Observing Statistics

The following table summarises time spent observing at Great Shefford each month:

	[A]	[B]	[C]	[D]	[E]	[F]	[G]	[H]
Month	Nights used	Hours spent imaging	Time CCD exposing	Avg. session (hours)	Images acquired	Avg. time between exposures	Average exposure length	Efficiency [G]/[F]	Comments
2008-Mar	16	58.7	1d 10h	3.7	6779	31s	18s	58.6%	Out of operation 7 nights, 2 clear nights missed.
2008-Feb	15	101.8	2d 22h	6.8	13810	27s	18s	69.2%
2008-Jan	12	53.0	1d 14h	4.4	5793	33s	24s	72.7%
2007 total	178	819.7	22d 03h	4.6	92025	32s	21s	64.8%
2007-Dec	15	82.5	2d 09h	5.5	7034	42s	29s	69.2%
2007-Nov	14	72.9	2d 00h	5.2	9979	26s	17s	66.1%
2007-Oct	13	52.5	1d 09h	4.0	6206	30s	19s	62.5%
2007-Sep	17	96.3	2d 13h	5.7	10615	33s	21s	63.6%
2007-Aug	15	71.0	1d 21h	4.7	7286	35s	22s	63.8%
2007-Jul	16	49.9	23h 38m	3.1	4578	39s	19s	47.4%	Poor weather continued, flooding on 20 July.
2007-Jun	8	20.4	12h 34m	2.5	3292	22s	14s	61.8%	Very poor weather across the UK in May & especially June, which was the cloudiest month since 2002 Dec.
2007-May	14	40.8	1d 03h	2.9	4343	34s	22s	65.5%
2007-Apr	20	98.7	2d 13h	4.9	12123	29s	18s	61.6%
2007-Mar	16	98.1	2d 12h	6.1	12030	29s	18s	61.6%
2007-Feb	12	52.4	1d 14h	4.4	5884	32s	24s	73.4%
2007-Jan	18	84.3	2d 16h	4.7	8655	35s	26s	75.4%
2006 total	169	798.5	21d 03h	4.7	80515	36s	23s	63.5%
2006-Dec	10	59.2	1d 20h	5.9	6583	32s	24s	74.3%
2006-Nov	16	105.1	2d 15h	6.6	9553	40s	24s	59.6%
2006-Oct	14	94.0	2d 12h	6.7	8989	38s	24s	64.2%
2006-Sep	14	70.2	1d 17h	5.0	7805	32s	19s	58.4%
2006-Aug	16	51.4	1d 07h	3.2	4282	43s	26s	60.7%
2006-Jul	16	61.6	1d 18h	3.9	5680	39s	27s	68.0%
2006-Jun	13	37.3	23h 49h	2.9	4473	30s	19s	63.9%
2006-May	13	38.9	22h 00h	3.0	4693	30s	17s	56.5%
2006-Apr	19	87.9	2d 12h	4.6	8056	39s	27s	68.2%
2006-Mar	11	67.0	1d 18h	6.1	6112	39s	25s	62.8%
2006-Feb	14	53.5	1d 09h	3.8	5520	35s	22s	62.0%
2006-Jan	13	72.3	1d 21h	5.6	8769	30s	18s	62.3%
2005 total	181	841.5	18d 06h	4.7	69239	44s	23s	52.1%
2005-Dec	17	101.5	2d 16h	6.0	9124	40s	25s	62.9%
2005-Nov	16	112.3	3d 03h	7.0	11225	36s	24s	66.8%
2005-Oct	14	60.5	1d 15h	4.3	6792	32s	21s	64.5%
2005-Sep	12 (9th-30th)	50.0	1d 06h	4.2	4297	42s	26s	63.5%	Out of operation from 15Aug-09Sep (CCD being upgraded)
2005-Aug	11 (1st-14th)	42.1	19h 11m	3.8	2800	54s	25s	45.6%	Out of operation from 15Aug-09Sep (CCD being upgraded)
2005-Jul	18	61.0	1d 01h	3.4	4267	51s	21s	40.3%
2005-Jun	11	35.5	15h 40m	3.2	2802	46s	20s	44.2%	Out of operation 7 nights (Telescope being upgraded)
2005-May	21	66.6	1d 07h	3.2	5787	41s	19s	45.8%
2005-Apr	18	79.7	1d 14h	4.4	6014	48s	23s	48.2%
2005-Mar	15	74.2	1d 08h	4.9	5281	51s	22s	43.4%
2005-Feb	13	55.0	1d 00h	4.2	3604	55s	24s	43.7%
2005-Jan	15	103.2	1d 21h	6.9	7246	51s	22s	43.4%
2004 total	182	774.6	12d 15h	4.3	53725	52s	20s	39.1%
2004-Dec	17	97.1	1d 13h	5.7	7005	50s	19s	38.4%
