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"pinpoints stars" at giant binoculars - really ideal points?

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#26 Rich V.

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Posted 13 July 2021 - 10:31 PM

Agreed, Fiske, I'd go for the largest exit pupil you can muster.  Too bad that naked filter arrangement would be a pain to switch back and forth from compared to screwing a mounted one on or off.  You'd end up with a dedicated pair of filtered eps.

 

IIRC, the APMs have enough focuser in-travel to allow a filter to be placed where it belongs and still reach infinity focus.

 

For me, I just prefer using filters with my scopes, primarily.

 

Rich



#27 Fiske

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Posted 14 July 2021 - 12:47 AM

Rich,

 

The main attraction would be things like the Veil nebula in Cygnus. That would be wonderful I expect with binoculars. It might make more sense to put filters on the OB 15x70s for that. I have the 22 and 14mm XL eyepieces, and their 1.25 inch tubes aren't as long as those of the Pentax eyepieces. So it's possible one of those might work. The 14mm is probably the more likely of the two. I'll try that.

 

It was a miserable evening to observe. lol So hazy I couldn't make out the keystone in Hercules, which I can usually see easily. As predicted, the Double Double is fully resolved with the 5mm XWs, thought the E1 components are still challenging due to the magnitude difference between them. Also 112x is definitely the highest magnification that is manageable with the current mount configuration. We'll see if the 117B is a little more steady. A much more substantial mount is needed to use higher magnifications with these instruments.

 

The OB 25x100 shows some CA on bright stars like Lyra where the 100XL-SD doesn't show any, but that is really the significant difference between the views. And the CA exhibited by the 25x100 is not objectionable for deep sky observing. It's well constrolled. I'll spend more time doing side by sides on a better night, but the Deluxe is remarkably fun to observe with. Really an unbeatable value at $470 USD. 

 

Neither instrument exhibits tails or other conspicuous artifacts. With the 25x100 eye position is more critical than with the 100XL but it is still comfortable for me with or without glasses. And a single set of the Pentax XWs cost about $100 USD more, which makes the performance of the 25x100 even more impressive. The Pentax XWs are hands down the most comfortable eyepieces I have ever used.

 

I didn't get the TV-101 out, but the stars in either binocular aren't as needle sharp. They are sharp enough though to provide excellent views. 

 

Rho Hercules was beyond what I could muster this evening -- near the zenith in a murky sky so I skipped it. But 70 Oph was a fine sight -- well resolved with a blazing warm white primary and a deep amber companion. Definitely makes my list of outstanding BT double stars.

 

When I was tracking down 70 Oph I wandered too far east and came across the open cluster NGC 6633 on the border between Ophiuchus and Serpens Cauda -- an enjoyable object even through all the murky soup. Viewed it with the 100XL-SD and Pentax 20mmXWs, which provided a nicely sized field for the cluster.

 

Fiske


Edited by Fiske, 14 July 2021 - 09:13 AM.


#28 Jon Isaacs

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Posted 14 July 2021 - 11:53 AM

I didn't get the TV-101 out, but the stars in either binocular aren't as needle sharp. They are sharp enough though to provide excellent views.

 

 

The TV-101 and NP-101 are what I call "sharp-sharp." That means, given a top quality eyepiece, I can get sharp focus anywhere in the field and the entire field will be in sharp focus.

 

Jon


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#29 Fiske

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Posted 14 July 2021 - 05:21 PM

The TV-101 and NP-101 are what I call "sharp-sharp." That means, given a top quality eyepiece, I can get sharp focus anywhere in the field and the entire field will be in sharp focus.

 

Jon

Agreed. I like the sharp-sharp thing, Jon. Well done! waytogo.gif

 

Also, when it comes to binocular edge performance, everything gets compared to the Nikon 7x50 SP once you've looked through one.

 

Fiske



#30 Fiske

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Posted 14 July 2021 - 05:46 PM

I made a mental note to myself that the next time I step out side and can't see the Hercules keystone when it is near the zenith, I'll go back inside and hang out on CloudyNights instead of trying to observe. lol.gif

 

Back on the pinpoint stars thing, I had intended to compare observing with and without glasses last night, but after an initial run wearing glasses with the 25x100, I just switched over to uncorrected and did that the rest of the evening. There are some differences in the view for corrected versus uncorrected vision. Notably, edge performance on many instruments tends to be better for corrected vision. Also, for closer doubles with a significant magnitude difference, wearing glasses sometimes helps because even mild astigmatism can be problematic for such observations. For general observing, however, I am not seeing a significant difference in star images between corrected/uncorrected vision, other than subtle astigmatism artifacts that are canceled out when observing with both eyes (versus looking through one barrel or the other to focus).

 

A pattern is emerging with my binocular use in that I find myself using glasses more frequently with smaller binoculars, in the 50-70mm range, and less frequently with larger binoculars and with binocular telescopes. Eye positioning becomes more difficult with larger instruments and adding glasses into the mix increases the problem. Whatever minimal difference in the view between corrected/uncorrected vision is less significant to me than the comfort factor when using larger binoculars.

 

Fiske


Edited by Fiske, 15 July 2021 - 06:42 AM.

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