BST Explorer/Starguider

[Charic]

4 hours ago, trynda1701 said:

Hmm, interesting. So what type of eyepiece type should I call my BSTs', other than the negative/positive type, if not Plossl? Are they classed as Nagler-like, without being Nagler? The same way I thought my ES Maxvisions were Plossl, but are actually a Panoptic clone?

 

Mark

I did start a similar thread suggesting the BSTs could be slotted into a group called, Paradigm, as they all (various brands ) seem to have evolved after the ATP? But Starguider sounds just as good.

sorry for any confusion though, Starguiders are not Plossls. My reference to Plossl was against my Revelations.

[John]

6 hours ago, trynda1701 said:

Hmm, interesting. So what type of eyepiece type should I call my BSTs', other than the negative/positive type, if not Plossl? Are they classed as Nagler-like, without being Nagler? The same way I thought my ES Maxvisions were Plossl, but are actually a Panoptic clone?

 

Mark

I'd call them BST Starguiders. A semi-wide angle design. Without dissecting or X-raying eyepieces you can never know precisely what optical layout is being used. To add to that, many eyepiece ranges do not follow a consistent optical design across all the focal lengths in the range, eg: the 5mm could be one design while the 12mm is slightly different. There are currently type 4, 5 and 6 Naglers and even within those types there are a number of optical design variations. Look at the Pentax XW's for another example:

 

[trynda1701]

@Charic

The confusion was mine, and the replies, including yours , have helped clear it up and inform me! I have learned something new today!

@John

And that diagram is interesting as well. I always thought it would just be the spacing or sizes of the lenses that would alter, not the actual arrangement, so again, I have learned something new!

 

Like @bingevader said above, SGL, helpful as always. 

 

Mark

 

P.S. My C8 is definitely a SCT and my 130P Flexitube is definitely a Newtonian, right?

[Louis D]

4 hours ago, trynda1701 said:

And that diagram is interesting as well. I always thought it would just be the spacing or sizes of the lenses that would alter, not the actual arrangement, so again, I have learned something new!

Note that many lines of eyepieces use a nearly identical positive group to form the final image at the exit pupil.  It defines the apparent field of view and the eye relief.  It is the negative group and the possible intermediary element(s) that tend to vary across focal lengths within a given line of eyepieces.  Notice how the positive group of 4 elements on the right of each 1.25" XW is identical (or nearly so in the case of the 20mm).