View Full Version here: : Need some help: Eyepieces for 10" Dob
21-10-2010, 11:59 AM
Have been reading a lot of threads about eyepieces and other people's recommendations. My apologies for starting yet another one, but I really would like some advice and feedback on people's usage of eyepieces.
I have a 10" collapsible Sky Watcher Dobsonian (not the go to), and two years after purchase believe it or not I am still using the original 10mm and 25mm super plossels that came with it (nothing wrong with that).
But I feel it's time to upgrade the eye pieces.
I have a x2 Tele Vue Barlow for a 1.25" eye piece.
I don't really have an objection to getting good quality eye pieces like an Ethos, but I do want to be sensible on cost v performace and so don't mind looking at "second tier" products. I would rather pay an extra $100 if the performance is worth it if you know what I mean. Fundamentally I do have budget constraints and want a sensible solution.
I feel I want to get three maybe four eye pieces over a period of time: high, medium and low. it would strike me that a low magnification, wide field of view eyepiece would expand my current range of eyepieces, and then I can purchase the higher magnification eyepieces and replace the plossels over time.
Some eye pieces stand out from my reading:
William Optics UWAN 28mm (2")
Tele Vue Nagler 4 17mm (2")
Pentax XW 10mm (1.25")
I can barlow the Pentax to get down to a 5mm.
I thinnk my main concerns which i want to get feedback on are:
1) What are peoples thoughts on mixing different brands across the spectrum to cherry pick the better performing products at those magnification points? Or is it better to stay within a range ie Naglers, Panoptics?
2) For a three eye piece set would would peoples recommendations be for focal lengths, and what would they be for a four eye piece set. I think I am tending to a four piece set but I would be interested on people's thoughts.
3) Bit hesitant to pick a low magnification eyepiece 30mm +. Would be interested to hear people's recommendations here as I think this may be my first purchase point.
4) One thing that confuses me a bit is the wider field of views being combined with higher magnification eyepieces. I wish to get an eyepiece that can give me a wide field of view, but does say thenew Ethos 21mm has a 110 degree AFOV make a 41mm eyepiece somewhat redundant ?
As an aside does anyone own the Ethos 10mm or 21mm and do you think they are worth the money compared to other products? Or are they a complete luxury?
5) I have read about the issue of coma with dobsonians. My focal ratio is 4.7. Is it wise to get a paracorr to use with the lower magnification eyepieces?
Thanks and look forward to your feedback.
21-10-2010, 03:11 PM
I'm using an eclectic mix of eyepieces from various manufactures and have never really been able to benefit from parfocality. I got used to that and prefer a best bang for my buck kit over a single manufacturer set. YMMV.
Hard to say, I can't remember when I last owned only three eyepieces (even GSO Dobs come with more I think). But I guess you mean three premium eyepieces, and I reckon the set you're looking at is pretty good in conjunction with a Barlow. The other thread had a number of experienced observers stating their 4-piece dream sets, have a look over there.
With 28mm you're already hitting 6mm exit pupil in your f/4.7 scope, if that is of any importance to you. I found that sometimes a really wide eyepiece (like 40mm or 55mm) is worth having, even if the exit pupil is 8mm or larger.
The same true field of view will look darker (and therefore potentially better/contrastier) at higher magnification. And yes, if you can swing a 21mm Ethos then what I said about having a 40mm or 55mm may or may not apply. Except… I'm not sure about their relative throughput. A Plössl or König has only two groups, surely a lot less than an Ethos. Also, the 21mm Ethos has a field stop of 36.2 mm which isn't all that much and limits the TFOV to about 1.7 degrees. The 55mm TV Plössl gives you 2.4 degrees...
Can't say, never owned one.
I reckon once you've got the scope and eyepieces it will become quite apparent whether or not a Paracorr is needed. If you're happy with the views you don't need one ;)
21-10-2010, 04:05 PM
Hi Gordon, the 17mm Nagler and 10mm XW would be very nice in your scope.
When I had a 10" dob I only used a 30mm eyepiece as a finder, never for observing, since object size and contrast always looked better at 70x to 80x magnification(observing from somewhat light polluted backyard). Thus I'd recommend you don't spend much on your longest focal length eyepiece and use the money for other purchases - argo navis or sky commander, observing chair, etc.
21-10-2010, 05:04 PM
I second that sentiment. In my experience the lowest power eyepieces are mostly used as finder eyepieces and for giving guest showy wide view of sky regions. There are also a few large objects that require 2+ degree fields to look their best, but on a whole I wouldn't spend a bomb on a low-power eyepiece.
Given the large number of 31T5 fans I'm sure a lot of people would disagree, but I'd personally draw the line (price wise) at the TV 55mm Plössl or thereabouts.
