Choosing eyepieces-tips?

[programmer]

Hi all

I'm keeping an eye on various classifieds for decent second hand EP's. I've determined the following focal lengths would be a reasonable spread for my f5 10".

35x=35mm
49x=25mm
68x=18mm
95x=13mm
133x=9.4mm
186x=6.7mm
260x=4.8mm

These are raw figures and I'd be aiming to get EP's with focal lengths close to those numbers. Is that a reasonable selection? I also have a 2x Bintel barlow and the stock 40/25/9/4 Plossls that I'm phasing out.

Should I be striving to get the same brand of EP each time? So far I have bought two, an Orion Lanthanum 12.5mm and a Baader Hyperion 17mm. Now I see there's a 7mm Type 1 Nagler up for sale which would fit in my list.

What's the general feeling about this approach? Any other tips? I'm willing to pay up to around $150 for a decent 2nd hand EP, to give you an idea of budget (less if possible of course!)

[koputai]

I use the spreadsheet below to help me decide on eyepieces.
Just put your scope dimensions in to the two pink boxes, diameter and focal length in millimeters, and it gives you various data for all the eyepieces I've gathered the specs for.

Here's what the columns mean:
Size: Focuser tube diameter in inches (2 inch, or 1.25 inch)
FL: Focal length of the eyepiece
Mag: Magnification of that eyepiece in your telescope
Exit Pupil: Self explanatory
Light Gath: The relative amount of light in the eyepiece of your telescope
App field: The apparent field of the eyepiece as stated by the manufacturer
Real Field: The field of view in arc-minutes using that eyepiece in your scope
Relief: Eye relief as stated by the manufacturer
Field stop: The eyepiece field stop as stated by the manufacturer

Real field is the one I look at most, then balance that up against the magnification.

The green section at the top is just where I copy the specs for the eyepieces I actually have, to give something to compare the others against.

OK, I can't attach a .xls file, so it's posted here:
http://www.deepdiving.net/misc/eyepieces.xls

Cheers,
Jason.

[dannat]

I don't think it matters about the different brands - except you will probably find a brand you will like & will then prefer oculars from that manufacturer.

One other thing to consider about the brands(same or different) is whether the oculars are parfocal - ie when you change ocular you hardly need to move the focus (ie my wo swan & vixen plossl happen to be parfocal but my meade plossl' focus is quite different to the other two)

I think a good barlow (premium brand) is a good investment. televue are the most popular choice, whether the standard or powermate range

If i was choosing I would only go for about 3 oculars.
# one providing about 50-75x
# one providing about 180x
# one about 300x
then you can barlow these for other mags.
I found when I had a finder I didn't use low power oculars like 25x, but then again I have a wide fov.

Lastly my now most important aspect looked for is eye relief - I find it uncomfortable with most oculars to look for any length of time.
Also don't find the wide fov oculars much advantage - I am quite happy with 50%, and don't like the 70% & up fov - but this is very personal

[rmcpb]

I only have one low power (35mm Panoptic) and a medium power (19mm Panoptic) then I get into a whole collection of moderate to high power lenses 9-4mm as I spend lots of time on luna and planetary observing and at these lengths each mm makes a huge difference to the magnification which is limited by the seeing so I can get the most out of the conditions.

While I have a good apo barlow it spends most of its time in the eyepiece box but is handy to have.

Cheers

[wavelandscott]

If you have not done so yet, go to the Televue website and read the articles there about eyepiece selection. In particular, the article about eyepiece choices for a small dob (6-10 inch)...not sure if the link will work or not... http://www.televue.com/engine/page.asp?cat=2

The ideas expressed in the article I agree with...

Assuming that you are willing to buy 7 eyepieces at an average cost of AUD$150 per that gives you a budget of AUD$1,050...

This illustrates what I think of as budget eyepiece "creep"...that is, people run out and buy several lower priced "moderately good" eyepieces in a hurry to expand their collection and very quickly spend as much or more than they would have had they chosen fewer high quality ones.

Instead of buying 7 "moderately good" eyepieces for your total budget, I would buy 2-3 high quality ones...these "premium" brands while expensive will last you a lifetime (if cared for) and retain a larger percentage of their resale value should you look to change your scope/set-up or leave the hobby later.

