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scholastic sledgehammer

Reged: 02/18/12

Short session in CrB
      #5951609 - 07/02/13 03:57 PM

No session without questions it seems. Yesterday clear night but arriving home late - so I preferred to select the 140mm refractor instead of the planned C9.25 to avoid thermal issues. Very good conditions for my location: Moon below horizon, NEML ~3.3mag, Pickering ~7, good transparency. Short session in CrB:

Name ID RA Dec Sep M1 M2

STF1951 HIP 75913, WDS15303+2739 15h 30m 20.3s +27:39:29.8 17.0 7.89 11.88: x40 very faint at 8 o'clock, x75 confirmend. Limit aperture 120mm - one more example how I overestimated the influence of light pollution on TML

STF1941 HIP 75519, WDS15257+2638 15h 25m 42.8s +26:37:40.5 1.4 9.65 9.77: x140 at 5:30, clear separation x200/280 only with averted vision, limit aperture 110mm

STF1936 WDS15211+2702 15h 21m 07.6s +27:02:23.4 19.8 9.92 10.09: x40 at 6:30, limit aperture with averted vision 55mm

STF1932 HIP 74893, WDS15183+2650 15h 18m 20.2s +26:50:24.7 1.6 7.32 7.41: x75 elongation at 2 o'clock, x140 clear separation. Limit aperture 60mm with averted vision - this is about 20% below Dawes. Something is odd here

Beta CrB HIP 75695, JEF1, WDS15278+2906 15h 27m 49.8s +29:06:19.8 0.2 3.68 5.2: Used only as Hop zu STF1937

STF1937 Eta CrB, HIP 75312, WDS15232+3017 15h 23m 12.2s +30:17:17.7 0.6 5.64 5.95: x280 clear elongation 11 to 5 o'clock. Result too good to be true. Eta CrB is a fast moving double, so may be 0.6" is no longer valid

STF1963 HIP 76536, WDS15379+3006 15h 37m 53.7s +30:06:10.4 5.1 8.54 8.85: x40 at 8:30. Limit aperture 45mm

Theta CrB COU610, HIP 76127, WDS15329+3122 15h 32m 55.8s +31:21:32.9 0.8 4.27 6.29: Again nothing

HU746 HIP 76242, WDS15344+3201 15h 34m 26.3s +32:01:01.3 2.1 8.85 11.59: No resolution

STF1959 WDS15347+3446 15h 34m 44.1s +34:43:22.8 2.1 9.79 10.81: x75 at 7 o'clock. Limit aperture 100mm

STF1964 HIP 76563, WDS15382+3615 15h 38m 13.0s +36:14:48.3 14.0 7.85 8.06: The given parameters are these of the main components - resolution x15 at 7:30. Should be a double-double. x140 resolution of the upper star at 11 o'clock with separation 1.6" with +8.07/9.02mag with aperture limit 95mm, no resolution of the lower star.

STF1965 Zeta CrB, HIP 76669, WDS15394+3638 15h 39m 22.7s +36:38:09.0 6.0 4.96 5.91: x40 at 8 o'clock. Limit 25mm

Finally a jump to 90 Her (BU130) 1.6" +5.28/8.76mag: No resolution despite near zenith position.

Remaining questions:
- advertised data of STF1932 correct? Limit aperture of 60mm suggests larger separation
- current separation of STF1937 (Eta CrB) still 0.6"? Observation suggests larger separation
- Theta CrB again - the probability that this one does not show with 140mm aperture at least a pointed elongation seems low, companion must be fainter
- configuration of STF1964 is somewhat unclear to me, especially the position of HU1167 and the advertized data in total. There should also be another 0.1" component with only 1 observation. I found only one photo on the web (,r:0,s:0,i:83&iact=rc&page=1&tbnh=153&tbnw=204&start=0&ndsp=1&tx=115&ty=89) suggesting that the companion of the second star is much fainter and that the second star may be even a triple
- 90 Her: Should be despite delta-m of 3.5 rather easy with 140mm, makes curious.


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super member

Reged: 05/24/13

Loc: United States
Re: Short session in CrB new [Re: WRAK]
      #5952086 - 07/02/13 09:01 PM

Great report, Wilfried. And very productive for a "short session".

I saw Eta CrB as extended and then eventually as resolved using the 8 inch.

I will take a peek at 90 HER again tonight with the 8 inch as it has given more trouble than expected lately with a few folks.

I also like the data for STF 1959 for assessing variables in my 8 inch calculator.

