PN.S Halpha Camera

why build a third arm for the PNS?

checklist (archival)

document review 2004

Following minor modifications to the position of the optics to allow for the dichroic to be placed, the current version is now V_18 (produced September 1998). A ZEMAX file is on the project page. Removal of the dichroic causes a simple lateral shift of the collimated beam. At our request Damien Jones has placed the grating assembly mid-way between the shifted and unshifted position.

current status

camera acceptance tests at RSAA Travel Log - Legacy of the fires

first tests at LPO

second tests at LPO

first light image Dec 2007
details: 25 sec image in the narrow filter, seeing 1.1 arcsec

dichroic page

Postscript and Autocad files are on the project page (corresponding GIFs are in image gallery).

  1. DICHROIC
  2. OPTICS
    • A first-pass design, based on the [O III] camera, was produced as part of the PNS-3 project by Damien Jones. Some optimisation and adjustment is required.
    • New design (2004) - see the optics page

  3. MECHANICAL WORK
    • Fabrication, focussing mechanism, and interfacing

  4. CONTROLLER
  5. MECHANICAL WORK
    • Fabrication, focussing mechanism, and interfacing

  6. CCD CAMERA
    • One early idea was to purchase a commercial camera, perhaps with a peltier-cooled CCD. In the end we were able to use a third ING detector, usually a Marconi.

      For interest here is some archival information on commercial options
      • Below I have used a quote from Apogee for a 14-bit camera based on a cooled Thomson 7899 2048x2048 (14 um) chip, best cosmetic grade, but this is front-illuminated (QE=35%). They do have a back-illuminated chip (1024x1024 x 24um) with QE=85%.
      • Nitrogen-cooled units are available commercially from Roper Scientific (formerly Princeton Instruments) with agents in NL
  7. FILTERS
  8. BUDGET ($A)
    Dichroic: mechanical construction 7,700 (Estimate 6/12/2001)
    Dichroic: optics 8,000 (Estimate 6/12/2001 - see also dichroic page
    Dichroic: coating 3,000 (Estimate 6/12/2001)
    Camera: final design etc 5,280 (Estimate 10/1/2002 by Prime Optics) new estimate
    Camera: optics 18,434 (Estimate 11/98, check 12,000 commercial quote)
    Camera: coating 7,000 (Estimate 6/12/2001 - see also here)
    Mechanical detailing and construction 10,000 (Estimate 6/12/2001) new estimate
    Focus module construction 6,000 (Estimate 6/12/2001)
    Three H Filters, total 98,000 (BARR quote - see filters for latest)
    Continuum Filters, each 12,000 (wide, does not need to have high transmission)
    Filter wheel/flipper 10,000 (guess)
    CCD camera 92,000 (Apogee AP16E with 4kx4kx9um grade 1 Kodak chip, QE 65%, quote 8/1/2002)
    Extra shutter, if reqd -- not required with above-mentioned CCD
    Assembly and test 4,000
    Total (approx) 282,000

Trip by ND to RSAA (Stromlo) for acceptance testing 15-20 May 2006


Remnants of the 2003 fire
RSAA webcam



note that the "twisted wreck" at bottom left is not a result
of the fire and is in fact the future home of the workshops!)





New fires: the policy of backburning created amazing, and sometimes frightening scenes.






 Previous work on the H-alpha camera

 PNS on telescope




The New Controller


ND brought the new controller with him in his hand luggage. (note: the casing and some of the interior hardware has since been replaced so what we call the V2 controller looks completely different) is required for the extra motors which have been implemented, as well as for the serial-controlled, iris-type camera shutter. The controller was partially tested, and then left at RSAA, whence it will be shipped directly to La Palma.



Optical tests in the RSAA workshops:



Damien Jones (left), Gabe Bloxham (right)


Some minor mechanical issues, such as removal of paint to ensure accurate alignment


dichroic mirror to separate OIII/H-alpha

(a) Insertion of the dichroic



A series of photos to illustrate how to insert the dichroic mirror. Note that three equal-sized blocks are required in the last stages.





(b) On-axis optics - the camera is of course designed to work with the PNS collimator and therefore could not be tested directly at RSAA since the collimator is on La Palma. Instead we tested the on-axis behaviour, with off-axis tests postponed until the camera is mounted on the PNS.


Although the optical quality was somewhat degrated by the quality of the collimator we obtained images of less than 10 microns diameter, as predicted by the designer. The CCD pixels were too coarse to accurately measure such small images. The image "budget" is 3 micron for the pinhole after demagnification (1/3), 3 micron for the diffraction limit of the optics, and 5.5 micron for the ray-tracing results - an r.m.s. of 6.9 micron, consistent with the measurements. therefore could not be tested directly at RSAA since the collimator is on La Palma. Instead we tested the on-axis behaviour, with off-axis tests postponed until the camera is mounted on the PNS.



(c) Filter changer - Inserting both filters

We were able to move the filters in and out using the new controller, and were able to open and close the iris shutter on command via a serial port. The controller needs further software development, since there needs to be sufficient "intelligence" for the one filter to be moved out of the way before the next filter is moved in. Final checks were done with the filters in place.



(d) The wide-band filter showed no anomalies but the narrow-band H-alpha filter appeared to produce multiple images, as can been seen in the images below. This was such a profound effect that it was taken to be the result of multiple reflections (as is quite possible giving the structure of such filter. It took a day before we realised that we were looking at a huge degree of astigmatism (in the two photos you can see the effect of moving the focus, which rotates the pattern). This is a dead filter!







Document date: January 4, 2004 Last updated ND 1/6/2006