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STF 1937: 2020 Version

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#1 rugby

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Posted 14 August 2020 - 12:23 AM

The night of 13 Aug 2020 had excellent seeing. There was a little high cloud but no moon or wind. I set up a 150 ES triplet and proceeded to climb down the ladder of sub arc-second double stars.
I started with 16 Vulp. 5.8-6.1; 0.85". Saw two discs with a slight separation using 400x.
Next came STT338 Hercules 7.2-7.3: 0.8" seen as two touching discs at 400x. Rather easy my notes say!
When pairs like the preceeding became almost pedestrian then it was time to ramp up the difficulty factor. I quickly rounded up HU 149 7.4-7.6: 0.6" and found an elongated bar with a small notch. The East-West orientation was seen at 400x . I could use a 2mm HD vixen eyepiece on this pair yielding 600x with little image breakdown.
Clearly I had pushed this 150 to its maximum. Did I dare to go further? Was anything left in the tank? Yes.... of course.
STF 1937 stood waiting for me to bring it into view. This was my first sub arc-second pair nearly forty years ago. Then, it was much easier. Today: 5.6-5.9; 0.4" a true challenge for this night's merits. At 600x maybe there was seen a slight oval shape of the diffraction disc. I was almost certain of an East-West elongation and yet maybe not.
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#2 R Botero

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Posted 14 August 2020 - 02:48 AM

Great post! I love those tight doubles! bow.gif waytogo.gif

Roberto



#3 nerich

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Posted 14 August 2020 - 11:46 AM

Nice work Rugby! I've got a post coming eventually on this same topic (I've been on a bit of a journey this summer with sub-arc-second pairs). 


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#4 rugby

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Posted 14 August 2020 - 12:56 PM

Looking forward to it Nick. I seem to have hit the resolution wall lately using 140 and 150 refractors. Depending on seeing and the star brightness I Peter out somewhere in the 0.6's. There are so many gorgeous pairs out there that need observing. They dont have to be a challenge to any scope.
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#5 Nucleophile

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Posted 16 August 2020 - 07:49 AM

Sounds like a night to remember, Rugby!

 

Quick question about that Vixen 2mm HD:  have you had it long and how do you rank it versus some of your other high end eyepieces? 

 

I have been looking for something to get me past what my Pentax 2.5XO can deliver while delivering as near the quality of sharp views.



#6 rugby

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Posted 17 August 2020 - 10:06 AM

Nucleophile: Thankyou for asking about the Vixen 2mm HD. Here are my non-professional opinions: You better have the optics and the seeng to handle the magnification. I have high end refractors up to six inches with superb seeing once a month.
Tracking is almost essential. I have written before about the eighteen seconds it takes for a star to pass through the field. Now think about having to refocus if you are lucky enough to actually have the target centered in the first place. At the power generated by any 2mm the image takes several crucial seconds to settle. Even slow motion cables would be helpful but not all altaz mounts have them (eg: DM6)
Experience at the eyepiece: spend time learning what small separations look like.
I am not negative on this eyepiece but in the wrong hands it becomes part of the stamp collection. When I purchased, I hedged my bets and only got the 2mm. The 1.6mm would,for me, be impossible to use and I have already a 3mm Delite. No, I won't sell my 2mm. It provides a very good image at really high powers

#7 Nucleophile

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Posted 17 August 2020 - 12:11 PM

I have the seeing, optics, tracking and experience with very high mag--I am wondering about the quality versus higher end eps like the Delite...Do you feel it is in the same league as TV or Pentax?



#8 rugby

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Posted 17 August 2020 - 05:15 PM

The Vixen 2mm Hd does not offer me the same clarity of resolution that the 3mm Delite does. The Delite has a larger field of view and it is sharper on most quality nights. I dont know how fair it is to compare these eyepieces. My next short FL eyepiece will be a Tak TOE
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