4 replies to this topic

[lwbehney]

On a night with a full Moon I used my six inch refractor to split the AB pair of Bu 31 at just 70X. Can this be right?  It was an easy split and perhaps even though my eyes can barely separate a 1" Double star at 150X.  Perhaps our eyes find it easier to separate stars with wider separations with superior resolution at lesser magnifications because the diffraction rings are not interfering. Have others noted this?

 

In any case, Bu 31 is very nice in the way it forms an interesting asterism with three other stars in the field. The AB pair is a beautiful yellow primary K0V star with an orange companion and forms the vertex of an equilateral triangle. The base of the triangle is formed from a line of three faint stars. Stelle Doppie lists this as a quadruple system. I cannot be sure I saw the faintest member at magnitude 12.5. 

Edited by lwbehney, 11 June 2025 - 12:09 AM.

[VanJan]

Some comparison observations.

 

90mm refractor -  A = white  B = no color  D = no color. 180X   20 May 2012

 

20cm reflector -  A = yellow  B = slate  C = no color  D = no color  250X   2 June 2025

 

I cannot comment on your lower power resolution. I generally use magnifications that give a best (read easiest  ) view, so I don't have much experience with "how low can I go" observations. So I'll just give you  on your split and a   for your post.

 

VanJan

[CHnuschti]

Can this be right?

I say yes.

Better post the sep next time, which is 2.0" ATM for BU 31.

 

Looked at the moon 2-3 days ago, noticed Pi sco just nearby, which had been just overrun by the moon, hadn't that on the radar. Nice seeing, with my 107/600. So I thought, have a look at Nu sco BU 120 & al.. The CD 2.4" was just so split at the limit, only to notice then only my 10mm was mounted, so at mere 60x. Gave me a good laugh. At 100x even the direction of the AB 1.4" was undoubtely to assess.

 

Hell, recently, was not aware of it, I noticed you can split Albireo 35" in cyg with a 8x42 binocular on tripod.

 

regards

Edited by CHnuschti, 11 June 2025 - 11:30 AM.

[lwbehney]

Some comparison observations.

 

90mm refractor -  A = white  B = no color  D = no color. 180X   20 May 2012

 

20cm reflector -  A = yellow  B = slate  C = no color  D = no color  250X   2 June 2025

 

I cannot comment on your lower power resolution. I generally use magnifications that give a best (read easiest  ) view, so I don't have much experience with "how low can I go" observations. So I'll just give you  on your split and a   for your post.

 

VanJan

Thank you for sharing this information. It could be that in a 20cm telescope the companion star is over-brightened and is seen as a white star instead of the orange color and that in the 90 mm refractor the B companion is too faint for the color to be discernible. However, in my Mewlon 210, the 61 Cygni pair blaze with a beautiful chrome-orange, so I am not sure if my explanation for why a slate color is perceived in a 20 cm reflector is correct. 

Edited by lwbehney, 11 June 2025 - 05:35 PM.

[ssmith]

Got out last night to take a look at BU31 and get a few photos.  it turned out to be an enjoyable triple, though I couldn't capture all 3 components in a single image.

 

There was a gusty breeze which made getting sharp images very difficult so the final product is a bit soft, something I hope to improve on in the future.

 

My some of my individual frames show C as distinctly yellow to yellow-orange though it has lost some of the color intensity in the final stacked image.

 

Scope: C9 @ f12.6