Thursday, January 11, 2018

finished on HR 3701 (Halifax)

I wanted to revisit the multi-star HR 3701 aka Struve 1338 to track down the C element. The BGO robot obliged and captured the target in Lynx. Something is visible to the south-west... But I don't know what it is.

multi-star HR 3701 in luminance

Luminance only, 3 seconds subexposures, 20 stacked shots. FITS Liberator, Paint.NET. North is up; east is left.

Viewed this triple on 14 Apr '17 and had split the tight AB pair. But the third companion eluded me.

SkyTools 3 Pro shows C to the south-east. On the Interactive Atlas chart is shows as bright, mag 11.4. But in the photograph, while it has the correct separation, appears very dim, about the same brightness as GSC 02991-0543 which ST3P says it mag 16.2. No wonder I couldn't see anything!

The Washington Double Star database shows very interesting information!

A and B are at a PA (theta) of 311° with a separation (rho) of 1.1" (as of 2016). ST3P is similar: 320 and 1.0 (calculated for 2019.2).

A and C are 166° and 144". Wait! What? ST3P says C is 167° and 10"! Oh. I see. That medium-faint well away star to the south-south-east is what the WDS says is the C star. So then, no problem, I've seen it, check. And it looks like the data in SkyTools is wonky.

But then, what's this super-faint thing about 20" away hovering around PA 195° at mag 16?!

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