Calar Alto Proposals Submission Tool

Applications for observing time at Calar Alto

General Information

Spanish open time at the CAHA 2.2- and 3.5-m telescopes

Applications for observing time at the 2.2- and 3.5-m telescopes
for the Autumn semester 2024 (1st July through 31st December)

As an ICTS (Spanish Unique Scientific and Technical Infrastructure), the Calar Alto observatory offers to astronomers every semester through an open call for proposals, a minimum of 20% of the available observing time on its two main telescopes: the 2.2m and the 3.5m, the largest of its kind in mainland Europe.

The Principal Investigator (PI) of the proposal must be affiliated with a Spanish Institution at the time of submission. Co-investigators (CoIs) from all countries are welcome to participate along with the Spanish PI.

Proposals of PIs from international organizations or based in non-European countries may be granted with observing time if they are considered among the best proposals by their scientific quality. Those proposals should, in particular, justify that they apply for CAHA time because they have no access to a similar instrument at their (inter)national facilities. Typically, up to 5% of the available open time might be granted to non-partners every semester.

Interested PIs are encouraged to read carefully this file which contains all the relevant information to submit a proposal.

April 19th, 2024, 14:00:00 (UT)
Earliest date for submission is March 21st, 2024

Open access protocol and committees for observing time requests

Twice a year, a Call for proposals is done to apply for observing time each semester, Spring (1st January through 30th June) and Autumn (1st July through 31st December). This is usually published about three months in advance at the following link:

This site specifies about one month in advance the deadlines for applying. After the dead-line a Time Allocation Committee (TAC, composed of half a dozen of internationally recognized astronomers having wide, complementary expertise) meets to evaluate them in a competitive open access, prioritizing the scientific excellence criteria subject to their technical feasibility.

Taking into account the rates given to the proposals the observatory elaborates the schedule of the corresponding semester and the TAC secretary informs the applicants if their proposals have been approved, or not, and the assigned dates and telescope.

Calar Alto also offers the option to buy observing time at the 3.5-m and 2.2-m telescopes

Interested PIs must email all the details of their proposed scientific case to the CAHA director (director at In case that the proposal is approved, a separate operation agreement (MoU) between CAHA A.I.E. and the respective user institution shall be signed. There is no dead-line for pay-per-night proposals, and their approval will be conditioned to scientific quality standards, and availability of observing time.

TelescopeGuaranteed nightNon guaranteed night
3.5 m13920 euro9280 euro
2.2 m3540 euro2360 euro

For Spanish institutions, and foreign institutions asking for visitor mode observations, 21% VAT taxes will be added to these prices.

1.23m telescope

There is no definite deadline for this telescope, but a scientific proposal must be submitted to the CAHA director (director at, and it will be internally evaluated all year long with the help of an external TAC if needed. For any use of the 1.23-m telescope, a separate operation agreement between CAHA A.I.E. and the respective user institution will be signed in the case of CAHA non-partners. Since the 1.23-m telescope with its CCD and CMOS cameras can be used remotely, experienced observers are welcome to use it from the distance. Yet, for new users, we strongly recommend that the first run is performed in visitor mode for several nights, to gain sufficient experience at the telescope. Limited support will be available (day and night, on a best effort basis) for remote users, considering that larger CAHA telescopes have a higher priority. CAHA non-partners will pay a fee. Contact CAHA's director for terms and conditions of use.

The price per night at the 1.23m is 550 euro. As for the 2.2 m and 3.5 m telescopes, 21% VAT taxes will be added to this price for Spanish institutions, and foreign institutions asking for observations in visitor mode.

Schmidt telescope

The Schmidt telescope (80-cm aperture, 1.2-m mirror) is currently under contract with the European Spatial Agency (ESA), with well-trained observers using it fully remotely, in an automated way, with Python scripts. The only instrument mounted is a 2k CCD (model FLI ProLine 23042, offering a field of view 44'x44' ), property of Deimos Space S.L.U., to do free band imaging. A filter wheel has been installed to perform multi-band imaging and photometry.


"Based on observations collected at the Centro Astronómico Hispano en Andalucía (CAHA) at Calar Alto, operated jointly by Junta de Andalucía and Consejo Superior de Investigaciones Científicas (IAA-CSIC)."

Alternatively, a similar phrasing appearing in the paper acknowledgements is acceptable. Failure to do so may result in penalties being applied by the TAC for future proposal submission from the same PI/Co-I(s).


Jesus Aceituno Castro
CAHA Director


» Spring'24
» Spring'23» Autumn'23
» Spring'22» Autumn'22
» Spring'21» Autumn'21

Application Procedure

Welcome to the new Calar Alto Observatory submission tool for observing proposals. This tool requires a user registration that you can do through the 'Create a new user' link. In order to complete this register you will have to provide and confirm your email account using the link you will receive after initial registration.

Once properly registered, the PI receives the password and then he/she is allowed to log into the system, where a web form is available to manage your applications. Before doing it, it is highly recommendable to complete non provided user details under 'USER ACCOUNT' tab.

With this interface you will be able to create new proposals, save, edit and complete them afterwards. During this process you can see how the associated pdf file is being generated. Please check it carefully, this file will be the document used for the evaluation.

Finally you will have to check and confirm your proposal in order to be submitted and evaluated for Time Allocation Committee. Note that drafts will not be automatically confirmed, and after deadline they will be ignored/discarded.

Detailed and updated information is available in the PDF file below. Please read the provided information carefully before creating your proposals:

Detailed Application Procedure

Finally you should take into account next issues:

  • proposals have to be written in English.
  • the only way to submit this proposals is via Calar Alto Proposals Submission Tool.
  • 'CHECK PROPOSAL' button shows errors and warnings detected in the form. Your proposals will not be submitted until no errors are detected and 'CONFIRM PROPOSAL' button is used. At this moment the status of this proposal will change from DRAFT to CONFIRMED.
  • Be sure to check the generated PDF file before confirmation, as once fully completed and confirmed no changes will be allowed in the proposals.
  • Beware that near the deadline the amount of submissions uses to increase considerably and it can be difficult or impossible to help you in an efficient way. You help us and yourself by preparing your proposal well in advance.
  • this system is only available during call for proposals procedure.

If you want to supply additional material (if absolutely necessary) to your referees, e.g. preprints, progress reports, or recommendation letters, please send it as an email attachment to

Finally, PIs will be notified by email as soon as possible (usually within ten working days after the TAC meeting) of the outcome of their proposal evaluations, including the final comments by referees, after being also checked by the TAC chair and secretary.

For any question or problem related to this call for proposals, please contact the TAC secretary Calar Alto welcomes feedback from its users’ community.

You are not allowed to access this form.
There isn't any Call For Proposals opened at this moment.
If you want to get your credentials (username and password) please use the email address you have stored in our system. You will get an email with your username and the procedure to set a new password to your account.
If you aren't be able to get into the system, please contact with our system administrator.
for any further information, questions or problems
Centro Astronómico Hispano en Andalucía/2023