Messier Objects by Daylight

[Xilman]

On 2024-02-16 I read that the moon was lying close to the Pleiades. I already know that bright stars are easily visible through a telescope as long as they are bright enough and their position known.

Although my scope doesn't have absolute positioning the moon was easily visible through the finder and MaximDL would tell me its position at that time of day --- 13:30 local solar time. A 50ms exposure through a Sloan i' filter (to darken the sky background) showed nice craters. Syncing the mount to the lunar position told the telescope where it was pointing to around 10' or so.

Slewing to Alcyone showed nothing, which was not too surprising given that the field of view is only about 13'. Lots of slewing around at random produced some images containing stars. All contained a bright sky and lots of dust donuts. The starless images were stacked to produce a master flat.

Identifying the stars was not easy. Luckily one contained a double star. I know the image scale (0.6"/px) and the camera orientation (-177o) and so could estimate the separation at 9.6" and the PA at about 225o. I also knew the approximate image centre, to within 10' or so.

Lots of rummaging around in the DSS2 images, SIMBAD and the Washington Double Star catalogturned up HD23964 where the AB components are too close to be resolved with the seeing and the relatively poor focusing, but the AC pair has a seperation of 10.4" in PA 235o. Their I magnitudes are 6.74 and about 9.3 (estimated from R=9.71 and J=8.93). A very satisfactory match!

Another star in another image was somewhat brighter than the pair. 26 Tau, at V=6.46 and J=5.68, lay well within an arc minute of the predicted position. I am reasonably confident of this identification.

 

Here is HD23964AC

 

and here is 26 Tauri

 

You can see how well the impromptu flats have worked.

Given how easy it is to pick up 9th magnitude objects in the near infra-red with an exposure where the sky almost but not quite saturates the CCD, I think I’ll try to find some more Messier objects in daylight. Call me crazy if you wish.

Edited May 3 by Xilman
Add comment about flats.

[Mandy D]

Impressive!