M1 and M2 reflectivity measurements using IRIS
M1 and M2 reflectivity 2023
The M1 and M2 were re-aluminised June 8th 2023 at WHT.
The Aluminising Report states:
- The reflectivity result is close to range of variations observed in previous aluminizations
- Scattering is minimal, indicating high quality finish of substrate, scratches notwithstanding.
Old reflectivity measurements
M1 and M2 reflectivity 2018
The M1 was washed on May 2015 and again November 2016. The plot below shows the
fresh aluminum literature reflectivity (black line),
the 2014 reflectivity before (magenta) and
after realuminisation (green) and reflectivity after wet washing, May 2015
(blue) and November 2016.
The briefcase
indicates test plates which are kept in a briefcase in the mechanics room.
These measurements were taken with the ING reflectometer.
A comment from Neil O'Mahony (the ING Optics Technician)
"Your scattering is also as good as we've got in the past.
So I think you can be happy with your cleaning technique, especially in the
extreme bands"
November 2018: "Compared with measurements 2 years ago, reflectivity
is down by less than 1% in blue, improved in red by about half of one percent.
Scattering losses show a similar trend from blue to red,
also observed in aged coatings at ING."
M1 and M2 reflectivity 2014
The M1 and M2 were realuminised on June 2014 (previously July 2009).
Date |
Reflectivity % 4700Å |
Reflectivity % 5300Å |
Reflectivity % 6500Å |
Reflectivity % 8800Å |
Mirror |
Device |
Comment |
27.03.2014 |
89.0+-0.4 |
88.7+-0.3 |
87.7+-0.4 |
82.7+-0.2 |
M1 |
TNG |
M1 washing 18.03.2014 |
20.06.2013 |
89.6+-0.4 |
89.5+-0.4 |
88.0+-0.4 |
83.3+-0.3 |
M1 |
TNG |
after washing |
20.06.2013 |
86.7+-0.6 |
86.5+-0.5 |
85.5+-0.4 |
80.3+-0.3 |
M1 |
TNG |
before washing |
20.07.2012 |
88.2+-0.5 |
87.7+-0.4 |
86.4+-0.3 |
81.2+-0.6 |
M1 |
TNG |
|
02.12.2011 |
89.1+-0.6 |
88.5+-0.4 |
87.4+-0.3 |
81.8+-0.3 |
M1 |
LT |
|
02.11.2009 |
88.6+-0.2 |
87.5+-0.2 |
85.7+-0.2 |
79.7+-0.3 |
M1 |
LT |
|
|
02.12.2011 |
91.0 |
90.0 |
87.8 |
82.2 |
M2 |
LT |
|
02.11.2009 |
91.6 |
90.5 |
88.6 |
82.6 |
M2 |
LT |
|
Scattering (6700Å)
|
Date |
BRDF -45 |
BRDF -15 |
BRDF +2 |
Mirror |
Device |
Comment |
27.03.2014 |
5.1e-4 |
1.1e-2 |
1.0 |
M1 |
TNG |
TIS=1.5% |
20.06.2013 |
5.4e-4 |
1.0e-2 |
0.8 |
M1 |
TNG |
TIS=1.7% |
20.07.2012 |
2.2e-3 |
2.8e-2 |
1.8 |
M1 |
TNG |
TIS=3.4% |
02.11.2009 |
3.2e-3 |
1.8e-2 |
2.1e-2 |
M1 |
LT |
|
|