Evaluation of seeing on a 62-cm mirror

Iye, Masanori; Noguchi, T.; Torii, Yasuo; Mikami, Yoshitaka; Ando, Hirokazu

doi:10.1086/132870

Cited by 24 publications

(8 citation statements)

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“…Our fit predicts that we obtain an additional 41.6 ± 1.2 nm of wavefront error when M1 is 3 • C warmer than the outside air. This behavior is consistent with results from previous studies of mirror seeing [25][26][27] when ∆T M > 0 • C. Past studies observed a weaker effect at ∆T M < 0 • C. Our data are consistent with an equal slope at both warmer and cooler temperatures, although hints of a weaker effect at cooler temperatures are present. We note that our data span a larger range of negative temperatures than most previous studies.…”

Section: Effect Of Temperature Differentials On Residual Wavefront Ersupporting

confidence: 93%

Effects of mirror seeing on high-contrast adaptive optics instruments

Tallis

Bailey

Macintosh

et al. 2020

J. Astron. Telesc. Instrum. Syst.

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Ground-based direct imaging surveys like the Gemini Planet Imager Exoplanet Survey (GPIES) rely on Adaptive Optics (AO) systems to image and characterize exoplanets that are up to a million times fainter than their host stars. One factor that can reduce AO performance is turbulence induced by temperature differences in the instrument's immediate surroundings (e.g.: "dome seeing" or "mirror seeing"). In this analysis we use science observations, AO telemetry, and environmental data from September 2014 to February 2017 of the GPIES campaign to quantify the effects of "mirror seeing" on the performance of the GPI instrument. We show that GPI performance is optimal when the primary mirror (M1) is in equilibrium with the outside air temperature. We then examine the characteristics of mirror seeing by calculating the power spectral densities (PSD) of spatial and temporal Fourier modes. Inside the inertial range of the PSDs, we find that the spatial PSD amplitude increases when M1 is out of equilibrium and that the integrated turbulence may exhibit deviations from Kolmogorov atmospheric turbulence models and from the 1-layer frozen flow model. We conclude with an assessment of the current temperature control and ventilation strategy at Gemini South. *Melisa Tallis, mtallis@stanford.edu * θFOV > 2λ Dρ , where λ = 1.65 µm, D = 8 m, and ρ = 0.4 .

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Section: Effect Of Temperature Differentials On Residual Wavefront Ersupporting

confidence: 93%

Effects of mirror seeing on high-contrast adaptive optics instruments

Tallis

Bailey

Macintosh

et al. 2020

J. Astron. Telesc. Instrum. Syst.

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“…The seeing contributed by a 3.5 m primary mirror warmer than the air outside the dome can range from 0.4 to 0.6 arcsec per Celsius degree (Zago 1986;Racine et al 1991), a value which is comparable or higher than the natural seeing in good astronomical sites. Several laboratory studies of image deterioration by convection (Lowne 1979;Iye et al 1991) confirm that microthermal activity grows significantly as soon as the temperature gradient between dome air and primary mirror is positive. The dome itself is a major source of seeing degradation (Bely 1987), and the seeing contribution is highly variable, depending on the telescope enclosure design.…”

Section: Introductionmentioning

confidence: 98%

Temperature forecast and dome seeing minimization

Buffa

Porceddu

1997

Astron. Astrophys. Suppl. Ser.

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Abstract. Dome seeing may strongly deteriorate the final sharpness of a point source astronomical image, reducing its Image Quality. Both the telescope enclosure and the mirrors may contribute to the dome seeing, if air convection is induced by differences of temperature between them and external air. The prediction of the external air temperature with respect to a given time interval allows one to preset in advance the air conditioning temperature value in the telescope enclosure. With the aim to study the neural networks capabilities and limits to make short term temperature prediction, a few case studies have been carried out by using an autoregressive neural network model. The actual goal is to understand if and with which constraints a neural network model can actually be used in a NTT-like dome (i.e. telescope is in open air when observing and heat sources are highly controlled when close or inside the telescope's dome) for steering the daytime air conditioning system. We do not present any interface with an actual telescope: this paper presents a feasibility study about the forecasting methodological approach rather than its operational application to a specific telescope.The results show that on site output prediction of a neural network are competitive with respect to a linear prediction approach.

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“…In order to develop active optics, a prototype telescope has been made at the National Astronomical Observatory of Japan with a monolithic 61-cm diameter 2.1-cm thick primary pyrex mirror [4]. The shape of the mirror was controlled by 12 actuators.…”

Section: Effect Of Telescope Mirror Thermal Condition On Degradation ...mentioning

confidence: 99%

“…Turbulence is usually characterized by the Rayleigh number. However, in our case a component of the Rayleigh number, the Brunt-Väisälä frequency [4], can be used as an objective characteristic of turbulence:…”

Section: Effect Of Telescope Mirror Thermal Condition On Degradation ...mentioning

confidence: 99%

Analysis of thermal conditions of the 6-m BTA telescope elements and the telescope dome space

Emelianov

2015

Astrophys. Bull.

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The results obtained using the temperature monitoring systems of the 6-m BTA telescope primary mirror, dome space, and external environment are reported. We consider the factors that affect the development of microturbulence in the near-mirror air layer and inside the dome space, variation of the telescope focal length with the temperature of its structures, variation of seeing due to temperature gradients inside the primary mirror of the 6-m telescope. The methods used in various observatories for reducing microturbulence are analyzed. We formulate suggestions concerning the improvement of the temperature monitoring system currently in operation and the system of automatic adjustment of the telescope focal length to compensate the thermal drift of the focus during observations.

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Evaluation of seeing on a 62-cm mirror

Cited by 24 publications

References 0 publications

Effects of mirror seeing on high-contrast adaptive optics instruments

Effects of mirror seeing on high-contrast adaptive optics instruments

Temperature forecast and dome seeing minimization

Analysis of thermal conditions of the 6-m BTA telescope elements and the telescope dome space

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