Rensselaerville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rensselaerville clear sky chart from 2005-11-05 to 2018-04-23.

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
27%
15736
16%
49527
7%
15705
37%
15705
17%
33269

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
16%
780
15%
2716
6%
776
28%
776
11%
1860
January16th to endNight
14%
832
15%
2853
3%
832
28%
832
10%
1961
February1st to 15thNight
9%
764
12%
2447
1%
761
23%
761
9%
1813
February16th to endNight
16%
683
17%
2049
5%
683
30%
683
13%
1448
March1st to 15thNight
13%
780
14%
2334
4%
780
26%
780
11%
1686
March16th to endNight
18%
832
21%
2159
6%
832
30%
832
17%
1489
April1st to 15thNight
16%
778
15%
1946
2%
778
23%
778
16%
1430
April16th to endNight
24%
702
17%
1816
4%
702
33%
702
22%
1247
May1st to 15thNight
24%
452
17%
1532
7%
452
36%
452
17%
1027
May16th to endNight
35%
374
14%
1497
10%
374
45%
374
17%
954
June1st to 15thNight
33%
360
13%
1440
9%
360
45%
360
15%
927
June16th to endNight
46%
360
12%
1440
12%
360
55%
360
25%
806
July1st to 15thNight
50%
340
12%
1360
15%
340
57%
340
23%
786
July16th to endNight
54%
376
15%
1418
12%
354
63%
354
25%
810
August1st to 15thNight
48%
482
17%
1553
10%
480
56%
480
30%
926
August16th to endNight
53%
764
20%
1910
10%
764
56%
764
35%
1233
September1st to 15thNight
43%
720
19%
1800
8%
720
48%
720
30%
1191
September16th to endNight
48%
717
25%
1965
17%
717
54%
717
35%
1184
October1st to 15thNight
34%
720
19%
2118
12%
720
43%
720
22%
1405
October16th to endNight
25%
768
15%
2418
7%
768
37%
768
17%
1640
November1st to 15thNight
28%
760
18%
2472
9%
760
40%
760
17%
1613
November16th to endNight
24%
780
17%
2642
10%
780
35%
780
15%
1763
December1st to 15thNight
17%
780
12%
2730
3%
780
29%
780
11%
1945
December16th to endNight
14%
832
13%
2912
2%
832
26%
832
8%
2125

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
14%7%36%6%35%5%5%7%33%
49993
Night
14%7%36%5%3445%7%36%
49697
Cloud CoverDay
14%7%36%6%35%5%5%7%34%
50002
Night
14%7%36%5%345%5%7%37%
49703
TransparencyDay
48%6%12%20%11%1
49681
Night
45%6%13%21%12%1
49527
SeeingDay
21%15%28%20%10%3
6377
Night
22%16%28%22%8%1
15737

By Month

Percentage Cloud Cover NE (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
11%9%37%6%48%6%5%6%29%
1552
16th to endDay
11%9%5%7%8%37%46%6%28%
1723
February1st to 15thDay
12%11%5%8%7%5%7%5%5%6%23%
1742
16th to endDay
14%9%47%6%35%5%5%6%30%
1710
March1st to 15thDay
16%10%47%6%25%45%7%28%
1943
16th to endDay
14%9%46%5%34345%36%
2416
April1st to 15thDay
16%9%46%6%34345%34%
2332
16th to endDay
15%7%25%5%35%45%5%38%
2257
May1st to 15thDay
19%9%26%6%45%45%432%
2429
16th to endDay
15%6%35%5%36%5%6%8%33%
2618
June1st to 15thDay
20%5%36%6%35%46%8%30%
2520
16th to endDay
14%6%26%7%46%7%6%8%29%
2520
July1st to 15thDay
11%5%36%7%46%5%7%9%33%
2520
16th to endDay
12%5%26%7%36%7%7%9%31%
2654
August1st to 15thDay
11%5%27%7%46%6%6%8%33%
2382
16th to endDay
12%5%25%5%35%6%6%8%37%
2292
September1st to 15thDay
13%6%36%5%35%45%7%38%
2160
16th to endDay
13%4243145%5%6%47%
1994
October1st to 15thDay
17%8%35%434435%38%
1839
16th to endDay
18%8%36%6%245%5%6%30%
1806
November1st to 15thDay
15%8%35%5%345%47%35%
1716
16th to endDay
14%7%35%5%36%5%46%35%
1644
December1st to 15thDay
15%11%48%7%35%5%5%6%26%
1560
16th to endDay
16%10%48%6%36%5%5%7%22%
1664
January1st to 15thNight
13%8%47%6%345%6%8%31%
2716
16th to endNight
12%9%47%6%35%5%5%7%32%
2853
February1st to 15thNight
12%11%5%8%7%36%46%6%27%
2446
16th to endNight
13%8%36%6%45%5%6%8%30%
2049
March1st to 15thNight
17%8%36%6%35%5%5%6%30%
2321
16th to endNight
15%6%345%3445%7%38%
2159
April1st to 15thNight
16%8%36%6%45%45%6%32%
1946
16th to endNight
17%6%26%43445%6%39%
1816
May1st to 15thNight
20%8%35%423346%36%
1532
16th to endNight
13%5%26%5%35%5%6%8%37%
1495
June1st to 15thNight
19%5%35%4245%47%36%
1440
16th to endNight
11%41442446%11%44%
1440
July1st to 15thNight
9%424435%6%5%8%44%
1440
16th to endNight
11%324336%46%8%44%
1514
August1st to 15thNight
9%5%15%4345%6%7%46%
1563
16th to endNight
13%424324447%47%
1910
September1st to 15thNight
14%41443445%6%46%
1800
16th to endNight
11%414323447%51%
1965
October1st to 15thNight
19%5%25%423446%40%
2118
16th to endNight
18%6%36%425%46%7%34%
2418
November1st to 15thNight
15%9%25%43345%7%38%
2472
16th to endNight
14%7%36%6%35%5%5%6%36%
2642
December1st to 15thNight
17%9%46%6%35%5%5%7%28%
2730
16th to endNight
15%9%47%7%35%5%6%7%25%
2912

