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Overwhelmed with eyepeice decisions

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#1 Sean13

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Posted 26 November 2012 - 12:46 PM

I recently bought a Celestron 6" Advanced Series SCT. My primary use for the scope is photography, so I hadn't planned on buying any additional eps for the scope. I see now that weather for photography is not always optimal, and some nights I would just like to be able to use the scope for visual purposes. I don't need to spend a fortune, just want some nice quality ep's that I can use to enjoy those not so perfect nights.

The Scope is a 6" SCT, f/10 with f/6 reducer. FL of 1500mm before reducer. I see eye pieces with different FOV's. How large of a FOV am I going to want with a scope like this?

Ideally I'd like to purchase a kit with some filters, any recommendations on a brand? I don't really like looking thru tiny holes so I'd like something with larger eye relief if this isn't a bad thing. Would like to spend in the range of $400 either for a kit or for a few eyepieces and a descent barlow. What would you recommend looking at?

#2 sg6

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Posted 26 November 2012 - 01:37 PM

You will get at the top about 1 degree FoV.
Based on the following:

32mm plossl = 47x = 1.1 degree FoV
25mm Astro-Tech Paradigm = 60x = 1 degree FoV

Smaller focal length eyepieces give less FoV

1 degree is the size of the Orion nebula and the Pleiades. Andromeda is somewhat bigger.

Used the above as the Paradigms are a fair selection of eyepieces, 6 of them at $60 each. You could get the 12mm, 15mm, 18mm, 25mm for your scope and a 32mm plossl for around $300, then pick a barlow.

#3 csrlice12

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Posted 26 November 2012 - 02:07 PM

I recently bought a Celestron 6" Advanced Series SCT. My primary use for the scope is photography, so I hadn't planned on buying any additional eps for the scope. I see now that weather for photography is not always optimal, and some nights I would just like to be able to use the scope for visual purposes. I don't need to spend a fortune, just want some nice quality ep's that I can use to enjoy those not so perfect nights.

The Scope is a 6" SCT, f/10 with f/6 reducer. FL of 1500mm before reducer. I see eye pieces with different FOV's. How large of a FOV am I going to want with a scope like this?

Ideally I'd like to purchase a kit with some filters, any recommendations on a brand? I don't really like looking thru tiny holes so I'd like something with larger eye relief if this isn't a bad thing. Would like to spend in the range of $400 either for a kit or for a few eyepieces and a descent barlow. What would you recommend looking at?


I'd grab a 30mm ES 82, the 18mm ES82, and the 11mm ES82, those will be right at $400. Get a GSO 2" barlow with 1.25" adapter. That would give you 50X, 83X, and 136X (double that for a barlow). Attached is an eyepiece chart you can use. Just plug in the f/l and size of the scope and the F/l and FOV of the eyepiece, and it will give you the TFOV (at least close, as all eyepieces will vary a little bit). You have also just discovered the SCT drawback-narrow FOV due to the long f/l of the scope.

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#4 MikeBOKC

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Posted 26 November 2012 - 02:14 PM

SCTs are pretty forgiving of eyepieces. The ES/Barlow suggestion is good . . . though it is only on nights of really good seeing that you will be able to push magnification much past 200-250 on planets and other seeing-senstitive objects. As for filters, a moon filter is pretty vital, maybe an O-III nebula filter, but the colored ones are not high priority in my view. If you are on a strict budget the comment on the Astro Tech paradigm line is a good one, or just a decent spread of quality plossls from someone like Televue.

#5 The Ardent

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Posted 26 November 2012 - 02:16 PM

Just get the 10mm Delos.

150x, 1mm exit pupil, giant eye lens and gobs of eye relief.

#6 Sean13

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Posted 26 November 2012 - 03:08 PM

So you would advise getting 2" eyepieces/barlow and using a 1.25" adapter instead of using all 1.25" components?

