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5mm eyepieces: are they about the same at F/10?

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#1 jimhoward999

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Posted 03 August 2020 - 03:15 PM

I am shopping for a 5mm eyepiece for my Celestron 8" EdgeHD.   I want a higher magnification view of planets for nights when it might be possible to take advantage.  My eyesight is pretty bad and so fairly empty magnification for others might not be so for me.

 

From specifications and reviews it appears that the ES 4.7mm 82 degree field, the Baader Morpheus 4.5mm 76 degree, the TV delos 4.5mm 72 degree and the TV 5mm delite 62 degree are all quality eyepieces.  And they are all about the same price ($200-$250), fairly reasonable, except the delos which is $100 more.

 

Is there any difference between the ES, Baader and TV short FL  eyepieces optically at F/10?    I would think not, but I wonder if anyone has experience.   How about stray light or ghosting issues? Opinions would be greatly appreciated.

 

 

 

 

 



#2 sg6

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Posted 03 August 2020 - 03:26 PM

What have you at the moment?

Unless you have a 6mm even an 8mm and they work almost all the time I doubt that a 5mm or 4.5mm will actually be much use. Simply too much for the scope.

A 4.5mm is 450x and a 5mm is 406x - note that a "small" 0.5mm difference is close to a 60x difference.

Just wondering if the idea is an 10mm works so lets half it.

 

Only my opinion but I wouldn't try less then an 8mm.

Hence the question What do you have at the moment.

 

But a 4.5mm I would guess usable once a year - maybe.


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#3 cst4

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Posted 03 August 2020 - 03:28 PM

Those are all nice quality EP's... at F/10, or even down to F/6 probably, there won't be much of a difference optically.  It's usually more about comfort and preferences at that price.  However, all of those are too high of a magnification for me to recommend.  Even the 6.5 Morpheus or 6.7mm ES is pretty high magnification... I would fill the 170x to 300x range first and then judge if something over 300x would even be useful. 



#4 J A VOLK

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Posted 03 August 2020 - 03:35 PM

400x is pretty rich for an 8" SCT.  Unless you have a particularly good OTA optically AND truly exceptional local seeing conditions, I doubt a 5mm eyepiece will be of much use.


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#5 sanbai

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Posted 03 August 2020 - 03:40 PM

Take a look at the actual optical train of your scope. I also have a c8edge and mine seems more into f/11 or longer due to the visual back and large 2" diagonal.

I rarely use my Meade UWA 5.5mm. seeing needs to be excellent to make it worth. Even there, the diffraction effects are obvious. There is no more than I can't see in a 11mm, it's just bigger, with less contrast. My 9mm sees still lot of light, the 6.7 have enough use, but the 5.5 shows the Airy disc in all its glory. Good for close double starts, though.

Thus, for planets I would not go beyond 5mm at all. For the purpose I would invest mostly in eyepieces in the range 11-7 mm. Between 7 and 5, nice to have, but not the bread and butter.

Aside that, the exit pupil is very small, and there floaters of your eye can be really annoying.

Edited by sanbai, 03 August 2020 - 05:07 PM.


#6 Mike W

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Posted 03 August 2020 - 03:43 PM

Buy a used Radian.



#7 ShaulaB

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Posted 03 August 2020 - 03:56 PM

Do you wear glasses and need at least 10mm of eye relief? The ER is usually stated in Specs for an eyepiece.


Sometimes an eyepiece is described as "comfortable" to use. That usually means you don't have to get your cornea a hair's width away from the ep. Like others have said here, just enlarging a mushy image of a planet will not yield much observing satisfaction. Or be worth the cost of the ep you want.

If you have the cash and want to experiment, go for it.

#8 Starman1

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Posted 03 August 2020 - 04:07 PM

I am shopping for a 5mm eyepiece for my Celestron 8" EdgeHD.   I want a higher magnification view of planets for nights when it might be possible to take advantage.  My eyesight is pretty bad and so fairly empty magnification for others might not be so for me.

 

From specifications and reviews it appears that the ES 4.7mm 82 degree field, the Baader Morpheus 4.5mm 76 degree, the TV delos 4.5mm 72 degree and the TV 5mm delite 62 degree are all quality eyepieces.  And they are all about the same price ($200-$250), fairly reasonable, except the delos which is $100 more.

