|
Gord
scholastic sledgehammer
Reged: 01/06/04
Posts: 850
Loc: Toronto, ON, Canada
|
|
Hi,
I'm wondering if you all can help me with a double I was looking at (or I should say for...) last night. It was Struve 382 in Perseus. The problem I'm having is I can't find it, or at least at the location it's noted at in Cambridge Double Star atlas.
It can be found on chart 7 in the atlas, on the right page just above the border with Taurus. Details on the double are:
RA 03:24 Dec +33:32, Mags 5.8, 9.3, sep 5"
I was using my Tasco, conditions were fairly average. Mediocre transparency, but good seeing. At these magnitudes and separation, this should have been super easy. But I saw nothing. Approx. mag 6 range star, but that's it.
I looked at plenty of other doubles just around this area, and had no trouble with them. For example, Burnham 535 (3.8, 8.3 @ 1") was strongly suggested as a double (oblong shape) at 300x. Struve 425 (7.5, 7.6 @ 2") was very pretty (and easy) at 113x. Struve 448 (6.7, 9.2 @ 3') was another easy one.
But 382 was nothing. 300x was still more nothing. I checked the map multiple times, navigated there (star hoped) several times even trying different routes. The star field definitely match the map.
Has anyone else had a look at this one? Could it be an error in the atlas, or did I really just miss it?
Fun night though. I continued down into Taurus from there stopping along the way at Burnham 533 (7.6, 7.7 @ 1.1") which was showing a deep notch at 300x. Nice. But I was really impressed with Struve 401 and Struve I 7. Two separate doubles lying close enough together to fit in the same field, even in my 3mm Radian at 300x. Not tight or difficult but just a very pretty arrangement. Highly recommend this one to anyone who hasn't looked at it.
I finished up the night with some open clusters and a very quick look at the Trapezium. Not the best conditions for sure as E was only visible half of the time or so, and F was only glimsed a couple of times in 10 minutes at 113x.
Anyways, I hope someone can offer some input on this "missing" double. 
Thanks and Clear Skies!
-Gord
--------------------
Gord
- Celestron C10/Normand Fullum/MoonLite/ProtoStar/Antares
- Tasco 11TR/Normand Fullum/JMI/ProtoStar
- IStar 6" F10 (Build in progress!)
- SkyWatcher 80ED
- Celestron CG5a, Antares EQ5, UniStar Lite, EQ2
- Burgess 15x70, Nikon Action IV 10x50
- PST, Orion StarBlast, Apex 102, MallinCam's, and some EP's with green lettering
... and an understanding wife 
|
David Knisely
Postmaster
Reged: 04/19/04
Posts: 8801
Loc: Beatrice, Nebraska
|
|
I think you probably missed it. The primary is pretty bright (magnitude 5.8), but the companion is rather faint at 9.3 (p.a. 153 deg.). At a separation of 4.8" arc, it may be a little hard to see in the glare of the primary. Clear skies to you.
--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org
|
Catapoman
scholastic sledgehammer
Reged: 06/06/03
Posts: 821
Loc: VA
|
|
I agree with David. You probably missed it. It's charted, but not listed on my S&T Pocket Sky Atlas pg 15). I'll be checking this one out in the near future.
--------------------
Pernel
Nexstar 11 GPS
Takahashi TSA-102
Mewlon 210
GM-8
|
fred1871
member
Reged: 03/22/09
Posts: 48
Loc: Canberra, Australia
|
|
Hmmm... I'm inclined to agree with David's comment regarding Struve 382.
About another pair you mentioned - Burnham 535 (Omicron Persei) I have some doubts about the "oblong shape" given the brightness difference of the components. "Oblong" is usually possible only with components of fairly similar brightness, which these stars are not.
There is incidentally an issue here on the magnitudes quoted in the Cambridge Double Star Atlas. Recent versions of the WDS give magnitudes 3.9 and 6.7 for the components (2009, 2006, and 2001 versions of WDS). The WDS in 1996 gave almost the magnitudes the CDSA lists (WDS then had 3.9 and 8.4).
If we take the more recent magnitudes listed, there's still a difference of 2.8 magnitudes between the components, or a factor of about 14:1 in comparative brightness. Can't say that I'd expect such a pair to look "oblong" when it was slightly short of resolution. So I suspect it's the effect of less than perfect seeing that suggested the "oblong" shape.
