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Newby eyepiece questions

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#1 FredOz

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Posted 26 January 2020 - 10:47 PM

Hi All,
I'm new to Cloudy Nights and I have a bunch of questions about eyepieces. 

I have a Skywatcher Classic 150P (Newtonian w/Dobson mount), 153mm/1200mm (f/7.4).

The scope came with 10 & 25 mm eyepieces.  I asked Skywatcher support for more info. on the eyepieces and was told "the eyepieces are a modified Kellner design with a 52 degree field of view. The factory does put coatings on them, as to the specifics we are not able to release that information."

 

Assuming this is correct, I calculate:
10 mm: magnif. =   48, Field of view = 1.08 deg, Exit Pupil = 3.125 mm
25 mm: magnif. = 120, Field of view = 0.43 deg, Exit Pupil = 1.25

and I have a 2x Meade Barlow.

I'm over age 70, thus I guess my eyes dilate to 5 mm.  I live in Prescott, AZ with moderately light-polluted skies (can dimly see the Milky Way in summer.)

I've been considering a 32-40 mm wide-field eyepiece and a high-power EP, perhaps 6-8 mm.  Although I have a 2" adapter, I'd prefer to stick with 1.25" eyepieces (Barlow & filters).

I'm tempted by the Meade Instruments 607001 Series 4000 1.25-Inch Eyepiece and Filter Set, which Amazon sells for $160.  This includes eyepieces of 6mm, 8mm, 13mm, 17mm, 32mm plus Barlow and 7 filters in an aluminum case.  But I've read that the shorter Plössl eyepieces have very little eye relief.  Also, I cannot find details on these eyepieces -- apparently only the 32 mm is sold separately.  Celestron has a similar set with a similar eye relief problem.

Perhaps better choices are for the wide-angle:
GSO 1.25" Plossl Eyepiece - 32mm, magnif. = 37.5, FoV = 1.39  deg, Exit Pupil = 4 and 20mm relief
or Meade Series 4000 32mm (similar except 26 mm relief -- is that too much?)

or Baader Planetarium 32mm Classic Ortho Eyepiece (also similar)

and for the higher power:Explore Scientific 52° 6.5mm, magnif. = 185, FoV = 0.28 deg, Exit Pupil = 0.81 deg and 15.9mm relief.  (I don't use glasses.)

or Baader 1.25" Hyperion - 8mm, magnif. =150, FoV = 0.45 deg, Exit Pupil = 1mm and 20mm relief.

 

Thanks for any suggestions.

 



#2 eyeoftexas

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Posted 26 January 2020 - 11:00 PM

Welcome FredOz,

 

A very helpful guide to details about most eyepieces is available in the Eyepieces forum entitled "2019 Eyepiece Buyer's Guide".  You find a spreadsheet compiled by Starman that lists all eyepieces and basic characteristics (and new prices).  You can download the spreadsheet, and insert the focal length and f ratio of your scope, and it will calculate magnification, exit pupil, and true field of view for the eyepieces.

 

Good luck and enjoy the views!


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#3 havasman

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Posted 26 January 2020 - 11:08 PM

Hi Fred,

 

Eyepiece sets, particularly the ones offered by major concerns, like Meade and Orion, are made to sell and not so much to use. A buyer can always do better making good choices of individual focal lengths.

 

The Astro-Tech Paradigm Dual ED eyepieces offered in several focal lengths by our forum sponsor rate very high on the price/performance scale and should be fine performers in your scope. That's what I recommend. They're 60 degree AFOV designs and I have used them in 6" f8 Dobs with fine results. At $60 a pop they're hard to beat.


Edited by havasman, 26 January 2020 - 11:08 PM.

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#4 whizbang

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Posted 26 January 2020 - 11:17 PM

The sets tend to have a bunch of stuff you won't use.  Just do your homework.

 

Your scope will work fine with Plossls.  A 32mm is the widest FOV you can get in the 1.25 size.  That is a good choice.

 

What you need to decide is if you want to go with wide field eyepieces, 62, 68, or 82 degrees.  Do your homework.

 

I highly recommend the 32mm, and maybe something 14 to 18mm just to hold you over for awhile.



#5 vtornado

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Posted 26 January 2020 - 11:17 PM

Welcome to CN Fred

 

I would not buy a kit, usually there is a lot of redunancy in eyepieces and some are not appropriate for your telescope.

 

You are correct plossls under 12mm have tight eye relief. 

I have chinese plossl made by meade/celestron/orion/high point.  All are about the same quality.

Our sponsor astronomics sells value line plossls for a good price, and you can pick and choose the focal lengths you want.

The 32mm will give you the widest possible field in a 1.25 inch format.  I use this eyepiece every night.

 

 

Your scope is f/8 so cheap widefield eyepieces work well.

The eyepieces below are referred to as orion clones.

The eye relief is much larger than an plossl and so is the field of view.

https://www.ebay.com...W-/181972227558

 

Other good eyepieces are the 60 degree paradigm ED eyepieces, in the shorter focal lengths.