CrB is overhead in Dobson's Hole for me once twilight has faded.

I have hundreds of observations with my 15 inch, but only a dozen or so good ones for the 8 inch--I need to fix that. Mining the 15 inch data for meaningful correlations will be a task indeed.

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professor emeritus

Reged: 03/22/09

Loc: Australia
Re: Short session in CrB new [Re: WRAK]
      #5952095 - 07/02/13 09:08 PM

Wilfried, Eta CrB has an ephemeris listing (6th orbit catalog) of 0.67" for 2013 and 2014.

I've observed it twice recently, as I mentioned in the "Comparative session..." thread. Both times, 140mm refractor, 400x, clear elongation with suggestions of notching in the best moments. So, yes, the modest increase from 0.6" to 0.67" makes a difference.

I'd think your "clear elongation at 280x" fits with the ephemeris and with what I'm also seeing.

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professor emeritus

Reged: 03/22/09

Loc: Australia
Re: Short session in CrB new [Re: Nucleophile]
      #5952120 - 07/02/13 09:23 PM

Agreed with Mark, a very productive session for a "short" one. And there are some doubles you've looked at that were not on my list; thanks for that. Most interesting is the "double-double" STF 1964 - I'll try that one on the next clear night. I'd think it should be possible with 140mm for both pairs in a dark sky; the current WDS gives AB (m 8.07, 9.87) as 1.2" in PA 079 for 2012, and CD (m 8.06, 9.02) as 1.5" in PA 021 for 2012.

The AB pair is likely to be difficult, closer than CD and bigger delta-m (1.8 compared to 0.96). Your success on CD with 140x makes me hopeful of AB as a "limit" observation with 140mm in good conditions. If not, there's always the 235mm SCT that we both have.

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scholastic sledgehammer

Reged: 02/18/12

Re: Short session in CrB new [Re: fred1871]
      #5952676 - 07/03/13 08:25 AM

0.67" makes the observed elongation of Eta CrB a bit more plausible.
Regarding STF1964 - the second double is certainly a bit more difficult than the first one, will try again.

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scholastic sledgehammer

Reged: 02/18/12

Re: Short session in CrB - repeated with C925 new [Re: WRAK]
      #5955745 - 07/05/13 09:21 AM

Reason was to check if I could do it better with a larger aperture compared to last time. Sky a tad darker with NEML +3.5mag (more or less the best I can get at my site) but air somewhat turbulent with seeing Pickering 5-6. The C925 had enough time for temperature adaptation and was equipped with the 225mm iris meaning a base CO of 0.4. Collimation was not checked as I hoped for some stability.
As a starter I visited Izar - with x335 the companion made the impression of a small planet using the third diffraction ring as orbit around the primary. Nice picture but not as beautiful as with the 60mm mask.
Then to the CrB session:
- STF1951: x100 very faint at 9 o'clock. Limit aperture 120mm with surface equivalent 80mm refractor - is this a possible TML value for NEML +3.5mag?
- STF1941: x180 at 6. Limit 150mm = surface equivalent 120mm refractor
- STF1936: x40 at 7. Limit 110mm = surface equivalent to 63mm refractor for TML statistics
- STF1932: x100 at 2. Limit 130mm = surface equivalent to 94mm refractor
- Eta CrB: No resolution but enhanced brightness in the diffraction pattern at the 5 o'clock position. The position would be OK but I suspect rather a collimation problem
- STF1963: x40 at 9. Limit 105mm = surface equivalent to 54mm refractor
- Theta CrB: Again no resolution and again enhanced brightness in the 5 o'clock direction. Would again ~ fit the position but as above
- HU746: x335 at 5, but very faint. Limit 225mm = surface equivalent to 206mm refractor
- STF1959: x180 at 7. Limit 160mm = surface equivalent 133mm refractor
- STF1964: AC x40 at 7:30. CD x100 elongation at 11, x180 clear split. Limit 180mm = surface equivalent to 156mm refractor. No resolution for AB (HU1167) - again collimation issue
- Zeta CrB: x40 at 8. Limit 100mm = surface equivalent to 44mm refractor.
Finally again 90 Her and again no resolution - probably collimation issue and also seeing has gone worse.

Result: Did not much better as with the 140mm refractor with the exception of HU746 as seeing was somewhat worse and collimation was neglected - will not do this again. Regarding limit apertures: Will have to check if the calculation of the surface equivalent refractor diameter is of any use.

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