Observations - 30/10/20

Hello everyone.

I did some early evening observing on Friday 30th October 2020 with my William Optics 158 mm F/7 apochromatic refractor in my back garden from 5.15 pm until 7 pm. Sunset occurred at 16.55 UT. The temperatures went down from 4 degrees C to 2 degrees. There was no wind whatsoever. The sky was very clear. I started with some old favourite double stars. Their figures are be checked on www.stelledoppie.it

1. Polaris is a true binary. Magnitudes: A = 2. B = 9.1. Sep = 18.4". PA = 236 degrees. But this time I was splitting it at 5.15 pm when the star was still invisible. The primary is yellow-white (F7). The secondary is white. It was very nice to see the secondary in the 10 o'clock position at 40X. Because of our Earth's rotation, the companion seems to go around the primary in a clockwise movement hour by hour through my scope. What fun! Of course there is precious little change going on with the true position angle. That has remained quite fixed over many years.

2. We all remember observing the constellation of Bootes about 5 months ago. It is a Spring time set of stars after all in the north eastern sky. Well, now Arcturus is setting in the north western sky. Its golden-orange K2 colour was simply glorious at 40X.

3. Straight up from Arcturus we have Izar which I found at 5.30 pm when it was still invisible to my eyes. Magnitudes: A = 2.6. B = 4.8. Sep = 2.8". PA = 347 degrees. Beautiful (Pulcherrima) split at 112X, 140X and 167X. The primary is yellow with a bit of orange. The secondary is slight dark blue.

4. Off now to Cassiopeia. Schedar (Alpha Cassiopeiae) is an optical double. As B & C are not visible in my scope, I have to make to do A & D. Magnitudes: A = 2.4. B = 9. Sep = 70.4". PA = 283 degrees. Very easy split at 40X of course. The primary is yellow.

5. Very close by is Achird (Eta Cassiopeiae). For those who haven't observed this true binary - you don't know what you are missing! Magnitudes: A = 3.5. B = 7.4. Sep = 13.4". PA = 326.6 degrees. But the colours are stunning. The primary is G1V yellow. The secondary is M. My scope sees it as almond brown. I know I have told you all about Achird before. But I do reckon it is worthwhile to put it up for discussion yet again. There is an optical C component whose magnitude is 10.2 and it is 75.6" from the primary. The PA is 126 degrees. Tonight I only used 40X to see all 3 stars. Other times I increase up to 112X. Achird is still my favourite 4th magnitude true binary.

6. STF 10 is next. A & B are a true binary. But C is optical. Magnitudes: A = 8. B = 8.6. C = 11.1. Sep's = 17.5" & 55.4" from A. PA = 176 and 103 degrees respectively. All 3 white stars split at 40X.

7. The reason I did observe STF 10 again is because there is an extremely faint carbon star near it. And what a weird Simbad designation it has including those square brackets: [I81] C 8. It is otherwise called GSC 04018-00410 and its spectral class is C. Stars whose designations start with GSC are very popular on my Guide 9 DVD and on Simbad also. So if anyone can explain that original designation - please explain it to the rest of us. Thank you.
The carbon star's magnitude varies from different sources. Simbad says it is 11.5 with the ~ symbol after that estimate. Presumably that makes it a variable star. Guide 9.1 DVD gives 14.0. Which means there is no way was I going to see it - especially with a Full Moon in the sky at the same time. I also checked the AAVSO website who give a magnitude of +12.9. So maybe I am going to see it. They also give this carbon star a very long designation: ZTF J001501.46+631209.8. These figures turn out to be the Right Ascension and the Declination of GSC 04018-00410.
The ZTF stands for Zwicky Transient Facility. I have since found out more about the ZTF on Google. It is a new time-domain survey which had its first light at the famous Palomar Observatory in 2017. Why the good people at AAVSO are using the ZTF abbreviation is beyond me. So please feel to explain that to the rest of us too. The ZTF system is used to observe Near Earth Objects {NEO's} and supernovae at Palomar.
Anyway, back to our carbon star. GSC 04018-00410. With that estimated +12.9 magnitude in mind I set out to find it. It was NOT easy. Although the star is right next to an 11.5 magnitude star called TYC 4018 1946 I saw the carbon star only once directly at 374X. 4 times I saw it using averted vision with that same magnification. I should also point out that there is another orange star which is shown on my Guide 9.1 DVD very close by and it is called 3UC307-007505. It has a magnitude of +12.3 and I saw it too. Therefore if anyone wishes to have a go at GSC 04018-00410, please do make sure you can see these 2 stars individually. This carbon star is the 15th I have observed in Cassiopeia; and my 92nd overall.

Thank you for reading my report which ended at 7 pm.

Comments and images are very welcome.
I would love to see an image of the carbon star GSC 04018-00410 and the surrounding area. Thank you in anticipation.

Clear skies from Aubrey.

Thanks for  the Report Aubrey.   I usually read each  Paragraph and then  switch to Stelarium so I can learn where each object is located.   Look forward to your next report

regards
Stephen