38 replies to this topic

[Fiske]

Here is a fun and easy Lyra observing project I started last week. It can be done with a hand held binocular (if you insist). 

 

Beta Lyrae, aka Sheliak, is a remarkable eclipsing binary star about 960 light years away. It varies in magnitude between 3.25 and 4.36 in a period of 12.9 days. What causes the change in magnitude is that mass has been transferred from what was originally the larger star of the spectroscopic binary pair to the companion star, forming a torus ring around the companion which shrouds its light, making it dimmer. A helpful visualization can be viewed in this Texas A&M astronomy department archive. When the secondary (spectroscopic companion star) is fully in front of the primary, Sheliak's magnitude is at its minimum of 4.36. When the primary star is fully in front of the secondary, Sheliak is at its 3.25 maximum.

 

What makes it a particularly easy variable star to follow is that the adjacent Lyra asterism p-gram stars provide convenient magnitude references.

 

 

Sulafat (southeast corner) is 3.25 magnitude, which is Sheliak's maximum and Zeta1 Lyrae is 4.34 magnitude, close to Sheliak's minimum. 

 

Last Wednesday night (28 June 2023) Sheliak was not quite as bright as Sulafat, but obviously brighter than Zeta1. Friday evening (30 June) Sheliak seemed slightly fainter -- still brighter than Zeta1, but not as close in brightness to Sulafat. It was cloudy and raining last night, so I wasn't able to observe it. But the next evening it is clear I'll take another look to see if its magnitude is declining now. 

 

An observation like this can be made in a minute or two, easily accomplished any clear evening.

 

 

[jrazz]

Wonderful!!!

I will look for it tonight. 

[Dale Smith]

Awesome! I had no idea about this eclipsing binary. Thanks for the heads up, and the helpful chart. I'm going to try for this if I'm up late enough (or get up in the "wee hours" 

[aznuge]

Thanks for the post!  I plan to put this on my routine visits of Lyra - its been right there all along, hiding in plain sight

[RMay]

I hope enough pros, novices, and peanut gallery participants like myself remind you - at least on a daily basis - what an invaluable service you provide to the binocular and general astronomy-loving community.

You are a rare gift to us all, and I thank you.

Ron

[northbynortheast]

I'm in the novice section of the novice section of the peanut gallery and I very much share the appreciative sentiments of all the posts here. I was greatly enjoying Lyra before the smoke and clouds settled in to New England, and now I'm all the more eager for the skies to clear.

 

Thanks, Fiske!

Edited by northbynortheast, 02 July 2023 - 09:56 PM.

[gwd]

Fiske has identified Sheliak as more than a binocular waypoint on the route to M57.   My binocular tours of Lyra (and every other constellation ) become longer as the years pass.   I used to find Sheliak and Sulafat then scan  a bit south of the segment joining them to see if I can see the smudge of M57.  Recently I visit the colorful pair hip 92833 hip 92829 first and use them to follow an almost perpendicular to the Sheliak Sulafat segment to look for M57.  After Fiske’s post, I’ll be spending more time socializing with Sheliak whenever I visit the neighborhood.   

[ckwastro]

Great post Fiske! Thank you!

[aznuge]

Tonight I would estimate that Sheliak is about 3.6-3.9. At least it is somewhere between Zeta1 Lyr and Sulafat in brightness in my opinion, and not matching either with its maximum or minimum.  This is based on glimpses with 15x50 IS bins under heavy light pollution.

[Fiske]

Thank you everyone for your kind remarks and enthusiasm. 

 

Cloudy Nights is a wonderful community. Honestly, central to my astronomy experience.

 

I did not mention in my original post that in addition to being a spectroscopic binary, Sheliak is a wonderful binocular double. (Actually an octuple system with six visible stars.)

 

Here are my observing notes from Sunday 25 June 2023.

