Help with Orion doubles please...
Posted 20 December 2012 - 06:27 PM
So far, no problem with the easier ones like Mintaka, sigma, Eta, Rigel,sigma (nice!!) and Meissa. In the trap we saw A through E but not F, but the seeing conditions were suspect because F was not visible in a friend's 8 inch flourite apo either.
I would like to split 52, 32 and 42 which are all in the neighborhood of 1.1-1.2 arc seconds with my 8 inch Dob. What kind of magnification are we talking about, and any suggestions for F other than waiting for better seeing?
Posted 20 December 2012 - 07:01 PM
Posted 20 December 2012 - 11:34 PM
In a thread on 32 Ori you mentioned seeing 32 and 52 with 300x. With 52 Ori the components are equal, making it not too hard; with 32 Ori, there's a difference of 1.3 magnitudes, so it's tougher; but it's not in the same league as 42 Ori in terms of brightness difference. And current measures in the WDS list 32 Ori at 1.3", a fraction wider than 42 Ori at 1.1".
I last checked 32 Ori two years ago - 200x on the 140mm refractor just split the thing.
So, have you seen 42 Ori separated with the 6-inch? It would be an achievement given the brightness difference and closeness, and a secondary mirror brightening the diffraction rings. Well done if you have. I haven't tried 42 Ori yet - I'm waiting for a (rare) steady-seeing night.
42 Ori visible with an 8-inch Dob? - unlikely if it's a basic quality f/4.5 version, and if it hasn't cooled fully.
Posted 20 December 2012 - 11:38 PM
Posted 21 December 2012 - 05:07 AM
Agree on F, wait for a calm night.
Posted 21 December 2012 - 01:11 PM
Posted 21 December 2012 - 01:44 PM
Posted 21 December 2012 - 10:30 PM
Anyway nothing but the best seeing your likely to get and about as much mag as your scope can put out. On doubles some folks profitably exceed 50x per inch but you've gotta have the optics to pull it off. You just may too.
Posted 22 December 2012 - 01:11 PM
Speaking strictly about 52 Ori,the lowest magnification I used to successfully split this fine double star was 116x/old 7.5mm Celestron Plossl on my 125mm F/7 Dobsonian.
This happen last Spring on a night with decent to good seeing.
I think you are right about stars E and F in Trapezium,to see them one need good seeing.But definitely they are within the reach of an 8 inch Newtonian.I saw them in my 8 inch F/6 Dobsonian at 200x/ Tele Vue Radian 6mm.
A picture of this Ravneberg style Dobsonian named ,,Toleascope'' -after the friend who gave it to me-may be seen on my blog,in the right column:
32 Ori is a very recent aquintance to me.
I don't know nothing about 42 Ori...but I'm listening.
I wish you good luck,and you will certainly have,Orion is a gold mine!
Posted 22 December 2012 - 06:22 PM
I've now checked the WDS and the current photometry - probably Tycho - gives a brighter magnitude for the secondary star. The listing is now for mags 5.43 and 8.75, so delta-m is 3.32, not 3.8. Therefore I'd say that 42 Ori will definitely be tougher than 2 Vul, as the delta-m on 42 Ori is not much less at 2.9, and the separation much tighter - 1.1", vs 1.7" for 2 Vul.
I'm now less optimistic about splitting 42 Ori.
Posted 22 December 2012 - 11:58 PM
Thanks for your input Fred. They SCT sounds first rate.
Posted 23 December 2012 - 01:35 AM
Posted 23 December 2012 - 12:58 PM
Give it a shot.
Posted 23 December 2012 - 02:13 PM
Orion comes into my field of view in January and I hope too for a clear night to try it myself even if I do see a zero chance with my 140mm refractor.
Posted 23 December 2012 - 06:29 PM
Posted 24 December 2012 - 05:26 AM
Last night I had a go with 140mm f/8.5 Achromat refractor.
I went into the observation blind as I don't have a position angle measurement for this star.
At 342 - 400x power I could see a faint speck of light at around the following position angle of 195 - 200 degrees.
Seeing conditions were not the best and the small speck of light would come and go.
