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90 Herculis

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#26 fred1871

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Posted 13 September 2013 - 02:07 AM

Pete, I'll quote myself from my note earlier in this thread:
Incidentally, 2 Vul (BU 248) has the primary star as ES Vul, a variable star designation. The WDS adds a note to this effect, saying that it's a Beta CMa-type variable (sometimes known as a Beta Cephei type - and not to be confused with classical Cepheids). That means the magnitude variation will be small - Sky Catalog 2000 lists a variation of 0.06 magnitudes, so not much to worry about there.

With such a small magnitude variation, there will not be any significant effect on resolvability from brightness changes.

#27 jrbarnett

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Posted 13 September 2013 - 10:21 PM

I separated the pair in a 127mm f/9 ED doublet at around 180x without much difficulty several years ago. Haven't checked it out since then. Reports of resolution in a 101mm scope have me now itching to go after it in a 111mm triplet.

I wonder how small can you go and still manage the split?

Regards,

Jim

#28 azure1961p

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Posted 13 September 2013 - 10:25 PM

Thanks Fred, as always, appreciated.

Pete

#29 rayden68

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Posted 08 October 2013 - 10:35 PM

A very clear night so I was waiting to try this one used my ES ar152, went 396x and could see a bump or flash on the bottom right. Put in a 4mm with a Barlow and again a bump or flash and maybe a dot? Checked the position and that's where it should be. I will put it down as a good try. Just wasn't distinct enough to claim a dead to rights victory. I want to try again on a better night or more aperture or both!

#30 Bill Boublitz

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Posted 08 October 2013 - 11:54 PM

By all means, try again. It sounds like you're getting there. This is a challenging, somewhat fugitive pair. What aperture are you working with?

#31 rayden68

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Posted 09 October 2013 - 07:08 AM

A was using my 152mm refractor.

#32 payner

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Posted 14 October 2013 - 04:32 PM

On 8/23/2013 I split 90 Herculis with a RuMak 228/3199 using a 5 mm LE eyepiece. I recorded this observation as very tight clean split (dark line between the stars). Seeing was recorded as 3/5.

On 10/11/2013 I split this pair with a RuMak 228/3100 using an 8 mm eyepiece. Seeing that night was a 4/5. I noted the primary as cream and the secondary white.

Best,
Randy

PS- If skies and opportunity allow, I want to try with a FS-152 refractor before it gets too low this year.

#33 WRAK

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Posted 28 August 2014 - 03:37 AM

90 Her remains a riddle for me - last night starting a session using my 140mm refractor with fair seeing with 90 Her at the end. Again no resolution. Seeing seems to have deteriorated during the session, image was meanwhile rather unstable, sometimes a hint for an elongation at 1:30 but nothing definite. From the data I would expect a fair chance for resolution with 127mm (5") so repeated non resolution with 140mm makes me curious. May be the companion is in the reddish spectrum - this is my meanwhile confirmed personal weakness regarding resolution. Else I have no explanation for this besides the obvious seeing factor.

Wilfried



#34 WRAK

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Posted 29 August 2014 - 04:52 AM

Last night again clear sky. Coming home late I decided to go directly to 90 Her. First just a look at Eps Lyr for checking seeing - this time excellent with limit aperture for resolution down to 50mm (the brighter pair might have been possible with even less aperture).
Then ~10° lower in altitude for 90 Her. Seeing quality changed dramatically - with 140mm and a magnification of x420 like last night a star disk out of liquid metal changing constantly contours ynd a first diffraction ring with running sparks like neon advertising.
May be a hint for an elongation at 1:30 but no serious hint for a companion.
Applied then CO 0.2 - image more stable, elongation more stable, sometimes a flicker at the right position but again no serious hint for a companion.
Tried then reduced 127mm (5") aperture without CO and with a magnification of x280 - image with better stability but again no trace of a companion.
Tried then even 100mm aperture - image very stable but first diffraction ring already a tad faint, no trace of a companion.
Then back to 140mm aperture and switch to Nagler Zoom 3-6mm. Background image somewhat darker and with 3mm (=x336) a rather stable elongation at 1:30. Might be enough for a guess but is again no serious "resolution".
Have to wait again for better seeing in the 90 Her field of view.
Wilfried

PS: Interesting experience with the drastic change of seeing quality with only 10° difference in altitude



#35 Perseus_m45

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Posted 29 August 2014 - 10:48 PM

I first viewed this star system july 25 20:19 est usa, Its on the Haas list and my notes are as such.

