Myrtle Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Myrtle Park clear sky chart from 2005-11-06 to 2024-12-02.

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	26% 10% 3 6% 4 4 4 3 5% 6% 31%	105760
	Night	30% 10% 3 6% 3 3 3 3 4 5% 30%	102476
Transparency	Day	56% 5% 13% 16% 7% 1	105509
	Night	59% 5% 12% 15% 7% 2	102374
Seeing	Day	32% 8% 20% 24% 13% 4	15437
	Night	37% 4 13% 25% 18% 3	23631

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	46% 14% 3 6% 5% 3 3 3 3 3 10%	2219
	11th to 20th	Day	32% 15% 4 6% 4 2 2 1 3 6% 26%	2199
	21st to end	Day	61% 9% 3 5% 3 2 2 2 3 2 10%	2791
February	1st to 10th	Day	36% 12% 4 8% 4 4 3 3 5% 5% 16%	1710
	11th to 20th	Day	33% 13% 3 7% 4 3 4 2 4 5% 22%	1665
	21st to end	Day	27% 16% 4 7% 7% 5% 4 3 4 4 20%	1428
March	1st to 10th	Day	29% 19% 4 8% 5% 4 4 4 4 5% 14%	3246
	11th to 20th	Day	26% 12% 3 6% 4 4 3 3 4 5% 31%	3490
	21st to end	Day	31% 16% 3 8% 5% 4 3 2 5% 5% 19%	3933
April	1st to 10th	Day	31% 13% 4 8% 5% 6% 4 4 5% 6% 15%	2280
	11th to 20th	Day	26% 12% 3 9% 5% 5% 4 3 5% 5% 22%	2346
	21st to end	Day	28% 12% 3 7% 4 4 5% 4 5% 6% 22%	2530
May	1st to 10th	Day	18% 10% 3 7% 4 4 4 3 5% 6% 37%	4420
	11th to 20th	Day	15% 8% 2 7% 5% 4 5% 5% 7% 9% 33%	4377
	21st to end	Day	31% 10% 3 7% 4 4 4 4 6% 6% 20%	4923
June	1st to 10th	Day	26% 10% 3 7% 4 4 4 3 5% 7% 25%	2850
	11th to 20th	Day	25% 11% 3 8% 6% 5% 5% 4 5% 6% 22%	2850
	21st to end	Day	18% 9% 3 7% 5% 4 5% 3 6% 6% 34%	2850
July	1st to 10th	Day	8% 4 2 4 3 3 3 2 4 5% 62%	4740
	11th to 20th	Day	7% 3 1 3 2 2 2 2 3 5% 68%	4740
	21st to end	Day	14% 5% 2 5% 3 3 3 3 5% 9% 49%	4885
August	1st to 10th	Day	7% 4 2 3 2 2 2 2 4 5% 67%	4376
	11th to 20th	Day	17% 6% 3 7% 4 4 4 3 4 7% 41%	4026
	21st to end	Day	20% 6% 2 6% 4 3 4 3 5% 7% 40%	4413
September	1st to 10th	Day	16% 8% 2 6% 4 3 3 3 5% 7% 44%	2280
	11th to 20th	Day	22% 8% 3 6% 4 4 4 2 4 5% 37%	2280
	21st to end	Day	29% 6% 3 4 3 4 4 3 6% 6% 33%	1997
October	1st to 10th	Day	29% 8% 3 7% 5% 4 4 3 5% 6% 27%	3180
	11th to 20th	Day	40% 7% 2 5% 3 4 4 3 6% 6% 20%	3161
	21st to end	Day	37% 13% 3 7% 3 4 4 4 6% 5% 14%	3175
November	1st to 10th	Day	44% 10% 2 7% 4 4 4 2 4 4 15%	1568
	11th to 20th	Day	42% 13% 2 8% 3 2 3 3 3 3 18%	1600
	21st to end	Day	42% 11% 3 5% 3 3 4 3 3 4 18%	1600
December	1st to 10th	Day	35% 16% 3 6% 3 3 3 2 3 4 24%	1505
	11th to 20th	Day	42% 16% 4 7% 3 3 3 2 3 3 15%	1685
	21st to end	Day	48% 13% 4 6% 4 4 3 2 3 4 10%	2442
January	1st to 10th	Night	44% 14% 3 8% 4 3 3 2 3 3 13%	4726
	11th to 20th	Night	34% 9% 2 6% 3 4 3 3 4 8% 24%	4699
	21st to end	Night	57% 12% 2 4 2 2 2 2 3 3 12%	4863
February	1st to 10th	Night	36% 12% 3 6% 4 4 3 3 5% 4 19%	2470
	11th to 20th	Night	30% 14% 3 7% 4 3 4 2 4 4 24%	2402
	21st to end	Night	31% 14% 3 6% 3 3 4 3 4 5% 24%	2025
