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Quick Field Report on Pentax XO 2.5mm

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#1 Sarkikos

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Posted 25 June 2012 - 08:46 AM

Last Saturday night I took my 10" f/4.8 Dob to my dark site. The Pentax XO 2.5mm was in my small case of planetary eyepieces. (I took out an old Kellner 10mm to make room. :grin:)

I was there to see faint fuzzies, but the Moon would not set until about 11 pm, so in the meantime I viewed the four-day-old Moon, Saturn and Mars. I tried the usual suspects on these objects, including an ES 100deg 9mm - with and without a 1.5x Barlow lens - and a Brandon 6mm. The seeing was about 3 out of 5.

Both eyepieces gave good and interesting views. I liked the expansive lunar landscape from the ES 9mm, but the Brandon appeared purer and cooler in tone. These Brandons are nice Moon EPs. With my glasses off, the Brandon 6mm was really pretty comfortable. (I really don't understand all this fuss about "tight" eye relief. :shrug:) I also like the slightly sharper features for Saturn that the Brandon gave me. Neither showed much on Mars except for Hellas, the NPC and a suggestion of markings in between. I didn't expect any more, because of Mars' small apparent size of less than 7 arcsecs.

Then I put in the Pentax XO 2.5. The seeing wasn't great, but it was steady enough from time to time for me to notice an improvement in sharpness of surface detail for Saturn and Mars - especially for Mars. It took patience to see the difference in Martian features, but it was there. Through the XO 2.5, I could not only tease out Hellas, the NPC and "some markings," but also Syrtis Major, Sinus Sabaeus following Syrtis Major, a dark rim abound Hellas (Iapygia Viridis?), and Utopia and related features in a dark rim around NPC. I'm sure if the seeing had been better, I would have seen even more.

I think I'll keep my XO 2.5 ... at least until after the next Mars opposition.

:grin:
Mike

P.S.: Overall, the night was terrible. The forecast was for clear all night, but after the Moon set, it was sucker-hole fishing through the clouds. I stayed until 3 am, hoping the sky would settle down and clear off, but it never did. Except for testing out my new XO, and finding out Paracorr settings for more of my eyepieces, I only found three objects I'd never seen before. A very slow night for me.

#2 Sarkikos

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Posted 25 June 2012 - 08:58 AM

A Disclaimer:

I know that ideally, comparable magnifications should be used when comparing eyepieces. I did not do that in this impromptu "test." Basically I just wanted to get a first-light impression of how the Pentax XO 2.5mm performs in my telescope on the sort of objects that I intended it for: bright planets. So the comparisions with the other eyepieces should be taken with a grain of salt.

In my 10" f/4.8, the ES 100deg 9mm yields 133x, 0.8 degree TFOV and 1.9mm exit pupil. With the 1.5x Barlow element, the ES 100 9 gives me 200x, 0.5 degree TFOV and 1.3mm exit pupil, basically the equivalent of an ES 100deg 6mm eyepiece. The Brandon 6mm provides 200x, 0.2 degree TFOV and 1.3mm exit pupil.

On the other hand, the Pentax XO 2.5mm yields 480x, 0.1 degree TFOV and 0.5mm exit pupil. Not exactly a fair comparison, perhaps, with the ES and Brandon. Mars likes high magnification, so that undoubtedly made some contribution to the better view of that planet in the XO 2.5.

Nevertheless, I was impressed by the XO's performance, especially given the mediocre seeing. I'll be interested to see how it performs for bright planets under better conditions. Yes, this one will definitely stay around for the next Mars Opposition.

Mike

#3 kepheus

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Posted 25 June 2012 - 01:42 PM

With my glasses off, the Brandon 6mm was really pretty comfortable. (I really don't understand all this fuss about "tight" eye relief.Posted Image)


+1

In comparison to my 8.8mm Meade 4000 UWA (eyecup version) and my 7mm Nagler T6, the 6mm Brandon offers the most relaxing observations. Kidney beaning or blackouts? Not in this Brandon. Glasses off? I wear contact lenses which even correct astigmatism.

- Brend

#4 gnowellsct

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Posted 25 June 2012 - 11:23 PM

A Disclaimer:

I know that ideally, comparable magnifications should be used when comparing eyepieces.
Mike


And how many 2.5mm eyepieces are out there for a comparo?

You can't really count barlowed 5s because that's adding an intermediate element to the eyepiece.

