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#1 CJK

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Posted 06 December 2012 - 10:13 PM

The scope kit I have on order is set up for 1.25" eyepieces and comes with one eyepiece. In looking at the many available eyepieces (and their prices!), I got to wondering if I should consider purchasing a 2" diagonal and 2" eyepieces instead, especially as I eventually intend to get a 2nd, larger scope.

Am I crazy?

-- Chris

#2 killdabuddha

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Posted 06 December 2012 - 10:20 PM

48mm vs 28mm field stop? Absolutely, especially if yer forward-lookin to a bigger scope. So you have to change the focuser too ($100)? As for use, and even tho we went this way, we use our 1.25" 24mm 68 for our LP WF EP, only usin the 31mm and 36mm under filter or at darker skies. But the big views are definitely worth having. You'll maybe wanna swap in a bigger secondary too. Maybe no if yer a slow enuf primary. Plug in yer values here

http://www.bbastrode...om/diagonal.htm

or check the tables here

http://www.loptics.c.../diagonals.html

Or maybe how much of a Richest Field Telescope you can reasonably get

http://www.bbastrodesigns.com/rft.html

Especially if yer gonna have a 2d, larger scope which will definitely give you more of the above by a faster primary...

Oops. Didn't consider the ED80. But still







#3 Achernar

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Posted 06 December 2012 - 10:46 PM

Not at all, they are the way to go if you want low-power, panaromic views. An 80mm refractor like yours is made to accomadate these eyepieces, and the star diagonal you will also need. A Dob or an SCT can also be used with 2-inch eyepices, I use two of them often with my Dobs, even the 6-inch.

Taras

#4 SeattleScott

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Posted 06 December 2012 - 11:42 PM

My 4.5" reflector only has a 1.25" focuser, and I can tell just by looking at the secondary that it is not going to illuminate much more than that. Upgrading the focuser and diagonal would cost more than the scope, and depending on the F ratio and secondary size, it could hurt the scope's performance. It would certainly hurt contrast if nothing else (not the case with refractors). So it really depends on your scope. For the ED80 it could be fun. I love the widefield views with 2" eyepieces and my 4" refractor. And the 2" ep's help with my big reflector too. Just not with my small reflector. So it just depends on the scope.

#5 CJK

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Posted 07 December 2012 - 04:22 AM

Thanks, everyone -- I appreciate the help!

The focuser on my (actually my daughter's) scope is a 2" one, so it sounds like other than purchasing a new diagonal, nothing else would need upgrading to use 2" eyepieces.

-- Chris

#6 Jon Isaacs

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Posted 07 December 2012 - 05:35 AM

The scope kit I have on order is set up for 1.25" eyepieces and comes with one eyepiece. In looking at the many available eyepieces (and their prices!), I got to wondering if I should consider purchasing a 2" diagonal and 2" eyepieces instead, especially as I eventually intend to get a 2nd, larger scope.

Am I crazy?

-- Chris


Chris:

Not crazy at all.. An ED-80 with a 2 inch diagonal and a decent 2 inch 30mm-40mm widefield eyepiece will provide some wonderful 3+ degree views, big and bright.

But you really only need one or two 2 inch eyepieces, the 1.25 inch format restricts the maximum possible field of view but this is only an issue with longer focal length eyepieces, otherwise 1.25 inch eyepieces are just fine.

Jon

#7 CJK

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Posted 07 December 2012 - 11:21 PM

@Jon - thanks for the reassurance! Oddly enough, although such stuff as OTAs and mounts cost much more than eyepieces, it's selecting an eyepiece that most intimidates me. Based on the advice I've received and the many great posts I've read here, I think I'm starting to feel a little more comfortable.

-- Chris

#8 Tony Flanders

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Posted 08 December 2012 - 07:11 AM

Oddly enough, although such stuff as OTAs and mounts cost much more than eyepieces, it's selecting an eyepiece that most intimidates me.


There's a famous saying that the reason academic politics are so bitter is that the stakes are so low. Likewise, the reason eyepiece choice is so tough is because the differences are so minor.

#9 Jon Isaacs

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Posted 08 December 2012 - 07:28 AM

Oddly enough, although such stuff as OTAs and mounts cost much more than eyepieces, it's selecting an eyepiece that most intimidates me.


There's a famous saying that the reason academic politics are so bitter is that the stakes are so low. Likewise, the reason eyepiece choice is so tough is because the differences are so minor.


:waytogo:

Indeed... If one has been peering through eyepieces for 20 years, the differences can seem blindingly obvious but if the fancy eyepieces that cost $700 were not available, we would be all using the $70 eyepieces and arguing about which one of them is best.

In general, all widefield eyepieces are clean and sharp in the center of the field of view. What you pay for is the sharpness towards the edge. Edge sharpness also depends on the focal ratio of the scope. Few eyepieces can provide sharp stars away from the center (off-axis) in an F/4 telescope, most all can in an F/12 scope.