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
10%9%46%5%47%6%6%7%31%
1552
16th to endDay
10%9%48%8%45%6%6%6%29%
1723
February1st to 15thDay
12%9%5%8%7%5%6%5%5%7%24%
1742
16th to endDay
14%9%38%6%345%5%6%32%
1710
March1st to 15thDay
16%9%47%6%345%5%7%30%
1953
16th to endDay
13%8%46%5%34446%38%
2415
April1st to 15thDay
16%9%47%5%34435%35%
2332
16th to endDay
15%6%26%5%35%45%6%39%
2257
May1st to 15thDay
18%8%25%6%45%45%5%32%
2429
16th to endDay
14%6%25%5%36%5%6%8%34%
2618
June1st to 15thDay
18%436%5%35%5%6%7%31%
2520
16th to endDay
13%5%26%6%46%6%7%8%31%
2520
July1st to 15thDay
9%5%26%6%5%6%6%7%10%34%
2520
16th to endDay
10%5%26%6%37%6%7%9%32%
2654
August1st to 15thDay
10%5%26%8%46%6%7%8%34%
2382
16th to endDay
12%4245%45%6%6%8%38%
2292
September1st to 15thDay
13%6%36%5%35%45%7%39%
2160
16th to endDay
12%5%2332445%7%47%
1994
October1st to 15thDay
16%8%26%434445%39%
1839
16th to endDay
18%7%25%6%245%6%7%32%
1806
November1st to 15thDay
14%7%36%5%3445%6%36%
1716
16th to endDay
13%7%345%36%45%6%37%
1644
December1st to 15thDay
14%10%48%8%46%446%28%
1560
16th to endDay
17%9%47%8%36%5%6%6%24%
1664
January1st to 15thNight
12%8%48%6%245%6%8%33%
2716
16th to endNight
11%9%47%6%45%45%7%33%
2853
February1st to 15thNight
12%10%48%7%46%45%6%29%
2439
16th to endNight
12%9%37%5%35%5%5%7%33%
2049
March1st to 15thNight
17%8%36%5%35%5%6%6%31%
2334
16th to endNight
14%6%25%5%345%5%7%39%
2159
April1st to 15thNight
15%7%37%5%35%447%33%
1946
16th to endNight
16%6%35%43435%5%40%
1816
May1st to 15thNight
19%8%26%424346%37%
1532
16th to endNight
13%5%26%425%5%6%7%39%
1495
June1st to 15thNight
19%5%344245%5%7%37%
1440
16th to endNight
10%314325%46%11%45%
1440
July1st to 15thNight
9%325%425%6%6%9%44%
1440
16th to endNight
10%325%325%5%7%8%44%
1514
August1st to 15thNight
8%415%5%245%6%7%47%
1563
16th to endNight
12%5%244235%5%6%48%
1910
September1st to 15thNight
13%4144245%6%6%45%
1800
16th to endNight
11%31442345%6%52%
1965
October1st to 15thNight
18%5%25%423446%41%
2118
16th to endNight
17%6%26%43445%7%36%
2418
November1st to 15thNight
14%8%2442445%7%39%
2472
16th to endNight
13%6%45%5%35%5%5%6%37%
2642
December1st to 15thNight
17%8%47%5%35%5%5%7%30%
2730
16th to endNight
16%9%36%6%45%5%6%7%26%
2912

