Saturday, April 4, 2020

procyon b snafu

Over a couple of nights earlier this week I felt certain I had observed Procyon B, and posted as such on Cloudy Nights.  I used my 20-inch with apodizing mask and a 9mm orthoscopic eyepiece to which I added a piece of black tape across the field stop in a crude attempt to make an occulting eyepiece.  The bar it formed in the eyepiece had a ragged edge and was out of focus.  I determined where north and west were before starting to track, and positioned the blocked out half of the eyepiece perpendicular to north-west -- as one would do when trying to block a bright object out. I saw what I truly believed to be a "hard point" of a star about three diffraction rings out from bright A.  In fact I thought my set-up was very clever, that the ragged edge and out of focus bar was allowing more of Procyon's light to be spread and cancelled leaving an airy disk (which it did) which would reveal the B star.  As fate would have it, the spot was right where it should be, to the northwest, and it happened to be about 5" separated, which I confirmed by looking at other 5" pairs later in the night.

The following night the seeing was better and I was able to "see" Procyon B in the same set-up, and even with a barlow, and even with my 8mm Ethos with tape across the field lens.  I did rotate the eyepiece a little, trying to test for ghost images, but I only moved it a little.  Bingo, I really thought I had it.

But then I tried using a 12mm ortho with a crosshair, and I noticed the ghost image or reflection of the bright star in the eyepiece, and it moved with the eyepiece as I rotated it in the field.  I had the same issue with a 9mm Ramsden I used on Procyon a couple weeks ago, where it was showing a star just outside of Procyon's glare, but in the wrong PA (to the south east).

So I put my occulting eyepiece back in and I rotated it around and that little spot rotated too, always perpendicular to the occulting bar.  Same for the 8mm.  My heart sank.  I had to post a retraction on Cloudy Nights and apologize; and hopefully people would not follow my example.  The lesson is to really, really make sure of an extreme observation, because it's easy to be fooled.

The other problem, which I should have admitted when I first made the observation, is that B really appeared obvious and bright -- I should have known better, from my own experience, that 11th magnitude stars even on good nights from my back yard are dim, and especially so when next to bright companions.  I guess I just assumed the occulting bar had done its magic to reveal the faint B star to me.

On the bright side, Venus passed through the Pleiades these last couple of nights, and I was able to take a look first through the 80mm monocular one night and then through binoculars the next night.  Very pretty and a memorable sight.

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