eye pieces

[daz01968]

what is the difference between an ordinary 6mm and a 6mm planatary eyepice

[Charic]

It suggests the Planetary is better optically,  for looking at the Planets, and the ordinary 6mm would suggest cheaper? maybe a marketing ploy.? At the end of the Day its  the user who decides whats best for them IMHO

[rwilkey]

Hi Daz, a true planetary eyepiece (such as the WO SPL 6mm) is optimized for bright planetary use and usually has good eye relief.  Such an eyepiece is also useful for double stars and the Moon.  In combination with a true planetary filter (such as the TV 'Planetary') it is stunning.

[ronin]

"Planetary" was sort of first used by Thomas Back for his eyepieces, maybe he picked a name and it suited.

Generally they seem to be not so wide a field of view, and go to shorter focal lengths.

I have also noticed that often in "planetary" eyepieces the focal lengths are in 1mm steps at the lower end.

Planets tend to be brighter so can take some magnifing and the short increments may simply be that a 3mm doesn't quite make it but a 4mm does.

I would assume the ifdea is you are looking at a planet for the rest of the vista can be ignored.

Even if you have the same magnification if the field of view is wide you tend to interpret the object as smaller.

I tend to think that whatever you re looking at you want the image to be sharp and of good contrast.

And that if it is a planet, a cluster, a galaxy, planetary nebula or a nebula you still want the same criteria.

So whatever you are looking at you really want a good eyepiece at the end of the day, immaterial of what is etched on the side. That may be a BST, X-Cel, ES or one of the TV's which includes their excellent plossl's.

Not sure if Thomas Back or Burgess trademarked the name "Planetary". They may have which could be why only one "style" of planetary is referred to.

[Charic]

Hi Daz, a true planetary eyepiece (such as the WO SPL 6mm) is optimized for bright planetary use and usually has good eye relief.  Such an eyepiece is also useful for double stars and the Moon.  In combination with a true planetary filter (such as the TV 'Planetary') it is stunning.

....this answers a question for me., and  my response to  a previous reply to another thread.

My view (excuse the pun)  that 55°fov is too tight  for me ( TMB 6mm PII ) but I've just  re-considered, Planets are not big at all, so the recommended small exit pupils of about 1mm and the tightness of the field of view may now be to my advantage for just  Planetary work alone.  One tool, one Job! ..........Maybe I should try one again, now that I'm learning more about the aspects of observation

[rwilkey]

....this answers a question for me., and  my response to  a previous reply to another thread.

My view (excuse the pun)  that 55°fov is too tight  for me ( TMB 6mm PII ) but I've just  re-considered, Planets are not big at all, so the recommended small exit pupils of about 1mm and the tightness of the field of view may now be to my advantage for just  Planetary work alone.  One tool, one Job! ..........Maybe I should try one again, now that I'm learning more about the aspects of observation

Hi Charic, 55°fov is not too tight when looking at planets etc, yes, you have to keep adjusting to keep the object in view, but for planetary use OK.  I have just bought the 6.7mm ExSc 82° to give this a go so will see how I get on. Tighter eye relief etc but I get on with other models in this series.

[John]

I don't think the term really has much meaning these days. I use 100, 70, 60 and 50 degree eyepieces to view the Moon and planets and they all do a great job. Todays glass and coatings do an excellent job of making multi element eyepieces perform like low glass designs. With undriven mounts I find the additional field of view helpful in tracking at high power too.

[Sirius Starwatcher]

Hi Daz Thanks for asking the question and thank you gentlemen for your replies I am researching eyepieces for myself at the moment and want to observe planets and am looking for a reasonably priced unit to do the job but not too cheap.