No, I think you take the 2.5 for what it is. You like it or you don't.

On my C14 the 2.5, barlowed 2x, offers clear crisp detailed views that makes you think you're having your own picnic right there on top of Olympic Mons. gn

#5 NickG

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Posted 26 June 2012 - 03:17 AM

Wow, that must be ridiculous magnification! Lucky you oh enlightened Pentax guru :) Wish I could see that Mars view!

I probably wouldn't have much use for the 2.5 myself, though I'm sure there are others that would/do like the OP, so great stuff!

I just received my XO 5 and will be doing some of my own testing compared to the TMB supermono 5 and a couple of others. Can't wait!

Clear skies to all.

#6 Sarkikos

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Posted 26 June 2012 - 07:06 AM

Greg,

And how many 2.5mm eyepieces are out there for a comparo?


There is a TMB Planetary 2.5mm, and I have one (the "IB" version). I didn't have it with me that night. It usually stays at home. My primary mission was not to do an extensive critique and comparo of the XO. That was just one of the things to occupy my time while I was waiting for the Moon to set. Now, though, I wish I had taken the TMB. It would have been an interesting comparision. I wonder which one would have pulled ahead? :thinking: :grin:

No, I think you take the 2.5 for what it is. You like it or you don't.


So far I like it. I was a little leary when I first looked through the XO 2.5 during the day. Eyepieces with such short focal lengths really make my eye floaters excruciantly obvious when I observe a bright background. I don't think I'll ever use this one to view the Full Moon. :p

But I was somewhat surprised when I looked at Mars and Saturn. The floaters were very bearable and did not prevent me from seeing fine surface detail when the seeing allowed.

On my C14 the 2.5, barlowed 2x, offers clear crisp detailed views that makes you think you're having your own picnic right there on top of Olympic Mons. gn


I think I'll pass on Barlowing the XO 2.5! My biggest apertures do not track. 480x is plenty good for my 10" f/4.8 Dob. Even though the AFOV on the XO 2.5 is only 44 degrees, my mount has fairly smooth motion, so nudging is not really a big deal. But I think about 500x or so is the highest I want to go.

480x gives me a 0.5mm exit pupil, which is about as narrow as I like to go, even for Mars. I'm not a big enthusiast for super-high magnification. There are techniques to see more without having to blow up the image. Maybe if I had tracking I would experiment with hyper-power, but I doubt if I'd like it. Floaters, you know.

Mike

#7 Sarkikos

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Posted 26 June 2012 - 07:20 AM

Brend,

In comparison to my 8.8mm Meade 4000 UWA (eyecup version) and my 7mm Nagler T6, the 6mm Brandon offers the most relaxing observations. Kidney beaning or blackouts? Not in this Brandon. Glasses off? I wear contact lenses which even correct astigmatism.


Yes, the Brandon 6mm is nice and comfy. What helps is to use one of the short eye-cups that Alvin Huey endorses on his website. They tend to position your eye at a comfortable distance and block the ambient glare. I've put these eyeguards on all of my shorter focal length flat-top eyepieces.

Eyeguards for Small Eyepieces

Mercifully, my eyelashes are short and manly - not like the Bambi lashes that some of these observers have :grin: - so I have no problem with lash oils slathering up the eye lens.

Mike

#8 kepheus

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Posted 26 June 2012 - 08:13 AM

Hi Mike,

I already attached an eyeguard to my 16mm flat top Brandon in order to block ambient glare and to steady my eye positioning.

Posted Image

I have an additional eyeguard left, but I don't feel a need to attach it to my 6mm Brandon.
I rest the brows of my observing eye on the outer part of this 1.25" to 2" adapter. By doing that, I can maintain an absolutely steady positioning of my eye.

Posted Image

- Brend

#9 Sarkikos

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Posted 26 June 2012 - 08:54 AM

The rubber eyeguard makes the Brandon 6mm experience very comfortable for me. :grin: I have one on my 16mm, also.

Mike

#10 gnowellsct

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Posted 26 June 2012 - 10:32 AM

I think I'll pass on Barlowing the XO 2.5!

Mike


Really? I don't talk about it much, but I often triple and quadruple barlow the 2.5 on my C14...I was just trying to be conservative in my last post. Quadruple barlowed, I find the .028mm exit pupil refreshingly different. The needle thin exit pupil slashing into the eye is kind of an optical acupuncture.

Then when you take the barlows away the 2.5 by itself serves as a widefield.

