 9% 31% 28% 8% 1	570
May	1st to 10th	Night	21% 7% 31% 30% 9% 1	570
	11th to 20th	Night	18% 6% 33% 30% 13% 1	561
	21st to end	Night	16% 6% 26% 35% 17% 1	617
June	1st to 10th	Night	16% 4 28% 36% 14% 1	570
	11th to 20th	Night	13% 7% 25% 38% 15% 2	570
	21st to end	Night	14% 3 22% 42% 17% 1	570
July	1st to 10th	Night	12% 2 19% 43% 22% 3	555
	11th to 20th	Night	9% 4 21% 41% 24% 3	552
	21st to end	Night	9% 2 20% 39% 26% 3	624
August	1st to 10th	Night	12% 2 16% 46% 22% 2	567
	11th to 20th	Night	12% 4 17% 35% 27% 5%	564
	21st to end	Night	15% 4 19% 39% 20% 2	627
September	1st to 10th	Night	14% 5% 20% 34% 23% 4	570
	11th to 20th	Night	15% 5% 21% 34% 21% 3	737
	21st to end	Night	20% 8% 20% 32% 18% 3	760
October	1st to 10th	Night	23% 9% 23% 30% 15% 1	760
	11th to 20th	Night	33% 10% 25% 26% 7% 1	760
	21st to end	Night	36% 10% 25% 22% 7% 1	836
November	1st to 10th	Night	29% 13% 28% 23% 6% 1	780
	11th to 20th	Night	31% 16% 29% 19% 4	800
	21st to end	Night	33% 14% 28% 20% 4	874
December	1st to 10th	Night	32% 19% 29% 17% 4	950
	11th to 20th	Night	29% 18% 31% 16% 4 1	950
	21st to end	Night	32% 16% 33% 17% 2	1045

Page generated at 2024-11-27 17:30:54. Version ac07

Copyright © 2024 Attilla Danko.