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Field of View

'Alopeke and Zorro have two sets of optics which allow selecting between "Speckle" mode and "Wide-Field" mode. Both modes slightly underfill the detector resulting in circular fields-of-view.

The diameter of the vignetted 'Alopeke wide-field is ~60", however, the diameter of the unvignetted 'Alopeke wide-field is ~35".

Speckle Wide-Field
Field of View 6.7" 60"
Camera Blue Red Blue Red
'Alopeke Pixel Size 0.00992" 0.01095" ~0.0725"
Zorro Pixel Size 0.00991" 0.01093" ~0.0725"
'Alopeke Vignetting
Zorro Vignetting
Speckle mode Wide-Field mode


Final results from the 'Alopeke and Zorro commissioning are still pending, but the speckle imaging sensitivity is expected to be similar to DSSI. Please see the DSSI Sensitivity web page for planning purposes.

Additionally, the following figure from Matson, Howell and Ciardi (2019), reproduced with permission of the authors, shows the 5-sigma detection limit curves for 'Alopeke.  Stellar companions with a separation and delta magnitude that fall below a given curve are detectable with speckle imaging. Note how the contrast for 'Alopeke is slightly better than DSSI, mostly given the improvement in the detectors. Zorro curves are expected to be very similar.

'Alopeke/Zorro sensitivity curve

Guiding Options

'Alopeke and Zorro use the Gemini peripheral wavefront sensor PWFS2 for guiding. PWFS2 operates at optical wavelengths and can guide on stars as close as 4' and as far as 7' from the science target. Guide star selection is done automatically by the Observing Tool, although it is recommended that users verify the guide stars, rejecting extended object and spurious catalog entries.