Eyepieces - upgrades worthwhile?

[geministar]

Hi all - 

I have a Nexstar 127 Mak, f = 1500mm.  Among my lenses are a 12mm (x125) and a 17mm (x88) Plossl.  These give respectively 0.42 and 0.59 degrees of real/true field.

I am thinking about upgrading these to a Celestron XCel 60 degrees 12mm and a Celestron Ultima LX 70 degrees 17mm, which would increase the RFOV to  0.48 and 0.79.

They are no doubt better lenses, but is it worthwhile to do this for small amounts of extra field, at those magnifications?  What more would I see over a range of objects?

Thanks in advance,

Doug.

[Laurie61]

Hi, I don't think I would swap either although the 17 mm 70 dg makes more of a case for itself. I would be looking at a 32 mm plossl or perhaps a 24 mm 68dg which would provide a 1 dg true field.  

http://www.rothervalleyoptics.co.uk/explore-scientific-68-maxvision-eyepieces-125.html

[Putaendo Patrick]

I may well be wrong, but aren't the Celestron Ultima LX line 2" EPs? I don't know if you're equipped to use these, or will need to upgrade your diagonal etc? If I'm right, 2" EPs are fantastic for wide views at lower magnifications but they also imply a certain cost!

I fully agree with Laurie that wide field EPs tend to excel at lower magnifications. In general  when I go for higher magnification, I have already identified my target and am looking for extra specific detail, so a wider view is less important. Another reason to upgrade EPs is simply to get a better quality view or greater viewing comfort - but if you're happy with your Plossls, I'd stick with them.

I'd certainly recommend trying before buying - if you have access to an astronomy club near you, their members will probably be very happy to let you look through their EPs so you can decide whether it's worth it!

[Jim78154]

Please understand that you have asked a purely subjective question. The only one that can answer that question is the person whose eye is at the ocular end of the telescope. Now, what you are going to see when you do look through that eyepiece is going to be different with the "upgraded" versions. You will see  more of the surrounding sky for certain due to the additional F.O.V. You may see the target more clearly due to better quality of components and construction, but that is the subjective part, as is how much of the field, i.e. the edges of the view, are in perfect focus due to coma and/or chromatic aberation. The magnifications will be equal, but the clarity and contrast may be subjectively different. 

[geministar]

Thanks everyone for the input.

I do have a 32mm Plossl, which gives a great view, and more than 1degree of field.

The 17mm Celestron is indeed a dual-fit ocular.  After much enquiry, I have established that its AFOV property holds whether you use it in a 1.25" or a 2" focuser.  This is because the optics are housed within the 1.25" nosepiece.  The dual fit aspect is just to make it easier for someone with a 2" focuser to swap up to higher mag.

(Hope I'm using the terminology correctly!)

And yes, there should be advantages in using a better quality lens - less distortion, more comfort, contrast, etc..

[ronin]

If you have a 32mm plossl then the reality is that you re not going to get much more in the FoV aspect  without a bit of effort.

If a Mak you need a 32mm plossl or the 40mm plossl simply for the field of view at least initially to find anything.

You say: "Among my lenses are a 12mm (x125) and a 17mm (x88) Plossl."

Then there comes the 32mm plossl, so I would gather that you have a selection of eyepieces not just the ones mentioned.

Do you want to change from plossl's to something else/better ?

If so then consider the longer 4 BST Starguiders - 12, 15, 18, 25mm - these are the ones I use in my Mak.

The 25mm BST giving almost identical FoV to the 32mm plossl.

The BST's have I think a better selection of focal lengths for use on something like a Mak, the Celestrons XCel-LX do not have one of either the 15mm or the 18mm. So there is a bit of a jump between 2 of them.

Another option is to collect the TV plossls, cost more but very good in a Mak.

[geministar]

Thanks, I'll check out your suggestions!

Doug.

[Gazabone]

Might be worth trying some out if you have friends with other ep. I recall the first time I looked through one of my scopes with something other than the type of ep that comes supplied with scopes.....I was blown away by the difference it made (that was a X-cel ep) and then once again when I started looking through 2" ones. Careful though, you may end up spending lots of money the next day!

[John]

The 32mm plossl should be showing you as wide a field of view as can be obtained with a 1.25" eyepiece and as wide as the 127mm mak-cassegrain can show due to it's rear port opening diameter.

Upgrading to premium eyepieces will deliver some benefits in terms of light scatter control around bright objects, and possibly a touch better sharpness and contrast but these may well be subtle rather than significant.

The slow focal ratio of the mak-cassegrain design means that it does not test eyepieces as severely as, say, an F/5 scope so most eyepiece designs will work pretty well in them.

Most eyepieces produced today work very well on-axis (ie: in the central part of the field of view) and it's the off-axis areas that gain the most improvement from premium eyepiece optics but, as already said, the slow focal ratios limit the issues off-axis as well so the gains are less.

I'm not saying don't upgrade your eyepieces but be realistic about the benefits that the additional investment will bring

[geministar]

Might be worth trying some out if you have friends with other ep. I recall the first time I looked through one of my scopes with something other than the type of ep that comes supplied with scopes.....I was blown away by the difference it made (that was a X-cel ep) and then once again when I started looking through 2" ones. Careful though, you may end up spending lots of money the next day!

Yes indeed - the list of stuff I want is growing all the time!

Doug.

[geministar]

The 32mm plossl should be showing you as wide a field of view as can be obtained with a 1.25" eyepiece and as wide as the 127mm mak-cassegrain can show due to it's rear port opening diameter.

Upgrading to premium eyepieces will deliver some benefits in terms of light scatter control around bright objects, and possibly a touch better sharpness and contrast but these may well be subtle rather than significant.

The slow focal ratio of the mak-cassegrain design means that it does not test eyepieces as severely as, say, an F/5 scope so most eyepiece designs will work pretty well in them.

Most eyepieces produced today work very well on-axis (ie: in the central part of the field of view) and it's the off-axis areas that gain the most improvement from premium eyepiece optics but, as already said, the slow focal ratios limit the issues off-axis as well so the gains are less.

I'm not saying don't upgrade your eyepieces but be realistic about the benefits that the additional investment will bring

Lots of good advice, thanks!

Learning every day, and loving it!

Doug.