6 replies to this topic

[Darryl Carlyle-Moses]

Hello everyone, I am relatively new to astronomy. I recently purchased a Skywatcher 250P Dob that I am very impressed with. Although I have various eyepieces in my collection (Plössls and Zooms) the scope came with a 20mm and a 12.5 mm wide angle eyepiece (both 70 degrees). I have looked everywhere, but I can not tell what type of eyepiece these are..Plössl, Kellner, modified Kellner (like the eyepieces that used to come with the Skywatcher Dobs, or other?  I am trying to include as much detail in my observing notes as possible and would love to be able to put the type of eyepiece I am using in those notes.  Thank you so much in advance. Also, is there a way to visually tell the difference between a Plössl and a Kellner eyepiece? Thank you. 

 

PS: A picture of the eyepieces I am asking about can be found here: https://groversoptic...x-tube-synscan/

 

[richardr]

Those are wide-field eyepieces, which would not be Kellner or Plossl.  Sometimes "super plossls" are 60 degrees but not 70.   Don Pensak or someone could tell you what brand those are by just looking.

[SeattleScott]

I couldn’t find a picture of the 12.5 or 20 eyepieces. I just saw a picture of an optional set of Plossls.

So all I can tell is they are 12.5 and 20 eyepieces that are advertised (not necessarily actually) as 70 AFOV. Certainly not a Plossl or Kellner. Could be Erfles. But no idea really given the lack of information.

Ultimately I don’t know that it matters what the optical design of the eyepiece is, for observing notes purposes. Some people note the magnification. But I don’t see people noting a specific eyepiece or optical design.

[Darryl Carlyle-Moses]

I couldn’t find a picture of the 12.5 or 20 eyepieces. I just saw a picture of an optional set of Plossls.

So all I can tell is they are 12.5 and 20 eyepieces that are advertised (not necessarily actually) as 70 AFOV. Certainly not a Plossl or Kellner. Could be Erfles. But no idea really given the lack of information.

Ultimately I don’t know that it matters what the optical design of the eyepiece is, for observing notes purposes. Some people note the magnification. But I don’t see people noting a specific eyepiece or optical design.

 Thank you so much. Yes, i am probably overthinking it when including eyepiece type into my observation notes. Magnification and FOV are probably all that is needed. 

[Darryl Carlyle-Moses]

Those are wide-field eyepieces, which would not be Kellner or Plossl.  Sometimes "super plossls" are 60 degrees but not 70.   Don Pensak or someone could tell you what brand those are by just looking.

Thank you so much. If I do list them in my notes I will just list them as wide-field. Cheers!

[eblanken]

Hi Darryl & All,

 

For note-taking, I would suggest that you adopt the following: Stock WF 20mm, 70 Deg. (and 12.5mm, 70 Deg.) but also add learning to drift-time them so as to get an estimate of the True Field of View (TFoV) and Apparent Field of View (AFoV) of your scope combined with each of these eyepieces. They will have some variation of Delta-AFoV as one migrates from-edge-thru-center-to-edge of your field. 

 

Also, please post a photo of each eyepiece . . . that would help us to ID them . . . 

 

Ed

Edited by eblanken, 06 February 2025 - 08:14 PM.

[Darryl Carlyle-Moses]

Hi Darryl & All,
 
For note-taking, I would suggest that you adopt the following: Stock WF 20mm, 70 Deg. (and 12.5mm, 70 Deg.) but also add learning to drift-time them so as to get an estimate of the True Field of View (TFoV) and Apparent Field of View (AFoV) of your scope combined with each of these eyepieces. They will have some variation of Delta-AFoV as one migrates from-edge-thru-center-to-edge of your field. 
 
Also, please post a photo of each eyepiece . . . that would help us to ID them . . . 
 
Ed

Thank you, eblanken, this is great advice. I can't seem to figure out how to post pics on this site...but the two eyepieces are pictured with the SkyWatcher on the top right of the photo in the following link: https://groversoptic...x-tube-synscan/