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EXT 125 PE Buying Additional Eye Peices

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#1 Lemonwood

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Posted 17 September 2012 - 07:32 AM

Hey Everyone

I hope this is correctly positioned (or perhaps it should be in eye pieces, sorry if this is incorrectly located).

I am new to astronomy and have a ETX125 PE that came with a 26mm 4000 series meade eye piece.

I am in South Africa, so the range and availablity here seems less goos than for example the US. So ordering from the US and getting delivered is also an option.

I read Weasners Guide to Eye Piece Slection dated April 2001
http://www.arksky.or.../eyepieces.html

Is there any changes I should take into account? Are there alternative brands that are less expensive and also good?

For example GSO? or Sky Watcher?

I plan to go with a 40mm, 15mm, 9.7mm, 6.7mm and a barlow, and filters over time.

I might buy the Meade 4000 set.

Any thoughts on this GSO set
http://www.scopesnsk...ssory-kit2.html

To be honest I am very much new to this and don't really know the features and benefits.

I was also considering to by the GSO 15mm Superview.....

What filters should I have to start with?

In terms of viewing I have been viewing a broad range of things....

Any advice will be grately appreciated. Appologies if this should be in the other sections.

Thanks in advance
Iain

#2 Christopher Erickson

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Posted 17 September 2012 - 04:57 PM

Don't waste your money on a 40mm 1.25" eyepiece. The 1.25" field stop makes eyepieces longer than 32mm mostly a waste of time. Scopes with 2" focusers can benefit from longer eyepieces.

I have read Weasner's/Clay's recommendations and I can't get excited about them.

There is one eyepiece that I would suggest that you invest in for your 125 and that you will love at first peek. The Televue Panoptic 24. It is expensive but once you try it in your 125, it will instantly become your favorite eyepiece and you won't have much desire to buy a whole bunch more eyepieces. It gives the widest true field of view possible in your 125 with it's 1.25" field stop. Your scope has a very long focal length and getting things like the Orion Nebula, Andromeda or the Moon to fit in the eyepiece is a challenge. Just about the only thing short focal length eyepieces are going to be good for in your scope is looking at planets. For that you can combine the "Pan-24" with a Televue Powermate or a Nagler 9.

In fact a Pan-24, Nagler-9 and a Powermate might just be your entire kit for years of enjoyment.

Put a $5 eyepiece in a $1,000 telescope and get a $5 view.

Do it once, do it right.

I hope this helps.


#3 Lemonwood

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Posted 17 September 2012 - 11:59 PM

Chris

Thank you for the advice, which is appreciated.

Iain

#4 Christopher Erickson

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Posted 18 September 2012 - 01:42 AM

If you have a local astronomy club, maybe someone there has a Pan-24 that you can "try before you buy."

#5 *skyguy*

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Posted 18 September 2012 - 12:56 PM

Don't waste your money on a 40mm 1.25" eyepiece. The 1.25" field stop makes eyepieces longer than 32mm mostly a waste of time.


I really don't 100% agree with this statement. While both the 40mm and 32mm eyepieces will show about the same FOV (.9 degree) due to the 1.25" field stop restriction, the 40mm does have a larger exit pupil (2.7mm vs 2.1mm). Since the brightness of extended objects (galaxies and nebulae) is proportional to the square of the exit pupil, that would make these objects 1.6x brighter in the 40mm over 32mm eyepiece. That does make a difference when viewing the faint outer regions of extended objects. I see this all the time when using my 40mm eyepiece in my ETX-125.

I also see some very solid eyepiece recommendations in the Weasner list. Plossl eyepieces are all you really need to use in the ETX-125. At f/15 this scope is very forgiving with simple eyepiece designs. Yes, the expensive Naglers and Panoptics will give you a wider FOV per any given magnification, but all their expensive field flattening optics are really somewhat of a waste when used on the ETX-125. They're more suited for ... and designed for ... use in much "faster" optics.

The real strength of this scope is high power views of the moon and planets ... here, less is usually more! Simple, quality eyepiece designs ... with a minimum number of optical elements ... will give you the best performance. My old style 10.5mm and 7.4mm smooth-sided "circle NJ" TV Plossl eyepieces (apprx. $50 ea. used) show better contrast and sharpness on the moon and planets than any modern ... and some very expensive ... eyepieces I've tried.

No matter what eyepieces you buy ... enjoy your new scope and have fun with it.

Jim

#6 Lemonwood

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Posted 18 September 2012 - 01:28 PM

Thanks a lot for your input Jim.

#7 Lemonwood

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Posted 18 September 2012 - 01:32 PM

Chris, That is a good idea. Durban is the closest to me......

#8 *skyguy*

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Posted 18 September 2012 - 02:04 PM


Iain,

BTW, I forgot to mention ... while I don't own any GSO eyepieces ... all the reviews I've read on them have been consistently excellent. I wouldn't hesitate to buy them to use in my ETX-125. Also, when the time comes to use the highest reasonable power on your scope. Don't rely on a barlow to get you there. Just use an eyepiece ... a barlow just adds an extra optical element to the view.

