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Equipment Discussions >> Eyepieces

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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Pentax XW's Toast? new [Re: Sarkikos]
      #5716289 - 03/06/13 12:23 PM

Went to the scope store to pick up the 5XO she had (still new in box) and someone had just beat me to it ($309). Got the XW instead.....then the next XW.....and the next....and the next....you're getting the picture....Think I'm done now for awhile, anybody know where you can buy some Cloud-B-Gone?????

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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Pentax XW's Toast? new [Re: csrlice12]
      #5716380 - 03/06/13 01:22 PM

No, but i think i saw a cloud filter on Amart last week... might still be there?

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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: Pentax XW's Toast? new [Re: Mike B]
      #5716417 - 03/06/13 01:36 PM

Wherever I go, Clouds follow me. I charge by the trip....

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Starman81
Carpal Tunnel
*****

Reged: 03/06/08

Loc: Metro Detroit, MI, USA
Re: Pentax XW's Toast? new [Re: csrlice12]
      #5716437 - 03/06/13 01:44 PM

Vendors must love it when it is cloudy... We end up buying so much stuff during those dreary days when we can't use what we already have!

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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: Pentax XW's Toast? new [Re: Starman81]
      #5716464 - 03/06/13 01:56 PM

It's why their first purchases were cloud machines........

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Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Pentax XW's Toast? new [Re: csrlice12]
      #5716809 - 03/06/13 04:37 PM

It's them gol'derned nerds at Apple Inc... marketing all that "cloud" storage... soon it'll be so stuffed we'll be lucky to sneak peeks past the edges!


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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: Pentax XW's Toast? new [Re: Mike B]
      #5716820 - 03/06/13 04:44 PM Attachment (33 downloads)

For those who are interested (and if the lenses end up in your lap, you'll need this).

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Dan Finnerty
sage


Reged: 09/11/11

Loc: Pasadena, CA
Re: Pentax XW's Toast? new [Re: csrlice12]
      #5716913 - 03/06/13 05:32 PM

That is really interesting how much the eyepiece designs change between focal lengths. I never would have guessed that.

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Ultron
super member
*****

Reged: 08/11/12

Loc: New Jersey
Re: Pentax XW's Toast? new [Re: Dan Finnerty]
      #5716985 - 03/06/13 06:13 PM

My XW 10mm arrived yesterday. Snow and rain arrived today. Can't wait to use it!

I was looking for a replacement for my 10mm plossl. Was going to wait for the ES82 11mm to be in stock, but jumped for the XW10 when I saw it might not be around anymore. Thank god these "scares" don't happen more often. I'd be spending too much money!

Does the 10mm Barlow well? I have a 6mm TMB planetary but I'd like to see how much better the views are with the barlowed XW10.


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Mike B
Starstruck
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Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Pentax XW's Toast? new [Re: Ultron]
      #5717039 - 03/06/13 06:44 PM

Quote:

I have a 6mm TMB planetary but I'd like to see how much better the views are with the barlowed XW10.



If you care even an ounce for that 6mm TMB, you won't allow it too near the Pentax... all it takes is a split second, and *ZAP* - the TMB will be reduced to a smoldering lump of salt.



Other than that, the TMB is a decent eyepiece...


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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Pentax XW's Toast? new [Re: Mike B]
      #5717101 - 03/06/13 07:20 PM

Quote:

If you care even an ounce for that 6mm TMB, you won't allow it too near the Pentax... all it takes is a split second, and *ZAP* - the TMB will be reduced to a smoldering lump of salt.






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ausastronomerModerator
Carpal Tunnel
*****

Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: Pentax XW's Toast? new [Re: Scanning4Comets]
      #5717210 - 03/06/13 08:25 PM

There is a lot of good information about all the Pentax Eyepieces on the Pentax Japan Website

Pentax XW lens configuration diagrams

Pentax XW Light Transmission Graphs

Pentax XW Astigmatism and Field Curvature Graphs

It's in Japanese but its easy enough to interpret the graphs. You can also translate it to read most of the commentary, if you wish.

Cheers,


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Mariner@sg
sage
*****

Reged: 06/28/12

Loc: Little Red Dot
Re: Pentax XW's Toast? new [Re: csrlice12]
      #5717485 - 03/06/13 10:54 PM

Quote:

Wherever I go, Clouds follow me. I charge by the trip....




Stay away from my area


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Pentax XW's Toast? new [Re: Mariner@sg]
      #5717906 - 03/07/13 08:31 AM

That's what the charge is for.....to NOT take the trip

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stevetaylor199
sage
*****

Reged: 09/21/11

Loc: SE Wisconsin
Re: Pentax XW's Toast? new [Re: ausastronomer]
      #5718389 - 03/07/13 12:57 PM

Quote:

There is a lot of good information about all the Pentax Eyepieces on the Pentax Japan Website

Pentax XW lens configuration diagrams

Pentax XW Light Transmission Graphs

Pentax XW Astigmatism and Field Curvature Graphs

It's in Japanese but its easy enough to interpret the graphs. You can also translate it to read most of the commentary, if you wish.

Cheers,




Great stuff -- thanks for these links! I had seen only one of these pages before.

