View Full Version here: : Which Ethos should I buy?
31-05-2010, 01:10 PM
Long time since I posted but I figured I needed some advice.
It's my birthday on Wednesday and I thoguht I'd buy an Ethos eyepiece for myself. My question is which one should I buy? This will be my first Ethos eyepiece. I have a Meade 8" LX90 and like to do planetary and deep space observing.
So I leave it to you.....which one should I start with?
31-05-2010, 01:59 PM
The 21E has a 36.2mm field stop diameter which is almost a perfect match for the 8" SCT's and will provide you with a 1 deg true field at 97x and 2.1mm exit pupil. (2032mm f.l.). This would be one very nice DSO eyepiece with plenty of true field and magnification. The classic alternative is the 35mm Panoptic with 38.7mm FSD and 1.1deg true field at 58x and 3.5mm exit pupil.
For planets either the 13mm for 156x, 10mm for 203x or 8mm for 254x.
The 21, 13, 8 would make a nice set but note on planets you may want something between the 8 & 13.
You could also go with the 17 & 10E. The 6E may be too much power most of the time. The 17E with 29.6mm FSD will give you 0.83deg at 119x and 1.7mm exit pupil. This would be fantastic for a full lunar disk at 119x and also good for the larger planets.
You know you will end up with more than one so toss a coin between the 21/13 combo or 17/10 combo. If you want the wider true field and do not have another eyepiece with a wide field stop diameter then go the 21E unless you plan on getting the 35 Pan or 31 Nagler later.
31-05-2010, 04:33 PM
May I chime in and also ask for an Ethos reccomendation? I have a 10 inch Skywatcher Newt and am tossing up between a 13 and 17 Ethos. I mainly like DSO observing and don't really care much for planetary stuff.
Cheers and sorry for hijacking, just didn't want to start another clone thread
31-05-2010, 05:35 PM
Go for the 17mm..best all rounder for an F5 ;)
31-05-2010, 05:50 PM
Either one is fine depending on how much true field and exit pupil you want. The 13E gives you 1 deg at 96x and 2.6mm exit pupil and the 17E gives nearly 1.4 deg at 74x and 3.4mm exit pupil (both 1250mm f.l.). If you have another low power eyepiece such as the 31 Nagler then go the 13 otherwise the 17 or 21E. Note the 13E is 1.25/2" and the 17E is 2" only in case it matters for any filters that you may have. You can add a Tele Vue EBX-2120 to convert the 13E to 2" and then use 2" filters but you cannot use 1.25" filters with the 17E.
The 17E or 21E would be better for larger objects such as Eta Carina nebula and truely spectacular when combined with a 2" O-III filter.
See http://www.televue.com/engine/TV3_page.asp?id=89 for more combinations of telescope and eyepiece.
Note at f5 you may also consider a Paracorr in which case your magnification wil increase by 1.15x and your true field will decrease by the same factor.
You'll have trouble getting the 21mm. There's a queue. I've had one on order from BinTel for months and I'm still waiting.
01-06-2010, 08:55 AM
Absolutley no problem. The more info we get the better.
01-06-2010, 09:55 AM
I bought a 13mm first as it was around the f/l that I used most. It ended up owning so much of the focuser time it lead to me clearing out all my other EPs of a similar f/l. So I would start with one that is going to be used most, maybe the 17mm for you, and maybe look at f/l combinations that wont be duplicated easily with barlows (they do barlow well).
I now have an 8mm too and will likely get a 21mm one day too.
01-06-2010, 10:42 AM
Yeah looks like I'll have to get a 13mm first. I just contacted Bintel and they reckon the 21mm won't be available until mid-June.
Good choice first up. I have the 13mm also and it practically never leaves the focuser.
01-06-2010, 12:29 PM
What do you mainly use the 13mm for?
Just about everything- open & globular clusters, nebulae, galaxies and even planets such as Jupiter and Saturn. It is a good all-rounder. On my 12inch Meade, it gives me a magnification of around 115 and a true field of view of about 0.87 degrees. I have an 8mm for closer views of the planets and binaries separated by less than 4" but it gets far less use. I would like the 21mm to expand the FOV for larger clusters and nebulae and also grab a few more galaxies in the same field e.g. Leo Triplet.
01-06-2010, 05:18 PM
Thanks guys, 17 it is. I am going to get a visual parracor and an imaging one as well.
02-06-2010, 09:40 AM
Thanks from me as well. I'm off to Bintel today to buy myself a 17mm. Now all I need is a clear night.
02-06-2010, 11:57 AM
In a 10" dob I'd get the 13. When the 10 was my primary scope my 14mm pentax had most of the focuser time.
02-06-2010, 12:39 PM
Depends on whether a Paracorr will be used and how often. The 17E with Paracorr is effectively a 14.8mm. (The 13E with Paracorr is effectively a 11.3mm).
You will use the Paracorr if you find the coma objectionable; some do some don't. In a 10" f5 it will certainly be noticeable.
02-06-2010, 10:04 PM
Of all the wide angle eyepieces I have looked through, the ethos needs a paracorr the least of them all. I own and use a paracorr, but have found the view through the 13 to be pretty damn good without one, and certainly better than equivalent naglers.
03-06-2010, 08:08 AM
We use both the 13mm and 17mm Ethos in the 18" f/4.5.
I agree with Geoff the 13E is pretty darn good but the 17E would benefit with the use of a Paracorr. Having said that of course I don't find the coma on edge objectionable to the point where I think a paracorr is a must.
04-06-2010, 08:53 AM
Well I took the plunge on Wednesday and bought myself a 17mm Ethos. First impressions...........OMG the thing is huge!!! Build quality looks and feels amazing.
Of course the weather has decided to be non-cooperative.
05-06-2010, 04:18 PM
The 17 mm is a nice EP, good choice. I have not noticed any appreciable coma on the edge of mine :shrug:.
07-06-2010, 01:00 PM
Apologies.......I bought the 13 mm not the 17 mm.
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