 

I generally use a eyepiece that has a focal length equal to the f ratio of my telescope for high power viewing. (1mm exit pupil)

For you that would be an 8mm eyepiece and 150x.  Some nights I go a little higher, but as you go under 1mm

ratio, the image starts to get dim, some nights I go to a .8 but this is about my limit.

 

If you are new to astronomy, don't buy a whole bunch of expensive eyepieces up front.  Go slow, use what you

have, and figure out what you like to look at, and what eyepiece can best fill that role.  If you fall in love with

planets, you will want to buy high power eyepieces, if you like open cluster you will want to get some medium

to low powered ones.

 

Some folks love the baader zoom.  A baader zoom, and a 32mm plossl could be all the eyepieces you ever need.

Well maybe throw in a 6mm eyepiece for high power on good nights.

 

Good Luck

VT


Edited by vtornado, 26 January 2020 - 11:18 PM.


#6 SeattleScott

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Posted 27 January 2020 - 12:00 AM

Meade 32mm Plossl.
Meade or some other brand 15-ish mm Plossl.
Meade HD-60 9mm and 6.5mm.
Total should be close to $200. Less if you buy used. About $150 if you could find it all used. I even have a 15mm Meade Plossl if you can’t find one sold separately; I would just ask that you buy my 32 also as these eyepieces are so cheap they aren’t really worth selling off individually.

Scott

#7 Barlowbill

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Posted 27 January 2020 - 12:12 AM

My recommendation is forget the colored filters.  You will probably do as most folks do.  Look through them once and never use them again.  Put your money towards a UHC filter.  It helps with some Nebulas.  Light Pollution filters are not worth investing in.  Good luck


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#8 TOMDEY

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Posted 27 January 2020 - 12:53 AM

Hi, Fred!

 

Those two eyepieces are OK for starters. With the 2-inch focuser on your scope, getting a couple of better wide-field, low & med power eyeps would be the biggest game-changers for you. Beyond that, I'd say enjoy what you have for a couple of months, and don't otherwise over-think things until you run the scope, and yourself, through some trial observing. By then, you will know what you will do next... I'm thinking that will be upgrade on eyepieces. You really don't need to go above the 120x that you already have.

 

(PS: you mislabeled the 25mm and 10mm lines... those should be swapped)    Tom



#9 CrazyPanda

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Posted 27 January 2020 - 01:52 AM

Hi All,
I'm new to Cloudy Nights and I have a bunch of questions about eyepieces. 

I have a Skywatcher Classic 150P (Newtonian w/Dobson mount), 153mm/1200mm (f/7.4).

The scope came with 10 & 25 mm eyepieces.  I asked Skywatcher support for more info. on the eyepieces and was told "the eyepieces are a modified Kellner design with a 52 degree field of view. The factory does put coatings on them, as to the specifics we are not able to release that information."

 

Assuming this is correct, I calculate:
10 mm: magnif. =   48, Field of view = 1.08 deg, Exit Pupil = 3.125 mm
25 mm: magnif. = 120, Field of view = 0.43 deg, Exit Pupil = 1.25

and I have a 2x Meade Barlow.

I'm over age 70, thus I guess my eyes dilate to 5 mm.  I live in Prescott, AZ with moderately light-polluted skies (can dimly see the Milky Way in summer.)

I've been considering a 32-40 mm wide-field eyepiece and a high-power EP, perhaps 6-8 mm.  Although I have a 2" adapter, I'd prefer to stick with 1.25" eyepieces (Barlow & filters).

I'm tempted by the Meade Instruments 607001 Series 4000 1.25-Inch Eyepiece and Filter Set, which Amazon sells for $160.  This includes eyepieces of 6mm, 8mm, 13mm, 17mm, 32mm plus Barlow and 7 filters in an aluminum case.  But I've read that the shorter Plössl eyepieces have very little eye relief.  Also, I cannot find details on these eyepieces -- apparently only the 32 mm is sold separately.  Celestron has a similar set with a similar eye relief problem.

Perhaps better choices are for the wide-angle:
GSO 1.25" Plossl Eyepiece - 32mm, magnif. = 37.5, FoV = 1.39  deg, Exit Pupil = 4 and 20mm relief
or Meade Series 4000 32mm (similar except 26 mm relief -- is that too much?)

or Baader Planetarium 32mm Classic Ortho Eyepiece (also similar)

and for the higher power:Explore Scientific 52° 6.5mm, magnif. = 185, FoV = 0.28 deg, Exit Pupil = 0.81 deg and 15.9mm relief.  (I don't use glasses.)

or Baader 1.25" Hyperion - 8mm, magnif. =150, FoV = 0.45 deg, Exit Pupil = 1mm and 20mm relief.

 

Thanks for any suggestions.

 

I think  you might have your focal lengths backwards with those calculations. The 25mm should have the lower magnification, wider field of view, and brighter exit pupil.

 

Other than that those calculations look roughly correct.

 

The SkyWatcher technically has a 2" focuser, but I doubt the secondary mirror is large enough to illuminate the field lens of a low power 2" eyepiece, so I think you're smart to stick with 1.25" eyepieces in that scope.

 

I would avoid those Meade and Celestron sets. Cheap plossls, mostly useless filters.

