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What's the best sized eyepiece for Lunar/Planetary


Olli

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Hi all,

i currently have a stock 10mm 25mm and a 18mm bst eyepieces and I'm looking to get a new eyepiece for lunar and planetary work to use with my 130p and would like to get the best views that I can get with my telescope. I was wondering what size should I go for, for example 5mm 10mm or a different size?  Also what make would you recommend? not sure on budget yet but probably be less than  £100. I wouldn't mind going second hand if I can get one for a good price. 

 

Cheers.

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You will get a range of replies to help you to think, my 2p worth would be that a 5mm or thereabouts would be a sound place to start - that would make for 130x magnification (that being the focal length of the scope divided by the focal length of the eyepiece so 650/5=130).

130x would be beneficial on a few of counts... it won't push the capabilities of the scope, it won't push against the limits of seeing by which I mean how stable the atmosphere is, and it won't require a lot of work to keep tracking the moon as it moves. This means it would give good and easy going views most of the time that won't be limited by other factors. I've got a 120mm f5 scope so similar to yours in aperture and focal ratio and on the moon I will usually end up using eyepieces in the range 10mm to 4mm.

In theory your scope could do magnification equal to double the aperture, i.e. 260x, but that is pushing the scope to the limit and you would more often find that the atmospheric seeing becomes a limiting factor.

That said everything is a compromise in the end and there is a a continuous spectrum of options with a sliding scale of pros and cons.

You could get a better quality 10mm, but I would recommend prioritising getting any additional focal lengths you want before starting to replace existing eyepieces.

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I would think that for an f5 reflector you will probably get the best results with a 4-5mm eyepiece for planetary. You could get a 5mm Starguider, which I think is a better eyepiece than the 18mm you've already got. If you want to spend more then I would look at the Explore Scientific 82° series which is slightly over budget or the Vixen SLV which should give the best optical performance but with a narrower field of view. 

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Hi, Olli. For your scope, I would suggest either a 5mm (or perhaps a 10mm with 2X barlow), with eye relief of at least 16mm or more. The more elements the better for the best light transmission. I'm a big fan of Orion products, so give this a look:

https://www.telescope.com/Accessories/Telescope-Eyepieces/5mm-Orion-Edge-On-Planetary-Eyepiece/pc/-1/c/3/sc/47/p/8885.uts?ensembleId=68

This 9mm and a barlow would make a nice combination:

https://www.telescope.com/Accessories/Telescope-Eyepieces/9mm-Orion-Edge-On-Planetary-Eyepiece/pc/-1/c/3/sc/47/p/8886.uts?ensembleId=68

The barlow lens will preserve the eye relief of the EP you're using it with while doubling the magnification; you would also want a multi-element barlow to reduce chromatic aberration:

https://www.telescope.com/Accessories/Barlow-Lenses/Orion-High-Power-125-2x-4-Element-Barlow-Lens/c/3/sc/41/p/113912.uts?ensembleId=260

With budget considerations, you may just want to go for the 5mm for now. A good barlow is an invaluable tool, though!

Hope this helps,

Reggie 

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3 minutes ago, Ricochet said:

I would think that for an f5 reflector you will probably get the best results with a 4-5mm eyepiece for planetary. You could get a 5mm Starguider, which I think is a better eyepiece than the 18mm you've already got. If you want to spend more then I would look at the Explore Scientific 82° series which is slightly over budget or the Vixen SLV which should give the best optical performance but with a narrower field of view. 

Thanks for advice  I will have a look at the prices for the ES eyepiece and see if there are any available on here, which one out of the three you mentioned would be the best bang  for the buck?

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4 minutes ago, orion25 said:

Hi, Olli. For your scope, I would suggest either a 5mm (or perhaps a 10mm with 2X barlow), with eye relief of at least 16mm or more. The more elements the better for the best light transmission. I'm a big fan of Orion products, so give this a look:

https://www.telescope.com/Accessories/Telescope-Eyepieces/5mm-Orion-Edge-On-Planetary-Eyepiece/pc/-1/c/3/sc/47/p/8885.uts?ensembleId=68

This 9mm and a barlow would make a nice combination:

https://www.telescope.com/Accessories/Telescope-Eyepieces/9mm-Orion-Edge-On-Planetary-Eyepiece/pc/-1/c/3/sc/47/p/8886.uts?ensembleId=68

The barlow lens will preserve the eye relief of the EP you're using it with while doubling the magnification; you would also want a multi-element barlow to reduce chromatic aberration:

https://www.telescope.com/Accessories/Barlow-Lenses/Orion-High-Power-125-2x-4-Element-Barlow-Lens/c/3/sc/41/p/113912.uts?ensembleId=260

With budget considerations, you may just want to go for the 5mm for now. A good barlow is an invaluable tool, though!

