Most of you probably know that the only lens included with the Meade etx 90 is the 26mm. I would like to add to this but would first like some advise on which lens should come next. I was thinking a barlow. Maybe one of you out there could give me some suggestions and if possible a list starting with the most important. Also is it best to stick with 'Meade' or are other brands OK? Is there another brand with as good or better quality yet more reasonably priced? Again my thanks to all! Kathy
Meade etx90 and lens
Started by lilkritter, 02/26/2005 04:49AM
Posted 02/26/2005 04:49AM
Opening Post
Posted 02/26/2005 04:48PM
#1
Kathy:
There are lots of decent quality eyepieces available these days. In a "slow" scope like the ETX-90 a good plossl will provide a nice sharp view to the edge of the field of view.
I believe Orion is having a sale on their Sirius Plossls, AT&WB has a nice selection as well.
For starters, I would consider 2 eyepieces, probably that is about 16 mm and one that is somwhere around 10mm. These will fit nicely with the 26mm and give you 78x and 125X magnifications.
A simple barlow like the Orion Shorty would also be useful.
jon
There are lots of decent quality eyepieces available these days. In a "slow" scope like the ETX-90 a good plossl will provide a nice sharp view to the edge of the field of view.
I believe Orion is having a sale on their Sirius Plossls, AT&WB has a nice selection as well.
For starters, I would consider 2 eyepieces, probably that is about 16 mm and one that is somwhere around 10mm. These will fit nicely with the 26mm and give you 78x and 125X magnifications.
A simple barlow like the Orion Shorty would also be useful.
jon
Posted 02/26/2005 05:46PM
#2
Jon gives good advice.
But you may actually want to go the other way in your eyepiece shopping. The ETX already has a long focal length, and therefore lots of magnification and relatively narrow field of view.
A barlow would give you magnification, and narrower field of view.
Consider any of the wide range of 40 mm eyepieces to expand your Field of view.
Incidentally, if you are into solar system objects, disregard what I just said.
When buying an eyepiece set, you should have 1)one that gets you in the range of 40-70 power, 2) an eyepiece that will get you about 250 power when barlowed (or, in a scope less than five inches, one that will get you about 50 power per inch of scope aperture when barlowed), and 3) a wide field/low magnification eyepeice. (Assuming your interests are general observing, and not focusing on double splitting, or solaar system observing, and whether I buy the wide field or the higher mag eyepiece second would depend on whether I wanted to observe solar system (buy higher mag) or deep space more (buy wide field).
Secondly, choose your eyepieces such that, when used with a Barlow, you actually get six eyepeices, and do not duplicate eyepiece length. (For instance, if you have a 26, and a two power Barlow, do not get a 12 or 13. (You would already have a 13 if you use the 26 with the Barlow).
Alex
But you may actually want to go the other way in your eyepiece shopping. The ETX already has a long focal length, and therefore lots of magnification and relatively narrow field of view.
A barlow would give you magnification, and narrower field of view.
Consider any of the wide range of 40 mm eyepieces to expand your Field of view.
Incidentally, if you are into solar system objects, disregard what I just said.
When buying an eyepiece set, you should have 1)one that gets you in the range of 40-70 power, 2) an eyepiece that will get you about 250 power when barlowed (or, in a scope less than five inches, one that will get you about 50 power per inch of scope aperture when barlowed), and 3) a wide field/low magnification eyepeice. (Assuming your interests are general observing, and not focusing on double splitting, or solaar system observing, and whether I buy the wide field or the higher mag eyepiece second would depend on whether I wanted to observe solar system (buy higher mag) or deep space more (buy wide field).
Secondly, choose your eyepieces such that, when used with a Barlow, you actually get six eyepeices, and do not duplicate eyepiece length. (For instance, if you have a 26, and a two power Barlow, do not get a 12 or 13. (You would already have a 13 if you use the 26 with the Barlow).
Alex
Posted 02/26/2005 11:06PM
| Edited 02/26/2005 11:08PM
#3
First - brands to get...
Most "name-brand" Plossls are in the same league or even better than the Meade Plossls. Orion's are a good deal, but with the recent price decrease the Meades are a good deal too (they were overpriced for a while). If you want a small step up in quality, Orion's Ultrascopics, Celestron's Ultimas, and Tele Vue's Plossls are the usual recommendations for very high quality at a moderate price. The difference may not be dramatic between these and the Meades, but side-by-side tests do show a difference. These are in the $75-$110 range. University Optics Orthoscopics are also available at an even lower price, and are favorites of many planetary observers.
Second, what focal length to get...
A barlow isn't a bad idea for a next eyepiece. Celestron's Ultima or Orion's Shorty-Plus are very good units at a modest price (although some people report that their magnification factor is actually more like 2.3x or 2.4x; hmmm). With a little planning, a barlow will save you money, and allows you to use longer focal length eyepieces for higher powers. If you don't know already, Plossls of less than about 10mm focal length (depending on personal preference) get uncomfortable to use (tiny little eyelens, have to get very close to it.)
Here's my personal suggestion:
Get a 2x Barlow, and a 15-17mm Plossl.
This will give you:
26mm: 48x, 96x w/barlow
16mm: 78x, 156x w/barlow
It's an idea. The 78x and 96x are a little close, but all in all this is a pretty nice range. About 150x is a good high power for the ETX90. You could push it higher - the optics on those things are usually pretty darn good, so it can probably handle 180-200x or more, but personally I think that 150x will be more generally useful (I rarely go over 200x with my 6-inch scope).
Not quite as succinct as I was planning, hope it's useful
Most "name-brand" Plossls are in the same league or even better than the Meade Plossls. Orion's are a good deal, but with the recent price decrease the Meades are a good deal too (they were overpriced for a while). If you want a small step up in quality, Orion's Ultrascopics, Celestron's Ultimas, and Tele Vue's Plossls are the usual recommendations for very high quality at a moderate price. The difference may not be dramatic between these and the Meades, but side-by-side tests do show a difference. These are in the $75-$110 range. University Optics Orthoscopics are also available at an even lower price, and are favorites of many planetary observers.
Second, what focal length to get...
A barlow isn't a bad idea for a next eyepiece. Celestron's Ultima or Orion's Shorty-Plus are very good units at a modest price (although some people report that their magnification factor is actually more like 2.3x or 2.4x; hmmm). With a little planning, a barlow will save you money, and allows you to use longer focal length eyepieces for higher powers. If you don't know already, Plossls of less than about 10mm focal length (depending on personal preference) get uncomfortable to use (tiny little eyelens, have to get very close to it.)
Here's my personal suggestion:
Get a 2x Barlow, and a 15-17mm Plossl.
This will give you:
26mm: 48x, 96x w/barlow
16mm: 78x, 156x w/barlow
It's an idea. The 78x and 96x are a little close, but all in all this is a pretty nice range. About 150x is a good high power for the ETX90. You could push it higher - the optics on those things are usually pretty darn good, so it can probably handle 180-200x or more, but personally I think that 150x will be more generally useful (I rarely go over 200x with my 6-inch scope).
Not quite as succinct as I was planning, hope it's useful
