Frequently Asked Questions

[Expand All]

[Expand All]

Observation Preparation


Frequently Asked Questions related to NACO and the NAOS-PS

  • When using the NAOS-PS is it necessary to set both the 'Dichroic' and the WFS, or even just one?
  • No. In general, the user will leave these options to FREE (see next questions). However, it is now possible to force the use of a dichroic, a WFS, or both. Usually one does not want to do that, but there may be a good reason to want it done. For instance, to observe an extremely red target, without the use of the Neutral Density filter for CONICA, one may select the N90C10 dichroic so that transmission to CONICA is only ~10%. It is possible to use this dichroic with both WFS.
  • Can I select a wrong configuration with the NAOS-PS?
  • You cannot. The Preparation Software server will allow only good configurations when one tries to optimize.
  • How does the NAOS-PS server select the dichroic when I choose the 'FREE' option?
  • First, the PS server will select from only those dichroics compatible with the selected CONICA filter. Then the PS server will return the configuration of dichroic and WFS giving the maximum Strehl ratio. This means that since the selected configuration depends on the flux incident on the WFS, the PS server will never choose a dichroic which favors CONICA (like the N20C80). To use such a dichoic, one must select it explicitly.
  • How can I get the NAOS-PS to work for reference objects that are fainter than V=16.5?
  • You cannot. Although we can sometimes close the loop on objects fainter than V=16.5, it is on the border of feasibility. If you wish to use objects fainter than V=16.5 as references, then use 16.5 as the magnitude of the reference and put a note in your README file that you have done this. We will try to close the loop, but we cannot guarantee that we will be successful. Furthermore, the Strehl ratio the PS then predicts will be an overestimate. The absolute limit is V=18.
  • How can I get NAOS-PS to work for reference objects that are further than 55 arcseconds from the target?
  • You cannot. You can cheat by entering a target co-ordinate which keeps your target in the field of view. However, the Strehl ratio the PS then predicts is an overestimate. Additionally, you will have to pay very special attention to where the object may land on the array and this will depend on the camera you choose to use and the offset sequence of the template. If you choose this method, we cannot guarantee the success of your observations.
  • What is the minimum possible transmission to CONICA to use?
  • It is 5.1% with N90C10 and filter Ks, 4.2% with N90C10 and filter H, 3.7% with N90C10 and filter J. To reduce the transmission to CONICA if the object is too bright, two neutral density filters are available.
  • I would like to generate automatically .aocfg files without using the Preparation Software tool...
  • You cannot. Users must use the Preparation Software to generate correct .aocfg files.
  • I forgot to save my NAOS-PS session (.jnps file), I only have the .aocfg file and I would like to modify it without doing all again...
  • You cannot modify the .aocfg file manually, because it will become corrupted. But there is a solution. Suppose your file is named saturn.aocfg. Copy it to saturn.jnps and then load this file into the Preparation Software. Don't forget to redo the optimization before you export to P2PP if you apply any change. That's it.
  • I would like to use the Laser Guide Star even though I didn't propose to use it. Is that possible?
  • Sorry, but this is not possible. If you want to use the Laser Guide Star Facility you must specify it in the proposal.

Instrument selector

On this page: