Telescopes I've Used - La Palma

Observatorio del Roque de los Muchachos, La Palma, Canary Islands,

This spectacular site, on the northern rim of the Caldera de Taburiente at an altitude of about 2400 meters, has some of the best seeing I've ever measured. Astronomical development of the international observatory began in earnest with the decision to relocate the Isaac Newton Telescope from Herstmonceux in Sussex (which had interesting mechanical effects on the mounting, since that entailed a 25-degree latitude change). The William Herschel telescope combines the excellent site with very well-thought-out instrumentation for world-class results. I used these facilities several times while on a two-year stint at the Sterrewacht Leiden, since the Netherlands astronomical community contributes to the support of the La Palma operation. And more recently, I've been able to use the Nordic Optical Telescope for galaxy dynamics studies.

Isaac Newton Group, La Palma Sunset over William Herschel Telescope Jacobus Kapteyn Telescope

1.0-meter Jacobus Kapteyn telescope (JKT)

JKT dome at twilight Working at the JKT console Peter Allan and I used the JKT to continue the quasar variability project that we started with the Kitt Peak 1.3-m telescope - this sort of thing can happen when both collaborators change continents. These data formed the basis of a Master's thesis by Jose Maria Castro Ceron, which should be submitted for journal publication any day now. We also used a CCD camera on the JKT for part of a study of H-alpha emitting regions in interacting galaxies.

The JKT lies closer to the rim of the Caldera de Taburiente than any of the other telescopes. This means that observers might want to take a flashlight along when walking uphill from the dome at night. It's a long way down...

After a period of shutdown, the JKT is being refitted for remote operations late 2014, and is scheduled to join the observatories of the SARA consortium as of early 2015.

2.5-meter Isaac Newton Telescope (INT)

Dome of Isaac Newton Telescope Isaac Newton TelescopeThe Isaac Newton telescope has a very efficient and flexible spectrograph, very important when the UK and Dutch communities were using it to compete with 4-meter telescopes elsewhere (a role now ably handled by the WHT). The superb seeing often encountered at La Palma made this an appealing setup for investigating galactic nuclei. I took a series of high-dispersion spectra to study composite nuclei, with signs of both star formation and nonstellar activity in close proximity. Among other things, these data furnished evidence of a massive black hole at the center of M81, as seen from the central rise of stellar velocity dispersion measured in subarcsecond seeing here. An INT spectrum also furnished a crucial clue to interpreting IUE and HST observations of the nucleus of NGC 4569, a spiral in the Virgo cluster whose core is so small that it was once mistaken for a foreground star. The optical spectrum showed absorption-line profiles inconsistent with the most obvious explanation of its colors, and that the nucleus must be (for whatever reason) loaded with A-type supergiant stars.

4.2-meter William Herschel Telescope (WHT)

Dome of William Herschel Telescope One of the new generation of large altazimuth telescopes, the WHT started regular operation in 1987. Looking at the elevated walkways to the telescope platform, I couldn't help thinking, "Another fine product of Krell technology". Our team got one of the earliest normally scheduled observing runs (almost canceled by brush fires). We used the Faint-Object Spectrograph (shown below attached to the WHT) to observe faint candidate active galactic nuclei (AGN) selected from the deep fields observed by IRAS, parallel to its all-sky survey. Encouraged by a period of subsrcsecond seeing which let us split the components even on the acquisition TV, we also sneaked in spectra of the different components of the Einstein Cross 2237+030. The only difference that shows up is in foreground Na D absorption from the foreground (lens) galaxy near 6070 Angstroms; it is strongest for those images, such as C, where the impact parameter from the galaxy nucleus is smallest.

WHT spectra of components of Einstein Cross 2237+030

William Herschel Telescope Bill works with the Faint-Object Spectrograph on WHT

Here are some sample spectra of faint active galaxies as measured with the WHT. This is a group of Seyfert 2 galaxies found as warm far-infrared sources from examination of the deep IRAS pointed data. These are arranged by increasing redshift (given at the right side), whosing how the strong lines of Hβ, [O III] Hα, and [N II] march out of the optical window for even larger redshifts. They have been rescaled for comparison, in fact spanning two orders of magnitude in line flux.

WHT spectra of faint IRAS AGN

2.56-m Nordic Optical Telescope

The compact, altazimuth-mounted NOT has achieved excellent images, not only through optical quality but due to its compact lightweight dome and the practice of opening huge vents to allow wind to flow right through the enclosure. The NOT dome turns as a unit with the telescope, allowing a very minimal layout. It also means you should be very careful with walking in or out of the dome at night... The telescope is operated by institutions in Norway, Sweden, Finland, Denmark, and Iceland. I've used it in a project with Gene Byrd and Mauri Valtonen to seek faint, tidally stripped companions of nearby edge-on galaxies, which would serve as tracers of the halo dynamics and history of these systems. Here is an R-band image of NGC 891, part of an acquisition image while setting up for spectroscopy of what turned out to be a background object.

Still to come: JKT data on QSOs and galaxy H-alpha image. INT spectra of NGC 4569, M94, M81.

La Palma Tourist Shots

Other instruments are also sited at the Roque de los Muchachos. These include the Telescopio Nazionale Galileo and the Dutch Open Telescope. Galileo is a 3.5-m near-duplicate of the ESO New Technology Telescope (right down to the details of the enclosure).

The Dutch Open Telescope is designed to improve image quality by having the telescope open to the air as far as possible. It currently hosts a 45-cm solar instrument, with the option of installing a primary as large as 70 cm. Any resemblance to a Martian tripod machine a la H.G. Wells is completely coincidental.

The La Palma site has also been used or high-energy gamma-ray astronomy via the atmospheric Cerenkov technique, detecting the gamma rays when they interact with atoms in the upper atmosphere to release showers of high-energy articles, some of which are moving faster than the speed of light in the atmosphere and in doing so release very brief flashes of light in a conical pattern. This is the Cerenkov effect, and I now know the conical pattern very well since it was the major screwup on my grad-school oral exam... The instruments for such work are large light buckets, where light grasp is important and resolution isn't, so arrays of cheap mirrors are often used. Here we see the sun setting on the original array in the late 1980s, which has since been replaced by a more extensive and complex combination of pointed Cerenkov detectors and all-sky particle monitors in a fly's-eye arrangement. Alas, last time I saw that one in daylight it was snowing too hard to get a decent picture.

La Palma air-Cerenkov array

Telescope Collection

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