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MOIRCS Stray Light Information Page

Current Status and the Update

This page is dedicated for sending the information about the current status of the stray light and the related updates by MOIRCS team to users.

  • 2006-08-22 update:
    The result of the stray-light blocking mechanism (SBM) installation has approved by Dr. Masahiko Hayashi, the director of the Subaru Telescope and Dr. Hiroshi Terada, the MOIRCS commissioning officer. Here we announce that the MOIRCS SBM refurbishment has successfully accomplished.
    The thermal-cut filter installation plan is still continuously going on. We will announce the progress through this homepage. If the filters deliver as planned, the installation will occur around October.

  • 2006-08-19 update:
    The stray-light blocking mechanism (SBM) movement test in cool condition has finished with no problem. The imaging test for SBM indicates that the level of the remaining stray light is now only 1-2% of its original level, which is consistent with the expectation for current SBM mechanism. The level of the remaining stray light is mostly well below the typical sky level, as shown below. Thus, the instrument team is well satisfied by the result of the refurbishment. The MOIRCS commissioning officer will assess the result soon, and then the final judgement for the refurbishment will officially be made.

Figures: (Left) The level of stray lights seen HK500 grizm spectra along x-axis before (top two lines: each indicates the cut at y=100--230 and y=1170--1300) and after the refurbishment (bottom two lines: near 0 and marged to one apparently). Shown here is the result for channel 2, with the exposure time of 300 seconds. (Right) The same as the left figure, but for zJ500 grism spectra.

Figures: The same as above figures, but only shows the data after refurbishment. The left panel shows the result for HK500 grism data (and right figure indicates the result for HK500 and zJ500, respectively. The data shown are for channel 2 and the exposures are 300 seconds for both panel. For reference, the typical sky count (measured the level between lines) under the same exposures are, 250 ADU for J, 160 ADU for H, and 400 to 800 ADU for K, under the 0".8-width slits (estimated from the actual sky data shown in the sky spectra page).

  • 2006-08-07 update:
    The stray-light blocking mechanism (SBM) has successfully installed on MOIRCS a few days ago! :-) Now MOIRCS is preparing for cooling down. Cooling process will be finished by next Monday. The mechanical test will start on that day.

  • 2006-08-05 update:
    A new version of the sky spectra has provided by the MOIRCS team (courtesy of Dr.Tokoku), so the old version is now updated to the new version. In the figure the level of stray light is now explicitly shown for the observers' convenience. Please check the sky spectra page.
    Also, the two-dimensional view of the stray lights are now available.

Figures: The "image" of the stray light in zJ500 grism. The figures to the left and right each represent the images of the chip 1 and chip 2, respectively.

Figures: The same as above, but for HK500 grism.

  • 2006-08-04 update:
    A revised version of the sky spectra (zJ500 grism) is now available. Note that this is the result for 0".3-width slit. The actual sky count will be proportional to the slit width used, while the stray light level remains constant. This mean that the stray light level is similar to the sky continuum level (between lines) in J band if we use 0.8"-width slit. The stray light will dominate the signal at the wavelength shorter than 11000 angstrom, where the residual of the light can be seen in the figure.
    The figure for HK500 will also come soon.

atlas_zJ500_200608h
(Click for larger version)

  • 2006-07-29 update:
    As you can guess from the sky spectra page, the level of the stray light in R500 grating is rather strong. We already started the refurbishment. Hardware installation to block stray light will occur in early August. And also, filters to suppress the affection of the stray light (thermal cut filter) have already planned to ship to Subaru soon. The filter for HK500 will hopefully be available in mid September. The filter for zJ500 (stray-light cut and order blocking) will be delayed.

The wavelength range of the thermal cut filter for HK500 is, cut-on: 1.3 +/- 0.010 micron, cut-off: 2.3 +/- 0.015 micron, with the slope < 3%.

Please make contact to the SS for more details.

Created by Ichi Tanaka