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goe
journeyman
Reged: 04/16/09
Posts: 7
Loc: MA
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Hi,
I recently bought ETX-90 however I discovered that it comes with "Meade Series 4000 Super Plossl Eyepieces 26mm" which is not really power full enough as it gives me about 46x magnification.
I want to spend about $100 for another two or maybe three eyepieces more to have the full range covered. However what are the best size for this telescope? I was thinking about getting: 15mm and 9mm for the 4000 series and a 2x barlow.
Do you think there's a better combination for this telescope? Should I bother buying 6.4mm?
Does the 2x barlow obscure the picture in any way?
Thanks,
goe
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ETX-90 PE (Premium Multicoated Optics)
DSLR Nikon D60 18-55 VR
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 RonBurgundy
sage
Reged: 06/16/09
Posts: 252
Loc: Philadelphia
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Hey geo. The etx90 is a great telescope; congrats on your purchase. It really does have fantastic optics! Now, to get down to business:
1) Your aperture is 90mm/3.5in. This means that your limit is about 3.5X8 = 175X magnification before your telescope starts getting degraded images, under most circumstances. With your focal length,1250mm/175X means that you should probably stick with eyepieces OVER 7.2mm in focal length.
2) If you can afford it, I would recommend getting as many eyepieces as possible without having to depend on the barlow. I don't even have a barlow anymore. I can't stand using them, because of the excessive focusing required.
3) Are you considering the Meade eyepieces? Or are you considering another brand as well? Because of your lightcone (f/13+), you won't have to be a slave to eyepiece quality like those with faster telescopes. This means you may be able to afford a wider variety of focal lengths! Also, many are parfocal! This makes observing much easier.
4) What are you interested in seeing? Do you prefer a narrower or wider AFOV?
5) With this being said, let's talk magnifications alone. Let's assume Meade products since you brought up your 4000 series:
a) Say you're going to purchase some things from the 4000 line.... I would certainly go for the 9.7mm, the 15mm, & the 40mm.
Along with your 26mm, this gives you:
128X, 83X,48X,31X at .4 degrees, .62 degrees, 1 degree, and 1.4 degrees. It's a good starting point, and will give you plenty of great views... The total cost of these additions will be $107 (opt corp has their Meade eyepiece sale, if I'm not mistaken), not to bad with all things considered. I have seen these 4000series super plossls in action on an ETX125, and due to the f/15 light cone, they all looked great!
Good luck to you!
P.S., if you wish, a barlow would not be a bad idea. They will effectively double your collection, asides from maybe the 9.7mm eyepiece. I would give it a try!
   
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Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
Edited by RonBurgundy (10/26/09 07:03 PM)
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brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2076
Loc: 55.215N 6.554W
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Quote:
Should I bother buying 6.4mm?
No, the scope is long focus and this will give more power than is useful.
Quote:
Does the 2x barlow obscure the picture in any way?
The Meade series 4000 "shorty" barlow is frankly not brilliant. With a long focus scope like yours you can easily manage without, though a good barlow might be useful for imaging. The cheapest barlow that I rate is the Celestron Ultima SV.
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stevenf
member
Reged: 10/11/09
Posts: 31
Loc: Vancouver, BC
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Hi goe, some excellent advice above. I just wanted to add, when I head out with my ETX90 for an evening of viewing, my typical eyepieces are the 26mm, a 15mm, and a 10mm, with a barlow lens, and I feel this is really all I need. Best of luck!
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Meade ETX-60BB
Meade ETX-90EC UHTC
Skywatcher ST80
Orion ST120
Skywatcher 90mm Mak
Meade 9x63 binoculars
Celestron Explorascope
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goe
journeyman
Reged: 04/16/09
Posts: 7
Loc: MA
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But is it better from the image quality perspective to buy a 15mm and us it with 2x barlow or rather go for the stand alone 6.4mm without a barlow? The magnification seems to be similar but there much a difference in image quality right?
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ETX-90 PE (Premium Multicoated Optics)
DSLR Nikon D60 18-55 VR
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stevenf
member
Reged: 10/11/09
Posts: 31
Loc: Vancouver, BC
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To be honest I'm not sure. I think the 6.4mm would be better, but the image at that magnification is kind of dim and fuzzy, at least that's my experience. I do own a 6.4mm Meade 4000 series, I got the amazing $100 deal for a full set several years ago. I don't regret owning it at all, it gets used in my other scopes.
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Meade ETX-60BB
Meade ETX-90EC UHTC
Skywatcher ST80
Orion ST120
Skywatcher 90mm Mak
Meade 9x63 binoculars
Celestron Explorascope
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CaptainTruss
member
Reged: 07/10/06
Posts: 61
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$100 can't get you much quality eyepieces but there's a few "unknown treasures" that many people haven't discovered that could fit your budget. I would recommend you looking into buying either BO/TMB Planetary eyepieces or Edmund RKE plossls. Both are excellent and worth more then what they cost in my book.
