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MAPCAT Observing Instructions |
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Observations shall be performed once every ~1month within service time.
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Every session, all observable pointlike blazars in Table 1 shall be measured in polarized light.
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Observations shall be carried out at the 2.2m with CAFOS+polarizer through an R-filter.
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Each object need to be measured with 4 position angles of the lambda/2 plate (0º, 22.5º, 45º and 67.5º).
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The observer is requested to repeat any of these four measurement on which any problem is detected in the frame, but maintaining equal integration time for each polarizer position angle.
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Please, window the CCD to a FOV of 7'x7' (1 kpixel x 1 kpixel) with no binning (1x1).
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Indicative integration times (per position angle) for every source are listed in Table 1.
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The observer is requested to increase such int. times, depending on observing conditions and source brightness, when the source peak counts (per position angle and individual image) gets <1500.
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Figure 1 shows the time ranges of observability (airmass<2) from CA for every blazar in the sample.
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Finding charts (FC) for the target sources are provided in Fig. 2.
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There are no priorities, please, observe all visible sources in the night looking for optimum RA.
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There are weak restrictions on the weather conditions (grey nights, weak clouds).
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Please, always measure two of the following four polarized standard stars (see also FC in Fig. 3), by using the proposed reference integration times, but without defocussing the telescope:
-HD 19820 (R= 6.8) RA(J2000)= 03h 14m 05.4s; Dec(J2000)= +59º 33' 49'' (tint=0.1s)
-HD 25443 (R = 6.6) RA(J2000)= 04h 06m 08.1s; Dec(J2000)= +62º 06' 07'' (tint=0.1s)
-HD 154445 (R= 5.5) RA(J2000)= 17h 05m 32.3s; Dec(J2000)= -00º 53' 32'' (tint=0.1s)
-HD 161056 (R= 5.9) RA(J2000)= 17h 43m 47.2s; Dec(J2000)= -07º 04' 47'' (tint=0.1s)
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Please, always measure 5 bias frames, as well as 5 dome flat fields per polarization angle.
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However, at least one photometric night/semester would be valuable to double check the photometry.
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When photometric conditions are present, please, measure photometric standards.
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Table 1: Proposed integration times and source visibility period |
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* Observe 1622-297 whenever airmass>3 (Elv.>20º)
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Figure 1: Visibility (airmass<2 for more than 1h)period for Calar Alto. |
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* Observe 1622-297 whenever airmass>3 (Elv.>20º)
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Figure 2: Finding Charts from ESO-DSS-red archive for all MAPCAT target blazars |
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Figure 3: Finding Charts from the ESO-DSS-red archive for the 4 polarized stardad stars |
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