The Fibre Optics Multi-Object Spectrograph (OPTOPUS) enabled multiple object spectroscopy (MOS) to be carried out at the Cassegrain focus of the ESO 3.6-metre telescope at La Silla Observatory in Chile. The instrument was named after it’s optical fibres which had an octopus-like appearance. OPTOPUS was the first fibre multiple object spectrograph at ESO.
A prototype of OPTOPUS was tested at the ESO 3.6-metre telescope in November 1982. After several tests and improvements, OPTOPUS was made available to ESO astronomers in March 1985. In 1988, OPTOPUS was upgraded to improve the overall efficiency and number of operation modes, becoming known as OPTOPUS2.
The fibre-fed design of OPTOPUS allowed the light from up to 54 sky targets within 25 arc-minutes of the Cassegrain field of view — almost half a degree, to be simultaneously launched to the entrance slit of the Boller and Chivens Spectrograph (B&C). In other words, it enabled the conventional use of the B&C to be extended to multi-object spectroscopy.
To take observations, OPTOPUS used circular aluminium disks with accurately drilled holes called starplates, engineered so that connected fibres collected light from one object at a time. One plate was used for a given field in the sky. Before observing with OPTOPUS, astronomers had to provide the positions of interest for the starplates. For that the user had to identify and measure the positions of the targets on Schmidt plates. A huge X–Y densitometer on a granite table was used to accurately measure the positions of the targets on the sky. The data was reformatted and entered in the new ESO workshop Computer Numerical Control (CNC) milling machine for the drilling of the starplates. Once drilled, each hole was properly labelled for target identification. Two additional holes were made to point to bright stars for alignment and guiding of the starplates on the focal plane of the telescope.
The milling process was expensive and extremely time-consuming. A single observation could require machining 1500 precision-reamed holes. Later, software updates to the machining equipment lowered the preparation time a little. The plates were packed and sent to La Silla well in advance to arrive in time for the observations. It was a very long and careful preparation process at the time, with limited facilities.
In December 1985, OPTOPUS2 was used for the first time by regular visitors at La Silla Observatory. It yielded measurements of roughly 1000 spectra over 9 nights, including quasar candidates, carbon stars in Fornax, planetary nebulae, galaxy clusters and selected regions of the coma of Halley’s Comet.
OPTOPUS2 was decommissioned from the ESO 3.6-metre telescope in 1992 to be replaced by MEFOS, the MOS instrument with deployable arms instead of fixed holes to position the fibres in the field of view of the ESO 3.6-metre telescope prime focus.
OPTOPUS at the ESO 3.6-metre telescope
This table lists the global capabilities of the instrument.
We use cookies that are essential for accessing our websites and using our services. We also use cookies to analyse, measure and improve our websites’ performance, to enable content sharing via social media and to display media content hosted on third-party platforms.
You can manage your cookie preferences and find out more by visiting 'Cookie Settings and Policy'.
ESO Cookies Policy
The European Organisation for Astronomical Research in the Southern Hemisphere (ESO) is the pre-eminent intergovernmental science and technology organisation in astronomy. It carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities for astronomy.
This Cookies Policy is intended to provide clarity by outlining the cookies used on the ESO public websites, their functions, the options you have for controlling them, and the ways you can contact us for additional details.
What are cookies?
Cookies are small pieces of data stored on your device by websites you visit. They serve various purposes, such as remembering login credentials and preferences and enhance your browsing experience.
Categories of cookies we use
Essential cookies (always active): These cookies are strictly necessary for the proper functioning of our website. Without these cookies, the website cannot operate correctly, and certain services, such as logging in or accessing secure areas, may not be available; because they are essential for the website’s operation, they cannot be disabled.
Cookie ID/Name
Description/Purpose
Provider (1st party or 3rd party)
Browser session cookie or Stored cookie?
Duration
csrftoken
XSRF protection token. We use this cookie to protect against cross-site request forgery attacks.
1st party
Stored
1 year
user_privacy
Your privacy choices. We use this cookie to save your privacy preferences.