21-10-2010, 06:34 PM
Much as I like my long focal length eyepieces I agree with Steffen and Tony, I wouldn't buy a really spiffy low power eyepiece first (for years I used a TV 32mm plossl). I have a 10" f/5 Dob and for deep sky objects I use my Pentax XW 10mm more than any other eyepiece. For planets I'll most commonly use a Pentax XF 8.5mm or Pentax XL 7mm eyepiece. I'd choose something around these focal lengths (~7-10mm) first. I am happy to cherry pick eyepieces from different series and manufacturers, e.g., my collection includes one T4 Nagler, a pair of Denkmeier 21mm oculars and some Radians (the Denks and Radians are mostly used in a binoviewer). Can you tell from my choices that I like lots of eye relief? :)
I see from your profile that you are a member of the Northern Sydney Atronomical Society. Can you attend some of their observing nights and try out some eyepieces belonging to others? Alternatively, perhaps buy your first spiffy eyepiece of any series secondhand so if you don't like it you can resell it for a relatively small loss. This is what I did when I was interested in the Pentax XL and TV Radian series several years ago but couldn't find any local users of these eyepieces at the time.
Best of luck with whatever you purchase!
21-10-2010, 07:13 PM
Easily the best advice is to try before you buy, if possible, as eyepieces are very subjective. To some people their goal is to maximise field of view and edge performance, others seek long eye relief, sharpness and high contrast. Others prefer a mix and match of all of these things.
I own or have used just about all the best eyepieces available at present, including all the Naglers. Ethoi, Pentax XW's and the Denkmeiers. I also own a 10"/F5 dob, a 14"/F4.5 dob and an 18"/F4.5 dob as well as regularly using 20", 25" and 30" Obsessions and SDM's.
Knowing what I know and liking what I like, this is what I would be doing.
1. 10mm Pentax XW. Simply one of the very very best eyepieces money can buy at any price for use in any telescope. It also barlows very well in the 2x TV barlow for a 5mm eyepiece.
2. 14mm Denkmeier. If you are happy to accept a 65 deg AFOV this is optically the best eyepiece available at this focal length. It has no faults and excels in every eyepiece performance criteria. That comment is coming from someone who owns a 12mm Nagler T4, a 13mm ETHOS and a 14mm Pentax XW. As an added bonus it has 20mm of eye relief. In addition, it is a 1.25" eyepiece and barlows very well in the 2x TV barlow for a 7mm eyepiece which will be a very handy focal length in your 10"/F4.7 scope.
Here is a comparison with the 14mm Denkmeier.
Nick Koiza who wrote this review actually purchased the 14mm Denkmeier on my recommendation a couple of years ago. I agree with about 98.5% of his review. It is a very accurate assesment.
3. 26mm Nagler T5. IMO this is a better eyepiece for use in smaller scopes than the 31mm Nagler T5. However, be aware it may cause balance issues in a 10" scope and you may need to adjust the tension control (if you have one) or use a counterweight. Note that it is smaller and lighter than the 28mm UWAN.
Some comments in regard to your original choices.
1. You may have read some good things about the 28mm UWAN. I have used one and do not like it. I know several other observers who feel the same way. I couldn't put it in the class of the 26mm or 31mm Naglers, or the 30mm Pentax XW, which in itself would be an excellent option.
2. The 17mm Nagler T4 ( I own one) is a very heavy eyepiece and could cause balance issues in your scope. On top of that it is a 2" eyepiece and you cannot barlow it in your 1.25" barlow, which means you are losing some versatility. Most importantly however IMO it is one eyepiece which really benefits from using a paracorr, particularly in scopes faster than F6. In your 10"/F4.7 scope the 14mm Denkmeier will, outside of FOV, be a clearly superior performer. Further, in a 10"/F4.7 scope I consider 14mm to be a far more useable focal length than 17mm.
22-10-2010, 12:57 AM
Hah, I like that, looks and sounds so much better than "Ethosses" :lol:
Thanks for the comments re the Denkmeier 14mm. This is one I've never even seen, let alone looked through. As it so happens I'm looking for 14 or 15mm eyepiece, I'll keep my eyes peeled for this one.
22-10-2010, 12:30 PM
John, Steffen, rmc,
Can I just say a HUGE thank you. They are some of the most insightful posts about my situation that I could have ever hoped for.
I thnk you have swayed me away from some of my original thinking. I first thought a low power eyepiece would be my first starting point but I was interested to hear your thoughts about starting with the 10mm Pentax XW. From all my reading of threads, this eyepiece is the pick of the crop at that end.
Thanks John about your comments on the Denkmeier 14mm rather than the 17mm Nagler. That was all very persuasive, and also very interesting about the 28mm UWAN - I was almost going there - have to rethink that one.
