Maria H. Pedrayes

Bio: Maria H. Pedrayes is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Primary mirror & Telescope. The author has an hindex of 4, co-authored 14 publications receiving 80 citations.

Active primary mirror support for the 2.1-m telescope at the San Pedro Mártir Observatory.

Abstract: We have designed and installed a new set of actuators for the suspension of the primary mirror of the 2.1-m telescope at San Pedro Martir. This active optics system has allowed us to correct low-order aberrations identified by several wave-front analysis techniques.

Edge effects with Preston equation

Abstract: In the polishing process, the wear tends to be greater when the tool extends beyond the edge of the workpiece. A linear pressure distribution (between the tool and the workpiece) has been used to explain this effect, however, this model also can predict negative pressures. This could mean that material is deposited instead of being removed. We present a new pressure distribution proposal, which presents like a skin effect. This means that the pressure is significantly higher at the border points than at internal points of the glass. With this model the material removal at the border points is increased considerably since, according to Preston, the wear is proportional to the pressure. This pressure distribution model is applied to calculate the wear produced by a square tool on a glass border moving along straight lines.

The Telescopio San Pedro Mártir project

Abstract: The Telescopio San Pedro Martir project intends to construct a 6.5m telescope to be installed at the Observatorio Astronomico Nacional in the Sierra San Pedro Martir in northern Baja California, Mexico. The project is an association of Mexican institutions, lead by the Instituto Nacional de Astrofisica, Optica y Electronica and the Instituto de Astronomia at the Universidad Nacional Autonoma de Mexico, in partnership with the Smithsonian Astrophysical Observatory and the University of Arizona’s Department of Astronomy and Steward Observatory. The project is currently in the planning and design stage. Once completed, the partners plan to operate the MMT and TSPM as a binational astrophysical observatory.

Mirror cell and active support system of the Mexican infrared optical telescope (TIM)

Abstract: We present the conceptual design of the primary mirror support system of the 7.8 m Mexican Infrared-Optical Telescope. The primary mirror consists of 19 hexagonal off- axis parabolic Zerodur segments, which are carried by a tubular, lightweight and high stiffness cell structure. Each segment is actively supported by 19 pneumatic actuators, that cover the whole back area and provide a uniform force distribution. The array of actuators will be able to correct for high order aberrations. Each of these actuators contains a hydraulic damping system to provide a stiff coupling to the tubular cell to sustain the wind buffeting. The tip/tilt and piston control of each segment will be done through three axial, nanometer resolution position defining actuators. The lateral positioning of each segment is performed through 3 independent electro-mechanical actuators. With the combination of the whole set of actuators and differential positioning sensors, the phasing or coherent superposition of images of the segments, will be more feasible. The whole system will be cost effective, since several subsystems have already been tested on our 2.1 m telescope.

Parametric modeling of edge effects for polishing tool influence functions.

Abstract: Computer controlled polishing requires accurate knowledge of the tool influence function (TIF) for the polishing tool (i.e. lap). While a linear Preston's model for material removal allows the TIF to be determined for most cases, nonlinear removal behavior as the tool runs over the edge of the part introduces a difficulty in modeling the edge TIF. We provide a new parametric model that fits 5 parameters to measured data to accurately predict the edge TIF for cases of a polishing tool that is either spinning or orbiting over the edge of the workpiece.

Edge effects with the Preston equation for a circular tool and workpiece

Abstract: In a polishing process the wear is greater at the edge when the tool extends beyond the border of the workpiece. To explain this effect, we propose a new model in which the pressure is higher at the edge. This model is applied to the case of a circular tool that polishes a circular workpiece. Our model correctly predicts that a greater amount of material is removed from the edge of the workpiece.

Active optics primary mirror support system for the 2.6 m VST telescope.

Abstract: The Very Large Telescope Survey Telescope (VST) is equipped with an active optics system in order to correct low-order aberrations. The 2.6 m primary mirror is supported both axially and laterally and is surrounded by several safety devices for earthquake protection. We describe the mirror support system and discuss the results of the qualification test campaign.

On the relationship between the H2 emission and the physical structure of planetary nebulae

Abstract: Mid-IR observations of planetary nebulae (PNe) have revealed diffuse emission associated to their main nebular shells and outer envelopes or haloes. The interpretation of this emission is uncertain because the broad-band mid-IR images may include contributions of different components. In particular, the Spitzer IRAC 8 {\mu}m images, that best reveal these nebular features, can include contributions not only of H2 lines, but also those of ionic species, PAH features, and thermal dust continuum emission. To investigate the nature of the emission detected in mid-IR observations of a sample of 10 PNe, we have obtained narrow-band near-IR H2 {\lambda}2.122 {\mu}m and optical [N II] {\lambda}6584 ?A images. The comparison between these images confrm that a significant fraction of the emission detected in the IRAC 8 {\mu}m images can be attributed to molecular hydrogen, thus confirming the utility of these mid-IR images to investigate the molecular component of PNe. We have also detected H2 emission from PNe whose physical structure cannot be described as bipolar, but rather as ellipsoidal or barrel-like. These detections suggest that, as more sensitive observations of PNe in the H2 {\lambda}2.122 line are acquired, the detection of H2 emission is not exclusive of bipolar PNe, although objects with this morphology are still the brightest H2 emitters. Finally, we remark that the bright H2 emission from the equatorial ring of a bipolar PN does not arise from a photodissociation region shielded from the UV stellar radiation by the ring itself, but from dense knots and clumps embedded within the ionized material of the ring.

Radial support analysis for large-aperture rotating wedge prism

Abstract: The different radial support ways for a rotation prism are presented to evaluate the strains and stresses induced by the gravity action and the thermal effects. Due to the large-aperture, non-uniform quality distribution and especially rotation from 0° to 360°, neither the multi-point support way nor the full surface-contact support can well meet the assembly requirements. The paper proposes a novel project of an adjustable partial surface-contact support way to solve this support problem. The maximum strain and stress under this support way both are less than the tolerance limit of the strength assurance regardless of the prism rotating to any position. Meanwhile, the thermally-induced structural analysis is performed to predict some specific work cases, which is much valuable for the improvement of the assembly design.