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Cosmic Challenge: Stephan's Quintet

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#1 PhilH

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Posted 01 October 2017 - 11:01 AM

The canvas on which our picture of the universe is painted relies on the unwavering acceptance of Hubble's Law. Hubble's Law states that a relationship exists between the distance to a galaxy and the speed at which it is receding from us. The farther away a galaxy is, the greater the speed of its recession and farther its spectral lines are shifted toward the red end of the spectrum. For Hubble's Law and the Red Shift Principal to be valid, it must work for not just a few galaxies, but for all. And indeed, it does -- well almost.

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#2 TOMDEY

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Posted 02 October 2017 - 09:48 PM

Heh... Phil, check the text... you got 7320 closer than Mars!  Anyway, one of my favorite targets; I was just savoring it Sept 24/25.  My encoders weren't behaving, so I had to find it ~the old-fashioned way~  And, my favorite DS objects have always been tight groups of galaxies.  Even perusing Uranometria for any pair or more.  It's always perplexed me that there are several other groups that are as/more notable than Stephan's.  It's quite nifty that galaxies like to associate with each other!  PS: Regarding my most recent look at Stephan’s.  They seemed "bigger" than I had anticipated.  Might just be that I think of them as "little" galaxies?  Yikes!  Tom


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#3 PhilH

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Posted 07 October 2017 - 04:55 AM

...check the text... you got 7320 closer than Mars!  

Ha!  Got it fixed.  Thanks!!



#4 John O'Hara

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Posted 08 October 2017 - 04:36 PM

Hi Phil,

 

I once glimpsed the group as an irregular faint patch in my 1986 6" f/8 A-P refractor.  I was using a 16.8 Orion MegaVista eyepiece providing 74x and 0.9 degree field.  I could not really say that I could identify individual members.  I may have done better if, as you did, employed higher magnification.  Of course, more aperture wouldn't have hurt!

 

John O.



#5 PhilH

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Posted 09 October 2017 - 06:48 AM

Hi Phil,

 

I once glimpsed the group as an irregular faint patch in my 1986 6" f/8 A-P refractor.  I was using a 16.8 Orion MegaVista eyepiece providing 74x and 0.9 degree field.  I could not really say that I could identify individual members.  I may have done better if, as you did, employed higher magnification.  Of course, more aperture wouldn't have hurt!

 

John O.

That's pretty darn good, John!  Must have been some great skies to see them in a 6".  Your comment made me dig back through my notes to see my impression through my RV-8 8" f/7 Newt.  Back on Aug 22, 1987, from Northfield, MA, I recorded that NGC 7320 appeared brightest, followed closely by 7319.  I didn't see any of the others.  I was using 17mm Plossl and 12mm Konig eyepieces at the time -- things like Naglers were still in the future!

 

gallery_7634_8137_1533.jpg


Edited by PhilH, 09 October 2017 - 06:54 AM.


#6 John O'Hara

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Posted 09 October 2017 - 10:20 AM

The dark skies of Cherry Springs State Park certainly helped!  I'd still like to give it another try using higher magnification.  At the time I reasoned that the approx. 2 mm exit pupil was optimal, but I've since learned the benefits of trying a variety of magnifications.   

 

BTW, speaking of Naglers, do you still use the 22 T-4 in your 18 f/4.5?  If so, do you use it straight or with a Paracorr, and do you notice any issue with field curvature?  I've reached a point where my astigmatism is very noticeable above a 2.5 to 3 mm exit pupil, and was considering replacing my 20 T-5 with the 22 T-4.



#7 PhilH

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Posted 09 October 2017 - 10:59 AM

Actually I never had the 22 and I sold my 18 about two years ago. I still have the Nag actually I never had the 22 and I sold my 18 about two years ago. I still have the 12mm Nagler T4, Which remains one of my favorites.

As far as a Paracorr goes, I never used one. Actually I had one of the originals, but sold it since I didn’t think it improved the viewing all that much in premium eyepieces. Plus the extra magnification cut down the field size, which I didn’t like either. Just my personal opinion.

Edited by PhilH, 09 October 2017 - 11:01 AM.


#8 John O'Hara

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Posted 09 October 2017 - 11:11 AM

Thanks, Phil.  Your personal opinion on such matters means more than most.  I think I'm remembering you had a 22 Pan.

 

John



#9 PhilH

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Posted 09 October 2017 - 11:48 AM

Yes! That I still have. My go-to eyepiece today actually is a 9mm TMB super duper wide. 👍🏻

#10 John O'Hara

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Posted 09 October 2017 - 01:17 PM

Phil,

 

Is this 9 mm one of the "Planetary Series"?  Or is it a new 100 deg. eyepiece I've not heard of?  I used to very much keep up on new introductions, but have falling into a state of contentedness with my collection of eyepieces.

 

John



#11 PhilH

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Posted 09 October 2017 - 05:32 PM

A real shame it's not marketed anymore, at least by that name, but this is the eyepiece I'm talking about...

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Edited by PhilH, 09 October 2017 - 05:33 PM.


#12 John O'Hara

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Posted 10 October 2017 - 04:58 PM

Ahh, an Ethos alternative.  I think Zhumell and Orion marketed them too.  My collection of eyepieces includes one Ethos (13mm), my only hyperwide, and probably the only Ethos I'll ever own.  It was purchased back in '07.  Other than that, I'm satisfied with my older eyepieces from the late 1990s/early 2000s.  I love the 13 Ethos, but in some respects miss my old 13 T-6 it replaced.  It was very nice in a Powermate, for example.  The truth is, if I had to go back to Kellners, RKEs, Erfles and Konigs, I'd miss the modern premiums, believe me, but I would still very much enjoy observing.



#13 Dave Mitsky

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Posted 10 October 2017 - 09:29 PM

A number of us had some rather good views of Stephan's Quintet through the 20" f/3.3 New Moon Telescopes Hybrid Dob that was at Cherry Springs last month.

 

Dave Mitsky

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#14 PhilH

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Posted 11 October 2017 - 06:30 AM

Ahh, an Ethos alternative. I think Zhumell and Orion marketed them too. My collection of eyepieces includes one Ethos (13mm), my only hyperwide, and probably the only Ethos I'll ever own. It was purchased back in '07. Other than that, I'm satisfied with my older eyepieces from the late 1990s/early 2000s. I love the 13 Ethos, but in some respects miss my old 13 T-6 it replaced. It was very nice in a Powermate, for example. The truth is, if I had to go back to Kellners, RKEs, Erfles and Konigs, I'd miss the modern premiums, believe me, but I would still very much enjoy observing.



#15 PhilH

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Posted 11 October 2017 - 06:32 AM

Zhumell called the 9 and 16mm variants the Z100 line. I believe they are no longer available. At least, I couldn’t find any in a quick search now.

#16 John O'Hara

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Posted 11 October 2017 - 06:31 PM

Me neither, I looked too.  I've been curious ever since I saw Rod Mollise's review of the 16 mm "Happy Hand Grenade" ;-)  



#17 Dave Mitsky

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Posted 11 October 2017 - 09:37 PM

The 13mm Ethos is the only one I own too.  I also have the 9mm and 20mm Explore Scientific 100 degree eyepieces, however.

I took the less expensive Delos route when I upgraded my shorter focal length eyepieces.

 

9mm ES 100 (center), 10mm Delos (left) & 13mm Ethos (right)

 

Dave Mitsky

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