1st party
Stored
6 months
_grecaptcha
We use reCAPTCHA to protect our forms against spam and abuse. reCAPTCHA sets a necessary cookie when executed for the purpose of providing its risk analysis. We use www.recaptcha.net instead of www.google.com in order to avoid unnecessary cookies from Google.
3rd party
Stored
6 months
Functional Cookies: These cookies enhance your browsing experience by enabling additional features and personalization, such as remembering your preferences and settings. While not strictly necessary for the website to function, they improve usability and convenience; these cookies are only placed if you provide your consent.
Cookie ID/Name
Description/Purpose
Provider (1st party or 3rd party)
Browser session cookie or Stored cookie?
Duration
Settings
preferred_language
Language settings. We use this cookie to remember your preferred language settings.
1st party
Stored
1 year
ON | OFF
sessionid
ESO Shop. We use this cookie to store your session information on the ESO Shop. This is just an identifier which is used on the server in order to allow you to purchase items in our shop.
1st party
Stored
2 weeks
ON | OFF
Analytics cookies: These cookies collect information about how visitors interact with our website, such as which pages are visited most often and how users navigate the site. This data helps us improve website performance, optimize content, and enhance the user experience; these cookies are only placed if you provide your consent. We use the following analytics cookies.
Matomo Cookies:
This website uses Matomo (formerly Piwik), an open source software which enables the statistical analysis of website visits. Matomo uses cookies (text files) which are saved on your computer and which allow us to analyze how you use our website. The website user information generated by the cookies will only be saved on the servers of our IT Department. We use this information to analyze www.eso.org visits and to prepare reports on website activities. These data will not be disclosed to third parties.
On behalf of ESO, Matomo will use this information for the purpose of evaluating your use of the website, compiling reports on website activity and providing other services relating to website activity and internet usage.
ON | OFF
Matomo cookies settings:
Cookie ID/Name
Description/Purpose
Provider (1st party or 3rd party)
Browser session cookie or Stored cookie?
Duration
Settings
_pk_id
Stores a unique visitor ID.
1st party
Stored
13 months
_pk_ses
Session cookie temporarily stores data for the visit.
1st party
Stored
30 minutes
_pk_ref
Stores attribution information (the referrer that brought the visitor to the website).
1st party
Stored
6 months
_pk_testcookie
Temporary cookie to check if a visitor’s browser supports cookies (set in Internet Explorer only).
1st party
Stored
Temporary cookie that expires almost immediately after being set.
Additional Third-party cookies on ESO websites: some of our pages display content from external providers, e.g. YouTube.
Such third-party services are outside of ESO control and may, at any time, change their terms of service, use of cookies, etc.
YouTube: Some videos on the ESO website are embedded from ESO’s official YouTube channel. We have enabled YouTube’s privacy-enhanced mode, meaning that no cookies are set unless the user actively clicks on the video to play it. Additionally, in this mode, YouTube does not store any personally identifiable cookie data for embedded video playbacks. For more details, please refer to YouTube’s embedding videos information page.
Cookies can also be classified based on the following elements.
Regarding the domain, there are:
First-party cookies, set by the website you are currently visiting. They are stored by the same domain that you are browsing and are used to enhance your experience on that site;
Third-party cookies, set by a domain other than the one you are currently visiting.
As for their duration, cookies can be:
Browser-session cookies, which are deleted when the user closes the browser;
Stored cookies, which stay on the user's device for a predetermined period of time.
How to manage cookies
Cookie settings: You can modify your cookie choices for the ESO webpages at any time by clicking on the link Cookie settings at the bottom of any page.
In your browser: If you wish to delete cookies or instruct your browser to delete or block cookies by default, please visit the help pages of your browser:
Please be aware that if you delete or decline cookies, certain functionalities of our website may be not be available and your browsing experience may be affected.
You can set most browsers to prevent any cookies being placed on your device, but you may then have to manually adjust some preferences every time you visit a site/page. And some services and functionalities may not work properly at all (e.g. profile logging-in, shop check out).
Updates to the ESO Cookies Policy
The ESO Cookies Policy may be subject to future updates, which will be made available on this page.
Additional information
For any queries related to cookies, please contact: pdprATesoDOTorg.
As ESO public webpages are managed by our Department of Communication, your questions will be dealt with the support of the said Department.