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Observing >> Double Star Observing

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Michael Rapp
Post Laureate
*****

Reged: 04/27/04

Loc: Dickinson, TX
A home for this weary traveler? new
      #5927560 - 06/18/13 01:42 PM

A few nights ago, in a fit of desperation to find something, anything interesting in my light-polluted skies, I stumbled upon the lovely cluster NGC 6231 in southern Scorpius.

While the cluster was indeed beautiful, Zeta Scorpius (just south of NGC 6231) really captured my attention. I was struck how beautiful the pair is. I found myself transfixed trying to determine the color of Z1. (Z2 seemed, to my very untrained eyes, quite blue.)

As I leaned back from my binoculars I noticed that I was quite relaxed; indeed, I was having fun! Curiously, much more fun than I had been having trying to discern the few Messier objects I could detect that night.

I wonder if I have finally found a "home." Don't get me wrong, I love all aspects of astronomy and particularly enjoy using my Mallincam on galaxies. But, I have longed for some photons-to-retina activities.

Unfortunately, my nearest dark-sky site is two-hours drive away and while I enjoy hunting galaxies there, the two-hour drive back at 2 am is brutal and is not something I can do regularly. And, finding and observing DSOs in my backyard is, well, painful.

So I've been trying to find something that I can do in my Mag-4 backyard that is relaxing, somewhat challenging, visually rewarding, and doesn't require dragging out all of the gobs and gobs of requisite equipment than imaging requires. The planets are fun, but just how many nights in a row can I look at Saturn before the effort to drag the scope out makes it not worth it (answer:3)? The Moon, of course, is very interesting, but so...so...monochromatic.

So after viewing Zeta Scorpii, maybe, just maybe, double stars are for what I have been looking. A great number of them seem very accessible in light-polluted environments and even in small grab-and-go scopes. They can provide a challenge in finding them and a challenge in splitting them. Plus, they seem to be so lovely....sparkling gems of color in a lonely void.

James Mullaney's Double Stars and How to Observe Them arrived this afternoon and I'm complete enjoying it.

Tonight is cloudy, but tomorrow is forecast to be clear and the seeing very steady (gotta love south Texas in the summer). I wonder what my first double will be?



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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: A home for this weary traveler? new [Re: Michael Rapp]
      #5927727 - 06/18/13 03:07 PM

Michael, welcome in the club. I always wonder why double star observing is not more popular in our light polluted world.
Wilfried


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: A home for this weary traveler? [Re: Michael Rapp]
      #5927843 - 06/18/13 04:08 PM

Great stuff Michael! I'm also a newcomer. Welcome to the club!

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Michael Rapp
Post Laureate
*****

Reged: 04/27/04

Loc: Dickinson, TX
Re: A home for this weary traveler? new [Re: R Botero]
      #5930226 - 06/19/13 10:35 PM

I've got this stubborn cloud over me, but if it moves off, I'm going to try for Alpha Herculis and Canum Venaticorum...bright and easy to find with this waxing gibbous moon.

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Mentor
professor emeritus


Reged: 09/30/10

Loc: Ontario, Canada
Re: A home for this weary traveler? new [Re: Michael Rapp]
      #5930369 - 06/19/13 11:48 PM

Yup, whenever the moon is out I hit my double-star lists. Finding some of them in my bright, light-polluted skies can be a challenge, but once found they bring a lot to the table. A wide-field scope helps with the search. I drop my 24mm or 35mm Pan into my refractor and search directly through the scope, where I can actually see the stars.

I just got back in from an hour observing doubles tonight. When the high thin clouds thickened up I packed it in in less than 5 minutes.


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Astrodj
professor emeritus
*****

Reged: 08/24/11

Loc: Missouri
Re: A home for this weary traveler? new [Re: Mentor]
      #5930501 - 06/20/13 01:23 AM

Rho Oph is one of my favorites, about 3 degrees N of Antares. I spent a while enjoying it tonight after Saturn and the Moon.

I almost always add a few doubles to a night out, even under dark skies. I really enjoy them. Sometimes I plan ahead for some I haven't seen, other times I just re-observe some old favorites.


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Michael Rapp
Post Laureate
*****

Reged: 04/27/04

Loc: Dickinson, TX
Re: A home for this weary traveler? new [Re: Astrodj]
      #5931403 - 06/20/13 02:26 PM

Well, the clouds didn't part until I had to go to bed, but I enjoyed refamiliarizing myself with my little refractor. It felt odd being able to take the scope and eyepieces out in one trip and not having to fiddle with counterweights, power, and star alignment. No wait, that wasn't odd, that was awesome!

While I didn't get to view any doubles, I couldn't help but notice in the few patches of open skies how pinpoint the stars looked against the velvet background. I had completely forgotten about that aspect of refractors.

One question has come to mind -- and I may have completely missed this in my research -- is there a general formula or rule of thumb for the requisite magnification needed to split a double in a particular scope? That is, if I have x scope, I would need at least y magnification before having a chance at discerning that there are two stars and not just one? If such a rule is out there, I am sure it involves the diameter of the scope's objective as that determines, all things being equal, the resolution. Mine is exceptionally modest: 66 mm.


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: A home for this weary traveler? new [Re: Michael Rapp]
      #5931425 - 06/20/13 02:36 PM

Quote:

One question has come to mind -- and I may have completely missed this in my research -- is there a general formula or rule of thumb for the requisite magnification needed to split a double in a particular scope? That is, if I have x scope, I would need at least y magnification before having a chance at discerning that there are two stars and not just one? If such a rule is out there, I am sure it involves the diameter of the scope's objective as that determines, all things being equal, the resolution. Mine is exceptionally modest: 66 mm.




Good question!

Indeed there are several and they have been much discussed here of late.

Several calculators can be found here:

http://fisherka.csolutionshosting.net/astronote/astromath/ueb/Unequalbinaries...

I also encourage you to scroll back a page or so on this forum for the Rule of Thumb (RoT) developed by Wilfried (WRAK). Some of us find attempted observations near the limits predicted by these calculators to be of great interest.


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Michael Rapp
Post Laureate
*****

Reged: 04/27/04

Loc: Dickinson, TX
Re: A home for this weary traveler? new [Re: Nucleophile]
      #5932302 - 06/20/13 11:41 PM

Thanks, Mark! This is great reading!

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