Shot Rock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shot Rock clear sky chart from 2005-11-05 to 2017-09-22.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
56%
15262
28%
46913
21%
15226
64%
15226
37%
25589

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
44%
717
20%
2506
16%
716
52%
716
26%
1442
January16th to endNight
41%
768
25%
2499
16%
768
53%
768
23%
1534
February1st to 15thNight
41%
700
24%
2221
17%
696
52%
696
25%
1373
February16th to endNight
44%
632
24%
1895
18%
632
54%
632
26%
1206
March1st to 15thNight
41%
720
17%
2104
12%
720
49%
720
26%
1385
March16th to endNight
42%
768
19%
2027
11%
768
48%
768
27%
1326
April1st to 15thNight
43%
719
19%
1799
8%
719
49%
719
27%
1237
April16th to endNight
51%
720
23%
1800
10%
720
56%
720
36%
1104
May1st to 15thNight
56%
583
26%
1663
16%
583
62%
583
45%
848
May16th to endNight
64%
374
23%
1496
26%
374
67%
374
35%
710
June1st to 15thNight
67%
360
27%
1440
30%
360
75%
360
42%
628
June16th to endNight
78%
360
36%
1440
43%
360
86%
360
61%
497
July1st to 15thNight
88%
340
33%
1360
44%
340
90%
340
66%
460
July16th to endNight
85%
449
38%
1483
39%
421
87%
421
60%
585
August1st to 15thNight
80%
613
35%
1686
25%
610
82%
610
64%
797
August16th to endNight
82%
764
43%
1910
27%
764
84%
764
75%
887
September1st to 15thNight
83%
720
42%
1800
27%
720
87%
720
77%
826
September16th to endNight
71%
683
42%
1842
33%
683
78%
683
63%
863
October1st to 15thNight
58%
660
31%
1969
26%
660
68%
660
42%
1018
October16th to endNight
62%
704
35%
2120
30%
704
72%
704
46%
1052
November1st to 15thNight
60%
700
30%
2275
27%
700
68%
700
36%
1214
November16th to endNight
47%
720
28%
2370
23%
720
57%
720
31%
1331
December1st to 15thNight
43%
720
22%
2520
15%
720
55%
720
22%
1529
December16th to endNight
35%
768
22%
2688
15%
768
47%
768
17%
1737

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 ForecastData
Points
Cloud CoverDay
7%7%23213335%58%
47962
Night
7%7%23223345%57%
47104
TransparencyDay
28%38%20%24%15%
47640
Night
28%47%20%24%14%
46925
SeeingDay
16%19%34%18%7%3
5828
Night
12%8%16%31%24%5%
15271

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
9%10%24323346%48%
1432
16th to endDay
12%15%33223346%42%
1722
February1st to 15thDay
11%11%34224337%45%
1631
16th to endDay
10%16%6%5%313335%38%
1579
March1st to 15thDay
9%17%6%5%324447%34%
1854
16th to endDay
10%15%45%424447%37%
2196
April1st to 15thDay
9%17%44323445%40%
2149
16th to endDay
11%9%13212245%53%
2160
May1st to 15thDay
7%6%13213247%58%
2284
16th to endDay
11%9%23423345%49%
2615
June1st to 15thDay
6%5%23213245%60%
2520
16th to endDay
211111222379%
2520
July1st to 15thDay
1111223479%
2520
16th to endDay
11111222379%
2582
August1st to 15thDay
11122222379%
2262
16th to endDay
11111223380%
2292
September1st to 15thDay
2121213477%
2160
16th to endDay
431211222472%
1930
October1st to 15thDay
8%423322446%59%
1658
16th to endDay
8%5%12322335%61%
1749
November1st to 15thDay
7%6%2232435%6%53%
1584
16th to endDay
8%9%3332335%5%51%
1587
December1st to 15thDay
14%7%35%425%346%43%
1440
16th to endDay
14%13%44323345%39%
1536
January1st to 15thNight
9%9%24323447%47%
2506
16th to endNight
10%12%33323345%46%
2499
February1st to 15thNight
11%9%3442345%8%42%
2221
16th to endNight
9%13%4422435%5%43%
1895
March1st to 15thNight
9%14%45%313446%41%
2104
16th to endNight
10%12%2332345%6%44%
2027
April1st to 15thNight
9%12%45%3245%46%41%
1799
16th to endNight
8%7%33223336%54%
1800
May1st to 15thNight
5%41231245%7%61%
1663
16th to endNight
7%8%22222346%58%
1496
June1st to 15thNight
5%41121333468%
1440
16th to endNight
21121212281%
1440
July1st to 15thNight
1211222282%
1440
16th to endNight
311121222278%
1585
August1st to 15thNight
221121223376%
1695
16th to endNight
11111123381%
1910
September1st to 15thNight
111112483%
1800
16th to endNight
312221225%76%
1842
October1st to 15thNight
6%412312345%63%
1969
16th to endNight
6%41222446%64%
2120
November1st to 15thNight
7%5%13324347%56%
2275
16th to endNight
7%8%23333446%52%
2370
December1st to 15thNight
13%8%24324447%43%
2520
16th to endNight
15%12%45%213345%40%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
36%310%20%21%7%
1432
16th to endDay
42%36%17%17%11%
1722
February1st to 15thDay
40%39%19%18%7%
1631
16th to endDay
48%47%22%14%2
1579
March1st to 15thDay
49%410%14%15%6%
1854
16th to endDay
45%6%14%18%12%3
2196
April1st to 15thDay
44%412%20%14%3
2149
16th to endDay
33%414%25%17%4
2160
May1st to 15thDay
24%313%33%21%3
2284
16th to endDay
36%411%26%17%4
2619
June1st to 15thDay
26%311%23%23%12%
2520
16th to endDay
11%1418%39%24%
2520
July1st to 15thDay
8%2311%30%43%
2371
16th to endDay
11%2413%26%42%
2421
August1st to 15thDay
11%2314%32%36%
2246
16th to endDay
10%1314%41%28%
2292
September1st to 15thDay
12%1316%39%27%
2160
16th to endDay
16%2427%32%15%
1930
October1st to 15thDay
25%27%24%26%13%
1658
16th to endDay
25%38%23%27%12%
1749
November1st to 15thDay
30%410%24%20%9%
1584
16th to endDay
34%47%20%27%5%
1587
December1st to 15thDay
41%5%7%21%18%5%
1440
16th to endDay
46%48%14%17%8%
1536
January1st to 15thNight
35%49%19%20%9%
2506
16th to endNight
39%46%15%18%15%
2499
February1st to 15thNight
39%47%22%15%10%
2232
16th to endNight
40%49%21%19%4
1895
March1st to 15thNight
42%410%16%17%8%
2104
16th to endNight
39%6%13%20%17%4
2027
April1st to 15thNight
42%5%11%22%14%3
1799
16th to endNight
30%5%12%27%19%3
1800
May1st to 15thNight
20%411%31%25%6%
1664
16th to endNight
25%415%28%20%5%
1496
June1st to 15thNight
20%410%23%28%14%
1440
16th to endNight
10%2321%34%28%
1440
July1st to 15thNight
9%139%30%45%
1360
16th to endNight
13%2312%24%44%
1483
August1st to 15thNight
13%2214%29%37%
1686
16th to endNight
8%1215%39%32%
1910
September1st to 15thNight
7%2414%41%28%
1800
16th to endNight
13%2329%32%17%
1842
October1st to 15thNight
22%45%26%28%11%
1969
16th to endNight
20%38%23%31%12%
2120
November1st to 15thNight
26%5%8%24%23%11%
2275
16th to endNight
31%46%22%26%8%
2370
December1st to 15thNight
39%5%8%19%20%6%
2520
16th to endNight
45%47%12%19%10%
2688