Once again many thanks that's just really brilliant.
22-10-2010, 12:34 PM
You would use a 7mm rather than Barlow the 10mm? Why is that just out of curiousity. I have seen on other threads people saying they would get a 10mm AND a 7mm. barlowing a 10mm for me is a work-around but I was curious why people go for the 7mm.
As for the NSAS viewing nights I am a regular and unfortunately the viewing members are small in number (but growing) and there isn't the range of equipment to enable me to try these kind of eyepieces.
22-10-2010, 12:43 PM
Would you be able to elaborate on this one a bit more John. What are the big factors for the 26mm over the 31mm to you?
The 31mm would give a 20% greater actual FOV than the 26mm (91.3 v 76.1). I see the exit pupil is quite different 4.8 (26mm) v 5.7 (31mm).
I quite enjoy viewing open clusters and want to make sure I can get en eyepiece that will allow me to put it all in the eyepiece so to speak.
22-10-2010, 05:02 PM
The seeing from my backyard where I do a fair bit of my observing is pretty poor (heat plumes from my own and neighboring houses, etc). I have a Pentax XL 5.2mm eyepiece but often the resulting image is soft and shimmery while the lower magnification image provided by the 7mm ocular is not as badly affected. When I observe from places where the seeing is better I reach for my 6mm and 5.2mm eyepieces far more often.
22-10-2010, 10:57 PM
22-10-2010, 11:36 PM
If you still use the finder scope that came with the Skywatcher, you may want to get yourself a Telrad or Quickfinder, your target finding will be much easier and eyepiece usage, low or high power will be much more accurate.
Clear Skies, Paul
23-10-2010, 08:33 AM
Thanks Paul. Yep got the Telrad about six months ago - you know what? I haven't put it on the scope yet it's still in it's box!!
24-10-2010, 10:27 AM
I've been on the three eypiece diet (10" 12" ) for quite a while and find its more than enough to get by with .
The 2k plus of eyepieces I've shuffled through to keep three
would likely get me a divorce if the truth ever be discovered;)
I'd suggest before thinking brand names think usefull focal lengths
In my 10" and 12" that for me was 170 x 110x 50x
Not to say more or less at each end of that range or a few more in between wouldn't work but for general use and regular use
I don't feel any need for more .
170 x dosn't sound a lot, but over time I found this to be the highest power I could regularly get reasonable and repeated use of .
I had a 7mm which worked well , up until I got my 12 " and discovered 200x was often a little to much , sold on for a 8.5 and alls good again.
100x or thereabouts , most used without a doubt
and theres some really high quality offerings around this range.
A 14mm would obviously ,with your barlow take care of both the above .
50x Low power , I found I the enjoyed the view most with
a high quality wide field .. There are some nice pricey examples in this range , and if you likely havn't given weight a lot of thought
these long F/L ultrawides can get seriously heavy in a smaller scope .
My 28 panoptic was a little heavy , my 22 nagler is heavy enough to kill a bear with and others get bigger still ;)
good luck with your choices
btw the denks are often listed as a a matched pair for binoviewing
but I believe you could once buy them seperately from some vendors ??
24-10-2010, 03:25 PM
Without trying to push the Denks (they are nice eyepieces but there are several others that are also nice), pretty much anywhere that offers Denks as a pair will also sell them individually, including Denkmeier themselves.
24-10-2010, 11:47 PM
If you have a 2X Barlow, make sure that the shorter focal length eyepieces are not any of the larger size divided by 2.
If you have 40,20 & 10mm e/pcs you would get 40, 20,10 & 5mm
If you have 25,15 & 10mm e/pcs, you would get 25, 15, 12.5, 10, 7.5, & 5mm
The second option is the better option giving you a greater spread of powers.
26-10-2010, 01:29 AM
In a 10"/F5 scope the 26mm Nagler gives 48X with a 1.7 deg TFOV. I rate this about the perfect low power scenario in a 10" scope. Consider that the 31mm Nagler in my 18" Obsession gives 67X and a 1.2 deg TFOV. In addition, I consider the 26mm Nagler to be marginally better optically than the 31mm Nagler. I think it is a touch sharper on axis and contrast is a little better because of the higher magnification (smaller exit pupil). Most importantly however, it is 1/2 the size and weight of the 31mm Nagler which IMO is an important consideration in scopes under 14" aperture.
26-10-2010, 05:07 PM
Thanks for the explanation John I found that very helpful, and together with your earlier post you have been a tremendous help. So thank you !
I haven't had a lot of experience in being able to test out different eyepieces and I am still getting to grips with some of the technical aspects of eyepiece technology, magnification, FOV etc and what constitutes a good combination for my telescope but I am getting there step by step.
Better still, I even have permission from the wife to go out and get some of these eyepieces
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