 

STFA 39 / Sheliak
18h50m +33*22'
3.63/6.69 sep 45.7" pa 149*
Distance: 960 LY
Spectral type:  B8.5Ib-II C / B7V C
Color Index: +0.00 white  / -0.08 blue-white

 

Glorious with the 120XL+20XWs (33.5x) Brilliant light yellow primary with a diminutive neon blue secondary at a comfortable distance. A sprinkling of faint stars hovering about – maybe also part of the system? Colors readily seen with Nikon 18x70 IF WF.

 

It was while reading about Sheliak after observing it Sunday that I learned it was a variable star.

 

I was able to observe it last night, hand held with my Nikon 7x42 EDG binocular. I would say it was closer to the brightness of Sulafat than the last few times I viewed it, so actually close to its maximum. Incidentally, variation in visual magnitude estimates is typical with observations like this.

 

I also viewed the region (one of my favorite star fields) with several mounted instruments, including the Nikon 18x70, in which I could see M 57 as a non-stellar gray ball in averted vision. I could not detect annularity, however.

 

The HIP 92833 / 92829 pair George mentions above is actually STT 525, and another enjoyable binocular double star for a mounted instrument. I observed it on 25 June as well, along with a nearby double which is easily overlooked. I "discovered" it with the help of a skylist imported from StelleDoppie. (So I knew to look for it. )

 

STT 525
18h54m +33*58'
AC 6.14/7.60 sep 45.4" pa 350*
Physical double star
Distance: 1482.13 LY
Spectral Type: G5III+A8 / A E
Color Index: +0.93 yellow-orange / -0.06 blue-white

 

Yellow primary with blue secondary. Generously spaced. A fine bright pair. Obvious magnitude difference.

 

STF 2421
18h56m +33*47'
8.13/9.34 sep 24.6" pa 57*
Optical double star
Distance: 1180.40 LY

 

Quite near STT 525 but the secondary is faint so it is easy to overlook and sweep past. Have I noticed this double before? Brilliant white primary with a tan secondary, close but not tight. Nikon 18x70.

Edited by Fiske, 03 July 2023 - 08:03 AM.

[Erik Bakker]

Such great reports Fiske, thank you for sharing!

 

As soon as the skies clear, I will have a look at Sheliak and the surrounding (comparison) stars. Star colors come through very vividly in my Nikon binoculars, though I think only my SP 7x50 and EDG 8x42 will fit all the comparison stars comfortably in the same field, similarly to your EDG 7x42. Should make for nice comparisons.

[Dale Smith]

Another wonderful report, Fiske! I viewed Sheliak and Sulafat in a 6.5x32 Vixen Astro ED and a Bushnell 10x42 Legend-L ED last night, both handheld. The two stars fit comfortably within the FOV of the Vixen. Sheliak appeared very close in brightness to Sulafat. I made multiple observations—at first they looked identical, then *perhaps* Sulafat was just slightly brighter than the variable star. The same in the 10x42s. I was making my observations in late nautical twilight and again in early astronomical.

[Fiske]

I meant to say in my report from last night (3 July 2023) that I could see both Sulafat and Sheliak fairly easily naked eye. My naked eye limiting magnitude is around 4.5. Third magnitude stars are easily seen most nights. On the other hand, Zeta1 (at 4.34 magnitude) was much more difficult to see. I could glimpse it in averted. When Sheliak is near it's minimum, I think the same thing will hold viewing it -- challenging in averted vision naked eye. The one star of the Lyra p-gram that should still be readily seen will be Sulafat.

[lenscapremoved]

What a nice homework assignment Fiske! And well timed. I'm on vacation and have my mounted 12x50. I was so close last night. I had checked out Zeta Lyrae, drove over to Sheliak and quickly turned south to Albireo. This will be my first variable OR eclipsing binary star to study.

[Fiske]

Thank you Erik, Dale, and Mike. 

 

Here are more details and additional double observations, along with images, from the observing session on Sunday 25 June when I was roaming the starfield around Sheliak. 