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
48%11%26%5%35%
60
16th to endDay
29%18%20%19%8%3
250
February1st to 15thDay
25%17%24%19%10%2
246
16th to endDay
28%20%26%18%32
238
March1st to 15thDay
30%25%17%14%10%1
270
16th to endDay
26%24%29%12%6%
288
April1st to 15thDay
28%24%24%15%7%
269
16th to endDay
27%24%28%16%21
270
May1st to 15thDay
20%23%29%16%6%3
288
16th to endDay
25%18%24%16%9%5%
330
June1st to 15thDay
14%21%37%17%6%2
315
16th to endDay
5%18%42%21%6%6%
315
July1st to 15thDay
214%51%17%8%5%
305
16th to endDay
314%51%17%8%5%
327
August1st to 15thDay
321%46%15%9%3
315
16th to endDay
211%49%21%8%6%
332
September1st to 15thDay
415%44%22%9%3
315
16th to endDay
11%14%38%28%5%1
280
October1st to 15thDay
10%22%35%21%6%2
255
16th to endDay
19%21%25%25%7%
261
November1st to 15thDay
12%12%14%18%35%6%
90
16th to endDay
17%21%25%24%8%2
85
December1st to 15thDay
31%21%26%13%33
60
16th to endDay
20%9%31%18%17%3
64
January1st to 15thNight
17%10%20%27%17%7%
720
16th to endNight
17%14%20%25%15%5%
768
February1st to 15thNight
17%11%19%28%17%5%
704
16th to endNight
21%10%19%26%17%4
632
March1st to 15thNight
21%9%21%25%17%3
720
16th to endNight
18%12%22%26%16%2
768
April1st to 15thNight
15%11%20%32%15%3
719
16th to endNight
14%11%17%29%21%5%
720
May1st to 15thNight
8%11%18%34%23%3
584
16th to endNight
10%5%11%34%32%4
375
June1st to 15thNight
7%416%38%28%4
360
16th to endNight
3111%46%33%2
360
July1st to 15thNight
1342%47%3
340
16th to endNight
315%30%50%9%
449
August1st to 15thNight
310%42%36%5%
613
16th to endNight
1110%41%38%5%
764
September1st to 15thNight
2110%38%39%7%
720
16th to endNight
4415%34%29%11%
683
October1st to 15thNight
10%9%16%29%25%8%
660
16th to endNight
11%8%15%28%25%11%
704
November1st to 15thNight
10%8%16%34%23%7%
700
16th to endNight
14%12%21%26%18%6%
720
December1st to 15thNight
20%9%20%29%14%5%
720
16th to endNight
24%14%17%26%13%3
768
Page generated at 2017-09-23 03:43:35. Version ac04

Copyright 2017 A. Danko


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