Euclid DDF Dithering

We’re starting to look at the best way to observe the Euclid deep drilling fields. For the other fields, we typically dither by shifting up to 0.75 degrees in a random direction. Since the Euclid field is a double field, we’re now trying out preferentially dithering in certain directions to better fill the planned Euclid footprint. Here’s an initial attempt where each field is dithered between -0.25 and 1 degrees towards the other field and between -0.25 and 0.25 degrees perpendicular to the other field.

As always, we’re looking for metrics that could help us tune these parameters so we maximize the scientific usefulness of the observations. Is it better to increase the dither size to get more overlap with the full footprint, or decrease the dither size to increase depth?

euclid_coadd Final coadded depth in g. Euclid footprint in red.

euclid_nvis Total number of visits after 10 years, Euclid footprint in red.

dither_positions The dither positions used.

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We are currently making deep field observations of EDFS with DECam (ugriz). Last week we observed hex_1, hex_2, and hex_4. We hope to expand coverage working outwards to eventually cover most of EDFS. We started with the central part of EDFS to maximize overlap with two planned VISTA/VIRcam pointings. One of the goals of these DECam observations is to have deep external reference data if EDFS is selected as one of the LSST DDFs. Note the EDFS is located with the DES wide survey footprint.

We can provide an update on the DECam observations in ~2 weeks when the next observing run is completed.