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21mm Ethos - Should I or shouldn't I ?

johninderby

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johninderby

johninderby

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I think john has a 1600mm focal length 14" Orion Optics dob? Which for me would make the 17mm Ethos the more useful eyepiece.....sell the 13mm, forget the 21mm and buy the 17mm Ethos ;)

Please, please no more choices :D:confused::D

John

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John

John

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When people say the 13mm is too useful what focal length or ratio are we talking about here?

As Russ says where the "sweet spot" is for eyepiece focal length does depend on your scope but 13mm is an incredibly useful focal length in most scopes - it's no accident that it was the first focal length Ethos to be released, ditto for the T6 Nagler and the orginal Nagler as I recall.

When I had a 12" F/5 dob (FL=1500mm) I found the Ethos 13 wonderfully versatile - enough power to show planetary detail on Jupiter and Saturn, wonderful sweeping views of the moon, fantastic on globular clusters, planetary nebulae and able to present glactic detail as we found at SGL4 clearly seeing the spiral structure in M51 and a mag 12.6 supernova in another faint Ursa Major galaxy.

When you are talking about the sort of prices we are here, versatility has to be an issue when justifying the cost IMHO and the 13mm Ethos has it in spades :D

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Moonshane

Moonshane

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I don't doubt the 3.7mm will be superb but how often will seeing allow it to be used well? I think this would be 432x? or are they so good they reduce the effects of bad seeing? maybe it's also for another scope than the 1600mm dob?

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Kef9

Kef9

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Yep. I have a f9 refractor and I currently have a 5-8mm speers waler zoom and a 13mm ethos also. I was just wondering what sort of magnifications people were talking about.

Im thinking of getting the 21mm ethos as my low power eyepiece to complete my collection.

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Kef9

Kef9

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I don't doubt the 3.7mm will be superb but how often will seeing allow it to be used well? I think this would be 432x? or are they so good they reduce the effects of bad seeing? maybe it's also for another scope than the 1600mm dob?

On this I was looking at the moon and saturn last week with my 100ED F9 refactor at 180x with my speers set at 5mm and I felt I could of pushed it alot more. I've read on these forums that 133x is about as far as you can go but I think you can go way past that.

Hence I'm considering getting a 2" powermate also.

God this is going to be expensive!

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johninderby

johninderby

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I don't doubt the 3.7mm will be superb but how often will seeing allow it to be used well? I think this would be 432x? or are they so good they reduce the effects of bad seeing? maybe it's also for another scope than the 1600mm dob?

Yes the 3.7 will be for more than the dob, and should be great in my FLT98. In the dob for lunar / planetary my 3.5mm Nagler actually gets a lot of use.

One of the benefits of having a premium mirror (99 Strehl) is the ability to handle high magnifications. A mirror with such a smooth surface reduces light scatter which helps to keep the image sharp as magnification is increased.

John

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Moonshane

Moonshane

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nice one John

I should point out the question was more for my own edification than questioning your own judgment. Your comments on the 3.5mm Nagler are interesting. Although my mirror won't be as sharp as yours, maybe I should try a short FL eyepiece with my Dob. Maybe a 5mm or 6mm Radian would fit the bill as this would mean I don't have to use the Powermate.

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johninderby

johninderby

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nice one John

I should point out the question was more for my own edification than questioning your own judgment. Your comments on the 3.5mm Nagler are interesting. Although my mirror won't be as sharp as yours, maybe I should try a short FL eyepiece with my Dob. Maybe a 5mm or 6mm Radian would fit the bill as this would mean I don't have to use the Powermate.

It's surprising what sort of mag you can use on the moon with most dobs. I tried a 3mm WO SPL eyepiece with a 10" Skywatcher dob and was surprised at how sharp it was. Worth giving it a go.

BTW I didn't in any way think you were questioning my judgment :D

John

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michael.h.f.wilkinson

michael.h.f.wilkinson

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Regarding the magnification you can get: the 2x the aperture in mm (or 50x the aperture in inches) rule is only really valid for those with very high visual acuity. For most mortals you can push further.

Regarding getting a 21 mm ethos right now or in August: I would go for August, because the skies are not fit for deep sky at the moment anyway.

Just my tuppence

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Kef9

Kef9

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I put off getting a 21mm ethos till august. I decided I wanted more time to think about it and by that time I would have more money for it.

I did get a 2" revelation diagonal and a televue 2" 2x powermate though in the sale so I can push the speers alot higher (upto 360x) and turn the 13mm ethos into a 6.5mm planetary eyepiece. Now the powermate combined with a fully extended speers at the 5mm setting is going to look mental!

It will be interesting to compare the speers at 6.5mm to the ethos at 6.5mm. I think the speers waler 5-8mm zoom was the bargain of the century and when you push it to the 5mm setting it gives a 90 degree fov.

Back to low power, I'm actually just wondering whether to just get the skywatcher 38mm panaview and see how it goes in the meantime. I like the price at £85, I like the look and they have had good reviews.

By the way does anybody actually have a 21mm ethos. They seem very rare indeed.

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Kef9

Kef9

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Just to ressurect this thread I'm in the same boat again only this time I have a 31mm Nagler which is on its way. I wondering if I get the 21mm ethos it will be a waste of money. What do you guys reckon?

31mm Nag gives a 2.8 deg Fov in my frac whilst a 21mm ethos would give me a 2.3 deg FoV.

Is this too close or do you think the step down from nagler 31 to a 13 ethos is about right or too great. The ethos 13 gives me a 1.3 FoV in my F9 frac by the way. :D

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John

John

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Well I'm 75% sure I want to hit the button. Oooohhhhh the tension. Its alot of money!

Why not spend the money on a lager aperture scope ?

- that really will show you more wheras the 21mm Ethos, won't.

Just a thought ;)

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Kef9

Kef9

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Because very good eyepieces are keepers for life.

Im not ready to move up the scope ladder yet. When I do my garden up and get a shed I might buy a big dob.

Also its very hard to move up on the refractor side from my current scope without spending a hell of a lot of money.

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John

John

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Because very good eyepieces are keepers for life.....

Thats true ;)

I suspect you won't be satisfied until you have tried the Ethos 21mm. If you do find that it ousts your Nagler 31mm you should be able to sell the latter fairly easily - there is always a good market for premium stuff.

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