Eyepiece groups

[Moonshane]

This might seem like a show off thread but it's a genuine attempt to explain why having options when it comes to eyepieces is an advantage. I also hope that my logic will influence and help others to make their own decisions when they see how I arranged my own set.

In principle almost any eyepiece can be used on any object and in any scope. However, the focal length, focal ratio, seeing conditions, size of object and other factors such as eye relief, weight and quality that can affect which eyepieces get most use.

Like many observers I have more than one scope and sometimes travel on family holidays (camping in the UK) with a scope. I also do some solar so there's different requirements for different situations.

Originally I thought I'd have one scope and buy maybe four eyepieces but now I have a 16" f4, a 12" f4 and a 6" f11, all dobsonians. This creates different needs and magnifications etc so I ended up with three scopes and 13 eyepieces plus a paracorr so the ratio is about the same at least! This number pales into insignificance compared with some members though, and certainly a lot of people in USA.

Here's my full set which I now consider complete. It consists of 32mm TV Plossl, 26mm Nagler T5, 25mm TV Plossl, 20mm TV Plossl, 16mm Nagler T2, 15mm TV Plossl, 13mm Ethos, 12.5mm BGO, 11mm TV Plossl, 10mm Radian, 9mm BGO, 8mm Radian, 7mm BGO, 6-3mm Nagler zoom.

Originally as I say, I planned to have four eyepieces and the four I originally chose form the backbone of this collection; the 26mm Nagler, 13mm Ethos, 10mm and 8mm Radian. However, I decided early on that I'd add the excellent 6-3mm Nagler zoom which makes a backbone of five really.

I am certainly a fan of good quality and also decided early on to stay with one brand, Televue, for the bulk of my set. I have only three non-Televue eyepieces and these are also by coincidence (in part at least) black and green - the much lauded BGOs. However, the key here is that other than the 'backbone' eyepieces referred to above, the remainder have been bought very cheaply in comparison. All but two of my eyepieces (and all of my scopes, finders, some of my filters and collimation tools) were bought in good used condition and I consider them to be 'fillers'.

My decision making centered around four functions; wide field DSOs with the bigger dobs, high magnification planetary with the smaller dob, solar observing with the smaller dob and traveling with a minimal kit. Later in the process I decided to find a 'Horsehead eyepiece' for use with my Hb filter. What I wanted though was a set I could buy and then use with any future scope purchased. I believe that I could buy (literally) any scope and never need another eyepiece.

The first set shown below provides the widest field at a compromise exit pupil size, a workhorse extra wide field and two higher magnification wide field in the Radians for higher powers when needed. I found though that sometimes the 13mm was too much power for the big dob when seeing was poor so I got the 16mm Nagler with the same field but a bit less power for these occasions. At a third of the used price it is just as good and I really like it.

The second set is my solar system and double star set. This contains all smaller eyepieces and many of them. The set contains 3-6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12.5mm, 15mm, 20mm, 25mm and 32mm. The seeing varies so much at high power that I often run up and down the sets in a night or even a short period as the conditions and positions of the object change. You'll note that the Radians play their role here too. This is mainly for my 6" f11. Balance can be an issue with this long, slim scope so 1.25" eyepieces are important.

Next is my small solar set. Usually I only manage to use the 32mm eyepiece with the sun at 50x but just occasionally I felt I could use a bit more. I got the 25mm to fill this gap and it works well.

the next set is my travel set with my 12" scope. The 16mm Nagler provides a lovely field and the others allow me to get the most magnification out of the scope given the seeing without a massive collection. I can get them all in a small box.

Finally my 'Hb' set which just constitutes one eyepiece really. This is an attempt to get to the magic exit pupil of 5mm with my scope and my Hb filter to see the Horsehead from darker sites. Not tried this but looking forward to late autumn to try.

In all I believe that for me I have the perfect set of eyepieces now and through prudent used purchases I have managed to do so at a reasonable cost per eyepiece. Other than the backbone eyepieces and the 16mm T2, the remainder have all been less than £60 which I believe is the key to building a good quality collection within even a relatively tight budget. Thankfully I managed to buy the backbone eyepieces when I had a better paid job but in all honesty there is not much lost other than field, eye relief and possibly Kudos when using these cheaper but highest quality fillers.

I hope this helps people think a little differently and see that the best quality need not cost the Earth.

Cheers

Shane

[Wolfgangwand]

Really great thread Shane , certainly plenty of food for thought - you've got a fantastic lineup IMO .

Rob

[nightfisher]

reading the above post, i consider myself lucky, just one min EP case that does 99% of my needs im my mak, fracs and now the newt, i do have a small wooden box with my TAL plossl`s in it, and as im going camping in july i might take that one instead of main box, to use in my 100rs travel scope

[Stargazer_00]

A really good display of strategic purchasing coupled with high quality. A lovely set of exotic glass.