 

Is there any difference between the ES, Baader and TV short FL  eyepieces optically at F/10?    I would think not, but I wonder if anyone has experience.   How about stray light or ghosting issues? Opinions would be greatly appreciated.

A great set for a C8:

40mm 2"

20mm

13-14mm

10mm

8mm

Those last 2 would be planetary/lunar/double star eyepieces..

I see no reason for an eyepiece shorter than 6.7mm in the 8".


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#9 Jon Isaacs

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Posted 03 August 2020 - 04:13 PM

A great set for a C8:

40mm 2"

20mm

13-14mm

10mm

8mm

Those last 2 would be planetary/lunar/double star eyepieces..

I see no reason for an eyepiece shorter than 6.7mm in the 8".

The 8mm is 250x.  

 

For a dedicated double star observer, there are moments where 80x per inch is effective for splitting the close doubles.  I would at least add a 2X barlow.  

 

Jon


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#10 oldphysics

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Posted 03 August 2020 - 04:14 PM

Take a look the the actual optically train of your scope. I also have a c8edge and mine seems more into f/11 or longer due to the visual back and large 2" diagonal.

I rarely use my Meade UWA 5.5mm. seeing needs to be excellent to make it worth. Even there, the diffraction effects are obvious. There is no more than I can't see in a 11mm, it's just bigger, with less contrast. My 9mm sees still lot of light, the 6.7 have enough use, but the 5.5 shoes the Airy disc in all its glory. Good for close double starts, though.

Thus, for planets I would not go beyond 5mm at all. For the purpose I would invest mostly in eyepieces in the range 11-7 mm. Between 7 and 5, nice to have, but not the bread and butter.

Aside that, the exit pupil is very small, and there floaters of your eye can be really annoying.

Basically agree.  I only go as far as a 7mm Pentax in mine ... and that, not often.  
 

Of course, we all have different eyes and different responses to optical systems.   
 

just remember that small changes in eyepiece focal length will make a big difference in this situation.


Edited by oldphysics, 03 August 2020 - 04:15 PM.

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#11 Xyrus

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Posted 03 August 2020 - 05:29 PM

I am shopping for a 5mm eyepiece for my Celestron 8" EdgeHD.   I want a higher magnification view of planets for nights when it might be possible to take advantage.  My eyesight is pretty bad and so fairly empty magnification for others might not be so for me.

 

From specifications and reviews it appears that the ES 4.7mm 82 degree field, the Baader Morpheus 4.5mm 76 degree, the TV delos 4.5mm 72 degree and the TV 5mm delite 62 degree are all quality eyepieces.  And they are all about the same price ($200-$250), fairly reasonable, except the delos which is $100 more.

 

Is there any difference between the ES, Baader and TV short FL  eyepieces optically at F/10?    I would think not, but I wonder if anyone has experience.   How about stray light or ghosting issues? Opinions would be greatly appreciated.

From personal experience, pushing 5mm on an 8" SCT is asking a lot. You're going to either need to be looking at the moon, or need some pretty good seeing.

 

I have the Meade 5.5mm ultra wide, and when it's feasible to use it is an excellent eyepiece for the price. My most used high power piece on my 8" grab-n-go SCT is the 9mm Clestron XCL (which is also a solid eyepiece).



#12 jimhoward999

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Posted 03 August 2020 - 07:25 PM

Thank you all for your advice and talking me out of going pushing my magnification so high.  Taking Mr. Pensack's advice, I'll keep it to 6.7mm (about 300x) or above

 

The answer to the question someone asked as what I have now is not much. I just bought the scope and  I am new to the hobby.  I have the 40mm Plossl that came with the scope, I have a zhumell 9mm Plossl that I stole out of my daughters dobsonian, and I have a pre-RKE vintage 18mm Edmunds Kellner eyepiece that I bought 40 years ago and found in a desk drawer.

 

But getting back to the basic question.  Does it make any difference?   Baader, Explore Scientific, and TeleVue.... at F/10 are they all more or less the same?