March	1st to 10th	Night	30% 20% 3 5% 4 3 3 3 3 4 22%	3626
	11th to 20th	Night	28% 10% 2 5% 3 3 3 2 4 5% 34%	3489
	21st to end	Night	35% 15% 4 8% 4 3 3 2 3 3 20%	3719
April	1st to 10th	Night	30% 13% 3 7% 5% 4 4 3 4 5% 21%	1900
	11th to 20th	Night	23% 13% 3 7% 5% 4 4 4 4 6% 27%	1781
	21st to end	Night	27% 11% 3 7% 5% 5% 4 3 4 6% 24%	1648
May	1st to 10th	Night	18% 8% 2 5% 4 3 3 3 5% 4 45%	2540
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 7% 10% 43%	2516
	21st to end	Night	27% 11% 3 8% 5% 4 4 3 4 5% 27%	2648
June	1st to 10th	Night	26% 7% 2 7% 5% 4 5% 4 5% 5% 31%	1330
	11th to 20th	Night	19% 12% 3 6% 5% 4 5% 3 6% 7% 29%	1330
	21st to end	Night	16% 6% 2 7% 5% 4 4 4 5% 6% 41%	1330
July	1st to 10th	Night	6% 3 1 4 2 3 3 2 4 5% 66%	2220
	11th to 20th	Night	6% 3 1 2 2 2 2 2 3 4 74%	2220
	21st to end	Night	11% 5% 2 4 3 3 3 3 5% 6% 55%	2664
August	1st to 10th	Night	5% 2 1 2 2 2 2 2 4 6% 72%	2552
	11th to 20th	Night	12% 6% 2 5% 3 4 4 3 6% 7% 49%	2812
	21st to end	Night	18% 5% 3 6% 4 3 4 3 5% 6% 43%	3257
September	1st to 10th	Night	10% 4 2 5% 3 3 4 2 5% 7% 54%	1900
	11th to 20th	Night	22% 7% 2 6% 3 3 3 4 4 5% 41%	1900
	21st to end	Night	25% 8% 2 6% 4 3 3 2 4 5% 37%	2178
October	1st to 10th	Night	26% 8% 3 7% 4 4 4 3 5% 5% 29%	3800
	11th to 20th	Night	37% 8% 2 5% 3 3 3 3 4 5% 27%	3777
	21st to end	Night	39% 12% 2 5% 3 3 3 2 4 5% 22%	4382
November	1st to 10th	Night	43% 11% 3 6% 4 4 3 2 4 4 17%	2730
	11th to 20th	Night	40% 11% 3 6% 3 3 3 2 3 3 21%	2800
	21st to end	Night	40% 11% 2 7% 4 2 3 2 4 4 21%	2800
December	1st to 10th	Night	35% 11% 3 5% 4 3 3 3 3 4 25%	2708
	11th to 20th	Night	47% 14% 3 6% 4 3 3 2 3 3 13%	3520
	21st to end	Night	49% 14% 3 5% 3 2 2 1 3 3 15%	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	78% 6% 7% 7% 2 1	2219
	11th to 20th	Day	64% 4 11% 12% 5% 5%	2220
	21st to end	Day	83% 3 5% 7% 2	2791
February	1st to 10th	Day	72% 5% 9% 8% 4 2	1710
	11th to 20th	Day	67% 5% 9% 12% 6% 1	1674
	21st to end	Day	70% 3 11% 11% 3 2	1428
March	1st to 10th	Day	70% 7% 10% 9% 4	3246
	11th to 20th	Day	58% 5% 11% 23% 2 1	3490
	21st to end	Day	70% 5% 14% 9% 3	3933
April	1st to 10th	Day	72% 6% 12% 8% 2	2280
	11th to 20th	Day	66% 4 12% 10% 7% 2	2346
	21st to end	Day	67% 5% 11% 11% 6%	2530
May	1st to 10th	Day	49% 4 18% 21% 7%	4420
	11th to 20th	Day	46% 7% 23% 19% 4	4380
	21st to end	Day	65% 7% 15% 11% 2	4924
June	1st to 10th	Day	61% 4 17% 11% 4 2	2850
	11th to 20th	Day	66% 5% 16% 10% 3	2850
	21st to end	Day	53% 6% 16% 16% 8% 1	2850
July	1st to 10th	Day	27% 6% 11% 26% 23% 7%	4666
	11th to 20th	Day	22% 3 15% 39% 19% 2	4659
	21st to end	Day	34% 7% 22% 22% 12% 2	4731
August	1st to 10th	Day	23% 4 11% 46% 15% 1	4359
	11th to 20th	Day	46% 7% 20% 17% 9% 1	4065
	21st to end	Day	46% 6% 19% 18% 10% 1	4412
