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Solar: GT130, CFF 92, and a Leica zoom

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#1 gnowellsct

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Posted 25 April 2019 - 10:40 PM

A few weeks ago I posted something of a joke thread (clouded out as soon as I set up) so let me get that out of the way with this pic.  Because as you can see there is actual sunlight in the picture.  And a scope configured for solar h-alpha.  Solar viewing did occur.

 

CFF92 and GT130 at Landis 4-25-19.jpg

 

 


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#2 Mike W

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Posted 25 April 2019 - 10:46 PM

Looks like Landis, thanks for the invite!tongue2.gif 



#3 gnowellsct

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Posted 25 April 2019 - 11:22 PM

The scopes are the GT130 f/6.3 and the CFF 92mm, one of two at f/6.9.  In the trunk of the car in back you can see a Manfrotto bag with a Vixen ED102SS f/6.5 in it.  That Vixen has been my buddy since way back in 2005 (riding on a C14).

 

So anyhow, the goals today were:

 

1.  Compare Vixen ED102SS f/6.5 to the CFF 92mm triplet.  I am debating whether I need to hang on to the Vixen which is a very nice scope and has admirers in my club.  The mode of the comparison was to set the GT130 up and let it carry the Vixen at first and then the CFF.   Since the CFF is about the same weight as the Vixen no rebalancing was necessary doing it this way.  But one had to be careful: the scope not in use had to be capped.  

 

2.  First light of the GT130 on the sun.  Not first light, just first light on the sun.  I had been deceived into thinking that oiled triplets cannot be used for solar with the UVIR cut on the diagonal, but that is not true.  So for years I have delayed doing solar with my GT130.

 

OK--well to make a long story short in spite of a favorable forecast high altitude clouds basically ruined the Vixen 102 vs CFF 92 comparison.  I guess I'll just have to try again.  Watched sun and clouds for about an hour through the Vixen and then decided to watch sun and clouds through the 92mm.  Very few views that were conclusive.  So I gave up on the Vixen vs CFF part of this expedition.

 

And then....the sun came out.   The 92mm was in position and the views were excellent.  I tried messing around with the 2x and 4x barlows....in the solar forum I have read that the chromosphere quark will behave like the prominence quark at 2x.  So I tried it out with the 2x power mate with 30, 17.5, and 10 mm oculars.  The  views were good.  But I'm not sure they were better than with the 4x (on the prominences).  There were several prominence groups available on the sun today including a large "hedge row" and a sharp pointing prominence (sort of like a cigarette lighter) and an arc.  (no active regions/sunspots).  So back to the 4x and it was excellent.  Very high definition in the prominences, very much like one sees in the solar images, and a nice tight well defined line of spicules on the limb, also with very good focus.    I was too transported to want to put the Vixen back on.  The CFF 92 does an excellent job on el sol.

 

But it wasn't that hard to switch from the CFF to the GT130.  Lock down the clutches so nothing moves.  Cover the objective of the CFF.  Pull everything out--diagonal, powermate, etalon, eyepiece, and insert it into the GT130.  Stick the GT130's diagonal into the CFF so balance stays the same.  And observe....

 

OMG it was fantastic. On the one hand...it's just like the moon.  It's very hard to nail down what it is you see in a 130mm apo on the moon that is different/better than what you see in a 92mm apo.  They're both excellent and offer bewildering detail.  But there is a feelilng somehow of "more to see, more easily."  There was more subtle feathering in the prominences and it seemed that a few extra faint prominences were detectable that had eluded me in the 92.  I was somewhat awestruck.  This is "just the quark combo" but it must be a very good one as it rivaled the views through much more expensive etalons at NEAF.  I was quite floored.  With a 20 mm ocular in you felt you were traveling in Dante's inferno.

 

Then I decided to go back to the 92mm to see if it was "disappointing."  Not at all.  Still a rich, highly detailed view.  Both of these scopes are NEAF-worthy solar instruments.  

