Jump to content

sgl_imaging_challenge_2021_annual.thumb.jpg.3fc34f695a81b16210333189a3162ac7.jpg

Most popular eyepiece size?


Recommended Posts

13mm seems to be a very popular and useful focal length. The 1st Nagler was a 13mm as was the 1st Ethos and I'm sure that was no accident :icon_eek:

Personally I find the 6mm, 13mm and 20mm my most used eyepiece focal lengths.

Link to post
Share on other sites

Some say if you multiply your scopes' focal ratio by 2 in mm this hits a "sweet spot" for that scope.

Not sure what the theory is behind this or why it should be so,or if indeed it is correct.

32mm,&20mm seem to work particularly well for me in all my scopes,irrespective of the eyepiece design.

Why? i don't know, & that does seem to fly in the face of logic!

Link to post
Share on other sites

I think it depends on your scope - the real 'popularity' value is magnification. The maximum magnification, given perfect seeing and a good aperture, is about 276x. Most of the time 200-225x is the maximum in the UK IIRC.

Here are examples of my Baader EPs:

scope fl / ep fl = magnification

675 / 3.5mm = 192x. Perfect for lunar and planetary. Medium use

675 / 13mm = 52x. Perfect for DSO hunting. Heavy use

675 / 31mm = 22x. Perfect for wide field. Low use (because I need to sort out the back focus as this is a 2" EP)

Pentax do an XO 2.5mm:

675/2.5 = 270x. Would be stunning for lunar and planets in perfect seeing conditions.

Edited by NickK
Link to post
Share on other sites

The 'twice focal ratio' rule is based on the idea that a 2mm exit pupil gives sufficient brightness for viewing fuzzy objects while still giving a good image scale. That rule worked for me from a moderately dark site - a 24mm ep in an F13 scope gave good views. From a city where I now live I prefer an exit pupil closer to 1mm.

Link to post
Share on other sites

It depends on target and scope.

For me:

Wide field: 80mm APO + 24mm, 32mm

Planets: 80mm APO + 3mm, 2x TeleXtender + 8-24mm

Planets: C6 + 13mm, 8-24mm

DSO: C6 + 13mm, 8-24mm

Grab n go: 80mm spotting scope + 8-24mm

so, I guess my SMC 8-24mm zoom is the most popular eyepiece for me in terms of use, but I prefer the view of my 13mm LVW.

Link to post
Share on other sites

For me, using a 1600mm focal length 14" Flextube GOTO,

31mm Nagler for widefield observing (x52)

11-16mm Naglers for medium magnification, mainly DSOs (x100-x145)

7-9mm Nagler for high power lunar observing (x178-x228)

However, the 13mm and 16mm Naglers get by far the most use.

Tom

Edited by Albireo380
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.