Jim

#9 blb

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Posted 18 September 2012 - 03:12 PM

There is one eyepiece that I would suggest that you invest in for your 125 and that you will love at first peek. The Televue Panoptic 24. It is expensive but once you try it in your 125, it will instantly become your favorite eyepiece and you won't have much desire to buy a whole bunch more eyepieces...


I whole hardily agree with this. The 24mm Panoptic is my favorite eyepiece in my ETX-125. I also use a 13mm Nagler and a 10mm Radian. Seeing does not allow using a 2x barlow more than once or twice a year where I live so I almost never pull it out.

I really don't 100% agree with this statement. While both the 40mm and 32mm eyepieces will show about the same FOV (.9 degree) due to the 1.25" field stop restriction, the 40mm does have a larger exit pupil (2.7mm vs 2.1mm). Since the brightness of extended objects (galaxies and nebulae) is proportional to the square of the exit pupil, that would make these objects 1.6x brighter in the 40mm over 32mm eyepiece. That does make a difference when viewing the faint outer regions of extended objects. I see this all the time when using my 40mm eyepiece in my ETX-125.


Although your math is correct, you are missing something really important for those of us living with light pollution. That is that the sky background gets lighter with longer focal length eyepieces, so the contrast really isn't there. I find that the field-of-view is almost exactly the same with my 40mm, 32mm and 24mm eyepieces, so I almost never use them because there is nothing gained with lower magnification and a brighter sky.

It's true that the 24mm Panoptic gives about the largest field-of-view in my ETX-125 so why go with a longer focal length eyepiece to only get a brighter FOV and see less.

#10 Christopher Erickson

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Posted 18 September 2012 - 07:44 PM

I have had a lot of scopes and a lot of eyepieces over the years and I have been so impressed with the Pan-24 in the ETX-90/105/125 scopes that I will make this offer:

If you buy a Pan-24 and don't like it in your ETX-90/105/125 scope, I'll buy it from you for exactly what you paid for it. I'll even pay for your shipping.

I have made that offer to other ETX-90/105/125 owners in the past and nobody who has purchased one has taken me up on my offer.

The only use I have found for 40mm 1.25" eyepieces is for afocal photography with small digital cameras. Visually, they are like looking through a soda straw at a tiny image of the sky. Very unsatisfying.

I hope this helps.

#11 *skyguy*

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Posted 19 September 2012 - 01:39 AM

It's true that the 24mm Panoptic gives about the largest field-of-view in my ETX-125 so why go with a longer focal length eyepiece to only get a brighter FOV and see less.


It takes an experienced deep-sky observer to know that the key to seeing more ... even in moderately light polluted skies ... is in the size of eyepiece exit pupil and not just its magnification ... only a rank beginner goes for the high power eyepiece, thinking he will see more.

The ETX-125 is not known as a deep-sky scope. However, with the right selection of eyepieces it can and it does a nice job in this category. The 2.7mm exit pupil on a 40mm eyepiece is hardly the optimum size most deep-sky observers would like or even want to use ... but, it's the best that can be reasonably expected in the ETX-125. In fact most deep-sky binoculars observers scoff at binoculars with exit pupils under 3mm and recommend using a 10x50 ... with a 5mm exit pupil ... under light polluted suburban skies. That said, I always use my 40mm as my "first look" eyepiece ... knowing I'm seeing all the faint nebulosity the scope can deliver ... before moving on to higher powered eyepieces, to resolve all the detail visible in the scope's focal plane. It's also usually my "last look" eyepiece before moving on to a new object.

#12 blb

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Posted 19 September 2012 - 12:25 PM

It takes an experienced deep-sky observer to know that the key to seeing more ... even in moderately light polluted skies ... is in the size of eyepiece exit pupil and not just its magnification ... only a rank beginner goes for the high power eyepiece, thinking he will see more.


Obviously you do not live in an area that has much light pollution, I do. I am not a rank beginner either, I have been observing since 1964. Everything your saying is correct but evidently you do not understand how light pollution effects the image in your field-of-view. You are aware that magnification darkens your view of the sky? Right? I am able to see objects using the 24mm Panoptic that are never visible in the 32 or 40mm eyepieces due to nothing more than sky brightness.

My eyepices that you are talking about for the ETX-125 are as follows:

E.P.=40mm Plossl, Mag.=48x, TFOV=54 arc min., Exit Pupil=2.7mm
E.P.=32mm Plossl, Mag.=59x, TFOV=51arc min., Exit Pupil=2.1mm
E.P.=24mm Panoptic, Mag.79x, TFOV=52 Arc Min., Exit Pupil=1.6mm

The sky is a bright gray with the 40mm, A light gray with the 32mm, and the sky is black with the 24mm Panoptic. So, since the sky brightness with my light pollution prohibits seeing some objects with any thing below the 24mm Pan., and the FOV is about the same size with the 32mm or the 40mm, what is there advantage? If I were living somewhere with dark skies instead of a light polluted city I would totaly agree with you, but not in town with my light polluted sky.