 

using 5.1 mm epic and 2 x barlow i have a clean split on this star with the primary being a ruddish orange yellow and the secondary to small for a good color reference,,,a very nice double but difficult to split in the 6 inch..

 

then again..

 

looked at this star on 5/23/2014..i was able to split this star using a 3.7mm epic eyepiece in my 6 inch f/8 refractor..seeing was pickering 6/7..

 

mike h



#36 drollere

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Posted 30 August 2014 - 10:11 PM

I'm not surprized in the least at the problems you folks are having. It's not an orange "bump" either. My 10" refractor shows a white companion hidden just beneath the broken first disc ring. I'm wondering if it is a variable star. :shrug: It just seems much dimmer than 8 mag. Maybe it's deceiving because of the 5 mag. primary. All I know is it is somewhat "difficult" in my big refractor. I don't see how a 6"-8" scope at high power to seperate 1.6" can be able to detect this little devil. It truly needs exceptional steadiness in the air.

 

glad the OP finally got it. my RoT for a 10" aperture (the OP's) is 1.6"/0.45 = 3.5, and 3.5 is around the magnitude difference 3.5, so the companion would definitely be a challenge at that aperture but should be detectable (at 3.5x the resolution limit, it is clearly resolvable).

 

there's no particular reason why a smaller aperture should detect it. (101 mm ... fred, seriously?) a 250mm aperture may need some coaxing -- try different magnifications, try blocking the primary star with a reticule -- try it when the seeing is exceptionally good, especially. it's a challenge.



#37 WRAK

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Posted 31 August 2014 - 04:37 AM

There is no reason to doubt that 90 Her can be very well done with 150mm aperture. For example Mike has reported twice positive with 150mm and the Sissy Haas website shows currently 7 positive reports for 90 Her with 150mm. And with favorable conditions it might also be done with somewhat smaller apertures, especially with 140mm. Yet it seems a tad more difficult as its naked data suggests. Last measurement with 1.6" is from 2009, first measurement was 1874 with 1.9" and a measurement from 1999 delivered 1.5". So maybe it is a tad closer than currently listed and yes - the spectrum of the companion might play a role.

Wilfried


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#38 Perseus_m45

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Posted 31 August 2014 - 10:03 AM

I believe 90 her can be split with a good quality 140mm refractor. But as Wilfried suggests there are many factors in the outcome of the observation.  

mike h



#39 Perseus_m45

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Posted 31 August 2014 - 10:17 AM

What gives here? This is a toughie or my transparency sucks. My book says magnitudes 5.8 and 9.2 with a seperation of just over 1.6"! But that is a hech of a contrast stretch. :confused: Mike

Mike, There are many factors in why you could have missed this split with such a scope.

Is the scope in perfect collimation? Sometimes larger aperture is not our friend when observing doubles. And so on,you know how it is. .Maybe try different aperture masks? Also I have found by taking it in and out of focus may in fact cause a minute secondary to pop out at times. I am able to do this at very this a very high magnifications because of the steadiness of my focus motor . So my image holds very steady .

mike h



#40 fred1871

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Posted 01 September 2014 - 01:48 AM

Bruce, I also wondered about the 101mm claim for 90 Her - as I mentioned last year in this thread. At the time I was not doubtful about 150mm, and am unsurprised by the added resolution successes for 150mm recorded on the Haas Project data base. At 140mm? - possibly so. I'll leave it to others, because this one stays too low from my latitude. No chance of the necessary very good seeing.