#7 faackanders2

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Posted 26 November 2012 - 04:30 PM

Explore scientific has the least expensive good widefields.
If your scope can take 2" I'd recommend 20mm 100 AFOV for $299. If your scope takes 1.25" only I'd recommend $99 14mm 82 AFOV or $TBD 24mm 68 AFOV. A barlow can effectively double the number of your eyepieces (just divide mm by barlow power).

#8 Sean13

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Posted 26 November 2012 - 04:34 PM

It has a 1 1/4" visual back on it, I'm not sure if its capable of taking a 2" eye piece with a different back?

EDIT: From the sounds of it, I want as wide of an AFOV as possible that my budget allows, correct?

#9 csrlice12

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Posted 26 November 2012 - 04:38 PM

If you can't use 2" eyepieces, then I'd recommend the ES68 24mm or 20mm, or even the ES68 28mm....

#10 Mike B

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Posted 26 November 2012 - 04:47 PM

A 1-1/4" VB is what i thot might be the case on that scope- so *yes*, you should constrain your collection to 1-1/4" EPs.

If you can find one, the Meade series 5000 18mm UWA should be a winner in that scope! Most other 18mm UWA's on the market therse days are 2" format. Yet a 24mm 68* EP (aka "SWA") would show a skosh more sky.

Otherwise, the 'Paradigm' EP suggestion sounds pretty decent... i've never used one, but i hear they're quite good... they compare favorably with EPs i HAVE used, and if i were headed that way myself, i'd be lookin' very closely at the Paradigms!
:grin:

#11 Mike B

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Posted 26 November 2012 - 04:58 PM

EDIT: From the sounds of it, I want as wide of an AFOV as possible that my budget allows, correct?



Well, sort of. *Apparent* FoV is just how wide the view circle *looks* to the eye... ie. "drinking-straw" or "picture-window". The TFoV ("True" FoV) is what you're actually after, and that's simply the EP's AFoV divided by the magnification produced therewith.

So if you're constrained to 1-1/4" EPs, you want the combination of FL+AFoV that nets you the most *true* field. As i suggested re: the Meade 18mm UWA, the scope at 1500mm used with the 18mm EP yields ~83x, and the 82* AFoV of this EP divided by that magnification is 0.98* TRUE field... whereas a 24mm SWA EP would yield 1500/24 = ~63x, and 68*AFoV/63 = 1.09* TRUE field... a bit more.

So MOST of what you're probably after is that net field seen. However, all things are seldom "equal", and after looking thru both of these EPs, you might totally fall in love with the ultra-wide display of the 18mm EP, and decide to forgo that extra 0.09* for the sake of the panache of the UWA! :lol:

We widefield addicts do this all the time. This forum is where we come to get therapy...
:tonofbricks:

#12 wky46

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Posted 26 November 2012 - 05:34 PM

I've settled on just one after nearly 20 yrs. with my sct @f10- 32mm Plossl (1 1/4"). All the other EP's in my case along with my Barlow gathers dust. The 32mm is a sweetspot through my eye, from the moon to mars to galaxies. Exit pupil to magnification, it's a joyous wedding of optical alignments. Now, I realize that could probably change if I went to 2" ep's but for 1 1/4", it's eyeball bliss :cool:

#13 faackanders2

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Posted 26 November 2012 - 09:57 PM

If you can't use 2" eyepieces, then I'd recommend the ES68 24mm or 20mm, or even the ES68 28mm....


ES68 28mm 1.25"???

#14 faackanders2

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Posted 26 November 2012 - 10:10 PM

es68 28mm is a 2" eyepiece.
widest es68 1.25" is a 24mm.

#15 ibase

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Posted 26 November 2012 - 10:30 PM

I recently bought a Celestron 6" Advanced Series SCT. My primary use for the scope is photography, so I hadn't planned on buying any additional eps for the scope. I see now that weather for photography is not always optimal, and some nights I would just like to be able to use the scope for visual purposes. I don't need to spend a fortune, just want some nice quality ep's that I can use to enjoy those not so perfect nights.