Hope this helps,

Reggie 

Thanks for those links and advice will have a look tomorrow.

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11 minutes ago, Paz said:

You will get a range of replies to help you to think, my 2p worth would be that a 5mm or thereabouts would be a sound place to start - that would make for 130x magnification (that being the focal length of the scope divided by the focal length of the eyepiece so 650/5=130).

130x would be beneficial on a few of counts... it won't push the capabilities of the scope, it won't push against the limits of seeing by which I mean how stable the atmosphere is, and it won't require a lot of work to keep tracking the moon as it moves. This means it would give good and easy going views most of the time that won't be limited by other factors. I've got a 120mm f5 scope so similar to yours in aperture and focal ratio and on the moon I will usually end up using eyepieces in the range 10mm to 4mm.

In theory your scope could do magnification equal to double the aperture, i.e. 260x, but that is pushing the scope to the limit and you would more often find that the atmospheric seeing becomes a limiting factor.

That said everything is a compromise in the end and there is a a continuous spectrum of options with a sliding scale of pros and cons.

You could get a better quality 10mm, but I would recommend prioritising getting any additional focal lengths you want before starting to replace existing eyepieces.

Thanks for the info I appreciate it. I mean I wouldn't really want to go over the top with the magnification as I'd probably want sharper views to be a priority. And of course the conditions will play a factor have realised how much it affects the experience from the short time I have had my scope but I will keep everything you said in mind thanks.

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6 minutes ago, Olli said:

Thanks for those links and advice will have a look tomorrow.

For some reason the links take to you the catalog page, so you would need to search for 5mm Orion Edge On Planetary Eyepiece.

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11 minutes ago, Olli said:

Thanks for advice  I will have a look at the prices for the ES eyepiece and see if there are any available on here, which one out of the three you mentioned would be the best bang  for the buck?

The Starguider is the best value, especially if you buy it from Skies the Limit where they are only about £40 new. However, I would probably try the SLV if it was my choice.

You can also get the Altair Astro branded version of the Orion eyepiece suggested above for £55, but I don't know much about its performance compared to the other options.

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All I can do is tell you about my experience with the EPs I own.

For planetary the 11mm Nagler type 6 is great on average seeing AND the LV 7mm and Celestron X-Cel 5mm eyepieces (used with a neodymium and contrast booster filters), (or the 11mm Nagler with a 2 and 2.5X powermates) are great for observing during the best seeing conditions. The detail I've seen with those eyepieces on Mars, Jupiter and Saturn is breathtaking.

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For Lunar observing, same applies as above for high power views, but for a low power full disc view, (especially during the full moon) I recommend the Televue 31mm Nagler type 5 used with a polirazer and/or ND filter...

The views need to be seen to be believed, text does not do them justice.

Remember that seeing will determine to how much detail you will see and there is no ONE eyepiece for everything it every condition.

 

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The telescope in question has a 650mm focal-length.  Such is primarily for low-to-medium power observations, and also for the taking of pictures.  The 750mm focal-length of my 150mm is also a bit on the short side.  But instead of using dedicated high-powered oculars, I barlow, and this 12mm 60° with a 3x...

12mm-3x.jpg.61e7edea7baeda33328b34a9171a805c.jpg

With that combination, I then have the equivalent of a 4mm, but with the larger eye-lens and greater eye-relief of the 12mm, and perhaps even the 12mm's 60° field-of-view...

650mm ÷ 4mm = 163x, and quite suitable for viewing the planets, particularly Jupiter and Saturn.  In theory, you can reach 250x with a 130mm aperture, as long as the atmosphere cooperates, and the equipment being used is of reasonable quality without being too expensive.  Also, it helps if the collimation of the Newtonian is spot-on.  I've witnessed snap-to focussing with that very combination, and with my 150mm f/5, at 188x.  Or...

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-32mm-ed-eyepiece.html

650mm ÷ 3.2mm = 203x, and quite doable for a 130mm aperture under better-than-average seeing conditions; and with a well-collimated Newtonian, for sharp views at those higher powers.

I realise that my combination there appears a bit dated, but it is most effective.

