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Which eyepiece focal length??

Peje

By Peje
in Discussions - Eyepieces

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Peje

Peje

Posted
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I have an Orion Europa 200, fl = 1200m, f/6.

I am looking to buy a Celestron Ultima Duo eyepiece and I'm trying to decide which one is best for my first. As they are £100 each I'd like to pick something I'll get plenty of use out of.

Initially I'll just be observing and I'd like to be able to view the planets fairly clearly. I will be attaching my DSLR to the back of this also once I'm feeling slightly more adventurous.

I was thinking the best option would be to just get the 5mm since the lowest FL I currently have is 10mm & 25mm (granted they are cheap Celestron lenses that came free with my ST80).

All advise welcome!

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Roy Challen

Roy Challen

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First off, Just wondering why you have decided on the Celestron Ultima Duo?

Secondly, a 5mm EP in your scope will give a magnification of x240 - close to what the limit of useability is in the UK. If you are looking to slowly replace the standard eyepieces that came with a scope, and you have £100 to spend (per eyepiece) and want to be able to use it regularly, then you could do worse than considering an EP with around 10-15mm focal length.

Depending on whether you are bothered by field of view, then I would recommend either Explore Scientific 11 or 14mm (just slightly over budget), or Vixen SLV 10, 12 or 15mm.

These will give good useable magnifications that you'll use most of the time and excellent quality of view.

HTH

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NGC 1502

NGC 1502

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How happy are you with your current 10 & 25mm eyepieces ? If you are, then I'd agree with Roy in post #2 that a 5mm will be at the top end of useful magnifications, so for me I'd get a 7 or 6mm to give a more usable 170 / 200x to go with what you already have.

But although I'm definitely no equipment snob, I'd sooner upgrade the basic freebies, because the mags they produce are more useful more often so that's where my money would go first.

Regards, Ed.

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Peje

Peje

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My primary reason for the selection of these lenses was that they seem to get reasonable reviews and I love the standard thread to allow me to connect my dslr with the standard t adaptor I have.

Your point about the may approaching the UKs limit is something I hadn't really considered but is certainly valid. I originally started at 10mm (partly to let me compare with my current lens ) and talked myself into 5mm.

FoV doesn't bother me that much at this stage. Do the ones you recommend offer significant optical performance over the celestron one I'm looking at?

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John

John

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I've not seen any reviews of the Celestron Ultima Duos ?

The Celestron Ultimas yes, and Ultima LX's but they are an entirely different eyepiece and out of production now.

Personally I'd go for a 6mm in the 8" F/1200 dob as a 1st higher power quality eyepiece. 200x is useful wheras 240x can be too much for Jupiter for example.

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Roy Challen

Roy Challen

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Site sponsor FLO has the Celestrons, Vixens and Explore Scientifics all approx the same price. In my opinion, the Vixens are the best optically, but only have 50 degree field of view (plenty good enough depending on your observing preferences). The ES is almost as good but has a huge 82 degree FoV. I haven't used the Celestrons so can't comment, but neither have I read many (any) reviews of these. They have a useful 68 degree FoV and the integrated T-thread, but beyond that I have no knowledge of these.

Or as triton1 suggests, you could try the BSTs. At that price you can have 2 EPs.

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John

John

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I think there's a thread on here started by FLO last year them.

Don't think they do a 6mm. I'm starting to lean back towards 8/10

There was this one but I didn't get around to trying any:

http://stargazerslounge.com/topic/226214-new-celestron-ultima-duo-eyepieces/

The 6mm Vixen SLV is a superb planetary eyepiece - one of the best I've used of any design :smiley:

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John

John

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Does the vixen accommodate t thread? Or have a thread that I can adapt from?

No it does not, sorry about that. I forgot that part of your requirement. The Hyperion zoom does. it's more expensive but covers a range of focal lengths so equals 3-4 eyepiece focal lengths. The Hyperion fixed focal lengths have a T-thread I think.

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Peje

Peje

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So optically, do you think that would be better than the fixed Celestron?

Also, do zoom lenses for telescopes suffer from the same 'slowness' issues that dslr lenses do? As in a fixed lens typically has a lower f number compared to a zoom equivalent.

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John

John

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So optically, do you think that would be better than the fixed Celestron?

Also, do zoom lenses for telescopes suffer from the same 'slowness' issues that dslr lenses do? As in a fixed lens typically has a lower f number compared to a zoom equivalent.

I've never used the Celestron Duo's but rumour has it that they are the same as the Baader Hyperion fixed focal lengths. The zoom is as good optically as the Hyperion fixed focal lengths ( bit better at the edges at F/6) but the field of view varies between 42 degrees at 24mm to nearly 70 degrees at 8mm.

Not sure what you mean about slowness because the focal ratio that applies is that of the scope. The zoom and fixed focal length Hyperions, and the Celestron Duo's use 6 lens element designs I think, it thats what you mean.

Have a search for Hyperion Zoom reviews and you will find plenty written about them, the vast majority of it positive :smiley:

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Peje

Peje

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One other thing,

Using the guide view embedded on the FLO page for these eyepieces it gives the option to see what it'd look like using them with my scope. This seems to differ drastically for planets compared to the field of view calculator on the sky at night website.

Going by the latter Saturn would fill the frame on nearly all of these lenses

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Charic

Charic

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Peje, I would suggest a 6mm eyepiece also mentioned by John.

To reach the  practical limit of your scope of @ 200X  your scope at F-1200 A-200 f/6 matches a 6mm eyepiece, Thats why the numbers are there? 

The 6mm will give you a working genuine 200x power. If you exceed  the 6mm/200x limit you actually  start degrading the image,  and unless you change the focal length/aperture to something longer/bigger, 6mm is the genuine limit. My Starguiders don't have the 6mm focal length, so I had to choose another brand, settling for the William Optics SPL. 

If you chose a 12 or 10mm eyepiece, you could Barlow those to the higher powers if/when required.

My 5 & 3.2mm EPs are ok on the Moon, but you need to track fairly quickly to stay up with the speed of the transit across the eyepiece at the higher magnifications. 

My 8mm Starguider was my first, and between that and the 12mm, they seem to get the most use if I sit back and think about it, although having so many eyepieces, allows me to frame the subject to get the best image. If I could have a 6mm Starguider, the field of view would be better for me, only 5° difference afov, but very noticeable.

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Peje

Peje

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I think I'm almost 100% decided to get the 8mm.

Spent a while there doing side by side on the features of the Baader and the Celestron, the Baader can take a 2" filter and given I just bought a 2" focuser and plan to upgrade my scope in the future to one with a 2" focuser as standard it seems the Baader may be the smarter choice in the long run

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John

John

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Fine.

None of the planets will look large in the eyepiece though. I've observed Saturn at 500x and even then it's far from filling the eyepiece. For imaging you may well need a barlow lens to increase the image scale.

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Peje

Peje

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I was looking for a 2" Barlow. Couldn't see any branded ones.

Going to order the Baader Hyperion 8mm with 14mm fine tune ring in the morning. That way of can convert it to be a 6mm

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John

John

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I was looking for a 2" Barlow. Couldn't see any branded ones.

Going to order the Baader Hyperion 8mm with 14mm fine tune ring in the morning. That way of can convert it to be a 6mm

There is a Revelation 2" ED barlow in Telescope House's "clearance" section:

http://www.telescopehouse.com/acatalog/Clearance1.html

Revelation = made by GSO

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