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Equipment Discussions >> Eyepieces

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Mike B
Starstruck
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Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: russell23]
      #5632471 - 01/20/13 12:03 AM

Quote:

I happen to think many of these "requirements" that discourage people from wanting to share their reviews and observations are detrimental.




Agreed. And i suspect that's the frustration Mark is alluding to... i think we've ALL seen someone's comparo get critiqued rather bluntly because of some perceived failure to match conventional wisdom, when in fact there was much good to be derived... possibly even including the questioning of said "wisdom".

On EP focal lengths & comparo's- i've got a goodie for ya:
I once stuck a 9.4mm Speers-Waler in my BVer, with a Pentax 10.5mm XL in the adjacent holder; the views actually MERGED! Quite nicely, too. Had me stumped, but good!

So, was the 10.5mm not really, exactly 10.5mm?... or was the 9.4mm not really, precisely 9.4mm?

What i went on to perceive, tho, was that star groupings near the FoV centers merged well, whereas star groupings in the periphery were slightly off. My eye was accommodating & forcing the "merge" when the angular distance diff was small enough... but when the FoV stretched out far enough, the angular distance diff between, due to the slight magnification diff, exceeded my eyes' accommodation abilities.

Yet my eye's own ability to override a ~10% magnification difference remains. For reference, the mags involved that night would've been ~169x and ~189x, with a 10" SCT. So, i'm wondering what ELSE my eyes might be capable of "overriding" without my being aware?


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GeneT
Ely Kid
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Mike B]
      #5633508 - 01/20/13 04:27 PM

Quote:

I once stuck a 9.4mm Speers-Waler in my BVer, with a Pentax 10.5mm XL in the adjacent holder; the views actually MERGED! Quite nicely, too. Had me stumped, but good!




Gueeze. I would never have thought of doing that. Very interesting!


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GeneT
Ely Kid
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: russell23]
      #5633534 - 01/20/13 04:42 PM

Quote:

I'm sure it won't take too long for someone else to come along and support you that the "FL must be the same" approach is the most valid approach.




There are times when the choice of eyepieces for comparision do not match up with exact focal lengths. For example, what if someone was trying to decide between some Pentax XW's or Delos eyepieces? Both make a 10mm for a direct comparison. However Delos than goes to an 8 and a 6. Pentax XW goes to a 7 from the 10. Delos makes a 4.5 and Pentax XW a 5--pretty close. However, how does one compare the Pentax 7? Do you compare it to the Delos 6, or 8? In any case, there is no way to compare these similar eyepieces directly against the criteria of matching exact focal lengths. And in this and other cases, I believe there still can be dome valid comparisons made when trying to determine which eyepiece(s) to buy even when one of the criteria does not exactly match.


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mountain monk
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: GeneT]
      #5633669 - 01/20/13 05:56 PM

Me too. Thanks for your review.

Dark skies.

Jack


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ausastronomerModerator
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: John K]
      #5633693 - 01/20/13 06:06 PM

Quote:

I am happy with my 6mm Delos for my planetary work.I don't feel any short comings with it.It is better than my previous Pentax 5XW.IMHO but that may have been due to FL and seeing.:-)




I have no doubt seeing and thermal equilibrium factors are what contributed to the perceived difference in performance between the 5mm Pentax XW and the 6mm Delos. If 6mm is a better more frequently useable focal length for your situation then you cannot go past the 6mm Delos, it is excellent. At the shorter focal lengths and smaller exit pupils a 1mm difference in focal length can make a huge difference. At the longer focal lengths it doesn't matter much, if at all.

I have a 5mm Pentax XW, a 6mm Delos and a 7mm Pentax XW and I am yet to see any performance difference in any criteria where I feel the 6mm Delos has an edge over either of the other two eyepieces. In fact the XW's outpoint the DELOS in some performance criteria, which are not critical to me. What happens quite frequently is that the 6mm DELOS will hold up under the conditions in my 10"/F5 scope and the 5mm Pentax XW will not. That's the conditions, not the eyepiece. When conditions are good enough for both eyepieces to deliver their best, there is nothing between them.