The Scope is a 6" SCT, f/10 with f/6 reducer. FL of 1500mm before reducer. I see eye pieces with different FOV's. How large of a FOV am I going to want with a scope like this?

Ideally I'd like to purchase a kit with some filters, any recommendations on a brand? I don't really like looking thru tiny holes so I'd like something with larger eye relief if this isn't a bad thing. Would like to spend in the range of $400 either for a kit or for a few eyepieces and a descent barlow. What would you recommend looking at?


My 1st scope was a Celestron 6SE SCT and the 1st thing I bought for it was a Celestron EP/filter kit. Not satisfied, I replaced the kit with a Baader Hyperion 8-24mm zoom and it worked great - the views were sharper, clearer, and wider. At 8mm zoom setting, the apparent field of view (AFOV) is around 70-deg (68 published), considered as a "widefield" but narrows down in the longer focal lengths. Still, it's a good option to consider for the 6SCT. The ES fixed focal length EP's are also good as others have suggested.

Best,

#16 jrbarnett

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Posted 26 November 2012 - 10:48 PM

The good news is that of all of the elements of the optical train - the atmosphere, the observer (eyesight and experience), the objective and finally the eyepiece - the eyepiece is the least important in terms of quality of the final image. There are few truly bad eyepieces, and SCTs are relatively forgiving of eyepiece designs (i.e., they work well with pretty much any eyepiece). The fact that yours is on a driven mount makes eyepiece choice even less important. A scope that doesn't track benefits from wide field eyepieces more than one that does track.

So honestly, the eyepieces it came with are probably fine. The prism diagonal that comes with the scope could be improved upon. Personally, I'd invest in this:

http://agenaastro.co...r-diagonal.html

And then I would get one of these...

http://store.smartas...com/smsmch.html

And one of these...

http://www.astrozap....p?idCategory=47

Those are the keys to many, many hours of comfortable, seated, contemplative observing, and will far and away improve your observing experience compared to any eyepiece upgrade. Notice, though, that I left ~$100 of your $400 budget intact. If you're desperate to try a different eyepiece, I'd take that $100 and buy one that puts up a 2mm exit pupil in your scope (i.e., ~20mm). The 20mm Sterling Plossl is a sweetie, at just $40.

http://store.smartas...0stpl55def.html

I'm also partial to the 20mm GSO Superview in SCTs:

http://agenaastro.co...w-eyepiece.html

Also about $40.

A third option with a decent reputation is the 20mm ES 68, which runs about $100.

https://www.astronom...ld-waterproo...

Lastly, I'd skip 2" accessories on this scope. It has an itty-bitty diameter baffle and anything 2" and truly wide field will show edge darkening due to vignetting.

Regards,

Jim

#17 SeattleScott

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Posted 26 November 2012 - 10:48 PM

The Baader zoom would be a nice combination with a 6" SCT, but it is also something like $275 and doesn't provide the widest possible FOV. From what I hear a 6" SCT is not really designed for 2" eyepieces - can be done, but negligible benefit. I would second the notion of a 32mm plossl. After using a very nice 24mm ES 82 deg eyepiece with my F9 refractor for a couple years, I was pleasantly surprised at the improved brightness of objects when I picked up a 38mm SWA. Both of these are 2" eyepieces, but the principle is the same. A longer focal length eyepiece makes a wider exit pupil, which makes objects brighter. How bright you want to go depends a lot on the light pollution where you are, but 3.2mm (using a 32mm eyepiece) is certainly not overkill. I would take that any day over a 24mm or 18mm eyepiece that gave the same field of view.

#18 Keith

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Posted 27 November 2012 - 07:25 AM

While OP's budget did not include a 2" upgrade (eats at least $99 for a decent GSO dielectric diag), I would have to say that 2" eps work fine with these scopes. It is the .63 reducers that cause vignetting on anything past a 20nagler/27panoptic/32 plossl 5k sized field stop. Without a reducer and they light up the EP just fine for visual purposes, we can handle 70% illumination on the edges just fine. IMO better than giving up the TFOV by making the 1.25" only sacrafice.