Pairs like this one - close, with quite a big difference in brightness - don't follow the Dawes Limit criterion. They're tougher. Frankly, I wouldn't expect BU 535 to yield to 4.5-inches aperture. 
|
Gord
scholastic sledgehammer
Reged: 01/06/04
Posts: 850
Loc: Toronto, ON, Canada
|
|
Thanks for the input everyone. I'm definitely going to go back and try this (and the others) again. I'm just really surprised that I could have missed it. It should have been a real easy one with such a wide separation, and at around mag. 6 the primary is really not very bright, as compared to 2-3rd mag ones.
Fred, I'll definitely try BU 535 again as well. It's certainly possible it could have been a seeing artifact as this was one of my first targets. The scope had been sitting for at least 45min before and it was a relatively warm night for late Nov.
The airy disk on this one wasn't a nice round circle as all the other stars were showing (at 300x), so it really seemed like it wasn't seeing. 1" is definitely at the edge for this size of scope, but I have had success down to this separation before.
Definitely will be visiting this area again. Lots of interesting sights is a relatively small area.
Clear skies!
-Gord
--------------------
Gord
- Celestron C10/Normand Fullum/MoonLite/ProtoStar/Antares
- Tasco 11TR/Normand Fullum/JMI/ProtoStar
- IStar 6" F10 (Build in progress!)
- SkyWatcher 80ED
- Celestron CG5a, Antares EQ5, UniStar Lite, EQ2
- Burgess 15x70, Nikon Action IV 10x50
- PST, Orion StarBlast, Apex 102, MallinCam's, and some EP's with green lettering
... and an understanding wife
|
John Fitzgerald
In Focus
Reged: 01/04/04
Posts: 2167
Loc: AR
|
|
I observed Struve 382 tonight with my 6" refractor at 170x and 200x. The companion blinked in and out due to bad seeing, but was definitely there. Not an easy object in poor seeing. This one is obviously very seeing dependent.
|
PJ Anway
Pooh-Bah
Reged: 06/04/03
Posts: 1295
Loc: Michigan's U.P.
|
|
With a 3-magnitude difference, the relative brightness of the primary is going to make the secondary difficult. Another star with a similar difference in magnitude is Delta Cygnii. I find that the biggest factor in splitting doubles of this type is the steadiness of the seeing. On night of average seeing the split will be rather difficult. On nights of excellent seeing the split is relatively easy.
--------------------
Clear Skies,
PJ
Lookum Observatory
|
John Fitzgerald
In Focus
Reged: 01/04/04
Posts: 2167
Loc: AR
|
|
I tried Struve 382 again tonight, and it was much easier in much better seeing. The comes was seen steadily at 170x in the 6" achro.
|
Gord
scholastic sledgehammer
Reged: 01/06/04
Posts: 850
Loc: Toronto, ON, Canada
|
|
Hi Everyone,
I finally managed to get out last night. It wasn't looking good earlier, but cleared up suddenly so I just grabbed the Tasco again. Not a bad night, but pretty cool and a bright moon.
Also, I had just nicely got setup and going when my neighbour decided to turn on his "holiday cheer". Full reinghdeer and sleigh all made with lights. And for some reason, he felt it necessary to set all this up 10' from where my pier is located. Oh well. Aside from the bright moon, it was looking like a decent evening for local light pollution until that happened.
You can still do quite a bit with doubles even in brighter conditions, but it's still difficult when it's so bright you can't see the field stop in the EP. Makes for kind of a tiring session with constantly trying to cup the focuser tightly enough to be able to see what's in the field.
Anyways, I went to Struve 382 as my first target at 113x (8mm TV Pl). Within my first glance I could see the double, at least until it disappeared and the star shapes went all funny. Not long enough cooldown and the tube currents were playing havoc with the view.
But, when it did settle down, the companion was quite obvious. I waited a bit longer for things to settle and jumped up to 300x (3mm Radian). Good moments were less frequent again, but the pair were obvious and well apart at certain moments.
The conditions weren't that much better last evening (if at all) over the other night. In fact, the tube currents were much worse. I'm really wondering now if I really must have just missed it earlier by being on the wrong star. I know I had tried a few times before, but it was just to obvious.
