Eyepieces - what's the real truth?

[Starkler (Geoff)]

Ron your scope is a 150mm f8 and it is said that the greatest visual acuity is with an ep that gives you a 2mm exit pupil. This corresponds to a 16mm eyepiece. I would try a 15mm for general medium power dso viewing at 80x, barlowed will give 160x or a little more. I doubt a 150mm achromat can be pushed much higher in power without the colour being objectionable.

If you buy a 40mm plossl, make sure its not in 1.25" barrel format or you wont get any wider field than you would with a 32mm plossl. This is why we have 2" format eyepieces to accomodate these larger fields

[DobDobDob (Ron)]

Originally Posted by Starkler

Ron your scope is a 150mm f8 and it is said that the greatest visual acuity is with an ep that gives you a 2mm exit pupil. This corresponds to a 16mm eyepiece. I would try a 15mm for general medium power dso viewing at 80x, barlowed will give 160x or a little more. I doubt a 150mm achromat can be pushed much higher in power without the colour being objectionable.

If you buy a 40mm plossl, make sure its not in 1.25" barrel format or you wont get any wider field than you would with a 32mm plossl. This is why we have 2" format eyepieces to accomodate these larger fields

That's magic advice, thank you so much, I'll take your tip and get a 15mm to go along with the 40mm that came with it. Apart from the obvious increase in size and cost, is a 3x Barlow different than a 2x Barlow in any other ways?

[rockit]

Hi tailwag, one thing is re-branding of ep's, meaning you get the $29 one for $200 with a nice name on it. Wide field eyepieces are so expensive because it is really difficult to reproduce the same quality viewing as an orthoscopic at 80deg field of view. What your interested in viewing will dictate what you will need(so take your time). It truly is a mine field of information and consumer bolg, let your own eyes make the decisions, there is a lot of very sound advice and also chest beating about mine is better than yours(tread carefully). Good luck with the hair, I wish mine would leave home.

[huckabuck]

hello ro,
as far as barlows go....a barlow fitted to the forward end of the diagional (rather than between the diagional and eyepiece) will yeild a 50% increase in mag. therefore a 2x barlow fitted between the diagional and scope would become a 3x.

[Gargoyle_Steve (Steve)]

Ron there's plenty of good advice in this thread already, but remember also that these kinds of topics have come up previously. Have a read back through a lot of the older threads as well - change your settings when viewing this category to see threads posted within the last year for instance instead of the last month.

I know there was a whole heap of extremely valuable reading in this category because when I joined about a year ago I read back over this stuff for 2-4 hours a night, almost every night, for weeks and weeks and weeks. I'm no expert, no where near it, and I haven't had opportunity too try most of the ep's mentioned, but I learned a hell of a lot about good and bad eyepieces, barlows, etc.

There is great advice on budget, medium, & top priced eyepieces - yes, they do differ, but different ep's suit different people too. Try to buy as good as you can comfortably afford I guess, there's little value in buying cheap ep's if you can afford better - remember that a good eyepiece can go with you on your journey as you grow in this hobby. No matter what scope you buy next, or how many scopes you leave behind, you can always take your eyepieces along with you.

In particular if you want to cut to the real gold in this topic search for any posts by Ausastronomer - read everything he has written, listen to what he says ... because most others listen pretty carefully to his opinions re eyepieces.

Cheers Ron, and always remember to have fun with your observing!

[DobDobDob (Ron)]

Originally Posted by rockit

Hi tailwag, one thing is re-branding of ep's,

Blimy, that's something I wouldn't have thought about, great tip this makes me immediately want to stick to long established and respected distributors and manufacturers. The old adage they must be doing something right to be in business so long, is one I pretty well believe in. Thanks for this useful and unexpected advice.

[DobDobDob (Ron)]

Originally Posted by huckabuck

hello ro,
as far as barlows go....a barlow fitted to the forward end of the diagional (rather than between the diagional and eyepiece) will yeild a 50% increase in mag. therefore a 2x barlow fitted between the diagional and scope would become a 3x.

There you go, another thing I have learned, this gives new meaning to the term, 'Position, position, position'....yes I know it's 'Location', I just changed it a little for dramatic effect

[DobDobDob (Ron)]

Originally Posted by Gargoyle_Steve

Ron there's plenty of good advice in this thread already.

