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The 2-channel focal reducer (FoReRo2): a new observing facility for the 2-meter telescope
Tanyu Bonev
Institute of Astronomy
Bulgarian Academy of Sciences
1. Optical parameters
2. Mechanical design
3. Modes of observations with examples
4. Conclusions
16 m Focal length 5.6 m
f/8 f ratio f/2.8
0.31 arcsec/px Scale (1 px = 0.024 mm) 0.88 arcsec/px
FoReRo2: Modes of Observations
1. Broadband imaging 2. Narrowband imaging 3. Long slit spectroscopy4. Fabry-Perot imaging5. Imaging polarimetry
FoReRo2: Broad band imaging and photometry
Available Filters: U, B, V, R, I
Example: Landolt field PG1633+099, filter V, Exposure = 15 sec
FoReRo2: long slit spectrography
Blue Channel Red Channel
600 lines/mm 300 lines/mm
0.3 nm/px 0.5 nm/px
Long slit:
Length: covers the full FOV
Width: 110 microns = 1.5 arcsec
Grating prisms (grisms)
< 445 nm > 490 nm
FoReRo2: long slit spectrography
Blue Channel Red Channel
FoReRo2: low dispersion spectra
< 445 nm > 490 nm
Blue Channel Red Channel
FoReRo2: Fabry-Perot Imaging
Name Kind Useful
range
nm
Reference wavelength
nm
Free spectral range
mounted
Quensgate visual
tunable 410 - 700 627 5.8 Before beamsplitter
Quensgate blue
tunable 355 – 510 374.7 4.3 Before beamsplitter
CSIRO visual
Fixed airgap
410-700 620 0.21 Before beamsplitter
CSIRO red Fused silica
450-700 615 0.26 Red arm
CSIRO blue
Fused silica
350-530 400 0.17 Blue arm
FoReRo2: Fabry-Perot Imaging
interferogram of
[OI] 6300 in comet Q4 (NEAT), obtained on May 23, 2004.
Interference filter + 500 micron Fabry-Perot etalon in the red channel.
Exposure: 600 sec
[OI] 6300 night sky emission
FoReRo2: Imaging polarimetry mode
Comet Q4 (NEAT)Optical arrangement
+45o
0o
90o
-45o
FoReRo2: Narrow band imaging
Part of the available interference filters
Blue channel Red channel
Filters for cometary observations
390 nm - CN 406 nm - C3 426 nm - CO+ 443 nm - Blue Continuum …
590 nm - Na
616 nm - H2O+
630 nm – [OI]
642 nm – Red
Continuum …
Filters of common
interest
[SIII] 3722
[SII] 4069, 4076
[OIII] 5007 …
[OI] - 6300
Halpha - 6563
[SII] 6716, 6731 …
Narrow band imaging of comet Q4 (NEAT)
On-line, 616 nm, H2O+ Off-line, 642 nm, Continuum
- k *
Comet Q4 (NEAT), May 26, 2004 H2O+ ions in the near nucleus region
Comet Q4 (NEAT), May 26, 2004
Dynamics of the
H2O+ ions in the near
nucleus region
11 frames
x 300 sec exposure
Total time of the sequence < 1 h
FoReRo2: Conclusions
• The 2-channel focal reducer increases the power of the 2-meter telescope by:
1. Changing the f ratio from f/8 to f/2.82. Allowing simultaneous data acquisition in two spectral
ranges
• The 2-channel focal reducer offers several modes of observations:
1. Broad band imaging2. Narrow band imaging3. Long slit spectroscopy4. Fabry-Perot imaging5. Imaging polarimetry