Most of my viewing is done on any given night with just 3-4 eyepeices...a low power, a moderate power and a high power...

3 good eyepieces combined with your barlow effectively give you 6 different magnifications...

As the eyepiece makes up a large percentage of the optical path I'd recommend fewer higher quality eyepeices instead of many "okay" quality...

Make no mistake, if your budget does not allow for the premium end of town, you can still get some very nice moderately priced eyepieces and they will work very well...however, if you are considering spending AUD$150 on 7 different eyepeices, I'd encourage you to re-think your strategy...AUD$1050 will buy you a few premium eyepieces that I think in the longer term may serve you better.

Good Luck!

[programmer]

wavelandscott
Yes I have read (most of) the EP selection article at the TV site. Just one of its recommendations was well over $800, but lots of good advice there. I should have said I'm not necessarily going to buy those 7 eyepieces immediately, or at all. That was just the theoretical spread that I calculated based on another article. But I still take your point about getting few, better, EP's.

Rob
I hear what you're saying.. buy EP's depending on you're going to be observing most. I do like my globs but I'd also like to have a high power EP or two for planetary. Interesting about the barlow.. some people swear by them, others never use them. I guess you have enough coverage of high power for your needs.

Daniel
Thanks for the tips. I do intend to get at least one good Barlow. Interesting that you prefer the narrower FOV.. I don't have enough experience to decide yet! I hear what you're saying about the parfocal aspect.. that was one of my main thoughts although I forgot to mention it. Surely that's a great time saving feature.

Jason
Cool spreadsheet! I notice there's a BIntel 252 sheet there so I'll just use that. Lots of info there.. will check it out presently. I notice no Baaders there.. Did you create the spreadsheet? Thanks again.

[koputai]

Oops, I forgot to delete a few sheets, only the one labeled Bintel 202 (now relabelled Eyepieces) has all the data on it. I've ammended the whole thing now down to just the necessary sheet. I've never considered the Baaders, so haven't added them, I don't know why, there's just something I don't like about them. If you can point me at the relevant specs I'll add them to the sheet. Yes, I created it, just to make the decision making process a bit more methodical.

Cheers,
Jason.

[dannat]

I also agree with what waveland-scott said - save and buy the premium oculars - then you will only buy a few keepers, rather than continually buying stop gap measures. I guess the same goes for scopes

[programmer]

No problem. I wonder what it is about the Baaders that you can't put your finger on? Anyway I'll see if I can get the specs.

[programmer]

I also agree, in theory, but it's a tough choice. If I buy a premium new EP ('realistically' how much, $300, $400? I know they go much higher) and buy the wrong one, that's an expensive mistake. You could say buying 2nd hand is offsetting the risk somewhat. Then again, I'm never sure the one I've bought is operating as per the day it was bought brand new. If I got to a LOT of star parties I could get a feel for various EPs, but that's unlikely to happen unfortunately.

I'm almost willing to have someone tell me OK, buy THIS exact EP as a starter, and you'll be right (e.g. brand, model and FL) and come back in 6 months for the next installment. :) Of course, I wouldn't hold the person responsible if I didn't like it :D

Sorry to rave on

[dannat]

Alright - I'll tell you one (& this goes against all of the tv nagler & pentax fans)
get a tak LE ocular
you can buy in Aus (about $290 I think) or if you want to save some bucks try this link http://www.tan14.com/gears.htm

[programmer]

Full points for sticking your neck out :) I shall read up on this item tonight.

[JethroB76]

Dannat, could you tell me what company is behind this website? Its kinda limited in detail...

[ausastronomer]

1) fewer high quality eyepieces are better than a lot of mediocre ones

2) You need more eyepieces at the high power end than the low/medium power end. You certainly don't need a 35mm, 25mm and an 18mm eyepiece with a 10"/F5 dob. When I use my 10" dob, I usually go from my 27mm TV Panoptic straight to my 10mm Pentax XW when observing DSO's.

I would look at getting a good 2" barlow and a 30mm widefield eyepiece of good quality. Barlowed it gives 15mm. Then add a 10mm and a 7mm or 8mm eyepiece, which will both double for high power lunar/planetary work when barlowed.

