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Interesting Porrima And Other Virgo Doubles


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8.35pm Weds. - 8SE with Focal Reducer (a configuration I now use a lot) – Moon waxing gibbous, east of south. I used binoviewers on Luna – x98, 213 – then back to Cyclops vision for Gassendi (on terminator), which was a silver ring, half of which spread across the background void. At x213, three central peaks stood out as close silver dots. Much later (with Luna much brighter), more floor detail was seen, going up to x320.

THE DOUBLES:

By 9.25, there were still no stars in the eyepiece, but minutes later I spotted -

Σ1627 Vir – a 6th mag pair, 21” separation. The stars were easily split at x36, sec at 7 o’clock, fairly close match, and faint against a lightish background. Nothing else in the FOV.

Porrima (γ Vir) – a 3rd mag pair – very easily spotted, being that much brighter.This is an interesting binary (35 ly away) with a period of about 169 years. In that time, the component stars go between 3AU and about 60AU apart, which reflects in angular separations of about 0.4 to 5.0 arcsec. At present, the sep is 3.16”, so it is easy to split. (Eight years ago, it was 2.11”; in eight years’ time it will be 3.93”. This indicates the rapidity of the changes.)

At x128 I think I got the split, but it was a bit tricky because of the brightness. By x191 the split was very clear, though still quite close, and a very good match. Less sharp at x256.

Σ1649 Vir – a dimmer, 8th mag pair, 15” apart. Easily seen in the darker sky (9.50), and a clear split at x36, good match, faint, with sec at 7 o’clock. Couple of other fainter stars in the FOV.

 

I finished after over two hours with a quick look at globular cluster M53 in Coma Berenices. This was a pale patch near some recognisable star patterns. Up to x160 it just became a bigger pale patch, which was to be expected, with the Moon so close. (Records show I’ve never seen detail with this target so far. I’ll try the Dob next time!)

A very enjoyable, mixed session.

Doug.

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18 minutes ago, cloudsweeper said:

That's disappointing Paul @wookie1965.  We've had a run of fairly clear nights here.  Problem is having to wait so long for darkness!  🤨

Doug.

I am what 6/8 miles away from you and I have had cloud. beautiful during the day blue skies then tea time comes and the cloud builds.

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