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Are you a serious deep sky observer?
http://www.avertedvision.net
14.5" F/6 Truss
10" F/4.5 Truss
120mm F/8.3 Refractor
4.5" Dobsonian
ETX-70
50mm Galieoscopes
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RonBurgundy
sage
Reged: 06/16/09
Posts: 252
Loc: Philadelphia
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Hi again, Goe... After more thought, I must recommend against the barlow. Like I said, I don't even have one, because they're such a pain. I would definitely recommend the spread of eyepieces that I gave you earlier post. It has a nice range of magnifications and TFOVs, and it's just a few bucks above your $100 limit. But trust me, barlowing is no fun! (at least it's what I think). Best of luck 
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Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
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blb
sage
Reged: 11/25/05
Posts: 214
Loc: Piedmont NC
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Quote:
I would certainly go for the 9.7mm, the 15mm, & the 40mm.
Along with your 26mm, this gives you:
128X, 83X,48X,31X at .4 degrees, .62 degrees, 1 degree, and 1.4 degrees. It's a good starting point, and will give you plenty of great views...
I totally agree! I have the ETX125PE that is capable of giving views of 250x but the seeing (steadiness of the atmosphere) rarely let's me go over 150x. So those realy high magnification views arn't there. I have a total of 9 eyepieces, that I use on different scopes, but find that I only use about three for almost all viewing with the ETX. Those are a 24mm (79x), a 19mm (100x) and a 13mm (146x). About once a year is the sky steady enough to allow me to use my 7mm (214x). I also have a 32mm (59x) and a 40mm (47x) but rarely use them because they gives me almost the same field-of-view as the 24mm but with a brighter sky. Also, I almost never use a barlow, so why buy it. That means I only need three eyepieces for the vast majority of the nights that I observe.
Good luck, Buddy
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C-11, C-6, XT10i Dob, ETX125PE, TV102, & AT66
Edited by blb (10/27/09 05:05 PM)
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Kfrank
super member
Reged: 12/20/08
Posts: 162
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Quote:
But is it better from the image quality perspective to buy a 15mm and us it with 2x barlow or rather go for the stand alone 6.4mm without a barlow? The magnification seems to be similar but there much a difference in image quality right?
One consideration with the plossel EPs that typically come with scopes is that as the focal length decreases, the eye relief decreases. A barlow tends to maintain the eye relief of the EP being used thus a 16mm EP used with a barlow will give an effective 8mm EP but with the eye relief of a 16mm. I believe the exit pupil of the EP is also preserved when using a barlow.
As to "excessive focusing", I don't get the complaint. Sure you have to refocus when going from the basic EP to using it with a barlow but so what. The only real issue is to make sure that your scope has the focus range to handle the barlowed eyepiece.
You might want a 32mm to gain a wider FOV. Also, if you want to push the mag to 175x (the theoretical max) and have limited funding, don't go for an EP that will give you this mag unless you've got the range pretty well covered. Atmospheric conditions often limit the magnification to well below the theoretical for a given scope. For example, I can usually get a decent image at 150 -200x in my 8 inch but can rarely push it to 300x even though the theoretical limit for the scope is 400x.
Better to have the shortest focal length (max magnification) covered via the use of a barlow. I think a good spread for an ETX90 given that the scope comes with a 26mm) is a 26/13 barlowed, a 20/10 barlowed, a 16/8 barlowed. This gives you a range of mags from 48x to 156x with only 2 additional EPs plus a 2x barlow. If you're lucky enough to be blessed with excellent skies, you may want to go for a 7m for mazimum power, but you might want to hold off and see how often you actually do push the magnification.
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Ken
ST80
SV80ED
ETX90 (Deforked)
Orion XT8
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goe
journeyman
Reged: 04/16/09
Posts: 7
Loc: MA
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Kfrank that's what I was actually thinking myself. That maybe I should get a barlow x2 and 17mm and 12mm. But except for the refocusing does the barlow cause any image quality lose?
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ETX-90 PE (Premium Multicoated Optics)
DSLR Nikon D60 18-55 VR
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Kfrank
super member
Reged: 12/20/08
Posts: 162
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Quote:
Kfrank that's what I was actually thinking myself. That maybe I should get a barlow x2 and 17mm and 12mm. But except for the refocusing does the barlow cause any image quality lose?
Sure, it almost certainly introduces SOME loss. The question is, how noticeable is it? I find that a decent 2x barlow still gives me good images when used with any of my eyepieces. BTW, if you're concerned about barlow quality, Televue sells a 2x for a very reasonable price.
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Ken
ST80
SV80ED
ETX90 (Deforked)
Orion XT8
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Joe Lalumia
Post Laureate
Reged: 01/24/07
Posts: 3600
Loc: Rockwall, Texas, USA
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You can NEVER have too many eyepieces. This is confirmed by the simple formula:
T=I Where T is the number of eyepieces and I is infinity.
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LX90 8" LNT, SV Nighthawk & TelePOD, SV 80/9D & M4 mount, ETX 90, Orion XT10i, 20x80 binoculars, SV-BV3s-- www.texasastro.org
"Great minds discuss ideas;Average minds discuss events;Small minds discuss people." Unknown
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blb
sage
Reged: 11/25/05
Posts: 214
Loc: Piedmont NC
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Quote:
You can NEVER have too many eyepieces. This is confirmed by the simple formula:
T=I Where T is the number of eyepieces and I is infinity.
  I like that. If I only could afford that.
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C-11, C-6, XT10i Dob, ETX125PE, TV102, & AT66
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