Jon

#10 sg6

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Posted 08 December 2012 - 08:22 AM

I would go the other way to most and say not worth it, well at this time anyway.

A decent 60 degree eyepiece at 25mm will give reasonable views and a fair enough field of view.

A 2" diagonal and a 2" eyepiece may be worthwhile on a bigger and longer scope, but on the 80 I would not consider the cost as worthwhile. Suspect I could buy 3 reasonable eyepieces for the outlay.

Another consideration is that a 2" diagonal makes changing to 1.25" eyepieces more time consuming.

I have a 2" eyepiece, I have 2 refractors, Megrez 90 and WO 81, that have a 2" diagonal and can take the 2" eyepiece. I can honestly say I have never used it on either.

#11 Jon Isaacs

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Posted 08 December 2012 - 09:15 AM

I have a 2" eyepiece, I have 2 refractors, Megrez 90 and WO 81, that have a 2" diagonal and can take the 2" eyepiece. I can honestly say I have never used it on either.



I have three refractors that take 2 inch eyepieces, an 80mm F/5 Achromat, a 80mm F/7 apochromat and a 101mm F/5.4 apochromat. Regardless of which one I am using, it's a rare night that I won't use a 2 inch eyepiece and some nights, that essentially all I use.

These scopes excel like no others at low power viewing, this is what they do better than any other design...

Jon

#12 Pat at home

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Posted 08 December 2012 - 12:50 PM

I now only have two 1.25" eyepieces I use regularly so to save the fumbling around in the dark I've got both in their own 2" adaptors.

#13 CJK

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Posted 08 December 2012 - 02:08 PM


There's a famous saying that the reason academic politics are so bitter is that the stakes are so low. Likewise, the reason eyepiece choice is so tough is because the differences are so minor.


:waytogo:

Indeed... If one has been peering through eyepieces for 20 years, the differences can seem blindingly obvious but if the fancy eyepieces that cost $700 were not available, we would be all using the $70 eyepieces and arguing about which one of them is best.


These are two of my favorite comments EVER. :grin:

-- Chris

#14 REC

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Posted 08 December 2012 - 02:23 PM

I have pretty much the same scope and from time to time use some of my 2" EP's in it for a nice wide view. Most times it is my 28mm SWA in it. The others I have are quite heavy on the back of that stock R&P focuser and the 28 is the lightest of the 2" EP I have. Nice on M45 and M42 now.

Bob

#15 CJK

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Posted 08 December 2012 - 02:59 PM

@REC - I wondered about the stock focuser, actually. I looked at some after market focusers, but they cost as much as the entire OTA!

-- Chris

#16 REC

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Posted 08 December 2012 - 03:08 PM

The cheapest one that I could find that was any good was from Agena. They are about $150 and have good reviews for this size scope. Most time I just use a 24mm SWA 1.25 for my widest views. I only switch to the 2" diagonal because I have one in my 8" SCT.

Bob

#17 CJK

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Posted 11 December 2012 - 02:31 PM

Okay, after much additional reading, I've decided to get two or maybe three eyepieces to start with. To review, my daughter's scope is an 80 mm (semi) apo doublet, f/7.5 and 600 mm focal length. We're beginners in a light-polluted location, so the moon, planets, and some bright stars will be the initial targets.

A 25 mm Orion Sirius Plossl is included with the scope kit

I am leaning toward TV Naglers, but I'm worried about choosing focal lengths that would be appropriate for our scope. My thoughts:

17 mm - 2", gives 35.3x, 2.3° FOV with 2.3 mm exit pupil & 17 mm eye relief
9 mm - 1.25", gives 66.7x, 1.2° FOV with 1.2 mm exit pupil & 12 mm eye relief
5 mm - 1.25", gives 120x, 0.67° FOV with 0.67 exit pupil & 12 mm eye relief

Any comments or suggestions? (I am leaning against a Barlow or PowerMate because of the added weight on what is after all a smallish scope, thus the EP choices above.)

Thanks!
-- Chris

#18 killdabuddha

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Posted 11 December 2012 - 02:51 PM

Naglers? Overkill? And for weight, consider the 36mm Siebert Observatory, AT II ED (35mm), or even the Hyperion Aspheric, since you originally asked about 2" which is where the LP WF EP bump is. But for the cost of 3 Naglers...Also, with the lightness of the Sieberts, you can even Barlow. Add the biggest 2" EP that'll give at least 6mm exit pupil, then an ES 24mm 68 to replace yer 25mm, a 1.5x Siebert parfocal Barlow for 16 mm on that, and an ES 11mm 82 that Barlows to 7.3mm. AND money for the next scope.

#19 REC

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Posted 11 December 2012 - 03:43 PM

I have the same scope and I use a 19mm Panoptic, 13mm Nag. and ES 6.7mm.

I tried a 5mm, but too much power most nights in this scope. Love the ES 6.7 for highest power and very comfortable views. You could also do the ES 11mm for $100!