[gwd]

Thank you everyone for your kind remarks and enthusiasm. 

 

Cloudy Nights is a wonderful community. Honestly, central to my astronomy experience.

 

I did not mention in my original post that in addition to being a spectroscopic binary, Sheliak is a wonderful binocular double. (Actually an octuple system with six visible stars.)

 

 

 

 

The HIP 92833 / 92829 pair George mentions above is actually STT 525, and another enjoyable binocular double star for a mounted instrument. I observed it on 25 June as well, along with a nearby double which is easily overlooked. I "discovered" it with the help of a skylist imported from StelleDoppie. (So I knew to look for it. )

 

STT 525
18h54m +33*58'
AC 6.14/7.60 sep 45.4" pa 350*
Physical double star
Distance: 1482.13 LY
Spectral Type: G5III+A8 / A E
Color Index: +0.93 yellow-orange / -0.06 blue-white

 

Yellow primary with blue secondary. Generously spaced. A fine bright pair. Obvious magnitude difference.

 

 

I used the Hipparcos numbers because it looked like there is a difference between WDS and an I-pad application called Triatlas by Norbert Schmidt based on charts by Jose R. Torres.  In the app I use it looks like the double I observe is labeled "STG 525".   Stellarium had the Hipparcos labels so I went with them for the post.    

Edited by gwd, 04 July 2023 - 04:31 PM.

[lenscapremoved]

Tonight I would estimate that Sheliak is about 3.6-3.9. At least it is somewhere between Zeta1 Lyr and Sulafat in brightness in my opinion, and not matching either with its maximum or minimum.  This is based on glimpses with 15x50 IS bins under heavy light pollution.

Last night when I made my very unscientific measurement, I was leaning towards +3.5. But now, 20 hours later, I realize that this is a logarithmic scale? And not linear? So my estimate was way off. I'll have to look at a curve and re-estimate. So for now..... Yeah, 3.6 - 3.9 sounds just right! I thought it was much closer in brightness to the brighter Sulafat than Zeta1 Lyrae.

 

Would it be easier to estimate magnitudes of brightness with a binocular with a wider FOV? and less magnification? and smaller objective? Would the differences be more apparent?

[Fiske]

I tried a few different instruments the first night -- Kowa 6.5x32, 8x32, Maven b.5 10x56 (mounted), Nikon 7x42 EDG, Canon 10x42L IS.

 

Interestingly, the magnitude variation was less apparent with the Canon than with the other binoculars. Any of the others. I am guessing a consequence of stabilization, somehow, compressing the brightness range. I'm wondering if my impression that the 10x42L view is dull compared with 10x50 or x56 binoculars is based in part on this effect?

 

Anyway, I have landed on the Nikon 7x42 EDG as being the easiest to use for a quick peek and magnitude estimate. I am planning to try the Nikon 10x50 WX, too.   That will be mounted of course.

 

The AAVSO site can be used to create magnitude charts for thousands of doubles. Interestingly, however, Sheliak does not lend itself well to this treatment because so few stars are available for comparison in its brightness range. The AAVSO site states that visual magnitude estimates can be accurate to within 1/10th of a magnitude, but that is predicated on having a number of comparison stars, not just two one on either end of the variable's brightness range. 

Edited by Fiske, 05 July 2023 - 07:00 AM.

[Fiske]

I used the Hipparcos numbers because it looked like there is a difference between WDS and an I-pad application called Triatlas by Norbert Schmidt based on charts by Jose R. Torres.  In the app I use it looks like the double I observe is labeled "STG 525".   Stellarium had the Hipparcos labels so I went with them for the post.    

The WDS (Washington Double Star) catalog is an internationally accepted standard widely referenced by both amateurs and professional astronomers, so I typically follow that. Though have actually corresponded with an astronomer at the US Naval Observatory regarding several doubles that had incorrect data listed (discovered in the Cygni 100 project last summer) and was told that they would be updated with correct information.