Oh, for higher power views I use a 19mm Pan., 15mm Pan, 13mm Nagler, 10mm Radian, and a 7mm TMB Planetary. Seldome does seeing allow me to use more magnification than the 13mm where I live.

#13 Lemonwood

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Posted 19 September 2012 - 02:20 PM

Guys,

I really appreciate all of your comments.

I bought the scope a few months back from a local photo store that had had it in stock for years at less than 50% of the retail price. So first of all I feel I got a really good deal on it for the local South African market, where there is not much choice, unless I drive 500 miles to Jo'burg.

I live on a golf estate beside the ocean up the coast from Durban, so I don't have much light pollution. In fact the fairway is in front of my house, so I can go there easily, or from the decks on the house. I started with binos after my daughter got me a bino adapter for my camera tripod last Christmas and we all saw the moons of Jupiter for the first time.

So I must say I am having an awesome time with the scope with the 24mm Meade 4000 that came with it. I'm not up to speed with all the math yet regarding views, but I understood there were limitations when I bought the scope. It was convenient to buy, and there is almost zero selection where I live. However I don't regret for one minute the purchase. Perhaps in time I might consider another scope. I am also enjoying the moon and planets. However I can easily feel the attraction to deep space objects and I understand that doing that properly will be really require a more expensive larger scope.

So for me it is real easy to get onto the deck, even just for 20 minutes in the evening, and it is good weather here most of the year. So I want to get up to speed on a broad spectrum of viewing, techniques, navigation, etc, and perhaps if I can afford it in a few years get a much more powerful scope.

So I am going to think this all through.......guys thanks again for the advice. Cheers for now. Iain

#14 blb

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Posted 19 September 2012 - 03:49 PM

Lemonwood,
With your dark skies you should disreguard all I said about eyepieces and sky glow from light pollution and follow skyguy's advice on eyepieces. He is spot on when it comes to darker skies.

#15 REC

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Posted 20 September 2012 - 03:23 PM

Good explanation and going to try this example out my self. Living in a red/orange zone, this may apply to me as well.

What a great forum, always something new to learn, thanks all:) Bob

#16 Jaimo!

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Posted 23 September 2012 - 06:12 PM

Here's something I wrote up a few years ago, about my theory for choosing eyepieces for the ETX...

In my experiences with the ETX-90 & ETX-125, I can get away with 3 or 4 eyepieces:

First you will want an eyepiece that will give you a maximum field for the 1.25" focuser. This can be a 32mm Plössl (52° AFOV), a 24mm wide field (70° AFOV) or an 18mm ultra wide field (82° AFOV); I feel this is a must have EP for the ETX as is acts like a finder when the Autostar occasionally misses the target. At the other end of the spectrum, you will want an EP that will give you maximum "useful" magnification. I have found you that the skies rarely permit me to use any EP smaller than 10-12mm in the ETX-90 or 125. At the higher magnifications, I am typically looking at planets, so AFOV is typically not an issue. A plössl will do fine here. Next you will want at least one eyepiece in between the two extremes. I like a ~20mm &/or a ~15mm for deep sky objects.

The eyepieces that I am currently using with my ETX-125 are the 24mm, 20mm, & 16mm Meade 5000 SWAs @ 70° AFOV, this is a VERY good combination for me. I am also beginning to experiment with a set of 12mm, 16mm & 24mm OU Königs which should work fine in the f/15 ETX, as a travel set. Before those I have used a 15 & 20mm wide field similar to the GSO SuperView (http://agenaastro.co...epiece-set.html) or UO 70° Ocular (http://www.universit...125inch.html#70) I feel for the middle magnifications a larger field of view is an awesome luxury. The Tele Vue Panoptics are also an option and while the Meade 5000 SWA's are no longer available the Explore Scientific 68° eyepieces have filled their niche.

Before I sat down an thought about it and broke it down, I used a bunch of assorted plössls and it seemed I spent more time swapping EPs than looking at the stars... I hope I helped and not confused you.

Good Luck,
Jaimo!

#17 teskridg

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Posted 07 November 2012 - 03:38 PM

Jaimo! I'm with you. I had an 8mm Radian I bought because Phil Harrington said the 7.5mm Pentax XW was great in the ETX-125; I found for my skies it was too much magnification. I'd limit the lowest focal length to 13mm (I like the Nagler T6) for my skies with this telescope. The 26mm Meade Super Plossl that comes with the scope is excellent (and I have Panoptic 24's also). I'd stick with these two; if your goto misses an object a little, the spiral search feature is terrific on the Meade and I wish my Celestron CPC-1100 had it. Tim

#18 REC

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Posted 11 November 2012 - 09:03 AM

A lot of good choices here. For my ETX I use a 24mm SWA, 19Pan and a 13T6. Can't go much higher mag. from where I live.

Bob






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