Celestron x-cel lens

[daren88]

I have a nexstar 4se and was about to get a barlow. I would also like a good quality eyepiece but not sure the best size to buy for my scope. At the moment I am only interested with looking at the moon and other planets. I understand magnification but not sure what size eyepiece would be to powerful for my scope

[Stargazer33]

Hi, It's not recommended to go more than 2x your objective size in magnification, your scope has a 102mm objective. That equals maximum recommended magnification of 204x

Now your focal length is 1325mm which you divide by your ep size so a 10mm ep would give you a magnification of 1325/10 = 132.5x, a 7mm ep would give you a magnification of 1325/7 = 189.3x, which is probably as close as you are going to get. 1325/6 = 220x. If seeing is really good then people do push the mag; we all do it!

HTH

[daren88]

Really helpful thanks. I am now starting to understand.

[ronin]

I would not got for the 2x diameter option, if it works you are pushing the scope to it's limits and oddly your eye. The 2x diameter gives the smallest exit pupil that is advised for the eye performance and problems.

If you want to go for reasonable magnification try 120x to 150x on that scope, meaning something around the 8mm to 12mm focal length(s).

The 220x sounds nice but consider that the scope may actually never deliver it and if it did you would need a good clear stable atmosphere, which you might be able to count on the fingers of one hand in a year.

[Stu_]

I find a 9mm x-cel works well on my 127mak for planets, this gives me 167x mag, the x-cels give good eye relief (this is how far you have your eye away from the ep), but as the x-cel has a fov of 60*, the planets may look a bit lost in the, but a 18mm would be good for the moon.

If you don't wear glasses & don't mind getting too close to the ep, a plossi design may be a good choice like a vixen NPL, a 8mm will give you 166x with 50* fov & a 20mm should frame the moon nicely, you can get 2 NPLs for about the same price of 1 x-cel.

Stellarium is free software & will give you a good idea of what you will see.

[daren88]

Thanks guys. Sounds like you all know yr stuff. Time to go shopping

[YKSE]

I hope you can take some more time doing research before spending your hard-earned money.

In my f10 C8, the most used EPs for DSOs are the ones around 20mm, for planetary 8-15mm depending on objects and seeing conditions. x-cels are nice eyepieces, rated as good as BST starguiders by many site members. I would however recommend Baader Classic Ortho 18mm together with baader Q-T 2.25x barlow, which can be screwed on EP directly for 1.3x, you get 8mm and 13.8mm equivalent EPs, the total costs will be virtually the same as x-cel and a cheap barlow:

http://www.firstligh...o-eyepiece.html

You read many of excellent reviews by John here:

http://stargazerslounge.com/topic/219151-5-years-of-reviews-and-reports/#entry2354015

[daren88]

Thanks good advice. I still haven't purchased yet so will look into your suggestion

[jonathan]

My 8SE is similar to your 4SE, same SCT design and approximately the same speed, but will give higher magnification just owing to its larger size.  I find that 10mm is usually my limit with a Celestron X-Cel, although frequently from my back garden in a village I do not get skies good enough to use it effectively so have to go to my 25mm.  If I had 12mm or 17mm I could use those and no doubt get the views I wanted when the 10mm won't work.

I'd say start at 12mm, if you find you can always use it then think about a 9mm.  You could also think about a zoom eyepiece such as the one from Baader, however they are expensive.  As someone else pointed out consider the field of view, you may want a narrow field for viewing planets but a wider field for the moon or clusters and nebulae.