MOIRCS Information for Imaging Mode

How To Make an OPE File for Imaging Observation

Please read the following documents before your observation.

Manual and sample OPE files (for imaging observation)

Description of an OPE file: Guide to Observing with MOIRCS [ Word ] [ PDF ] (Last update: 2006-04-11)
Sample OPE file after the chip-1 replacement on Nov 2007: download here. (UNIX or Linux only!! -- Last update: 2008-04-20)

Optical Distortion

The distortion of the MOIRCS optics is expressed well by the third-order polynomial as a function of the distance from the optcal center (xc=858, yc=1034 for chip 1, xc=1178, yc=1012 for chip 2). The distortion coefficients will change every time when we execute the warm-up / cool-down process for engineering or when we move the internal focus adjustment system. The date of occurence after the open use is as follows.

If you need the geotran database file (for IRAF) for correcting distortion, please contact to the SS.

Stray Light from Nearby Bright Stars

If your observing field is close to very bright (JHK < 1 mag) stars, the data may suffer from a significant contamination by that stars, like the examples below. It is caused by the interferred stellar lights that come through the side of the secondary mirror. As the secondary mirror does not have a blocking buffle to suppress it (or, we cannot put it as it emits strong thermal emission), it is currently very difficult to eliminate it. The light tends to contaminate the field when the bright star is located between 2.5 to 0.5 degrees from the target. As the pattern is localized in the focal plane, it is not always happen even if the star is located in that range.

We strongly recommend to check whether there are such bright stars or not before the observation. If there is such a star within 2.5-0.5 degree from your target, please prepare the backup targets beforehand.

The Website below (VizieR) may be useful for the check.

VizieR -- "2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)"
Put the target coordinate, and set 2.5 degree Radius to "Target Dimension" tab. You can add the magnitude constraint to JHK < 2.

Affection of Moon for Imaging Mode

The affection of th Moon to the background level in near infrared is generally smaller than in optical wavelength. But the sky tend to be brighter than dark night a bit, especially in bluer band. The affection is large when there is a cirrus in the sky.

On bright night we checked how the background level go up with the distance from the Moon. The figure below is the result of our experiment. In the figure, plus marks at >30deg is the reference sky magnitude that are measured far away from the moon. Clearly, the rise of sky level is negligible until ~15 degrees. At 10 degree a clear affection is observed. We also saw a scattered pattern in background at <10 degree.

As the AutoGuide is operated in R-band wavelength, the affection of the moon is serious. Autoguider failed automatic sky estimation at 15degrees. If the observation uses the Autoguider, <20 degree from the moon may be with high risk of AG failure.

In conclusion, the affection of the moon may be negligible if your targets are away from the moon by ~15 degrees or more.

Flat Fielding

The dome flat in J band shows a tilt along x direction with a level of ~6 %. In H-band a slimilar level of tilt is also suspected. These tilt pattern should be removed from the raw dome data using the sky flat. On the other hand, the sky flat generally contain some level (< a few %) of affection by the fringe pattern caused by filter substrate.

If the sky during an exposure varies rapidly due to cloulds etc, you will see a tilt pattern at each detector quadrant on the image. It is the artificial pattern caused by the CDS readout method. If such pattern appears frequently and strongly on your data, the accuracy of the sky flat by these dataset will become poor, though it depends on the level of tilt patterns on your dataset (low-level pattern is usually seen). We recommend to use the domeflat as well as the sky flat if the sky changes significantly during your observation.

User Filters

We have been accepting the user filters since S07A. However, the number of vacant slot on filter turret is VERY LIMITED (e.g. no vacancy during S07B period). MOIRCS filters are cooled to 120K in the main dewer. So we have to do the thermal cycle for whole system to install the filters. Usually it takes nearly 1 month. Therefore, the filter install schedule strongly depends on the scheduling. Although we will consider it as best as we can, we can not guarantee the user filter to be install in MOIRCS by the requested date. Users planning to make your custom filters should first make contact to Support Astronomer for filter specification. Currently the number of vacant turret slot is very limited. The user filter acceptance policy can be found here (Microsoft Word document).

Data Reduction Packages

"MCSRED", an IRAF-based data reduction package, is being developed by Ichi Tanaka. You can download the package from the website below.

MCSRED public homepage

"SIMPLE", an IDL-based data reduction package by Dr. Wei-Hao Wang, is now open to public.
One of the great feature in the package is that it includes the fringe-supression software invented by him. Those who have annoyed by the fringes shoud try.
You can download the package from the website below.

SIMPLE Imaging and Mosaicking Pipeline Website

* IT greatly appreciates the author for his great contribution for MOIRCS users!

Questions/comments are welcomed. Please contact to each author.

Please note that all data on these pages are subject to change as the evaluation of the performance of MOIRCS progresses.

Created by Yuka Katsuno Uchimoto (Feb 2006)
Revised by Ichi Tanaka (update: 2008-02-05)