#41 drollere

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Posted 01 September 2014 - 11:31 AM

There is no reason to doubt that 90 Her can be very well done with 150mm aperture. For example Mike has reported twice positive with 150mm and the Sissy Haas website shows currently 7 positive reports for 90 Her with 150mm. And with favorable conditions it might also be done with somewhat smaller apertures, especially with 140mm. Yet it seems a tad more difficult as its naked data suggests. Last measurement with 1.6" is from 2009, first measurement was 1874 with 1.9" and a measurement from 1999 delivered 1.5". So maybe it is a tad closer than currently listed and yes - the spectrum of the companion might play a role.

 

well, i'm with wilfried on this one. i see absolutely no trace of a companion with my 140mm up to a 0.2 exit pupil (barlowed Tak 2.8 mm). very thin, lacy, rippling diffraction rings and continuous low frequency turbulence, easily "C" seeing and very good transparency, leisurely, extended observing.

 

btw, my first good night of viewing in 3 months! -- can i get an OH YEAH!?

 

as a check, i searched my database for a matching system and came up with HU 235 nearby, 1.6" and delta-m of 2.2. identified the companion at an easy separation and estimated position angle of 285-290º. survey says: 283º. (once you align your diagonal to your declination axis, position angles get really easy.)

 

my notes show that i did detect this companion with my 300 mm SCT a few years ago. i didn't fire it up last night because i didn't want the distraction. maybe tonight.

 

i'm not interested to tell other people what they should or shouldn't see ... and the range of visual acuity and instrument quality is very large.

 

i will say that the right way to go about a detection task is to observe a system with no prior knowledge of its parameters. if you can't see it without knowing where it is, then you're too easily misled to see something you've been told or you believe exists. (that is why we use blinded protocols in behavioral research.)



#42 drollere

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Posted 02 September 2014 - 01:44 AM

tried again tonight with the 300 mm SCT: no luck. leisurely inspection, seeing about "C" with low frequency rippling, magnification from 300x up to 2200x. it should be located beyond the 3rd ring, but nothing. nada. finally made a wild guess as to what i thought might be the position angle: i was off by about 120º.



#43 R Botero

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Posted 02 September 2014 - 12:56 PM

I have not observed 90 Her this season but last year at around this same time I spent three nights on it and got a suspected split at 215x using my 6" refractor with PA ~150 and secondary pretty much on first and only diffraction ring detectable. Not much colour noted apart from white primary and possible blue hue to secondary. I will try the 10" Mak next time I have a chance.
Roberto

#44 drollere

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Posted 02 September 2014 - 01:37 PM

Also I have found by taking it in and out of focus may in fact cause a minute secondary to pop out at times. I am able to do this at very this a very high magnifications because of the steadiness of my focus motor. So my image holds very steady .

 

yes, the focal trick is a good one and not widely appreciated. if you are extrafocal then you are essentially focusing on a target at a finite distance -- in other words, the upper atmosphere. (as you increase the telescope focal position, focus applies to objects at a closer distance.)

 

by taking the focus slightly in the direction of the intrafocal position without expanding the star image through defocus, you minimize atmospheric turbulence. this is, incidentally, the benefit of long focal ratio refractors: they have a large latitude of focus, so "going intrafocal" without degrading the image focus is more readily done.



#45 Rutilus

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Posted 02 September 2014 - 02:19 PM

I tried the other night with a 6" f/15 refractor, usig powers
from 200x - 940x, but alas nothing was detected.