 

So now on to the Leica.  This was my first view of an astronomical object through the Leica.  Skies have been that bad.  I was a little worried that it would be too much magnification (remember for solar one is using either a 2x or 4x barlow) but I gave it a go.   Well--in spite of the frequent mentions of its supposed deficiencies in the EOFB threads in EYEPIECES--so far the Leica has passed very well what I could throw at it in terms of terrestrial and now solar observing.  I did a detailed comparison between the Nikon 17.5 and the Leica at its lowest power of 17.9.  What can I say.  It seemed to me that there might be a little extra in the Nikon fixed focal length 17.5.  But the Leica could be characterized as "highly competitive."  The view was contrasty and sharp.  I saw no obvious edge defects.  The zoom feature was really cool.  It is clear that for this particular occasion the 8.9 to 10 mm range was too much magnification, and in the 92 mm (as opposed to the 130mm) you could get some dimming.  But there was also loss of crispness as one is, with the 4x barlow, approaching 2.2 mm equivalent focal length which is really pushing an optic under any conditions, let alone the turbulent sun.  When you backed off the magnification the image steadied and became very sharp.  It also offers good field of view (60 degrees at low power, 80 degrees at high power) and very comfortable eye relief and ergonomic design.  

 

In summary, if you like Pentax XWs, you're probably going to get along very well with a Leica 8.9 - 17.8.  I'm not sure I'd say get rid of your XWs and go with the Leica.  But it's not crazy to discuss the option (some have done it).  

 

I wish I had the words to convey how extraordinary (if rather time limited) the solar views were.  Although the 130 "brings in more" I can't honestly say that you would be depriving yourself if you limited your solar views to the CFF 92mm.  When you take these systems and put in a some high end glass like the XWs or the Leica zoom you have an effect that is--well, all I can say is it's a real privilege to have gear like this and I hope everyone gets a chance some day.    I came away musing about getting a Baader Herschel Wedge and using these scopes in tandem for solar outreach, one in white light and one in h-alpha.  I would have a real hard time deciding which one to use which way.  The CFF 92mm is an extremely competitive optic that, well, I'm sure it has to obey THE LAWS OF PHYSICS.  But d*mn it sure seems to punch above its weight.  I can't wait to get it out for night observing.   And the GT130 is a superb solar instrument.  Wow.   

 

Greg N


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#4 gnowellsct

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Posted 25 April 2019 - 11:24 PM

Looks like Landis, thanks for the invite!tongue2.gif

Well I didn't know you were into solar or available for a daytime sortie.  Let it be for next time, then.  Greg N



#5 BGazing

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Posted 26 April 2019 - 12:45 PM

Leica Zoom and XW for H-alpha? How are they coping with internal reflections and distortions?

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#6 gnowellsct

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Posted 26 April 2019 - 01:32 PM

Leica Zoom and XW for H-alpha? How are they coping with internal reflections and distortions?

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Did I answer that in review? ...views were superb enough to make me forget I was supposed to be evaluating the view.

I keep seeing daystar recommendations about this and that including eyepieces. I have a 32 plossl but keep forgetting to try it. But much of what the say...such as no oiled triplets for solar or UVIR solar, are dismissed by refractor OEMs. They don't like complex eyepieces because of light scatter and reflection but I'd lay odds these are better controlled in an XW than in my Celestron 32 plossl.

I live near NEAF and have seen a lot of different solar rigs over the past fifteen years. Yesterday was as good as it gets IMO.

I did inspect edge of field of Leica at 17.8 and have no bad news to report. Just a really nice to use high performance ocular. It did tend to dim out at 9 to 10 mm equivalent but that's with a 4x barlow. A lot of things get dimmer at 2.5 and lower equivalent magnifications.

#7 dscarpa

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Posted 27 April 2019 - 11:23 PM

 Very good report! Did you use ERFs?  I' m thinking about swinging for a WO 132 which has a robust focuser to use with a Quark. About the same cost wise as a Lunt 100 and usable at night.  David


Edited by dscarpa, 27 April 2019 - 11:29 PM.



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