I have also used the 5mm Pentax XO on many occasions and confirm that it marginally outpoints the 5mm Pentax XW, under the very best observing conditions, in a premium telescope. However, I came to the conclusion that on the basis the performance gain was very marginal and the Pentax XW was infinitely more comfortable to use for long observing sessions, there was no place in my eyepiece case for a 5mm Pentax XO. In fact after a 2 hour lunar / planetary observing I have no doubt I am seeing more in the 5mm Pentax XW, or 6mm Delos, than I would be seeing in a 5mm Pentax XO due to eye fatigue and strain.

Cheers


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GeneT
Ely Kid
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Reged: 11/07/08

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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: ausastronomer]
      #5633708 - 01/20/13 06:13 PM

Quote:

I have also used the 5mm Pentax XO on many occasions and confirm that it marginally outpoints the 5mm Pentax XW, under the very best observing conditions, in a premium telescope. However, I came to the conclusion that on the basis the performance gain was very marginal and the Pentax XW was infinitely more comfortable to use for long observing sessions, there was no place in my eyepiece case for a 5mm Pentax XO. In fact after a 2 hour lunar / planetary observing I have no doubt I am seeing more in the 5mm Pentax XW, or 6mm Delos, than I would be seeing in a 5mm Pentax XO due to eye fatigue and strain.




Excellent points!


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russell23
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Mike B]
      #5633780 - 01/20/13 06:57 PM

Quote:

Quote:

I happen to think many of these "requirements" that discourage people from wanting to share their reviews and observations are detrimental.




Agreed. And i suspect that's the frustration Mark is alluding to... i think we've ALL seen someone's comparo get critiqued rather bluntly because of some perceived failure to match conventional wisdom, when in fact there was much good to be derived... possibly even including the questioning of said "wisdom".




Yes -- don't ever suggest one eyepiece has better contrast than another or you will be forced to defend your claim against a long list of other possible explanations besides the eyepiece actually having better contrast.

Quote:

On EP focal lengths & comparo's- i've got a goodie for ya:
I once stuck a 9.4mm Speers-Waler in my BVer, with a Pentax 10.5mm XL in the adjacent holder; the views actually MERGED! Quite nicely, too. Had me stumped, but good!

So, was the 10.5mm not really, exactly 10.5mm?... or was the 9.4mm not really, precisely 9.4mm?

What i went on to perceive, tho, was that star groupings near the FoV centers merged well, whereas star groupings in the periphery were slightly off. My eye was accommodating & forcing the "merge" when the angular distance diff was small enough... but when the FoV stretched out far enough, the angular distance diff between, due to the slight magnification diff, exceeded my eyes' accommodation abilities.




That is a fascinating example.

Quote:

Yet my eye's own ability to override a ~10% magnification difference remains. For reference, the mags involved that night would've been ~169x and ~189x, with a 10" SCT. So, i'm wondering what ELSE my eyes might be capable of "overriding" without my being aware?





That's why there should be more flexibility tolerated in eyepiece comparisons.

Dave


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tomcody
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: GeneT]
      #5634263 - 01/21/13 01:15 AM

Quote:

Quote:

I have also used the 5mm Pentax XO on many occasions and confirm that it marginally outpoints the 5mm Pentax XW, under the very best observing conditions, in a premium telescope. However, I came to the conclusion that on the basis the performance gain was very marginal and the Pentax XW was infinitely more comfortable to use for long observing sessions, there was no place in my eyepiece case for a 5mm Pentax XO. In fact after a 2 hour lunar / planetary observing I have no doubt I am seeing more in the 5mm Pentax XW, or 6mm Delos, than I would be seeing in a 5mm Pentax XO due to eye fatigue and strain.




Excellent points!



