Informations for users


Documentation and general information


SPARC4 Observer Guider - PDF file


Table of suggested exposure times for dome flat-fields - pdf (1 page).

It is recommended to acquire flat-field images using the same operational mode of the scientific images.

Instrument FoV for Aladin - link.


Manual for VPN connection to OPD - link.


Scientific detectors Guide (Ixon Ultra 888 Hardware Guide 1.0) - link.


Performance sheets of the scientific detectors:


Southern SDSS photometric standards - link.


Spectral response for the four channels of SPARC4 in photometric mode - png file / csv file.


The SPARC4 team has used rich field and astrometry simple tools to calculate the plate scale and FoV for the photometric mode. The values are shown below:

Channel 1: plate scale = 0.3390 arcsec/pix; FoV = 5.79 arcmin.

Channel 2: plate scale = 0.3406 arcsec/pix; FoV = 5.81 arcmin.

Channel 3: plate scale = 0.3436 arcsec/pix; FoV = 5.86 arcmin.

Channel 4: plate scale = 0.3415 arcsec/pix; FoV = 5.83 arcmin.




Reduction software

SPARC4 data can be reduced using the Astropop software, developed by Julio C. N. Campagnolo et al., and the pipeline, developed by E. Martioli et al. They can be downloaded from the github pages below. They are python-based software and are fully operational, but in constant development and improvement.

https://github.com/sparc4-dev/astropop 

https://github.com/edermartioli/sparc4-pipeline

An IRAF package can also be found in the following link. However, it is not optimized for SPARC4 data.

https://github.com/claudiavr/pccdpack_inpe

 

Header problems


Images obtained using SPARC4 in the polarimetric mode can have wrong headers. Specifically, the keyword WPPOS, which can assume values from 1 to 16 and reflect the waveplate position, can be incorrect. This error is not present in all SPARC4 data sets. In all cases the SPARC4 team detected the problem, the data sequence was correct, i.e., it was a software problem and not a problem in the positioning of the waveplate. 


For those who use the SPARC4 pipeline, the problem can be solved using the following routine:


sparc4_fix_wppos.py,


which can be found in the tools directory of the SPARC4 pipeline distribution. This routine does not work correctly if the polarimetric sequence was interrupted. Use it with care. 


Some examples of the use of this routine are shown below.


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs1/20241120/20241120_s4c1_000663_dflat.fits" --object="DOMEFLAT" --ncycles=1 --nframes=20 --npos=16 --channel=1


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs2/20241120/20241120_s4c2_001353_dflat.fits" --object="DOMEFLAT" --ncycles=1 --nframes=50 --npos=16 --channel=2


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs3/20241120/20241120_s4c3_001353_dflat.fits" --object="DOMEFLAT" --ncycles=1 --nframes=50 --npos=16 --channel=3


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs4/20241120/20241120_s4c4_001303_dflat.fits" --object="DOMEFLAT" --ncycles=1 --nframes=50 --npos=16 --channel=4


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs1/20241120/20241120_s4c1_001040_stdpol.fits" --ncycles=4 --nframes=1 --npos=16 --channel=1


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs2/20241120/20241120_s4c2_002210_stdpol.fits" --ncycles=4 --nframes=1 --npos=16 --channel=2


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs3/20241120/20241120_s4c3_002210_stdpol.fits" --ncycles=4 --nframes=1 --npos=16 --channel=3


python tools/sparc4_fix_wppos.py --datadir="/home/sparc4/data/" --night="20241120" --firstimage="/home/sparc4/data//sparc4acs4/20241120/20241120_s4c4_002160_stdpol.fits" --ncycles=4 --nframes=1 --npos=16 --channel=4


The problem should be solved by Dec. 2024. Please let us know (writing to opd.suporte@lna.br) if you detect this problem in data obtained after (including) 2024 Dec.



Documentation for observatory staff


SPARC4 Initialization Manual (in portuguese) - PDF file - Version 20240529


Manual for installation in the telescope (in portuguese) - PDF file



Operation with filters


SPARC4 is designed to support an additional filter in each channel. However, this operational mode is not yet comissioned and therefore it is not going to be offered in 2025A. On the other hand, SPARC4 team and LNA staff are working to comission this mode during 2024B and 2025A. See this call for acquisition of filters done by LNA.


The installation of the filter is done manually and it should be done during day. The filters should be circular with a diameter of 40 mm. The maximum width is 5 mm.




Updated: 10 Apr 2025