Design of the near infrared camera DIRAC for East Anatolia Observatory

Ross Zhelem*, Robert Content, Vladimir Churilov, Yevgen Kripak, Lew Waller, Scott Case, Slavko Mali, Rolf Muller, Mario Gonzalez, Dave Adams, Nick Binos, Timothy Chin, Tony Farrell, Urs Klauser, Yuriy Kondrat, Nirmala Kunwar, Jon Lawrence, Nuria Lorente, Summer Luo, Erica McDonaldHelen McGregor, Vijay Nichani, Naveen Pai, Minh Vuong, Jahanzeb Zahoor, Jessica Zheng, Barnaby Norris, Julia Bryant, Annino Vaccarella, Nick Herrald, James Gilbert, Cahit Yesilyaprak, Bulent Gucsav, Deniz Coker, Onur Keskin, Laurent Jolissaint

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

1 Citation (Scopus)


The 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the " DAG InfraRed Adaptive optics Camera", is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance

Original languageEnglish
Title of host publicationGround-based and Airborne Instrumentation for Astronomy IX
EditorsChristopher J. Evans, Julia J. Bryant, Kentaro Motohara
Place of PublicationWashington, DC
Number of pages12
ISBN (Electronic)9781510653504
ISBN (Print)9781510653498
Publication statusPublished - 2022
EventConference on Ground-based and Airborne Instrumentation for Astronomy IX - Montreal, Canada
Duration: 17 Jul 202222 Jul 2022

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceConference on Ground-based and Airborne Instrumentation for Astronomy IX


  • infrared
  • camera
  • diffraction limited
  • cryogenic
  • wavefront budget
  • cryostat


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