I just replaced my 5mm Pentax XO with a 4.7mm Ethos for exactly the same reasons. I think the Ethos equals the views in any of my orthos and its hard to beat the 110 deg views.
Rex


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Sarkikos
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Loc: Scotophobe Maryland, USA
Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: GeneT]
      #5634590 - 01/21/13 09:45 AM

Gene,

Great comparo. So I guess you won't be giving up your XO 5 anytime soon? Same here. I have the XO 5 and 2.5. I don't see them leaving me in the foreseeable future.

I haven't done a direct comparison between the XO's and other 5 or 2.5mm eyepieces. But from my direct observations of Jupiter and double stars, I'm confident that the XO's are excellent planet and double stars eyepieces.

So far I've been most impressed with the XO's performance on double stars, even though I'm not really a double star enthusiast. According to my own personal interests, doubles are below DSO, planets and the Moon. That's just the way it is. But since seeing the Pup star recently for the first time - and that was through the XO's - my interests might shift more toward the doubles.

Quote:

[From Gene's comparo:] Sirus was up, so I put both eyepieces on this gem. Again, both eyepieces performed superbly. The 5XO is going to make a nice double star eyepiece.




I wish you would have gone into more detail in this comparison of the two eyepieces on Sirius. So you did see the Pup through both the Delos 6 and the XO 5? How did the view look in each eyepiece?

In my 10" f/4.8 Dob, I could not tease out the Pup with a BGO 7 (171x) or 6mm (200x). The seeing and transparency that night were at least 4/5. Maybe there was too much scatter in the BGO's or the spider spikes were too prominent for those magnifications. In any case, as soon as I put in the XO 5 (235x), the Pup star was obvious. A good, clean split. But Sirius B was a beautiful sight in the XO 2.5: a crystal clear image at 456x, 47x per inch! The Pup was a sharp, light-steel-blue point between two sparkling spikes of Sirius.

Caught the Pup for the First Time

For my eyes, I did not find either XO uncomfortable. Yes, they have short eye relief. So I had to take off my glasses to view through them. No big deal. That's why I keep my glasses on strings. Also, the relatively narrow 44 degree AFOV and high power did not bother me. My Dob does not have tracking, but I can nudge with the best of them. That's no problem. My mount is well balanced and has smooth motion. The superb view was worth any of these minor inconveniences.

No, I don't think I'll be giving up these XO's anytime soon, either. I believe there will always be a place in my equipment case for both XO's!

Mike


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Sarkikos
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Loc: Scotophobe Maryland, USA
Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Sarkikos]
      #5634650 - 01/21/13 10:26 AM

But will I get a Delos 6?

Probably not. There is the Instajust eyeguard - or whatever TeleVue is calling it now - on the Delos. Judging from recent experience with my used Radian 4, I don't think I'd like that feature on the Delos. So far, for me, the Instajust is more of a nuisance than short eye relief would be. Besides, the Delos - as usual for TeleVue - are priced higher than I want to pay. Maybe I'll go for a used one sometime.

In the meantime I am considering an XW 5. Unfortunately, as soon as I started thinking about a specific used eyepiece, there were none to be had. But even new, they are available at quite a savings off the price of a new Delos 6.

Now since I already have an XO 5, why would I bother with an XW 5? Is the eye relief and narrow field of the XO a pain to me? No, not at all - and especially not for the views I receive. The XW 5 would be mostly for deep sky, not planets or doubles. The wider field and high transmission of the XW's are great for DSO.

Mike


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turtle86
Pooh-Bah Everywhere Else
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Reged: 10/09/06

Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: tomcody]
      #5634776 - 01/21/13 11:42 AM

Quote:

Quote:

Quote:

I have also used the 5mm Pentax XO on many occasions and confirm that it marginally outpoints the 5mm Pentax XW, under the very best observing conditions, in a premium telescope. However, I came to the conclusion that on the basis the performance gain was very marginal and the Pentax XW was infinitely more comfortable to use for long observing sessions, there was no place in my eyepiece case for a 5mm Pentax XO. In fact after a 2 hour lunar / planetary observing I have no doubt I am seeing more in the 5mm Pentax XW, or 6mm Delos, than I would be seeing in a 5mm Pentax XO due to eye fatigue and strain.




