ZTF21aaeyldq CAHA 2.2m detection and power-law decay

We observed the position of the GRB-less afterglow ZTF21aaeyldq (Ho et al., GCN #29305; de Ugarte Postigo et al., GCN #29307) with CAFOS at the 2.2m telescope at Calar Alto, Almeria, Spain, in the Rc band. We obtained 10 x 360 s exposures, centered at 1.74430 days after the transient discovery, under fair conditions but mediocre seeing. The afterglow (Kumar et al., GCNs #29308; Ahumada et al., GCN #29309; Zhu et al., GCN #29310; Hu et al., GCN #29312) is clearly detected. We measure Rc = 22.89 +/- 0.12 mag. (AB mag, vs. the same SDSS star as in our GTC observation, GCN #29307 converted to Rc following the Lupton transformations, then transformed back to AB mag). We take data from Ho et al., GCN #29305; de Ugarte Postigo et al., GCN #29307; and Zhu et al., GCN #29310 (all in r'), and here assume a trigger time 22 minutes before the discovery (at the last non-detection). We find this data is fit well with a single power-law, a straight decay slope alpha ~ 0.91 +/- 0.02. The magnitude we report now lies slightly (0.3 mag) below the extrapolation of the afterglow decay. Further observations are needed to determine whether this represents a jet break.