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In terms of value for money vs performance, I reckon the Baader Classic Orthos are pretty good. You can pick them up for around £30 on the used market and they are just under £50 new. The 2.25x Baader Q-Turret barlow works very well too and with the orthos gives a lot of options :smiley:

Currently I'm really enjoying the combo pictured below. A 7.2 - 21.5mm zoom and a Baader 2.25x barlow. This combination gives a range of 21.5mm to 3.2mm and seems to deliver excellent image quality on the moon, planets and double stars. The purchase cost is around £100-£120 for both items:

 

zoombarlow.JPG

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1 hour ago, John said:

In terms of value for money vs performance, I reckon the Baader Classic Orthos are pretty good. You can pick them up for around £30 on the used market and they are just under £50 new. The 2.25x Baader Q-Turret barlow works very well too and with the orthos gives a lot of options :smiley:

Currently I'm really enjoying the combo pictured below. A 7.2 - 21.5mm zoom and a Baader 2.25x barlow. This combination gives a range of 21.5mm to 3.2mm and seems to deliver excellent image quality on the moon, planets and double stars. The purchase cost is around £100-£120 for both items:

 

zoombarlow.JPG

Hi john thanks for the help, Can i ask a silly question?  how does zoom eyepiece a work? i didn't know they existed. But will have a look into them thanks.

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12 hours ago, Ricochet said:

The Starguider is the best value, especially if you buy it from Skies the Limit where they are only about £40 new. However, I would probably try the SLV if it was my choice.

You can also get the Altair Astro branded version of the Orion eyepiece suggested above for £55, but I don't know much about its performance compared to the other options.

I can vouch for the performance of the Altair Astro LER eyepieces. At least to my eye they were very good. A slightly warmer tone than the ES's if memory serves correct but very capable and comfortable eyepieces.

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2 hours ago, Olli said:

Hi john thanks for the help, Can i ask a silly question?  how does zoom eyepiece a work? i didn't know they existed. But will have a look into them thanks.

Not a silly question. You twist the knurled ring to change the focal length of the eyepiece. You can stop at any point between 21.5mm and 7.2mm (with this zoom) but in practice you can just find the point where the image looks as you want it to and is sharpest. With the barlow in place the focal range is 9.5 mm to 3.2mm. The downside of zooms (most of them anyway) is that the apparent field of view is narrower at the longer focal length but it does widen as the focal length gets shorter.

I've had mixed experiences with zooms but the combination I describe above has turned out rather nicely. 

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3 hours ago, Olli said:

how does zoom eyepiece a work?

Technically, they work by moving a middle group of elements forward or backward relative to a Smyth group at the bottom and the image forming group at the eye end to achieve different focal lengths without varying focus too much.  As John says, turning the zoom collar will change the focal length just like on a zoom lens for a camera by moving internal elements.

Practically, it varies greatly how well they work.  The more expensive ones tend to work better than the cheaper ones, but it's not a linear relationship.

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1 hour ago, John said:

Not a silly question. You twist the knurled ring to change the focal length of the eyepiece. You can stop at any point between 21.5mm and 7.2mm (with this zoom) but in practice you can just find the point where the image looks as you want it to and is sharpest. With the barlow in place the focal range is 9.5 mm to 3.2mm. The downside of zooms (most of them anyway) is that the apparent field of view is narrower at the longer focal length but it does widen as the focal length gets shorter.

I've had mixed experiences with zooms but the combination I describe above has turned out rather nicely. 

 

1 hour ago, Louis D said:

Technically, they work by moving a middle group of elements forward or backward relative to a Smyth group at the bottom and the image forming group at the eye end to achieve different focal lengths without varying focus too much.  As John says, turning the zoom collar will change the focal length just like on a zoom lens for a camera by moving internal elements.

Practically, it varies greatly how well they work.  The more expensive ones tend to work better than the cheaper ones, but it's not a linear relationship.

Thank you both, very helpful. I'm very tempted to bite the bullet and get a ES eyepiece probably if I can find a good second hand one. Thanks again for the help

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1 hour ago, swiss75 said:

What make is that zoom John

Mine is actually branded Orbinar but the same item (and they do they seem identical apart from the branding) seems to be around under a variety of brand names and at a wide variety of prices !

https://www.harrisontelescopes.co.uk/acatalog/skywatcher-hyperflex-7e-7.2---21.5mm-zoom-eyepiece-1.25.html

http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_330

https://www.telescopehouse.com/lunt-7-2-21-5mm-zoom-eyepiece-1-25.html

https://www.teleskop-express.de/shop/product_info.php/info/p4651_HR-Planetary-Zoom-Okular-7-2---21-5mm---1-25----7-Elemente.html

https://www.astroshop.eu/eyepieces/omegon-premium-1-25-7-2-mm-21-5mm-zoom-eyepiece/p,32987

Mine cost £55 delivered from Germany. I went for the lowest priced clone I could find !

 

 

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