Would anyone mind explaining the aberration curves?

Translated by Google into my native language, it reads, "how to shift the focus in the direction of radial and concentric This astigmatism curves, which indicates the amount of focal shift (the apparent angle), and the horizontal axis the distance from the center of the field of view in the vertical axis, solid line concentric The amount of focal shift direction (DS), the dashed line indicates (DM) in the direction of the focal shift amount of radiation."

I'm not grasping what the DS and DM lines actually represent. I get that the x-axis is marked at -0.2m and +0.2m (which sounds like a LOT, btw), and that the y-axis is the distance from the center.... but I'm not getting what's represented by DS and DM. It looks like nearly all of these eps have some amounts of field curvature (and astigmatism?), except the 10mm, on one of the two measures.


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Pentax XW's Toast? new [Re: Mike B]
      #5718431 - 03/07/13 01:23 PM

The only praise a TMB Planetary ever deserved was faint.

Mike


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Ultron
super member
*****

Reged: 08/11/12

Loc: New Jersey
Re: Pentax XW's Toast? new [Re: stevetaylor199]
      #5718439 - 03/07/13 01:28 PM

Quote:



Great stuff -- thanks for these links! I had seen only one of these pages before.

Would anyone mind explaining the aberration curves?

Translated by Google into my native language, it reads, "how to shift the focus in the direction of radial and concentric This astigmatism curves, which indicates the amount of focal shift (the apparent angle), and the horizontal axis the distance from the center of the field of view in the vertical axis, solid line concentric The amount of focal shift direction (DS), the dashed line indicates (DM) in the direction of the focal shift amount of radiation."

I'm not grasping what the DS and DM lines actually represent. I get that the x-axis is marked at -0.2m and +0.2m (which sounds like a LOT, btw), and that the y-axis is the distance from the center.... but I'm not getting what's represented by DS and DM. It looks like nearly all of these eps have some amounts of field curvature (and astigmatism?), except the 10mm, on one of the two measures.




I was curious too. I found this post Pentax XW Astigmatism and Field Curvature

The description is in the last post.


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stevetaylor199
sage
*****

Reged: 09/21/11

Loc: SE Wisconsin
Re: Pentax XW's Toast? new [Re: Ultron]
      #5718496 - 03/07/13 01:55 PM

That's a perfect explanation. Looks like the 5 is a real winner, in that it has very little astigmatism and field curvature (possibly) canceling that of many scopes. And, as that poster notes, FC is less of an issue at smaller exit pupils.

Funny how that info and these eyepieces are 8 years old, btw.

Edited by stevetaylor199 (03/07/13 01:56 PM)


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Pentax XW's Toast? new [Re: stevetaylor199]
      #5718669 - 03/07/13 03:23 PM

Quote:

Quote:

There is a lot of good information about all the Pentax Eyepieces on the Pentax Japan Website

Pentax XW lens configuration diagrams

Pentax XW Light Transmission Graphs

Pentax XW Astigmatism and Field Curvature Graphs

It's in Japanese but its easy enough to interpret the graphs. You can also translate it to read most of the commentary, if you wish.

Cheers,




Great stuff -- thanks for these links! I had seen only one of these pages before.

Would anyone mind explaining the aberration curves?

Translated by Google into my native language, it reads, "how to shift the focus in the direction of radial and concentric This astigmatism curves, which indicates the amount of focal shift (the apparent angle), and the horizontal axis the distance from the center of the field of view in the vertical axis, solid line concentric The amount of focal shift direction (DS), the dashed line indicates (DM) in the direction of the focal shift amount of radiation."

I'm not grasping what the DS and DM lines actually represent. I get that the x-axis is marked at -0.2m and +0.2m (which sounds like a LOT, btw), and that the y-axis is the distance from the center.... but I'm not getting what's represented by DS and DM. It looks like nearly all of these eps have some amounts of field curvature (and astigmatism?), except the 10mm, on one of the two measures.



Simply this:
The two curves represent the Sagittal (essentially vertical) and tangential or Meridional (essentially horizontal) surfaces. The deviation between them is zero at the center of the field (the bottom of the graph), and the deviation at the top (the edge of the field) indicates astigmatism.
The units on the bottom are diopters of deviation and, ideally, the curves should not deviate by more than 1 diopter or the astigmatism will be visible.
And the vertical center line would indicate a perfectly flat field, with a curve to the left indicating negative field curvature and a curve to the right indicating positive field curvature. However, the Petzval curve usually lies between the S and M curves, and it is that deviation from the center line that more determines whether or not field curvature is visible. The Petzval curve is not illustrated. As I mentioned, a deviation of 1 diopter is usually accommodatable.
If the S and M curves are very close together, there is little astigmatism. If both curves go to the right or left, it may indicate that focusing somewhere in the field other than the center may be necessary to bring the whole field into focus. If the two curves are identical and one goes right and the other goes left, the field will appear flat but there may be excessive astigmatism.


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teskridg
Pooh-Bah


Reged: 01/15/08

Loc: PA
Re: Pentax XW's Toast? new [Re: Starman1]
      #5730697 - 03/13/13 04:56 PM

S and M curves? Isn't this a family forum? Tim

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