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Selecting Filters

From the Main Menu of the TCS.

  • 5 GAM Menu
  • 1 Set Motor Position
  • Motor: 3
  • Position: 1 to 6, depending on filter required as listed above
  • Any Changes: N

After about 30 seconds or less, the filter wheel will have rotated into position. The status of the filter wheel is given in the lower left box on the TCS monitor. It will read M3=# and the number should equal the one you selected. The exception is for filter 1, which is selected as filter 1 but is reported as 0. Ask DFM about that one.

Wide-Band Filters

We have the standard astronomical series of filters: U-B-V-R-I. When in use, please keep the wide-band filters in the filter wheel position listed below:

Filter Filter Wheel Position Spectral Range Peak Transmission Range Width
Clear 1 2900 – 8500 98% 5600
Ultraviolet 2 3100 – 3900 65% 800
Blue 3 3800 – 4800 70% 1000
Visible 4 4800 – 5800 80% 1000
Red 5 5300 – 7000 80% 1700
Infrared 6 7200 – 10040 90% 2800

Narrow-Band Filters

There are 20 narrowband filters and each has a full width of 10 nm.

These are the filter’s central wavelength in nm

OII H beta/OIII H alpha
380 486 656
390 490 660
400 500 670
410 510 680
520 690
530 700
540 710
550 720

The filters are 50 mm circular interference filters. Peak transmission in the bandwidth is about 70% and transmission outside the bandwidth is 10-4.

Location of the Filters

The narrow-band filters and wide-band filters are located in two white boxes with orange labels on them in the first cabinet from the door to the control room. There is a filter installation tool (to put in and take out the narrow-band filters filters), and the metal filter holders. The filters themselves come in plastic cases in small square boxes. There should also be a box of purple nitrile powderless gloves in the same cabinet (if there is not, Please tell someone).


Preparing the Narrow-Band Filters for Use

  1. Put on a pair of purple nitrile gloves; it is very important to wear them whenever handling the filters because hand oils will destroy the filter.
  2. Find the desired filter in the white box. There are labels on the side of the filter box and also printed on the side of the filters; the first 3 numbers after P/N: gives the wavelength in nanometers.
    • ex. P/N: 656FS10-50 is the label for the H alpha 656 filter.
  3. Use a phillips head screwdriver to take the 3 screws in the filter holders out.
    • There are 6 metal filter holders for the narrow band filters. The filter wheel holds square filters, however, the narrow band filters are round. These holders allow the narrow band filters to be placed securely in the filter wheel. The metal holders have 4 holes, but only 3 screws holding the two pieces together. The last hole is larger than the other 3 and used for the installation tool.
  4. Take the top piece off and put the filter into the bottom piece. One side of the filter is reflective and the other transparent; make sure the reflective side is face up in the holder.
  5. Put the top piece on, replace the 3 screws in the opening they came out of.
  6. Screw the end of the tool in the hole. The tool is needed to put the filters in the wheel because it is a tight fit.

Follow these instructions for inserting and removing filters from the filter wheel.