#13 gnowellsct

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Posted 03 August 2020 - 09:41 PM

Buy a used Radian.

Ooh no don't.  I understand there are some people who love Radians out there but many of us had bad ones.


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#14 Jon Isaacs

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Posted 03 August 2020 - 09:46 PM

But getting back to the basic question.  Does it make any difference?   Baader, Explore Scientific, and TeleVue.... at F/10 are they all more or less the same?

 

 

I assume your EDGE is on a tracking mount.  In that case, the object will be centered and there will only be subtle differences in the performance of the eyepieces, this is includes eyepieces like the Plossls etc.

 

Things like eye relief are more important because they can be the difference between a comfortable view and an awkward view. 

 

Jon



#15 gnowellsct

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Posted 03 August 2020 - 09:47 PM

One of the things you need to understand is that at 200x and above the c8 will get difficult to focus.  This is because at 200x you are at 1 mm exit pupil and as you increase to 300x it will get even smaller.  The zone of correct focus, in terms of your physical movement of the mirror (which is how it is done in an SCT), gets increasingly smaller as the exit pupil decreases.  Whenever I pull out the c8 after using the C14 I notice this immediately.  (At 200x the C14 is at 2 mm exit pupil which is generous and fairly easy to focus.)   In refractors they help you focus at small exit pupils by thoughtfully providing a dual speed focuser.  It definitely helps.  Unfortunately, and I say this as someone who very much likes his SCTs, the focus mechanisms on SCTs are not nearly as refined.  And the more's the pity.

 

Personally I think every scope should have a 2x per mm ocular option but it is not high priority and you can pick up a Televue plossl or maybe even a UO ortho when the arises.  You may not sustain that 400x magnification on Jupiter (but you never know) but it might rather be the case that you want it to see the stellar core of a planetary nebula.  Something like that.  

 

The c8 is about the last aperture for which I would recommend a 2x per mm ocular.  On a C14 it would be ridiculous (a 5mm would yield 712x) outside of anywhere except Florida and the Canary Islands.

 

But on the whole Don has it pegged, 6 or 7 mm is about right for your c8.  On my c8 that would be a 7 mm Pentax XW.  

 

Greg N


Edited by gnowellsct, 03 August 2020 - 09:51 PM.

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#16 GeneT

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Posted 03 August 2020 - 11:45 PM

You mention that your eyesight is not all that good. I own a 12.5 inch F5 Portaball. On nights of good seeing, I cruise between 20 and 30X per inch, or 250X and 375X. Most nights that is my upper limit. Many nights I can't do much better than 150X. I don't recommend going up to 50X per inch very often, except to split close doubles or similar unique situations. I owned a C8 for about 10 years. It had excellent optics. However, my most useful magnification ranged between 160X and 240X. Let us know which eyepieces you buy, and give us a report on how the images play out, especially in the high power ranges.  



#17 rkelley8493

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Posted 04 August 2020 - 07:45 PM

Hello Jim, and welcome to Cloudy Nights welcome.gif 

The Morpheus, Delos, and Pentax XW are very similar eyepiece lines. They all feature long eye relief and give the views a 'floating' effect where the image hovers just above the eye lens. The DeLite's also have long eye relief, but the field of view is noticeably smaller. Any of these will be good if you wear glasses while observing, but they're also good even if you don't wear glasses.

The Explore Scientific 82º has standard eye relief but a wider field of view, so it gives a different viewing experience. They give more of a 'port-hole' type of view, as if you are looking thru a window to outer space. The Explore Sci will also probably be easier for a beginner to use because long eye relief eyepieces are prone to blackouts if your eye isn't positioned correctly. The Delos, DeLite, and Pentax XW's have an adjustable eye guard to help keep your eye positioned in the right place, but the Morpheus doesn't.

Visually, you probably wouldn't be able to tell much difference in a blind study between the Delos, DeLite, XW, & Morpheus in your SCT [in terms of color & contrast]. The biggest difference in those is the body style, size, and weight [and much smaller FOV in the DeLite; it's basically a "Lite" version of the Delos]. The Explore Sci is in a different category altogether because of the 'standard' eye relief, ultra-wide FOV, & compact size [14mm and under; the 18mm and up get progressively larger].

