This page contains information on the weekly inspection of the WHT primary mirror.

Visual inspection of the primary mirror at WHT


 

Date

Weather in past period?

(rain, humidity, dust)

Appearance of

the primary

Reflectivity

Surface roughness

RMS

Action taken

Comments

Link to photo

Inspector's name

25 Feb 15 High cloud and possible rain in previous 2 nights Dusty all over with a few dozen water streaks crossing the dust vertically, mostly on lower half. No major exposure to rain. - - none To be measured and CO2 cleaned in the coming week.    Neil O'Mahony
8 Aug 14 Calima followed high thick high cloud. slight fog, similar to condensation, a pattern seen at high AoI from application of sponges during water wash. - - none To be measured and CO2 cleaned by 2 Sept. Fog    Neil O'Mahony
26 May 14 Period of high humidity Clean but with new drip marks, possibly there since wash in April - - none Drips    Neil O'Mahony
24 Feb 14 Period of high humidity Extensive water-borne dust stains, from rain and/or condensation - - Program a water washing (10 April) Water Stains    Neil O'Mahony
23 Aug 12 New calima espisode. Observing stopped due to thick high cloud. Same as on 01 Aug, slightly dustier. - - To be cleaned with CO2 once weather stabilises.    Neil O'Mahony
6 Aug 12 Calima, high cloud No new rain spots since 2 Aug wash. Old spots discernible. Long water drip marks under Nasmyth baffle. - - None 20120802
Far side washed, near side with rain spots
 
 Neil O'Mahony
14 Mar 12 calima and high cloud A light covering of small spots caused by rain containing calima dust. Also larger dribble marks (photo). 85.0% 49 Cleaned with CO2. Measurement afterwards. 1 and 2 Water dribble marks    Neil O'Mahony
2 Feb 12 N/A
Straight from Alum tank
Crescent shaped area ~1m wide in lower part (from AP3), half radius distance, where fresh aluminium appears different shade. Half a dozen Al 'drops'. No sign of Feb 2011 tool damage. 89.7% (IRIS) - None Shaded area attributed to cleaning marks. Reflectivity here (GTC IRIS) only 0.5% less. Scattering also lower.    Neil O'Mahony, Juerg Rey
26 Sept 11 Fault 19867
Rain on 22/9
A light covering of small spots caused by rain containing calima dust. 82.2% 81 Will clean with CO2 ASAP    Neil O'Mahony
17 Feb 11 Fault 19511 Spotted, despite washing 1 month previously. 3 small damage marks at 3 o'clock (AP3) ~30cm from edge. Microscope lens inspection suggests coating damage, metal deposits. Longer, shallow scratches in same area. 83.4% 66 none Possible substrate damage cannot be determined. Has not influenced decision to forego aluminization this year. anotated photo    Neil O'Mahony
26 Feb 08 high clouds, high humidity The spots and the stains are there. There are new stains on the right side (AP3) 83.0% 76.610 CO2 cleaning All the reflectivity, scattering and surface roughness have been improved    Tibor Agocs
13 Feb 08 high clouds, high humidity The spots and the stains are there. Apart from it the mirror is in a good state. 83.8% 77.375 none CO2 cleaning is necessary (today the humidity was too high)    Tibor Agocs
29 Oct 07 high clouds, high humidity, calima The spots and the stains are there. Apart from it the mirror is in a good state. 86.7% 49.140 none The results are almost the same as from the last measurements after the CO2 cleaning.    Tibor Agocs
04 Oct 07 high clouds, high humidity, calima The spots and the stains are there. 84.1% 61.996 CO2 cleaning All the reflectivity, scattering and surface roughness have been improved    Tibor Agocs & Neil O'Mahony
24 July 07 Strong calima last week The spots and the stains are there. Surface visibly dustier than in previous inspection. 87% 57.159 CO2 cleaning Surface dust noticeably improved, reflectivity too.    Tibor Agocs & Neil O'Mahony
22 May 07    high clouds, rain,  humidity, petals were left open on the 21th of May The spots and the stains are there 87.2% 44.0 none The reflectivity and the surface roughness is still good in contempt of the spots see below Tibor Agocs
24 April 07    high clouds, humidity The spots and the stains are there (see image) 87.3% 36.6 none The reflectivity and the surface roughness is really good in contempt of the spots spots

stains

Tibor Agocs
13 April 07    All kinds: dust, rain, high cloud, humidity Large water/dust spots all over. No water streaks.

Small opaque stains at 9 o'clock, 30-50 cm from the baffle. Looks like dirt falling from small distance (no splash).

N/A N/A CO2 cleaning after inspection Condensation or possibly light rain. 1 month since last inspection. photo4 Neil O'Mahony
13 March 07 humidity high on some days Clean. Two small drops (5-10 mm) at 6 o'clock N/A N/A none It seemed as some kind of liquid dropped down to the mirror photo3 Tibor Agocs
28 Feb 07 humidity high on Sat and Sun during the day Clean. The spots are still there. N/A N/A none The spots are probably because of the aluminising. photo2 Tibor Agocs

21 Feb 07

humidity (1/2 night) Clean. 3 or 4 black spots < 5mm N/A N/A Blowing, did not remove spot Oil? Too small to concern. photo1 Neil O'Mahony