I made better note of the position angles on this session to check later against the WDS catalog. I was especially interested to see if my split of BU 533 @ 1.1" was real or an artifact. I was pleased that all of my observations matched up correctly.
Speaking of BU 533, it and Struve 427 make for an interesting comparison. They are located relatively close to each other, and the components brightness as well as position angles are very similar as well. The only difference is 427 has a 7" separation vs. 1.1" for 533.
I ended up in Orion before packing it in. Rigel is a beautiful sight at 300x with the primary blazing and the delicate companion off a little to the side. A great way to finish off a short but fun evening. Christmas lights and all!
Clear skies,
-Gord
--------------------
Gord
- Celestron C10/Normand Fullum/MoonLite/ProtoStar/Antares
- Tasco 11TR/Normand Fullum/JMI/ProtoStar
- IStar 6" F10 (Build in progress!)
- SkyWatcher 80ED
- Celestron CG5a, Antares EQ5, UniStar Lite, EQ2
- Burgess 15x70, Nikon Action IV 10x50
- PST, Orion StarBlast, Apex 102, MallinCam's, and some EP's with green lettering
... and an understanding wife
|
fred1871
member
Reged: 03/22/09
Posts: 48
Loc: Canberra, Australia
|
|
I got the telescope on to STF 382 this week - the weather finally has come good where I live, after several months of too much cloud (and not a lot of rain).
Using my 14cm refractor the little companion was just visible at 114x, close to the primary; 160x gave a better view. Seeing at the time was ok but not great - in poor seeing I'd expect this one to be difficult, as it didn't jump out as obvious. With steadier atmosphere I'd expect it to be not too hard.
I've tried for Omicron Persei (BU 535) a couple of times, without success, though the seeing was not great either time. Last night the seeing steadied to very good later in the evening, so I moved the 'scope to BU 535 again and found it had gone behind a tree.
|
John Fitzgerald
In Focus
Reged: 01/04/04
Posts: 2167
Loc: AR
|
|
I suppose Perseus is pretty low in the north for you. Tight or unequal doubles near the horizon can be hard to resolve.
|
fred1871
member
Reged: 03/22/09
Posts: 48
Loc: Canberra, Australia
|
|
Yes, Perseus is a low northern constellation from where I am at 35 deg S latitude. So these doubles - STF 382 and BU 535 - only rise to about 22-23 degrees above my horizon when on the meridian. So there are fewer nights when the seeing is good at that modest altitude.
|
payner
professor emeritus
Reged: 03/22/07
Posts: 513
Loc: Bluegrass Region, Kentucky
|
|
I just came in from observing STF 382. It was an cleanly split at 78x (lowest magnification available to me) in the Rumak; seeing was 3/5. At 194x I'd call the primary white and the secondary light orange, although the secondary could look lilac at times. With the disparate magnitude trying to gauge the color is difficult.
Thanks for the post, Gord. This brought a nice double to my attention I had not observed.
Randy
--------------------
Santel MK91 Deluxe Rumak
Takahashi TSC-225
Takahashi FS-128
Takahashi FS-152
|
John Fitzgerald
In Focus
Reged: 01/04/04
Posts: 2167
Loc: AR
|
|
Quote:
Yes, Perseus is a low northern constellation from where I am at 35 deg S latitude. So these doubles - STF 382 and BU 535 - only rise to about 22-23 degrees above my horizon when on the meridian. So there are fewer nights when the seeing is good at that modest altitude.
OTOH, Alpha Centauri NEVER rises here (36 deg N.), but Perseus is partly in the zenith when on the meridian.
|
fred1871
member
Reged: 03/22/09
Posts: 48
Loc: Canberra, Australia
|
|
Yes, Alpha Centauri is one of the great doubles.
But we're straying a long way from Perseus.
Another of Gord's pairs that he found had a "deep notch at 300x" is BU 533. This one I split with the 14cm refractor - a little more aperture helps, as Gord used a 4.5-inch (11.5cm telescope) - I saw it as an evenly bright separated pair of stars at 230x. It was clearly a double at 160x, but the higher magnification gave a better view with clean separation.
A pleasing result with the quoted magnitudes of 7.6 and 7.7 at only 1.1" separation.
|
|
0 registered and 2 anonymous users are browsing this forum.
Moderator: EdZ, RLTYS
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 593
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 