Here is a drawing (not to scale) Anyone know the current P.A. for this star. If the speck of light is near too the
current P.A. then I think the companion is certainly doable in better seeing conditions, at least with my 140mm refractor.
Posted 24 December 2012 - 05:38 AM
Posted 24 December 2012 - 10:16 AM
Great catch and illustrations.
Posted 24 December 2012 - 10:34 AM
Seeing was about 7/10, transparency 4/5, maybe, gibbous moon not far. The trap, well, E was readily seen, F only maybe twice.
So, if this is correct, then I split 42 Ori. If not, then I failed. But, I am reasonably sure I was able to detect a companion, not as a distinct spurious disc, but as a brightening of the first ring near PA 190. There were some moments where it looked like a much more difficult version of 32 Ori. (Sketch coming to be added below.) No nebulousness noted.
Well, I located 42 Ori at 109x and could not see any indication of a double star. Jumping to 174x, no indication. So, jumping to 380x still showed no immediate signs of being a binary pair but did seem a nice blue color (compared to 45 Ori which was more yellow.) If you didn't know this was a binary star, you'd probably never see it under these relatively average conditions - not according to my experience tonight. So, I decided to drop back down to 320x (6mm TMB II @ f/13) to get the best chance given the seeing.
Observing for many minutes, I did get some indications of a bright knot forming on or very near the first ring at about PA 190. Of course the rings were not entirely steady, blurred fairly often, but showed arcs most of the time and were calm only infrequently.
So, while the rings did dance a bit, it seemed there was a more consistent bulge at PA 190. There were a few moments when I was very sure the companion was there. You know, sometimes when you work and wait to see something and you silently whisper, "yea" when you see it. I had a few of those moments. So, I backed down to 260x (OU 12mm HD Ortho and 1.6x Barlow.) I got that same observation a few more times during the observation.
So, I decided to try again at 380x (8mm TMB II and 1.6x Barlow.) Again, pretty much the same result with the bulge at PA 190. However, at this magnification I did see that same effect once or twice at about PA 330. I suspect, however, my collimation might have been even so slightly off in that direction, so I am not sure about this sighting at PA 330.
Okay, so a difficult, very difficult observation over the course of an hour. If I have to call it, and I am reasonably certain I can, then the companion is PA 190 (+/-) and right on the first ring @ 1.2" arc. Man, I would love to be right and to have split it. It certainly seems consistent with Rutilus' observation. That's great!
Posted 24 December 2012 - 11:19 AM
Seriously though Im glad you got it. The impression sounds like my 2ES experience and while it was outside of the rings it was utterly spirit like!!! Congrats for an ob that'll stand appreciated for time to come!
It's a great region actually - I did the 70x-91x thing when I saw the seeing was *BLEEP* and it was fun but I wish I could've seen it. Nice drawing love the color - the elongation of the star on the ring. This is an effect of diffraction huh?
Posted 24 December 2012 - 11:41 AM
What is the magnitude of the companion? And where did you get the actual PA? Dare I ask from where you pulled it? (Serious, do you know where to find it?)
Man, that was a tough one, Pete. Maybe that one shows what everyone means by diffraction and unequal pairs being difficult. Rutilus looks to have had a better view of it, probably less diffraction helped. And he seems to have noted a little nebulousness. I wonder if that played a role even though I really didn't notice any.
Thank you, Pete, your turn will come. That was a challenge.
Posted 24 December 2012 - 01:18 PM
I usually use the interface to it provided by the StelleDoppie site, which shows this data for 42 ORI.
The most recent observation for this one is 1995. There's no orbital data for it, and it shows very little proper motion, so there's no reason to expect any noticeable change in the PA and separation. I also noticed that the eagle-eyed Reverend Dawes is credited with discovering 42 ORI as a double in 1848.
Nice work, though -- looks like both Norm and WRAK got it. From the looks of those sketches, it looks very similar to Delta Cygni in a 60mm refractor, and every bit as difficult. Would love to give it a try with my six inch f/10 if the weather would just cooperate for a night.
Posted 24 December 2012 - 06:50 PM
I am sure you will be successful. Staying tuned.
Posted 24 December 2012 - 07:39 PM
Posted 24 December 2012 - 07:42 PM