That being said, the f6.3 reducer does get you about as wide as a 35mm panoptic without the reducer, so given the budget I would not suggest 2" at this time, but it would be a good thing to consider for the future.

24SWA or ES68 would be my low power EP, considering the f6.3 will only bring it to about 4mm exit pupil

#19 Bob S.

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Posted 27 November 2012 - 08:33 AM

The good news is that of all of the elements of the optical train - the atmosphere, the observer (eyesight and experience), the objective and finally the eyepiece - the eyepiece is the least important in terms of quality of the final image. Jim


Jim, I do not disagree with your basic premise about the other variables that have greater weightings in the variance of telescope performance. However, I think for some of us, eyepiece performance carries more weight in the overall visual experience than possibly for others? I know that my eyes really have fairly strong preferences for certain brands (an particular eyepieces within a brand) and types of eyepieces and the viewing experience for me is either enhanced or diminished by the final part in the optical train which is the eyepiece. For this reason, I have generally made my eyepiece selection based on what looks the best for my eyes and the types of equipment I am using. I tend to stay pretty exclusively with high-end equipment because I do not want to have to worry about the equipment limiting what I am seeing. OTOH, I fully agree that the seeing is EVERYTHING. Bob

#20 t.r.

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Posted 27 November 2012 - 09:01 AM

As a few others have said, get the Baader Zoom 8-24. It is a perfect match to the 6" SCT. Get a longer focal length eyepiece later in the 30-40mm range for the really wide experience and you're done with two eyepieces! ;)

#21 ibase

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Posted 27 November 2012 - 09:05 AM

The eyepiece is important, period.

Best,

#22 jrbarnett

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Posted 27 November 2012 - 10:56 AM

That's true, Bob. But eyepieces are the "special effects" of the rock and roll stage show that is observing. Because the OP is a newer visual observer, rather than a veteran like Jeff Beck, he probably doesn't know if he prefers dry ice smoke, laser light effects or pyrotechnics. Because he has a driven mount, and because most observing with a narrow field scope like an SCT will be on-axis, he won't likely *see* any detail in any of the eyepieces being recommended that he would not also see in the eyepieces that came with the scope.

Until he's actually used the ones that came with the scope he won't really have an idea as to what his "special effects" preferences are, and what he doesn't like about the current eyepieces. Does he need eye relief? Does field curvature bug him? Does he like wider AFOVs and if so, does he like 68 better than 82?

Because eyepiece preferences are high subjective and personal, the opinion of another user who likes a particular eyepiece isn't all that valuable without some personal reference points. Developing these personal reference points is a thing that is better done borrowing peeks through eyepieces owned by others than through buying and trying, especially if on a budget. Buying used would be another option. That way he can try different eyepieces without having to eat the depreciation, and spend only shipping costs to find his way (i.e., discover his preferences).

Nonetheless, using the original eyepieces (simple stage lighting) he can still play his music for the crowd and invest instead in a better guitar, voice lessons and the essential trip to India to meet with a guru. Everyone knows that you'll never crack the Billboard Top 100 without a guru visit. :grin:

Regards,

Jim

#23 Sarkikos

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Posted 27 November 2012 - 11:46 AM

I second - or third, I think - the motion for a Baader Zoom 8-24mm. That, and maybe a 32mm Plossl, is all you really need. For grab-n-go with my 90mm Mak, all I take out is the Baader Zoom, and maybe my Orion Ultrascopic 35mm. Often when I have my 10" Dob at the dark site, the Baader Zoom is in the focuser 90% of the time.

Mike

#24 Bob S.

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Posted 27 November 2012 - 11:49 AM

Jim well said and VERY funny!

#25 Rick Woods

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Posted 27 November 2012 - 12:20 PM

What kind of eyepieces does Jeff Beck use?






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