September	1st to 10th	Day	42% 6% 13% 23% 12% 4	2280
	11th to 20th	Day	51% 6% 10% 17% 14% 2	2280
	21st to end	Day	55% 6% 14% 15% 9% 1	1997
October	1st to 10th	Day	60% 6% 14% 14% 6%	3180
	11th to 20th	Day	67% 6% 10% 11% 6%	3161
	21st to end	Day	71% 7% 8% 9% 4 1	3175
November	1st to 10th	Day	75% 4 8% 8% 4 1	1568
	11th to 20th	Day	74% 3 8% 8% 6% 2	1600
	21st to end	Day	72% 3 7% 9% 8% 1	1600
December	1st to 10th	Day	66% 4 9% 10% 9% 1	1505
	11th to 20th	Day	77% 4 7% 7% 3 2	1688
	21st to end	Day	80% 5% 5% 7% 2 1	2442
January	1st to 10th	Night	77% 4 5% 10% 2 1	4726
	11th to 20th	Night	59% 5% 13% 12% 7% 3	4740
	21st to end	Night	81% 3 5% 8% 3 1	4863
February	1st to 10th	Night	70% 4 10% 9% 4 3	2470
	11th to 20th	Night	64% 7% 10% 10% 8% 2	2404
	21st to end	Night	64% 3 11% 14% 6% 3	2025
March	1st to 10th	Night	66% 6% 9% 12% 6%	3626
	11th to 20th	Night	55% 4 13% 22% 5% 1	3490
	21st to end	Night	70% 5% 12% 10% 2	3719
April	1st to 10th	Night	66% 5% 15% 11% 3	1900
	11th to 20th	Night	59% 5% 12% 14% 7% 2	1781
	21st to end	Night	63% 4 12% 13% 7%	1648
May	1st to 10th	Night	43% 6% 15% 25% 10%	2540
	11th to 20th	Night	36% 10% 26% 23% 5%	2516
	21st to end	Night	61% 6% 20% 11% 3	2648
June	1st to 10th	Night	57% 4 18% 13% 4 3	1330
	11th to 20th	Night	56% 7% 19% 13% 4	1330
	21st to end	Night	44% 8% 20% 16% 8% 3	1330
July	1st to 10th	Night	22% 4 13% 32% 21% 8%	2185
	11th to 20th	Night	16% 4 13% 42% 23% 1	2178
	21st to end	Night	29% 6% 18% 28% 16% 3	2580
August	1st to 10th	Night	16% 3 16% 38% 25% 2	2544
	11th to 20th	Night	37% 8% 28% 16% 9% 3	2839
	21st to end	Night	43% 5% 20% 22% 9% 1	3257
September	1st to 10th	Night	33% 6% 17% 25% 14% 5%	1900
	11th to 20th	Night	47% 6% 11% 16% 15% 4	1900
	21st to end	Night	52% 6% 15% 18% 8% 2	2178
October	1st to 10th	Night	58% 6% 16% 13% 6%	3800
	11th to 20th	Night	63% 4 9% 16% 8%	3777
	21st to end	Night	69% 5% 7% 13% 5%	4382
November	1st to 10th	Night	74% 4 8% 8% 4 1	2730
	11th to 20th	Night	71% 4 8% 9% 6% 2	2800
	21st to end	Night	70% 4 8% 8% 9% 1	2800
December	1st to 10th	Night	65% 5% 10% 11% 8% 1	2708
	11th to 20th	Night	80% 3 7% 5% 4 1	3516
	21st to end	Night	78% 3 6% 9% 4 1	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	50% 6% 11% 18% 9% 7%	180
	11th to 20th	Day	52% 9% 10% 12% 14% 2	180
	21st to end	Day	54% 5% 12% 14% 13% 2	216
February	1st to 10th	Day	45% 6% 21% 17% 10% 1	370
	11th to 20th	Day	41% 8% 20% 21% 9% 2	365
	21st to end	Day	37% 12% 23% 20% 8% 1	315
March	1st to 10th	Day	37% 10% 21% 20% 10% 2	460
	11th to 20th	Day	40% 8% 15% 19% 16% 2	460
	21st to end	Day	42% 10% 23% 16% 7% 2	506
April	1st to 10th	Day	39% 13% 18% 19% 10% 1	460
	11th to 20th	Day	35% 10% 21% 20% 10% 4	452
	21st to end	Day	37% 11% 24% 18% 9% 2	460
May	1st to 10th	Day	25% 9% 23% 28% 12% 2	463
	11th to 20th	Day	29% 6% 21% 26% 14% 4	488
