Banner
Home · Search · About ING · Astronomy · Public Information · Engineering

Changing The Filters

The JKT has a filter wheel with a capacity for loading 6 filters. The filters that are currently loaded are displayed on the white board in the control room. Each filter is described by its waveband and a number. All filters at the ING are included in the filter database. It is useful to consult this database when planning which filters to use.

An important thing to note is that when handling filters special gloves are recommended in order to avoid putting fingerprints on them.

Removing The Filter Wheel

To remove the filter wheel from the telescope, follow the procedure below:

  1. Raise the dome floor (using the control pad).
  2. Open the black bag via the velcro strip.
  3. Open the door on the filter wheel.
  4. Loosen the white screw underneath the filter wheel.
  5. Push in the button underneath the filter wheel.
  6. Slowly remove the filter wheel using the handle, being careful to avoid touching the filters directly or knocking them.
  7. Take the filter wheel to the "Plate Change" room.

In The "Plate Change" Room

You will find the filters that you need in the JKT filter cabinet in this room. For each filter that you need to change, carry out the following:

  1. Unscrew the little black "holders" and remove the black plastic rectangle.
  2. Carefully remove the filter by its edges, and place it wrapped up in the correct box.
  3. Place the box in the filter cabinet (remembering not to place U filters inside the plastic storage case).
  4. Unpack the required filter and, again handling it only by its edges, place it in the correct slot on the filter wheel.
  5. Place a black plastic rectangle around the filter (a thin one for a thin filter and a thick one for a thick filter).
  6. Screw down the black "holders" to hold the filter in place. Note that the larger "holders" go on the inner screws and the smaller "holders" go on the outer screws. Also note that a thin filter requires the "holders" to be screwed on thickest bit first and vice versa for a thick filter.
  7. Finally, stick tape around the filter to prevent light leaks. The tape should only be in contact with the filter wheel and the black plastic rectangle, not the filter itself.

Replacing The Filter Wheel

To replace the filter wheel in the telescope, follow the procedure below:

  1. Test that the air pump is clean by blowing air on your hand or some white paper. Then blow air over the filters in the filter wheel to remove any loose dust particles.
  2. Slide the filter wheel carefully back into its slot.
  3. Screw in the white screw underneath the filter wheel.
  4. Push in the filter wheel handle.
  5. Close the door on the filter wheel.
  6. Close the black bag via the velcro strip.
  7. Lower the dome floor (using the control pad).

Updating The Filter Wheel Contents In The Control Room

On the white board in the control room is the list of filters currently loaded in the filter wheel. Amend this list as appropriate.

Updating The Filter Wheel Contents in The ICS

To update the filter information in the ICS, type:

SYS>changejag

A window will appear. Click on "View wheel contents" under the heading "MAINFILT". Another window with a table will now appear listing the filters loaded in the filter wheel and their properties. Edit the entries in this table as appropriate. You may require information that may be found from the filter database. When you have finished the editing, click on "Calculate" and then "Save changes". Click "Yes" at the next window and then click "Exit". Now in the first window that appeared, click "Save changes" and then "Exit". Finally, on the ICS, type:

SYS>zeroset mainfilt

Updating The Filter Database

You must also update the filter database as follows. Open an xterm and login to the machine you usually use. Now type:

$>/data/quality/filter/filter.script

This command runs a program which prompts you for answers. At the menu always choose (1) to change an entry in the filter database and when you have finished, choose (5) from this menu.

Back To Contents

Home · Search · About ING · Astronomy · Public Information · Engineering
ING Logo

Last Updated: 10 Nov. 2000
Dan Bramich dmb@ing.iac.es