 

Discoverer codes are intriguing in their own right and fun to dig into. I recently had a lot of fun digging into SHY double stars after coming across one example while writing notes about observations.

 

STT 525 and and STG 525 are the same double, I expect.

 

STT in its various guises (which include STTA) is/are the code(s) for Otto Struve (19th century astronomer). STG is listed on the WDS Discoverer Codes page, with mid 20th century dates. I'm not sure who that refers to. The discoverer code for Friedrich Georg Wilhelm von Struve (father of Otto Struve) is STF, also a 19th century astronomer. 

[Fiske]

I had a look at Sheliak tonight (Thursday 6 July 2023) with the 10x50 WX, which takes top honors for making the observation. 

 

It is fainter than Sulafat now, but brighter than Zeta. I can still see it naked eye, and more easily than Zeta, but Sulafat is notably more conspicuous.

 

I also picked out HK Lyrae, a carbon star not far from Zeta, which I noticed on an Aladin image from another observing project soon to be shared.  It has an orange tint and is fun to pick out.

 

An issue I noticed with the 7x42 EDG is that Zeta can just be seen as a double with it hand held, which makes it look out of focus and interferes with the magnitude estimate. I was using the OB 4000 tripod with the 10x50 for a quick hit, but the WX on the Farpoint p-gram will  be the ultimate view. 

Edited by Fiske, 06 July 2023 - 11:02 PM.

[Dave Mitsky]

I just came across this thread and will give it a try soon.

[Trapezium]

Last night, about 10 pm PDT, Sheliak matched the magnitude of Zeta1 Lyrae. It was definitely fainter than Sulafat. Observed through my BT100 at 25x. This variable star observation is fun and easy to do. Thanks Fiske! 

[Fiske]

Thanks for your report, Trapezium! 

 

Here is a screenshot of the AAVSO Ephemeris for Beta Lyrae. If I'm understanding this correctly, the minimum should be at the Mid date -- which is the mid-eclipse. So Sheliak would have been at its faintest on July 7. (I think the time given is Universal time.) The next time it will be at minimum would be July 20.

 

So, the ephemeris confirms your observation. 

 

Edited by Fiske, 08 July 2023 - 10:08 AM.

[Erik Bakker]

Over the last 2 nights I observed Sheliak. On July 7th, when it was around it’s minimum brightness, it was very similar to Zeta Lyrae (Mv 4.34) . And on July 8th, it was already visibly brighter, somewhere in between Zeta Lyrae (Mv 4.34) and Sulafat (Mv 3.25).

 

What struck me is the beuaty of the whole Lyra area. A wonderful, easy to see, fast changing variable eclipsing binary star amidst very easy reference stars of the Lyra p-gram. Add the beautiful surrounfing starfields and the striking color differences between the two components of the wide binocular double Delta Lyrae. I found great joy in observing this region and eclipsing binary with hand held binoculars.

 

The whole p-gram of the brighter Lyra stars fit into the field of my SP 7x50 and EDG 8x42. I bet it would be even easier in the EDG 7x42 with it’s slidely wider true field than these 2.

 

Skies where the not quite dark summer skies from my mid northern lattitude, making the 8x42 a very strong contender. It’s view of the Lyra region where marvellous, with the 7x50 being a bit easier on the eye/brain to take the whole p-gram in at once, but really needing the darkest part of these summer nights to catch up to the 8x42. Which gave wonderful views with rich starcolors and superb pinpoint stars.

 

The 10x70 and 18x70 showed more stars and detail, but with a field of view too small for my liking for these observing sessions.

 

Thank you Fiske for putting this wonderful binary on my map!

[Dale Smith]

Wonderful observing report, Erik. Lyra is truly a treasure chest of celestial gems. I also enjoy sweeping the area with handheld binoculars. It’s always a joy.