	21st to end	Day	26% 8% 25% 26% 11% 4	587
June	1st to 10th	Day	31% 8% 24% 26% 10% 1	680
	11th to 20th	Day	31% 11% 25% 24% 7% 2	680
	21st to end	Day	25% 7% 23% 28% 15% 3	680
July	1st to 10th	Day	19% 6% 22% 36% 15% 3	671
	11th to 20th	Day	13% 7% 27% 35% 14% 4	668
	21st to end	Day	13% 5% 19% 39% 18% 6%	587
August	1st to 10th	Day	17% 5% 18% 31% 20% 8%	487
	11th to 20th	Day	14% 4 18% 35% 22% 6%	477
	21st to end	Day	20% 8% 23% 28% 15% 6%	539
September	1st to 10th	Day	21% 7% 26% 27% 15% 4	490
	11th to 20th	Day	30% 7% 17% 27% 17% 3	490
	21st to end	Day	33% 6% 19% 22% 15% 5%	490
October	1st to 10th	Day	35% 4 19% 19% 18% 4	490
	11th to 20th	Day	43% 6% 15% 16% 15% 5%	490
	21st to end	Day	47% 7% 16% 17% 9% 4	396
November	1st to 10th	Day	43% 13% 17% 15% 12% 1	200
	11th to 20th	Day	51% 6% 11% 12% 13% 9%	200
	21st to end	Day	48% 10% 14% 14% 7% 9%	200
December	1st to 10th	Day	50% 6% 13% 8% 15% 9%	182
	11th to 20th	Day	53% 5% 9% 18% 11% 4	180
	21st to end	Day	46% 7% 16% 22% 7% 2	198
January	1st to 10th	Night	55% 5% 10% 19% 9% 2	850
	11th to 20th	Night	46% 6% 13% 23% 12% 1	850
	21st to end	Night	48% 4 14% 21% 11% 1	845
February	1st to 10th	Night	42% 6% 16% 27% 9% 1	760
	11th to 20th	Night	38% 7% 17% 26% 12%	744
	21st to end	Night	38% 7% 18% 24% 12% 1	628
March	1st to 10th	Night	41% 7% 15% 21% 15% 1	760
	11th to 20th	Night	45% 6% 13% 21% 13% 1	760
	21st to end	Night	44% 5% 13% 23% 13% 3	836
April	1st to 10th	Night	39% 5% 13% 28% 13% 2	760
	11th to 20th	Night	34% 5% 17% 28% 13% 2	653
	21st to end	Night	37% 4 15% 29% 13% 2	508
May	1st to 10th	Night	21% 3 15% 34% 24% 2	380
	11th to 20th	Night	24% 3 10% 31% 28% 4	374
	21st to end	Night	25% 3 11% 34% 25% 1	411
June	1st to 10th	Night	29% 3 13% 31% 23% 1	380
	11th to 20th	Night	26% 5% 18% 30% 19% 2	380
	21st to end	Night	21% 3 14% 31% 27% 4	380
July	1st to 10th	Night	13% 2 11% 34% 38% 2	370
	11th to 20th	Night	11% 2 7% 32% 42% 6%	368
	21st to end	Night	8% 2 7% 31% 44% 7%	416
August	1st to 10th	Night	14% 2 3 28% 43% 11%	388
	11th to 20th	Night	11% 1 4 28% 45% 11%	564
	21st to end	Night	18% 3 11% 30% 35% 4	686
September	1st to 10th	Night	15% 2 12% 36% 31% 4	760
	11th to 20th	Night	27% 2 10% 22% 31% 7%	760
	21st to end	Night	33% 3 14% 27% 21% 3	760
October	1st to 10th	Night	31% 3 15% 25% 22% 4	760
	11th to 20th	Night	42% 2 13% 24% 15% 4	760
	21st to end	Night	45% 2 17% 24% 9% 3	836
November	1st to 10th	Night	51% 5% 16% 21% 7%	780
	11th to 20th	Night	51% 4 15% 18% 11% 1	800
	21st to end	Night	46% 6% 16% 19% 11% 3	800
December	1st to 10th	Night	40% 5% 16% 26% 12% 2	779
	11th to 20th	Night	53% 8% 14% 19% 6% 1	850
	21st to end	Night	52% 7% 16% 18% 6%	935

Page generated at 2024-11-29 07:43:08. Version ac07

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