2004-Nov	14	62.5	1d 03h	4.5	4235	53s	23s	43.9%
2004-Oct	15	57.6	1d 01h	3.8	4226	49s	22s	44.5%
2004-Sep	17	93.4	1d 18h	5.5	7402	45s	21s	46.0%
2004-Aug	18	67.6	1d 06h	3.8	5184	47s	21s	44.8%
2004-Jul	15	30.4	14h 43m	2.0	2173	50s	24s	48.5%
2004-Jun	17	41.4	17h 38m	2.4	3395	44s	19s	42.6%
2004-May	13	46.0	18h 05m	3.5	3872	43s	17s	39.3%
2004-Apr	13	63.2	21h 37m	4.9	4964	46s	16s	34.2%
2004-Mar	16	70.3	23h 31m	4.4	4492	56s	19s	33.5%
2004-Feb	16	75.7	1d 00h	4.7	3592	1m16s	24s	32.0%
2004-Jan	11	69.6	19h 47m	6.3	3185	1m19s	22s	28.4%
2003 total	183	701.1	7d 13h	3.8	28090	1m30s	23s	25.8%
2003-Dec	13	83.6	1d 01h	6.4	3965	1m16s	23s	30.8%
2003-Nov	10	36.2	8h 48m	3.6	1539	1m25s	21s	24.3%
2003-Oct	15	77.7	23h 46m	5.2	3713	1m15s	23s	30.6%
2003-Sep	23	110.7	1d 03h	4.8	4334	1m32s	22s	24.4%
2003-Aug	18	61.6	16h 22m	3.4	2146	1m43s	27s	26.6%
2003-Jul	16	42.7	9h 39m	2.7	1619	1m35s	21s	22.6%
2003-Jun	7	20.9	7h 06m	3.0	967	1m18s	26s	34.0%
2003-May	13	30.9	8h 47m	2.4	1242	1m29s	25s	28.5%
2003-Apr	17	52.5	12h 03m	3.1	1992	1m35s	22s	23.0%
2003-Mar	18	68.9	13h 35m	3.8	2674	1m33s	18s	19.7%
2003-Feb	16	58.5	13h 31m	3.7	1983	1m46s	25s	23.1%
2003-Jan	17	57.0	14h 37m	3.4	1916	1m47s	27s	25.7%
2002 total	87	164.3	1d 02h	1.9	3042	3m14s	31s	15.8%	16 May - 31Dec = 230 possible nights
2002-Dec	5	11.6	2h 38m	2.3	323	2m09s	29s	22.8%
2002-Nov	13	16.3	3h 27m	1.3	419	2m20s	30s	21.2%
2002-Oct	9	35.6	4h 03m	4.0	506	4m13s	29s	11.4%
2002-Sep	15	24.1	4h 14m	1.6	509	2m51s	30s	17.6%
2002-Aug	18	34.7	5h 05m	1.9	645	3m14s	28s	14.7%
2002-Jul	15	26.0	3h 40m	1.7	411	3m48s	32s	14.1%
2002-Jun	8	12.7	2h 11m	1.6	169	4m30s	47s	17.3%
2002-May	4	3.4	35m	0.8	60	3m21s	36s	17.7%

[A] A night is counted as being used if at least one image is obtained from dusk until dawn, the date being taken as the date at dusk.

[B] Hours spent imaging or the total session time is taken as the number of hours between the first and the last image obtained in each session, so doesn't count waiting for the CCD to cool down, focussing, warming the CCD up at the end of each session and other non-productive activities...

[C]Time CCD exposing is the length of time the CCD stutter is open, actively imaging objects

[D] Average session length is (Hours spent imaging / Nights used) or [B]/[C]

[F] Avg. time between exposures is the average time between the start of one exposure and the start of the next exposure and is affected by CCD image download times, clouds interrupting observing, human 'thinking' time etc.

[G] Average exposure length = (Time CCD exposing / Images acquired) = [C] / [E]

[H] Efficiency [G]/[F] shows how much of the time spent in a session was used actually collecting light and is calculated as the percentage [G]/[F] or [C]/[B]. Note the increase due to the CCD upgrade shortening image download times between August and September 2005.