Excellent points!



I just replaced my 5mm Pentax XO with a 4.7mm Ethos for exactly the same reasons. I think the Ethos equals the views in any of my orthos and its hard to beat the 110 deg views.
Rex




Same here. I briefly owned a Pentax 5XO but after putting it head to head with the 4.7 Ethos over a few nights I came to the conclusion that for my viewing preferences, the ergonomic advantages of the Ethos greatly outweighed any advantages the 5XO might've had, with the result I was actually seeing more with the 4.7 than the 5XO, especially over extended periods of time. Just as I want comfortable shoes when I go on long hikes, I've come to find that I want comfortable eyepieces for long observing sessions. I suspect that a lot of folks would also find something like the Pentax 5XW a lot easier on the eyes than the XO as well. The 5XO is a great, great eyepiece, just not my cup of tea.


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Sarkikos
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: turtle86]
      #5634818 - 01/21/13 12:08 PM

For planets and double stars, finer detail and less scatter are much more comfortable to my eyes than longer eye relief and a wider field. For deep sky objects, I want wider field and higher light transmission. I know that many planet, double star, and deep sky enthusiasts have come to the same conclusions.

My feet merely have to get me from point A to point B and back in relative comfort. My eyes have to perform much more delicate work along the way. YMMV. To each their own.


Mike


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Mike Foreman
sage
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Reged: 04/06/07

Loc: Texas
Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Sarkikos]
      #5634934 - 01/21/13 01:05 PM

Quote:

But will I get a Delos 6?

Probably not. There is the Instajust eyeguard - or whatever TeleVue is calling it now - on the Delos.




They are not the same.

The Delos lock in very securely with a collet type grip and do not jump like the instajust do.
First time I had an Instajust slide when I removed a Radian from the eyepiece holder I nearly had a heart atack.

Never say never untill you actually try it.


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Scanning4Comets
Markus
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Mike Foreman]
      #5635048 - 01/21/13 02:09 PM

Yep,

You're right Mike F. Two completely different beasts altogether. The Radian just shifts up or down. In the Delos you have two parts. The bottom half you hold and you unscrew the top half and when you find the right relief, you "lock 'em in".

Cheers,


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Sarkikos
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Mike Foreman]
      #5635054 - 01/21/13 02:14 PM

Mike F,

I know they are not the same. But I've also read that the Delos adjustment cup can be a hastle to use as well. Twist up or down and then lock. Why should a lock even be necessary if the cup is well designed? My XW's adjust easily and stay put without a lock. Sometimes these companies try so hard to make things "easier" for the consumer they wind up making them more difficult. Upgrades of some operating systems come immediately to mind.

I'm not about to try everything that comes along. I've heard that siren song before. It ignores the fact that most human knowledge is indirect and all human time is finite. I accept those limitations.

But this doesn't mean I won't pick up a used Delos some day at a decent price.


Mike


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Scanning4Comets
Markus
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Sarkikos]
      #5635077 - 01/21/13 02:22 PM

Quote:

I know they are not the same. But I've also read that the Delos adjustment cup can be a hastle to use as well. Twist up or down and then lock. Why should a lock even be necessary if the cup is well designed? My XW's adjust fine and stay put without a lock. Sometimes these companies try so hard to make things "easier" for the consumer they wind up making them more difficult. Upgrades of some operating systems come immediately to mind.

I'm not about to try everything that comes along. I've heard that siren song before. It ignores the fact that most human knowledge is indirect and all human time is finite. I accept those limitations.

But this doesn't mean I won't pick up a used Delos some day at a decent price.

Mike




You need to lock it in place because there are two halves to the system Mike. Some actually find the Delos locking system easier to use than the Pentax XW. Either way, I owned BOTH at the same time and I set them both up and left them... I actually leave my XW eye cups all of the way in the "down" position. The only reason you may need to move either eye cup would be for someone who needs glasses to observe. Personally I wouldn't use either one for "pulic" viewing because people stick their fingers everywhere. "Is this where I look?", putting their fingers right on the top lens.....LOL! Meh, I don't even do public viewing anyways.

