1 Getting Started

Create a quick summary of all files:

makelog

Create a folder named after our standard star and copy into it the star spectra, neon lamp, and flat lamp files:

mkdir BD+25d4655
cp `cat .log | grep 20200721 | grep '1024 200' | grep BD+25d4655 | awk '{print$3}'` BD+25d4655/

Create the following lists:

Star spectra: list.sp
FeAr lamp spectra: FeAr list.neon
Halogen lamp spectra: Halogen list.flat

cat .log | grep 100.0 | awk '{print$3}' > list.sp
cat .log | grep Fe-Ar | awk '{print$3}' > list.neon
cat .log | grep Halogen | awk '{print$3}' > list.flat

2 Initial Spectrum Reduction

2.1 Bias Averaging

Create a folder for spectral bias files and copy them in:

mkdir biassp
cp `cat .log | grep '1024 200' | grep bias | grep 0.0000 | grep -v flat | awk '{print$3}'` biassp/

Check the bias frames before combining:

cd biassp/
ls *.fit > list.biassp
gedit list.biassp & # optional to remove "bad" bias frames
ds9 &
xs `cat list.biassp`

Before averaging, we must fix FITS header keys because the GAIN value is incorrect. Run:

../bin/repair_tfosc_andor_keys *.fit

Combine bias frames using median in IRAF (noao.imred.ccdred):

epar zerocombine
input=@list.biassp
output=Biassp2.fits
combine=median

Run:go, then copy the result:

Скопируем Biassp2.fits в папку ../Caldata

cp Biassp2.fits ../Caldata/

Go to BD+25d4655 and fix header keys again:

../bin/repair_tfosc_andor_keys *.fit

2.2 Subtracting the Averaged Bias

Subtract the averaged bias from all spectra:

../bin/process *.fit | si

2.3 Averaging Flat Field Frames

In IRAF, open noao.imred.ccdred:

epar combine
input=@list.flat
output=flat
combine=average

Run :go

2.4 Averaging FeAr Lamp Spectra

In IRAF, open noao.imred.ccdred:

epar combine
input=@list.neon
output=neon
combine=average

2.5 Creating the Response Function

In IRAF, open twodspec.longslit:

epar response
calibrat=flat
normaliz=flat
response=nflat

Run :go

2.6 Dividing Star Spectra by Flat Field

In IRAF, open imred.ccdred:

epar ccdproc
images=@list.sp
flatcor=yes
flat=nflat.fits

Run :go

2.7 Wavelength Calibration

In IRAF, open twodspec.longslit

epar identify
images=neon.fits
section=middle line
coordli=linelists$idhenear.dat
cradius=8

epar reidentify
cradius=8
coordli=linelists$idhenear.dat
referenc=neon
images=neon

epar fitcoords
images=neon

Remove bad points with d p

y y r

y``r``r

Everything fits well.

2.8 Applying Wavelength Calibration to Star Spectra

Transform the spectra using the solution from fitcoords:

epar transform
input=@list.sp
output=tr//@list.sp
fitnames=neon

Run :go

Note: in the database folder, files fcfear, idfear are created even though fitnames=fear

2.9 Cosmic Ray Removal

 ~uskov/runTmp/do_cleancrspec trfosc025*.fit

2.10 Aligning Star Spectra for Stacking

In IRAF package iki, use the alignspectra command:

epar alignspec
images=tr//@list.sp
refimage=trfosc0254.fit
prefix=rg
imreg=[160:670,85:145] # region used for alignment

For BTA data, a better region is [500:3000, 300:700]

2.11 Combining Aligned Spectra

In IRAF imred.ccdred:

combine input=rgtr//@list.sp output=sp.fits

3 Extracting the Spectrum

In IRAF twodspec.apextract:

apall input=sp.fits output=sp.ms.fits

Key controls:

m create and center a new aperture
d delete aperture
l set left boundary
u set right boundary
b enter background mode
- zdelete background region
- sset left then right boundary
- qquit background mode
:o 3 set background fit order to 3
frefit background

Result: extracted star spectrum:

4 Flux Calibration

Create the standard star file std.fits using package noao.onedspec:

epar standard
input=sp.ms.fits 
output=std.fits 
star=mbd25d4655
caldir=./

Apply DQE and extinction correction:

epar sensfunc 
standard=std.fits  
sensitiv=sens

Now convert the spectrum to absolute fluxes:

epar calibrate 
input=sp.ms.fits 
output=sp.ms.c.fits
sensiti=sens.0001.fits

5 Notation

flat – flat field frame
nflat – normalized flat field frame
neon – lamp line spectra
sp - final 2D spectrum, corrected for optical distortions and cosmic rays
sp.ms.fits – extracted 1D spectrum
sp.ms.c.fits — 1D spectrum calibrated in flux
@list.sp — list of spectra
@list.neon —list of arc lamp frames
@list.flat — list of flat lamp frames