Cheers,
John B

[Kokatha man]

Have to agree with John here: small-scale increments in magnification rarely seem to provide any worthwhile improvement in image/detail.

A low power, a medium, then a reasonably higher power again with a good barlow to fill in the range, and provide a very high power for those occassional nights of great seeing, imho is the most logical selection.

Apart from a low power widey such as a 2" GSO which, again imho, gives you good "general scanning" and/or star-hopping capabilities; I also think that quality ep's (whether they are the blue-ribbon jobs or lower-priced but good quality clones etc) are ultimately the most money-saving purchases.

Cheers, Darryl.

[omnivorr]

:thumbsup::thumbsup::thumbsup:

[programmer]

After are-reading my original questions and taking into account people's tips (and doing some more reading)..

I'm happy with the 12.5mm EP I bought, it's a good low power and barlows as a nice moderate power. I think good value for $70.

I probably could've done without the 17mm Hyperion for now and gone the other way, maybe an 8mm. 12.5mm and 17mm are too close. The 8mm would've given me 100x, 156x, *B200x and B312x (along with the 25mm and 40mm cheapies as finder EP's).

Instead I have 73x, 100x, B147x and B200x, not including my 4mm and 9mm cheapies. I do love the wide view in the Hyperion though. Again I think good value for $155. I will either keep it or sell/trade. Both EP's have wide views and good eye relief.

Perhaps a good 3x Barlow (additional to my 2x) would be the go, giving me 73x, 100x, B147x, B200x, B219x and B300x all up. Would still like something higher than 300x though, for those good nights.

There's still a bewildering range to choose from though, even within the one brand, but in the end it boils down to eye relief and field of view when choosing between better brands, as they are all very good mechanically and optically. Please correct any glaring errors :D


*B for Barlow

[programmer]

I found one here for $225 (http://www.optcorp.com/), delivered in 2-3 days. Is that a good price? :)

Anyway I'm going to go through methodically and see what I come up with, perhaps it will be the Tak .

[programmer]

I love this site! http://www.optcorp.com/category.aspx?uid=105-30

Especially these links, helpful for choosing eyepieces:

Choosing Telescope Eyepieces By Focal Length (http://www.optcorp.com/category.aspx?uid=30-719)
Choosing Telescope Eyepieces By Manufacturer Series (http://www.optcorp.com/category.aspx?uid=30-718)
Choosing Telescope Eyepieces By Price (http://www.optcorp.com/category.aspx?uid=30-720)

These don't just link to information but to their actual catalog with prices ($US). Of course, they don't stock all brands, but they do have a lot! Postage is reasonable for a single item, and a doddle for multiple items!

Apologies if this is old news :)

[dannat]

you should still try & lok thru some oculars - maybe some of the melb IISers could meet & you could try some out - mornington Peniins has regular meets - look up their website (MPSA.org)

[programmer]

Yes I almost went last month, but this month was clouded out. If any neighbouring IIS'ers reading this want to show off their wares, please let me know :D

[dannat]

If anyone is interested - maybe we could continue the great spots to observe in Melb thread - last time we went out I think everyone enjoed the night.

If people want to travel - I live about 100kms to SE melb- we enjoy darker skies than the previous location, but it is farther to travel

[programmer]

Sounds like a good idea. I can guarantee you one of the places won't be my place! I'm planning to travel to Whittlesea (friends place) for some observing this weekend, weather permitting, but that's about the only place I've taken my scope.

[erick]

Tempting Daniel, should be a fairly dark south and east of your location?

Why don't you thow up a thread in "Star parties, Clubs and Observing Sessions" with suggested date(s) and an offer we cannot refuse and see what happens. :)

[Starkler]

Neerim sth looks like a nice little spot :) Hows your tree line to the north?

[dannat]

Ooh:shrug:, forgot about a location - Our backyard has some tall & vicious trees both Nth & Sth, I usually wander to the loca football oval, which is about 70m away - when I want ot do some observing.
Occassionally there are events on at the club rooms though -
I will investigate a couple of locations tonight & then see if i can get a thread started
daniel