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 and mechanical design

2. Modes of observations with examples

3. 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. Broad band imaging 2. Narrow band 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