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Observation Eta CrB (0,38 ") 9\04\2019

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#1 Konstantin 1980

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Posted 08 April 2019 - 06:00 PM

Last seen this star for a long time. Seeing that the closer stars that I knew are either already inaccessible (too close) or have gone beyond the horizon, I decided to observe those that are less mobile. In particular, this one. Since there are days with an excellent atmosphere and they should be used. In comparison with the double in the zet boo, this star looks obviously wider and accessible. It is interesting that the difference in the sizes of fragments of diffraction disks is visible. This is quite unexpected, considering that the difference in brightness is only 0.2. Maybe this star is variable? and therefore I see that parts of diffraction discolves of different sizes (this happens when the difference in brightness is more than 1 ... 1.5 magnitudes). This is weird.  I used a large piece of paper to accurately mark the track of the star and its position. Such dimensions allowed me quite accurately, without using devices, to note how exactly the disc is stretched..eta crb1.png


Edited by Konstantin 1980, 08 April 2019 - 08:32 PM.

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#2 Konstantin 1980

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Posted 08 April 2019 - 06:15 PM

I went once again to watch after a half-hour break. More attentively . Obviously, a hint of division, and not just elongation, began to be seen .. Before that, it seemed to me that there was no such thing and the disc was simply extended. Now I understand why the difference in the disks seemed to me more than it seems to be. Although still the satellite (the side where it is located) still has obviously smaller dimensions. That is, the difference in brightness still takes place to be greater than 0.2


Edited by Konstantin 1980, 08 April 2019 - 06:17 PM.


#3 Astroman007

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Posted 08 April 2019 - 07:01 PM

"Constellation Volopas?" confused1.gif


Edited by Astroman007, 08 April 2019 - 07:04 PM.


#4 Konstantin 1980

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Posted 08 April 2019 - 08:34 PM

"Constellation Volopas?" confused1.gif

This is a translator error, I did not notice smile.gif in Russian and in English, these constellations sound quite differently :)


Edited by Konstantin 1980, 08 April 2019 - 08:36 PM.

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#5 Astroman007

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Posted 08 April 2019 - 08:48 PM

This is a translator error, I did not notice smile.gif in Russian and in English, these constellations sound quite differently smile.gif

Ah, I get it. No problem, do your best. smile.gif



#6 fred1871

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Posted 08 April 2019 - 08:48 PM

Eta CrB has an orbit calculated, Period 41.6 years, Grade = 1 which means "definitive" - in other words, any appreciable change in the orbit calculation is not to be expected. Based on the Ephemeris listed in the 6th Orbit Catalog, the separation will indeed be 0.38" to two decimal places, as you've listed.

 

The WDS gives a magnitude difference of 0.31 between the stars, 5.64 and 5.95. These are most likely Tycho magnitudes, which sometimes vary a bit from other measuring methods, including Hipparcos magnitudes.

 

   Photometry via Simbad: A is listed Vmag 5.577 (2000), B is listed Vmag 5.95 (2002) - Dm on those is 0.37. Photometry can be a bit uncertain because it depends in part on the waveband used as well as accuracy levels. The numbers available don't in themselves indicate a variable star, one would need to monitor the star in question over time using preferably the same equipment.

 

Interesting sketch of the appearance of the pair, with notched elongation.



#7 R Botero

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Posted 09 April 2019 - 09:30 AM

Great report Konstantin! Thanks for sharing. I last observed this one in May 2017 when it was wider with my 10” f/20 Mak. My notes then were:
“From elongated to kissing discs. Closer than 2yrs ago. Runnig SENW.
Location: Petts Wood
Equipment:TEC MC250M F/20, Baader Hyperion Zoom
Transparency:9
Seeing:9”

Roberto

#8 rugby

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Posted 09 June 2019 - 07:14 PM

I have been following eta CrB since the late 1980's having observed it with several apertures ranging from a C8 to a 10" f5.4. My notes from May 20 to June 3  1991  are as follows: An equal pair widely split 10-290, so to 200, not seen 60.both yellow white. Seems 1991 was a very good year to observe Eta .

because of its maximim separation.

Now 38 years later under a clear and stable sky I tried again using a Meade 8" sct. I did not expect much but thought I could detect an elongated bar in the approximate correct p.a.  There was no separation and no notch. I used a 5mm Hyperion with a 2.4 Dakin barlow . Thats a lot of magnification but I knew something was happening with just the 5mm alone.

Would others weigh in on this result. I will return to Eta with a 10" soon.


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#9 Nucleophile

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Posted 11 June 2019 - 09:31 PM

I have been following eta CrB since the late 1980's having observed it with several apertures ranging from a C8 to a 10" f5.4. My notes from May 20 to June 3  1991  are as follows: An equal pair widely split 10-290, so to 200, not seen 60.both yellow white. Seems 1991 was a very good year to observe Eta .

because of its maximim separation.

Now 38 years later under a clear and stable sky I tried again using a Meade 8" sct. I did not expect much but thought I could detect an elongated bar in the approximate correct p.a.  There was no separation and no notch. I used a 5mm Hyperion with a 2.4 Dakin barlow . Thats a lot of magnification but I knew something was happening with just the 5mm alone.

Would others weigh in on this result. I will return to Eta with a 10" soon.

 As the seeing is above average tonight, I decided to give this one a try with the 8" reflector at high power (627x.)

I went in blind of pa and sure enough I most definitely detected elongation in the correct pa ("either 90 or 270" is what I said aloud at the time.)  What I saw was not notched like Konstantin's sketch--just oblong.

 

I think I must have lucked out mirror-wise with this Orion XT8i.  smile.gif

Thanks for the mention of this with your 8" scope--I likely would have passed on it.


Edited by Nucleophile, 11 June 2019 - 09:33 PM.


#10 rugby

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Posted 11 June 2019 - 11:21 PM

Nucleophile.   Thanks for the confirmation.  Your reaction to seeing eta at high power mimicked mine. Right away I knew the shape was elongated. I forgot to try the paracorr however so will need to revisit. Recently I purchased an 8 inch f5 dob with a conical Royce mirror.  Should be interesting to see how it works on close pairs.


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#11 mccarthymark

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Posted 21 June 2019 - 04:30 PM

8" (f/13 aperture mask on my 20"), 5/10 seeing & 2/5 transparency -- though it was near zenith, so that helped:

 

STF 1937AB: 8" 333x  Suspect elongation.  8" 667x definite egg shape.  20" 667x: Can't get a good focus.



#12 Nucleophile

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Posted 21 June 2019 - 04:58 PM

8" (f/13 aperture mask on my 20"), 5/10 seeing & 2/5 transparency -- though it was near zenith, so that helped:

 

STF 1937AB: 8" 333x  Suspect elongation.  8" 667x definite egg shape.  20" 667x: Can't get a good focus.

Great!  So that is three observations of this one with 8" objectives.

 

Mark:  what eyepieces do you use for your observations?



#13 mccarthymark

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Posted 21 June 2019 - 07:25 PM

Mark M:

 

I'm using Ethos; 8mm, 13mm, and a Televue big barlow.  Occasionally a 5mm Nagler.

 

--Mark M


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#14 rugby

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Posted 21 June 2019 - 08:41 PM

thanks for the info Mark. I will soon have a 20 inch f 4.5 up and running and will try a similar mask




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