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

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Stay away from my area

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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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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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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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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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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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