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
51%6%11%19%9%1
1553
16th to endDay
53%5%13%18%7%
1723
February1st to 15thDay
59%5%10%15%8%
1745
16th to endDay
51%7%10%18%10%1
1710
March1st to 15thDay
54%412%17%8%1
1953
16th to endDay
48%48%18%16%3
2416
April1st to 15thDay
51%39%20%12%1
2332
16th to endDay
45%410%20%15%3
2257
May1st to 15thDay
52%48%20%11%1
2429
16th to endDay
46%8%13%19%10%1
2622
June1st to 15thDay
50%6%13%19%9%
2520
16th to endDay
48%7%15%18%10%
2520
July1st to 15thDay
43%8%14%21%11%1
2371
16th to endDay
44%6%15%20%11%
2487
August1st to 15thDay
45%7%15%20%9%
2368
16th to endDay
40%7%14%25%13%
2292
September1st to 15thDay
43%6%12%22%14%1
2160
16th to endDay
35%5%11%27%18%1
1994
October1st to 15thDay
46%5%10%22%13%1
1839
16th to endDay
49%6%14%19%8%1
1806
November1st to 15thDay
47%412%21%11%1
1716
16th to endDay
46%5%14%20%12%
1644
December1st to 15thDay
57%5%13%16%7%
1560
16th to endDay
59%6%13%13%6%
1664
January1st to 15thNight
48%7%12%17%12%1
2716
16th to endNight
49%6%11%20%9%1
2853
February1st to 15thNight
55%7%11%16%8%
2447
16th to endNight
50%5%12%19%10%1
2049
March1st to 15thNight
52%5%12%19%8%1
2334
16th to endNight
43%5%10%22%14%3
2159
April1st to 15thNight
50%5%12%20%10%1
1946
16th to endNight
44%411%20%16%2
1816
May1st to 15thNight
48%39%20%15%2
1532
16th to endNight
42%8%15%21%11%1
1497
June1st to 15thNight
45%6%13%23%9%
1440
16th to endNight
33%7%18%28%12%
1440
July1st to 15thNight
35%8%14%27%12%1
1360
16th to endNight
34%7%18%25%11%1
1418
August1st to 15thNight
33%7%17%28%11%1
1553
16th to endNight
35%5%13%30%14%
1910
September1st to 15thNight
37%6%12%25%16%
1800
16th to endNight
32%412%26%22%1
1965
October1st to 15thNight
44%412%20%16%1
2118
16th to endNight
46%5%14%22%9%
2418
November1st to 15thNight
44%5%12%21%14%2
2472
16th to endNight
46%5%14%22%9%1
2642
December1st to 15thNight
53%6%14%17%7%
2730
16th to endNight
55%6%13%16%8%
2912

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
30%26%26%10%5%1
90
16th to endDay
29%21%34%13%
110
February1st to 15thDay
31%28%30%7%1
169
16th to endDay
26%23%34%14%1
291
March1st to 15thDay
31%20%31%14%1
330
16th to endDay
26%22%29%15%32
352
April1st to 15thDay
32%21%26%14%6%
330
16th to endDay
22%17%30%15%7%5%
289
May1st to 15thDay
28%18%25%14%9%3
288
16th to endDay
18%13%32%21%10%3
331
June1st to 15thDay
21%12%31%22%11%
315
16th to endDay
17%13%28%28%11%1
315
July1st to 15thDay
13%7%30%29%16%2
305
16th to endDay
13%6%29%29%15%4
326
August1st to 15thDay
11%8%29%26%16%7%
313
16th to endDay
13%6%20%30%16%12%
332
September1st to 15thDay
14%10%24%22%19%9%
315
16th to endDay
15%6%25%19%19%13%
314
October1st to 15thDay
22%10%20%26%16%3
315
16th to endDay
26%17%28%18%8%
307
November1st to 15thDay
24%17%23%21%11%1
280
16th to endDay
20%26%26%21%41
174
December1st to 15thDay
23%24%34%8%7%1
90
16th to endDay
34%27%33%5%
96
January1st to 15thNight
24%22%32%17%3
780
16th to endNight
24%22%33%17%1
832
February1st to 15thNight
22%24%35%15%
764
16th to endNight
25%23%30%18%2
683
March1st to 15thNight
30%23%29%15%1
780
16th to endNight
24%24%28%16%4
832
April1st to 15thNight
25%20%33%17%2
778
16th to endNight
22%20%29%17%9%
702
May1st to 15thNight
25%15%29%22%6%
452
16th to endNight
17%10%29%30%10%1
375
June1st to 15thNight
24%12%24%24%13%1
360
16th to endNight
13%5%28%37%13%
360
July1st to 15thNight
11%5%23%40%17%
340
16th to endNight
13%322%40%19%
376
August1st to 15thNight
12%5%26%35%17%2
482
16th to endNight
14%420%34%20%4
764
September1st to 15thNight
16%7%25%29%18%2
720
16th to endNight
13%7%23%29%19%5%
717
October1st to 15thNight
23%12%23%25%14%1
720
16th to endNight
24%17%27%24%5%
768
November1st to 15thNight
23%17%25%22%9%1
760
16th to endNight
23%18%28%20%6%1
780
December1st to 15thNight
26%20%32%16%4
780
16th to endNight
29%25%27%15%2
832
Page generated at 2018-04-24 10:03:01. Version ac04

Copyright 2018 A. Danko


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