Greg N

#11 Sarkikos

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Posted 26 June 2012 - 12:02 PM

Greg,

But then your scope does have tracking, right? I don't think I'd enjoy nudging the Dob at 1000-1500x. There's too much of a chance of repetitive motion syndrome. I don't know if my health plan would cover it.

And I'm sure such hyper-high powers would turn my telescope into a microscope for examining all the floaters and other imperfections in my eyes. I'd be able to see bacteria sailing by on the flotsam and jetsam of my vitreus humour. :crazyeyes: Not exactly my idea of a good time under the stars.

:grin:
Mike

#12 Sgt

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Posted 26 June 2012 - 12:59 PM

Really? I suppose in cyberspace no one can hear you joking?


I think I'll pass on Barlowing the XO 2.5!

Mike


Really? I don't talk about it much, but I often triple and quadruple barlow the 2.5 on my C14...I was just trying to be conservative in my last post. Quadruple barlowed, I find the .028mm exit pupil refreshingly different. The needle thin exit pupil slashing into the eye is kind of an optical acupuncture.

Then when you take the barlows away the 2.5 by itself serves as a widefield.

Greg N



#13 Sarkikos

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Posted 26 June 2012 - 06:18 PM

Sgt T,

Really? I suppose in cyberspace no one can hear you joking?


Well, they can read you joking. It's just more obvious when you put when of these little fellers :grin: at the end.

:grin:
Mike

#14 Scanning4Comets

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Posted 26 June 2012 - 07:23 PM

Ummm Mike, I'm pretty sure Greg just trolled you hard. :lol:

Cheers,

#15 Sarkikos

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Posted 26 June 2012 - 09:48 PM

You can't troll a troll. Or can you? :thinking:

:grin:
Mike

#16 NickG

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Posted 27 June 2012 - 06:17 PM

I'd like to know the details of quadruple barlowing. Is that 4X or 4 Barlows stacked on top of each other. The XO Buddha says sending probes to Mars is now obsolete.

#17 Sarkikos

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Posted 27 June 2012 - 07:32 PM

Ask Greg about the Mysteries of Quadruple Barlowing. I don't follow those creeds.

Since I'm now an owner of the complete line of XOs, I may well be following the Enlightened Path of the XO Buddha.

What is the sound of one XO? "Buy my Brother and see the Light." Now the one has become two, and the two are as one.

:grin:
Mike

#18 Sarkikos

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Posted 21 July 2012 - 10:38 AM

A footnote about acquiring the Pentax XO 5 to complete my XO set:

I ordered the XO 5 from four US vendors in the hope that at least one would come through for me. Each of them sent me emails stating that the XO 5 was backordered, discontinued, unavailable. Eventually, they all cancelled the order. As Sgt T and Greg N would say, "Really?" :p

Finally, I ordered one from Markus Ludes at APM. I received it from Germany within one week. I've yet to find the time or the weather to give the XO 5 first light, but based on eye witness reports, and my own experience with the XO 2.5, I have high hopes for this eyepiece. Both the XO's have a permanent home in my small case of planet-eyepieces.

:grin:
Mike

#19 Sarkikos

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Posted 04 April 2014 - 10:32 AM

I just reread this thread. Sometimes the Neurotypicals really like to tease the Aspies, don't they?

Mercifully, the sarcastic "Really?" has nearly disappeared in colloquial English.

:grin:
Mike

#20 Sarkikos

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Posted 04 April 2014 - 10:43 AM

By the way, since this thread started, I've sold all my Brandons, all my XW's, all my Plossls except for the Sterlings, and almost all my orthos.

I still have both the XO 2.58 and XO 5.1.

Mike

#21 JCAZ

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Posted 04 April 2014 - 06:42 PM

Really.

#22 tomcody

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Posted 04 April 2014 - 07:36 PM

Now the one has become two, and the two are as one.

:grin:
Mike

Is that some of the new "core math" the schools are using?
:foreheadslap:

#23 Sarkikos

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Posted 07 April 2014 - 11:57 AM

Really.


Don't go there!

Really...

:grin:
Mike

#24 Sarkikos

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Posted 07 April 2014 - 11:58 AM

Now the one has become two, and the two are as one.

:grin:
Mike

Is that some of the new "core math" the schools are using?
:foreheadslap:


No, not ... really. It is the wisdom of the XO Buddha. :sumo:

:grin:
Mike






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