Mike, It seems as though YOU ARE trying almost everything that comes along, LOL! One good look at your posts or sigline shows you are trying almost everything that everybody seems to be talking about these days. I guess the Delos is not one of them at the moment haha.

Just kiddin' broski. Try not to get too agitated, after all, this IS a fun place to be in "kookoo eyepiece" land.


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Sarkikos
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Scanning4Comets]
      #5635094 - 01/21/13 02:30 PM

You should see obvious holes in my sig. No Naglers, no Ethos, no Delos. There is a definite pattern here. The reason for the pattern should be obvious also, as well as the few exceptions.


Mike


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Sarkikos
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Sarkikos]
      #5635109 - 01/21/13 02:40 PM

Yes, I set the XW's eyecups all the way down, too, and leave them that way. The XW's have 20mm of eye relief, so there is no problem for me to leave my glasses on when I observe.

Mike


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RAKing
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: GeneT]
      #5635153 - 01/21/13 02:58 PM

Quote:


On a related note, I was seriously thinking of purchasing a 13mm Ethos. I have a 12mm Nagler. I don't know if TeleVue used to make a 13mm Nagler, but if they did, they no longer do. Therefore, I had to compare my 12mm Nagler against a 13mm Ethos that a friend owned. Again, the focal lengths did not line up. I had to draw conclusions with these eyepieces. I decided that the main issue for me was the 17 degrees of eye relief of the Nagler vs. the 15 of the Ethos. I could get all of the field of view in the Nagler while wearing glasses where I could not with the Ethos. I liked the 'whiter' tones of the Ethos better than the warmer tones of the Nagler. However, I also did not feel that the 100 AFOV suited my viewing needs compared to the 82 of the Nagler. Therefore, I stuck with the Nagler and did not upgrade to the Ethos.

I would be interested in someone comparing a 6 ZAO with a 6 Delos. Has anyone compared a 6 ZAO with a 5 XO? (With all the caveats that we have to remember that they are of differing focal lengths.)




Gene,

Televue still makes a 13mm Nagler - it's one of the little Type 6 eyepieces and works very well if you need to save weight or money.

Yes, I have compared my 6mm ZAO-II against the 5mm XO. I also compared the XO with a Barlowed 10mm ZAO-II and with my 5mm A-P SPL. All of these eyepieces are superb and I enjoy the views out of every one. But in the long run, I let my XO go to someone who wanted to use it and I stayed with the eyepieces that were more comfortable for me to use.

Having said all that, I also use a 5mm Pentax XW and a 6mm Delos for public outreach. These eyepieces are easier for the public to use and still put up great views.

I enjoyed your report. I don't care if these are vastly different eyepieces - it's still fun and educational to read the opinion of someone I admire.

Ron


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ibase
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Re: A 6mm Delos Compared to A 5mm Pentax XO new [Re: Sarkikos]
      #5635189 - 01/21/13 03:16 PM

Quote:


I know they are not the same. But I've also read that the Delos adjustment cup can be a hastle to use as well. Twist up or down and then lock. Why should a lock even be necessary if the cup is well designed? My XW's adjust easily and stay put without a lock. Sometimes these companies try so hard to make things "easier" for the consumer they wind up making them more difficult. Upgrades of some operating systems come immediately to mind.

I'm not about to try everything that comes along. I've heard that siren song before. It ignores the fact that most human knowledge is indirect and all human time is finite. I accept those limitations.

But this doesn't mean I won't pick up a used Delos some day at a decent price.






Mike, do pick up a Delos one of these days to try out, you might take a liking to it, no hassle at all really in using its eyecup. In the meantime we can race putting the eyecups all the way up for your Pentax XW vs my Delos 6mm (which I like very much). The Delos would finish in a jiffy, and I'll have time to drink coffee as you twist the Pentax eyecup around and around and around.. (you get the idea )

Best,


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