#46 WRAK

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Posted 02 September 2014 - 03:35 PM

Basically no amount of aperture might be enough if the seeing is not fair but the number of negative or indecisive reports makes curious. I checked my data set of limit observations and found the following examples for similar targets:

A146 (Fred)  140mm  1,7"  +7,31/10,77mag

STF1171 (myself)  125mm  2,1"  +6,48/9,95mag

STF2022 (myself) 140mm  2,2"  +6,54/10,03mag

Theta CrB, COU610 (Mark)  200mm  0,8"  +4,3/7,8mag

HU932 (myself) 140mm  2"  +7,26/10,85mag

KUI17 (Fred)  140mm  +1,8"  +4,26/7,85mag

BU655 (myself) 140mm  +2,1"  +8,34/11,95mag

99 Her (Roberto)  152mm  1,25"  +5,13/8,96mag

BU1074 (Roberto)  152mm  2,5"  7,2/11,2mag

Psi Ori (myself)  67mm  2,9"  +4,6/8,6mag.

 

Quintessence: According to the advertised data 150mm for 90 Her should be not this difficult and 140mm should be doable with fair seeing. But this is obviously not the case - again: My impression is that there has to be some detail making this double extra difficult.

Wilfried

PS: My RoT calculator proposes 127mm for 90 Her - but I admit that this seems a tad optimistic



#47 azure1961p

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Posted 02 September 2014 - 05:24 PM

Rutilus,

 

I had tried last summer to no avail with the 8" and some very very stable seeing.  The moment those transparent fall evenings kicked in and seeing was at least good - there it was at 364x.   What was a little frustrating is that exactly where I suspected it during summer but with no clincher moment - is exactly where it ended up being. That happened again the other night with Triton. It simply was too suspect to confirm.

 

have you had any suspect moments?

 

Pete


Edited by azure1961p, 02 September 2014 - 05:25 PM.


#48 WRAK

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Posted 03 September 2014 - 03:48 AM

So far I had no real idea how to interpret the Fuzzy Logic Difficulty Index for resolving doubles as it works without reference to a given aperture diameter - now I think this might be an additional information that if you have a scope large enough to resolve a given double then the DI might give a hint that it might still be very difficult and thus very demanding in terms of seeing quality etc.

For the "usual" RoT approach this might mean that the resolution probability for a proposed aperture is then not 50% but seriously less for a double with a high DI.

Wilfried



#49 fred1871

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Posted 03 September 2014 - 08:30 AM

Given the varied reports on 90 Her, I thought I'd run some numbers on the pair. Long-term, it's pretty clear the separation has been near-enough 1.6" for quite a long time. Also, the recent magnitudes are not much different from the old ones.

 

Running a Rayleigh calculation, gives the surprising result of about 85mm aperture - companion in the first dark ring. Any takers on that?

 

The first bright diffraction ring will centre on the lesser star with about 115mm aperture, roughly 4.5-inches. Given the width of that ring, using figures for an unobstructed aperture, suggests the secondary star will be in the brighter part of the ring with apertures from about 4 to 5 inches - 100mm to about 130mm.

 

A 140mm aperture will put the secondary on the outer part of the ring; 152mm locates it just outside the ring, likely to be seen attached to the outside of the ring. By 200mm aperture the star is distinctly beyond the first ring.

 

Because the brightness difference of the stars is considerable - 3.5 magnitudes - the least likely apertures to resolve this one are in the 4-5-inch range, where the diffraction ring brightness superimposed on the companion will make the companion very difficult to discern.



#50 Rutilus

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Posted 03 September 2014 - 02:01 PM

 

Rutilus,
 
I had tried last summer to no avail with the 8" and some very very stable seeing.  The moment those transparent fall evenings kicked in and seeing was at least good - there it was at 364x.   What was a little frustrating is that exactly where I suspected it during summer but with no clincher moment - is exactly where it ended up being. That happened again the other night with Triton. It simply was too suspect to confirm.
 
have you had any suspect moments?
 
Pete

 
Pete - The seeing the other night was not the best, I did once/twice suspect
something just outside the diffraction ring. However, after checking the P.A.
with the information in this thread, I noted that my suspect was degrees off
with the given P.A.
I've been wanting to get back to this star, but it's wall to wall cloud cover
here at the moment.






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