 

RK


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#18 whizbang

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Posted 04 August 2020 - 07:54 PM

+2 what Don and Greg said.

 

I wouldn't go below 8mm in a C8.


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#19 Ernest_SPB

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Posted 05 August 2020 - 12:07 AM

I thought that Delos, ES82, Pentax XW, Morpheus, etc. are eyepieces for fast scopes when observer just has to use complex optics to get wide field with acceptable image quality. In case of slow telescopes with good RA driving and not critical FOV requirements eyepieces with classic designs alike Plossl, Ortho and similar (may be powered with simple one-component Barlow) are more adequate (less elements - less scattering, more contrast). 



#20 Starman1

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Posted 05 August 2020 - 12:17 AM

Ernest,

What if you want a wide field?

Those same eyepieces would work just fine.


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#21 Dan84

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Posted 05 August 2020 - 02:05 AM

I wish I could have found this company earlier, could have saved a lot of money.

 

https://www.astronom...anufacturer=360



#22 25585

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Posted 05 August 2020 - 04:31 AM

+2 what Don and Greg said.

 

I wouldn't go below 8mm in a C8.

+3

 

Maybe try an 8 - 24mm zoom such as the Baader Mk 4, then you can see what your best FLs are for comfort and use. 


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#23 rkelley8493

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Posted 05 August 2020 - 10:14 AM

The Explore Sci 8.8mm 82° got a lot of use when I had a 10" SCT. But the highest I could usually go on an average night was the 7mm Pentax XW. Both are excellent eyepieces.


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#24 rhetfield

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Posted 05 August 2020 - 10:29 AM

Thank you all for your advice and talking me out of going pushing my magnification so high.  Taking Mr. Pensack's advice, I'll keep it to 6.7mm (about 300x) or above

 

The answer to the question someone asked as what I have now is not much. I just bought the scope and  I am new to the hobby.  I have the 40mm Plossl that came with the scope, I have a zhumell 9mm Plossl that I stole out of my daughters dobsonian, and I have a pre-RKE vintage 18mm Edmunds Kellner eyepiece that I bought 40 years ago and found in a desk drawer.

 

But getting back to the basic question.  Does it make any difference?   Baader, Explore Scientific, and TeleVue.... at F/10 are they all more or less the same?

Exit pupil of 1-2 is the most for most DSO's (10-20mm for you)

 

Jupiter is starting to get fuzzy by 0.8 exit pupil (8mm)

 

Saturn and Mars can go a bit further (maybe 0.7)

 

Venus is good and Moon OK at 0.5 exit pupil (5mm). 

 

All this assumes good atmosphere.  Most of us most of the time can't push beyond 150x due to atmosphere.



#25 turtle86

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Posted 05 August 2020 - 10:29 AM

I am shopping for a 5mm eyepiece for my Celestron 8" EdgeHD.   I want a higher magnification view of planets for nights when it might be possible to take advantage.  My eyesight is pretty bad and so fairly empty magnification for others might not be so for me.

 

From specifications and reviews it appears that the ES 4.7mm 82 degree field, the Baader Morpheus 4.5mm 76 degree, the TV delos 4.5mm 72 degree and the TV 5mm delite 62 degree are all quality eyepieces.  And they are all about the same price ($200-$250), fairly reasonable, except the delos which is $100 more.

 

Is there any difference between the ES, Baader and TV short FL  eyepieces optically at F/10?    I would think not, but I wonder if anyone has experience.   How about stray light or ghosting issues? Opinions would be greatly appreciated.

 

F/10 is fairly forgiving of optics so you have a lot of choices.  For higher power viewing, especially for extended observing, I think comfort is very important and tends to get overlooked in these discussions.  I personally wouldn’t go higher than 7mm in an 8” SCT.  I used to have an 8” with very good optics and found that a 6.7mm EP was really pushing it, and I have pretty good seeing in my location.  I would recommend something like the 7mm Pentax XW—ample mag, optical quality, and comfort.  If you ever want more mag, you could always Barlow a 10 or 12mm eyepiece.


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