Have fun:)

#20 Jon Isaacs

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Posted 11 December 2012 - 03:45 PM

I am leaning toward TV Naglers, but I'm worried about choosing focal lengths that would be appropriate for our scope. My thoughts:

17 mm - 2", gives 35.3x, 2.3° FOV with 2.3 mm exit pupil & 17 mm eye relief
9 mm - 1.25", gives 66.7x, 1.2° FOV with 1.2 mm exit pupil & 12 mm eye relief
5 mm - 1.25", gives 120x, 0.67° FOV with 0.67 exit pupil & 12 mm eye relief



The Naglers are very good eyepieces, I have a set of 8 Naglers, all purchased used and I have approximately $2000 invested. Historically they have been the best eyepieces for those with faster (F/4-F/5) scopes.

The three you mention are right at $1000, that's a lot of money and at F/7.5, there are other eyepieces that are good performers that are much more affordable. The difference between a 9mm Nagler type 6 and a $50 TMB Planetary is apparent to a trained eye but the difference still small... small enough that many nights I use the 9mm TMB Planetary.

The thing about eyepieces is that there are a lot of good ones but what a constitutes a good eyepiece varies between observers. The Naglers are well suited to my equipment, to my style of observation, others make different choices. Until you have a clear idea of what works for you, start with something more affordable, they are still plenty good.

The Explore Scientific 82 degree eyepieces seem to be very good values and quite good eyepieces. Had they been available when I was building my eyepiece set, I certainly would have seriously considered them.

A few more thoughts:

The ED-80 with it's FPL-53 F/7.5 double offers very good color correction, I had one, I did not consider it a "semi-apo", I felt it deserved status as a full apo.

Your eyepiece choices are reasonable, I have an 80mm F/7 apo, I find that I often use 160-180x on double stars as well as on the planets. And too, regardless of the light polluted environ, a longer focal length widefield eyepiece is worth owning... something close to 30 mm.

Jon

#21 Dave Mitsky

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Posted 11 December 2012 - 03:53 PM

I have a 2" eyepiece, I have 2 refractors, Megrez 90 and WO 81, that have a 2" diagonal and can take the 2" eyepiece. I can honestly say I have never used it on either.



I have three refractors that take 2 inch eyepieces, an 80mm F/5 Achromat, a 80mm F/7 apochromat and a 101mm F/5.4 apochromat. Regardless of which one I am using, it's a rare night that I won't use a 2 inch eyepiece and some nights, that essentially all I use.

These scopes excel like no others at low power viewing, this is what they do better than any other design...

Jon


I also own 80 and 101mm refractors and use 2" eyepieces in them every time that I have them at dark sites. A 35mm Panoptic produces a wonderful 4.4 degree true field of view in the 101mm f/5.4 refractor.

Dave Mitsky

#22 CJK

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Posted 11 December 2012 - 05:33 PM

Great comments, much appreciated! I have more thinking to do, it seems clear!

@Jon - I stand corrected on the ED80: it *IS* a true apo, now that I've read more about it (and understand the definition better, too)

-- Chris

#23 WAVT

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Posted 12 December 2012 - 01:39 PM

I really like the Teleview Panoptic 27mm in my ED80. It provides over 3° field of view. The 11mm ES82° is an other great match for the ED80 as is the 6.7mm ES82°

As was said above, that type of scope really shines on wide field views. You should not hesitate to open up the possibilities with a 2" eyepiece. You can get out even wider than what the 27mm Pan will offer. I hear good things about the 30mm ES82° (I haven't tried one). You can really open up the field of view in your scope without worrying about the exit pupil getting too big. For instance, the 41mm Panoptic will have an exit pupil of 5.3mm and provide over 4.5° field of view. (I haven't tried one of these either)

The entire Pleaides cluster is just plain jaw dropping beautiful with a 27mm Pan in my ED80. The amount of framing really puts it in context. The double cluster is another stunning view with that 27mm/ED80 combo. Cruising the southern Milky Way is another summertime favorite. I highly recommend it.

#24 CJK

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Posted 12 December 2012 - 03:16 PM

@Mike - Thanks VERY much for the recommendations -- they're especially helpful since you have the same scope! I hope to get my final choices together in the next day or so and get my order in to Astronomics or OPT or whomever.

FWIW, the scope and mount arrived today, and I just finished setting it up in the living room to make sure nothing was missing and everything works. I must say that I am smitten -- it's absolutely beautiful to look at, and I can't wait to see my daughter's face when she sees it on Christmas morning.

Now to figure out the GoTo system!

-- Chris

#25 CJK

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Posted 14 December 2012 - 10:32 AM

Just a quick follow up note: I finally placed my order today (with Astronomics) for three of of Uncle Al's "glass hand grenades" (See, I'm learning the lingo already!)

Thanks one and all for your input and advice! Much appreciated!!!!

-- Chris






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