Saturday, December 07, 2019

removed logged status from Altair

Late November I noticed something strange. Today I reviewed my life list entry for Altair aka α Aql aka STFB 10. It was on my life list with a 0.9 separation.

The life list entry said: "I'm a little confused. Not sure if I've actually split these. Looks like I tried at the DDO on 20 Jul '07 but couldn't figure out which of the surrounding "small faint stars" was the "violet" one. Inspired by the CDSA I attempted on 2 Jul '10 at the CAO and at the time misread Haas's notes thinking it was a wide pair. ST3 says it's a triple. And curiously the ST3 software shows a log entry, suggesting I tagged it before the summer of 2010. Now that said, the View Again reference shows... Anyhoo, there are no clear notes so we need to have another go. AB magnitudes: 0.8, 9.6."

I checked a few sources for the separation values:
  • Haas says AB 192 but the mag of 1st is 0.9, oops
  • CDSA says AB 192 and AC 247 (with A at mag 0.9)
  • ST3 says a triple with AB 187.0 and AC 247.2
Reviewed the first blog entry: July 20, 2007 entitled the "DDO show (Richmond Hill)". I viewed some double stars using my C9 and with Haas's book in hand. "Looked briefly at Altair, a very bright star, surrounded by many small faint stars. I could not tell which star was the 'violet' companion."

Read the second entry: July 02, 2010 entitled "Canada Night observing (Blue Mountains)". At 1:11 AM, I helped a RASC member. Then I returned to my C8. "As the sky brightened, I shifted to double stars. I pulled my new Cambridge Double Star Atlas and flipped to constellations crossing the meridian. The CDSA said that Altair is a double! I targeted it. Didn't see anything per se. Started zooming in but couldn't split the white star. I wondered if it was a another wide double. Consulted double stars by Haas. Yep, she says it is separated by 192". Didn't think to put the binos on it..." And at 1:27 AM, I helped the RASC member again.

So, inconclusive. No clear indications of sighting the B or C stars.

Pulled the WDS data for WDS ID 19508+0852. Noted the A star magnitude: 0.95.

disc       pair   PA   sep    mag
STFB 10 AB    286 195.8  9.82
STFB 10 AC    110 186.4  10.3
DAL  27 AD    105  26.8  11.9
SMR   5 AE    354 151.3  11.0
SMR   5 AF    48 292.4  10.3
GMC   5 AG    121 185.1  13.0

I plotted the stars in Excel.

plot of Altair elements

Again, Haas only refers to B. There is correspondence in PA and Sep between the WDS and ST3P for B and C. SkyTools shows a double called J 3019 at the location that WDS says is the F star. The primary of J 3019, aka HD 187716, is magnitude 10.3. That matches the WDS mag for F.

I looked in Aladin. Switched to the 2MASS view, in infrared. Annotated the image.

image of Altair from Aladin

I spotted the B, C, E, F, and G stars. D is lost in the glare. I see the bright star north-north-west of F, like in SKyTools. ST3P says this is GSC 1058-1773.

My conclusions after this review...
  1. I incorrectly recorded the separation in my life list as 0.9 misreading, at some point, the magnitude number from Haas's book. I need to change this.
  2. I don't know why I set the "logged" status in SkyTools. I should remove it as I have never clearly noted the companion(s).
  3. I need to add the AB designation to my life list entry.
  4. Too bright to photograph.
  5. I should be sketching this the next time!
  6. With the 8-inch 'scope, I should be able to get all 7 stars!

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