In particular if you want to cut to the real gold in this topic search for any posts by Ausastronomer.

Cheers Ron, and always remember to have fun with your observing!

Thanks Steve, your three main points (snipped above) are well made, I'll do all three out of respect, but I'll especially do the third point because there is little point to it, if you're not having fun. I appreciate your input Steve

UPDATE: I see what you mean Steve, I searched and found 95 threads and read just two so far and you are right, interesting to say the least - Thanks again.

[shredder]

Hi Ron,

No one seemed to pick up on a few of the questions about number of eyepieces, and barlows.

I would suggest on a 1200mm scope you probably dont want to go below 9mm in focal length. So I would suggest 3 eyepeices, 9-10mm, 20mm and your existing 40mm. Personally I prefer 9, 15, and 25mm but since you already have the 40 you need something more inbetween...

I wouldnt suggest a barlow, for cheap ones they arent all that good, and if you are buying one eyepiece and a barlow or two eyepeices there probably isnt much $ difference anyway so just get the two eyepeices...

Oh the reason for not going below 9mm (at least to start with) is they are more difficult to focus, and have a shorter focal length which generally means you need to be right up close with your eye (essentially glued to it) if you arent used to this is can be a bit difficult at first to do comfortably... especially if all you are used to is a 40mm.

[DobDobDob (Ron)]

Originally Posted by shredder

I would suggest on a 1200mm scope you probably don't want to go below 9mm in focal length. So I would suggest 3 eyepieces, 9-10mm, 20mm and your existing 40mm. Personally I prefer 9, 15, and 25mm but since you already have the 40 you need something more in-between...

Originally Posted by shredder

Oh the reason for not going below 9mm (at least to start with) is they are more difficult to focus, and have a shorter focal length which generally means you need to be right up close with your eye (essentially glued to it) if you aren't used to this is can be a bit difficult at first to do comfortably... especially if all you are used to is a 40mm.

Ah Shredder, you hit the jackpot for me, I thought I was going crazy, I was trying to press my eye as hard as I could against the rubber surround of the eyepiece and every other moment the whole FOV would go black. I eventually worked out that if I had my eye back (an inch I would guess, but have no real way of measuring accurately), that my view stayed constant and gave me less eye strain as well.

In the beginning, I was squeezing my left eye so hard and observing with my right eye, that I was aware that I was constantly telling myself to relax the left eye. I attribute all this to being a beginner and understand that I'll find my groove in time and all these tiny things will be distant memories.

Thanks also for your input on the 3 EP sizes, given my telescope and the fact that I already have a 40mm. I think you are right and this concurs with the overwhelming majority of advice given by the many members who have assisted me on this issue.

I can tell you that I am just waiting for the means to get to the shop to purchase the EP's and I have also made a decision to wait on the Barlow's until I can go to the Societies Dark Site and see the actually difference in a range of scopes and sizes as to what a Barlow really can and can't do.

From all I have already, given I have only had one night out with my scope so far, that just the new EP's I purchase later this week, will give me a heap of added flexibility I currently don't have and keep me swapping and learning about each EP for a good while. So a pause on the Barlow's until I can field test them and understand them more.

Thank you Shredder and also all the other members who helped out, I plan to simulate my first night's observing as close as possible on my next night, for about an hour to get back to where I left off, then I will introduce the new EP's in an effort to truly observe the differences (to me) that the EP's bring. Doing this as opposed to just jumping straight into the new EP's without a systematic approach won't teach me as much as if I take my time and use a controlled and pre-planned methodology.

I very much remember the differences (to me) of both Saturn and Jupiter and they will be the focus again of my testing. provided I write my observations down relatively quickly in my log book, I should establish, as far as I'm concerned what the real differences the EP's mean to me.

I presume this will give me a very good baseline as a beginner for the future when the telescopes I either purchase or have access to are better scopes, doesn't overshadow the need to select the correct EP for the object/conditions at hand.

What I mean by that last sentence is I don't want the equipment to dictate to me what I select for each new session, but rather use experience and knowledge to select the correct equipment for the task at hand. I hope I have made that somewhat tricky point clear.