 

If you want a good spread of focal lengths that will work well in that scope, I recommend this set of "gold line" eyepieces on Amazon:

 

https://www.amazon.c...y/dp/B01MR78I42

 

They all offer reasonably good eye relief, and a wide 66 degree apparent field. At a little over $25/each if you get the set, they are as cheap as Plossls but much more immersive and easier to look through. I own the 6mm and 9mm and they are good performers - much better than their price point suggests. The 15mm and 20mm will work well in your F/8 scope.

 

I would also get the GSO 32mm Plossl to compliment the set.

 

Here are the calculations for those 5 eyepieces in your scope:

 

https://eyepieceplan...95&t=150,8,1.25


Edited by CrazyPanda, 27 January 2020 - 01:54 AM.

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#10 scngc7317

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Posted 27 January 2020 - 02:57 AM

come to the Dark Side we have cookies rofl2.gif

 

3520


#11 FredOz

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Posted 27 January 2020 - 09:46 AM

Hi Guys,

 

Thanks for the great advice.

 

I'd noticed the "Eyepiece Buyer's Guide" but had not tried it yet.  I'll check it out.  I'll also check astronomics.  And, yes, I switched the details on the EP's included with my scope.  I have the info. correct in my spreadsheet.

 

A couple new questions:

(1) I found very positive comments on Agena Astro.  How about their 

Agena 1.25" Enhanced Wide Angle Eyepiece - 9mm

(2) What would be a reasonable minimum for eye relief?  (I do not use glasses with a scope.  Just for reading.)



#12 SeattleScott

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Posted 27 January 2020 - 11:11 AM

Your scope is fairly slow so affordable eyepieces work well with it. The Meade HD-60 or Celestron Xcel can rival (not quite equal) the performance of premium eyepieces at a fraction of the cost, in the 9 and 6.5/7 focal lengths. Hence I suggested those but cheaper eyepieces will work fine also.

I like Agena. But there are several vendors I have purchased from, depending on who carries what and price.

Personally I like 10mm ER minimum or 17 if wearing glasses.

Scott

#13 CrazyPanda

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Posted 27 January 2020 - 12:11 PM

Hi Guys,

 

Thanks for the great advice.

 

I'd noticed the "Eyepiece Buyer's Guide" but had not tried it yet.  I'll check it out.  I'll also check astronomics.  And, yes, I switched the details on the EP's included with my scope.  I have the info. correct in my spreadsheet.

 

A couple new questions:

(1) I found very positive comments on Agena Astro.  How about their 

Agena 1.25" Enhanced Wide Angle Eyepiece - 9mm

(2) What would be a reasonable minimum for eye relief?  (I do not use glasses with a scope.  Just for reading.)

The Agena Enhanced Wide Angle 9mm is the same as the one I linked to on Amazon. They are also the same eyepiece as Orion Expanse.

 

Very good eyepiece, especially for it's price. That said, since they're all the same, I would try to shop around for the cheapest price. The ones on Agena are a bit more expensive than the Svbony branded version on Amazon. If you shop around on Ebay or AliExpress, you can get it for as low as $23 brand new, but you have to wait a few weeks for shipping from China.

 

For me personally, 11mm of eye relief is my limit. Any shorter and I feel like it's very difficult to take in the view. Note that stated eye relief and effective eye relief are never the same.


Edited by CrazyPanda, 27 January 2020 - 12:12 PM.

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#14 eyeoftexas

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Posted 27 January 2020 - 01:44 PM

The advice about going slow, and buying certain eyepieces to try and to also decide what you prefer to see, will help you to decide about eye relief.  It will really depend on your preference.  After a while I realized I did not like longer ER because I found it difficult to properly place my eye and hold my head steady enough to where I could see the full view.  But, that's what works for me.  You may find it quite different.  There are some relatively inexpensive eyepieces that offer longer eye relief, and so at some point you could pick one of those up to test.  Go to all the Star Parties near you, and ask about the equipment when you use the various scopes available.

 

Clear Skies.


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#15 FredOz

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Posted 27 January 2020 - 06:58 PM

Hi All,

 

Once again, thanks for the great advice. 

 

For those interested, I ordered the following 3 eyepieces from Agena Astro.  I got a shipping confirmation less than 2 hours later.  The book "The backyard astronomer's guide" suggests that a most-used eyepiece should have a focal length about twice the telescope f-ratio.  Since I have an f/7.4, that suggests 15mm so I bought a slightly more expensive 15mm eyepiece.

 

Agena 1.25" Starguider Dual ED Eyepiece - 15mm --- $60

Agena 1.25" Enhanced Wide Angle Eyepiece - 9mm --- $35

GSO 1.25" Plossl Eyepiece - 32mm -- $32.95

 

I also bought a SVBONY UHC, O-III filter from Amazon plus a neutral-density filter for the moon & Venus.

 

Now I am considering a right angle finderscope to replace the 6x30 that came with the telescope (also from Agena).  Hopefully this will be kinder to my sore neck plus yield a brighter & wider image.

 

GSO 8x50mm Right Angle Correct-Image Finder with Bracket -- $58.95


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