Filter Wheels

There are two filter wheels in Clio placed just after the pupil stop. Each wheel is capable of holding 8 one inch filters. As of April 2014 the filter wheels contain the following filters. Listings below are listed in clockwise order from the home position, as seen from filter wheel 1.


NOTE: The wheel positions are not the same as the motor positions. To move the motor in a script, see the scripting page for the correct command.


Last updated: 2015/05/04:

Wheel 1 (motor 3)
  1. Blocked
  2. MKO M’
  3. 3.3 um filter (JDSU W03311-6E passband 3.12-3.53 um)
  4. Direct vision prism (narrow edge toward cold plate)
  5. 3.1 um filter (JDSU N03095-8E)
  6. MKO L’
  7. 3.9 micron filter (JDSU N039042-8E)
  8. PK50 long-wavelength (<2 um) blocker

Wheel 2 (motor 4)
  1. MKO J (Home)
  2. ND2 -- 0.1% transmissive ND (Janostech P/N FX90-0099)
  3. ND3 -- ~"4.4%" transmissive ND (Janostech P/N FX90-0098)
  4. Open
  5. Lspec (2.8-4.2um pass filter, for use with Prism)
  6. Brackett Gamma (2.166 um)
  7. Barr Ks
  8. "MKO" H (from Asahi)

J, H, Ks, and BrGamma are used with PK50 to provide long-wavelength blockage.


Field Stop Pupil Stop FW1 FW2 Camera Lens Collimator Lens
50um Pinhole f/21.5 Open MKO J f/21.5 3/37.7
Open M APP MKO M' 0.1% ND2 Pupil Imaging f/21.5
Narrow Slit L APP 3.3um 4% ND3 f/37.7
Medium Slit f/37.7 Prism Open

Wide Slit 3 hole NRM 3.1um Lspec

Rectrangle 6 hole NRM MKO L' Blocked



3.9um Barr Ks



PK50 "MKO" H

The associated text files for the filter transmission curves are in this tarball:

Download file "clio_filters_v3.tar.gz"

In Fall 2008, a 3.1-3.5 micron filter was added:


Around the same time, an Ice band filter was added:




New H-band filter as of 2014/03/14: (From Asahi Spectra)

Download file "Clio2_H_2014.png"

Data: Download file "H filter.xls"


New PK-50 long-wavelength blocker as of 2014/03/25: We believe we have the 2-mm one. This filter curve is in the box of Clio filters spares in the LCO clean room.



Photo of Filter Wheel 1 as of 2012/08/22:

Filter Wheel 1

Clockwise from red arrow: MKO J, Blocked (for darks), Open (home), MKO M', Barr M, Direct vision prism, 3.1um, Barr L'.

Dated Summer 2012.








Historical Filter Information: 2014A-2014B:

Wheel 1 (motor 3)

  1. Open (Home)
  2. MKO M’
  3. 3.3 um filter (JDSU W03311-6E passband 3.12-3.53 um)
  4. Direct vision prism (narrow edge toward cold plate)
  5. 3.1 um filter (JDSU N03095-8E)
  6. MKO L’
  7. 3.9 micron filter (JDSU N039042-8E)
  8. PK50 long-wavelength (<2 um) blocker

Wheel 2 (motor 4)
  1. MKO J (Home)
  2. ND2 -- 0.1% transmissive ND (Janostech P/N FX90-0099)
  3. ND3 -- ~"4.4%" transmissive ND (Janostech P/N FX90-0098)
  4. Open
  5. Lspec (2.8-4.2um pass filter, for use with Prism)
  6. Blocked
  7. Barr Ks
  8. "MKO" H (from Asahi)

3.4 micron filter (JDSU N03401-6E) was removed 2014-03-27 and placed in storage in LCO clean room. BK7 windows also removed from JHKs slots 2014-03-27, so instead use JHKs with PK50 from 2014A on.



Historical Filter Information: Comm1 (2012B) and Comm2 (2013A) :

Wheel 1

  1. Open (home)
  2. MKO M’
  3. Barr M
  4. Direct vision prism (narrow edge toward cold plate)
  5. 3.1 um filter (JDSU N03095-8E)
  6. MKO L’
  7. MKO J +uncoated 5mm thick BK7 window
  8. Blocked
Wheel 2
  1. 3.3 um filter (JDSU W03311-6E passband 3.12-3.53 um)
  2. 0.1% transmissive ND (Janostech P/N FX90-0099)
  3. ~1% transmissive ND (Janostech P/N FX90-0098)
  4. Open
  5. 3.4 micron filter (JDSU N03401-6E)
  6. 3.9 micron filter (JDSU N039042-8E)
  7. Barr Ks+uncoated 5mm thick BK7 window
  8. Barr H + Thorlabs AR-coated 5mm thick BK7 window