I guess the only problem now is thinking of something else to buy

I have only 82 degree eyepieces and one BGO and I find myself actually wanting a range of different AFOVs. You quickly lose the wow of ultra wide fields when all your eyepieces have it. I think I may like to stick a few different variants so shake it up a bit. I'm thinking possibly a 10mm Delos, a Nagler 3-6 zoom and possibly a 24mm panoptic so I can get the low magnification without going to 2" (to aid travel)

I do intend to get a 30mm ES 82 at some point as well as I hear it is so close to the 31mm Nagler for considerably less cost.

[John]

Thats an interesting post Shane - thanks for sharing your thought processes

Interesting to see that you are happy to mix fields of view that vary between 42 and 100 apparent degrees despite having manually driven alt-az scopes - your nudging technique will be well honed by now !

It's a good feeling to eventually get a set which you feel fully satisfied with - I believe I've got there myself now too, and about time

I reckon you are right that your eyepieces will cope with any scope you care to put them in now and will serve you for many years.

[michael.h.f.wilkinson]

Lovely collection and nice explanation (did the missus accept all those excuses for a new EP, did they creep in under the radar, or did she believe you when you said they were breeding )

[John]

I've just realised that I don't have a "Horsehead" set yet so my set is still incomplete after all !

[Stu]

Nice one Shane, very useful to understand your logic and you've clearly put together a very nice set of eyepieces which work for you.

I have developed my collection over the years and similarly have built them up around my varying scopes. One challenge is having shorter focal length fracs and also the stupidly extreme f20 mak :-).

I've struggled to find a balance between widefield Naglers and Ethos which work beautifully in the refractors but are not ideal in the mak.

Ultimately, I guess I've ended up at a similar conclusion in having sets of eps for different purposes. Widefield is covered by a range of Nags/Ethos, whilst planetary in the refractors is largely orthos and the nag zoom. I've also got a few Delos now which are lovely to use at higher powers, lovely eye relief and good enough fov.

The PST has its own dedicated 11mm TV Plossl which suits it perfectly.

Finally, the Mak. I've concluded that I should just play to its strengths as a high mag lunar, planetary and glob eater, and have a set of TV Plossls from 15mm up to 32mm which cover all the bases from x125 up to x267. The Orthos can give me higher if needed on rare occasions. The idea here is a range of higher mags with optimum light throughput and minimum scatter to show maximum detail.

I know exit pupil is a very useful measure to choose eps, and I do keep it in mind, but I confess I still tend to very things in terms of magnification and field of view required to see an object. I avoid going too large on exit pupil at the low end, and know that too small gives a dim image and shows floaters quite badly. However, on the fracs by definition, to achieve high enough mag on planets the exit pupil gets small so I just live with the floaters if the seeing is still giving me sharp images.

Lastly, I have some duplication with, for example 22t4 and 21mm Ethos. The 21e is a wonderful ep, particularly in the 106mm apo but too large to take away with me with my TV 76 so for the moment I keep them both.

Cheers

Stu

[Naemeth]

Interesting post Shane, and I certainly see why you have the collection you do . I doubt you'll be adding anymore scopes though .

I've just realised that I don't have a "Horsehead" set yet so my set is still incomplete after all !

26.5mm, 32.5mm and 37.5mm would all be 'Horsehead' eyepieces for you John, but I don't think you can get any of those focal lengths exactly.

[RikM]

Great explanation Shane It really shows that there are many ways of building a collection, and they are all correct.

I am two purchases away from my final set that will also see me set up for life. (well three if you include a 2" O-iii filter) I currently use a 10" f/4.7 Dob and a 70mm f/6.4 refractor. One day I will get a 16" f/4.5 Dob and my eyepieces will work there as well.

Right now, I have completed my version of your DSO set but I have the added complication of not liking ultra-wide fields and needing long eyerelief (being a spectacle wearer). I also prefer a fixed aFOV throughout the range rather than mixing it up. I have a 28mm ES 68°, then 20, 14, 10 and 7mm Pentax XW.

My 'solar system' set are the XW's with a 2.5x TV Barlow to fill in the gaps. This gives gives me a potential 20, 14, 10, 8, 7, 5.6, 4, & 2.8mm. The XW's are effectively 70° ortho's, so I get the performance with the comfort. Both my two future purchases sit in this set, I will swap the barlow for a 2.5x Powermate and I will cave in to pure desire and get a 5mm XW. Given how rarely I can use 4mm, I don't see any need for the 3.5 XW. Although I have these effective focal lengths available, the vast majority of the time I just use either 5.6 or 4mm depending on seeing. With the incredible light throughput of the XW's, the 5mm will also work well for small planetaries as a DSO eyepiece.

I don't really 'do' double-stars and have only a passing interest in lunar observing so I don't optimise the high power quite as much as you.

My 'white light solar' set is the 10mm and 7mm XW with a solar continuum filter. This gives me 45x and 64x used with a TV Pronto and full aperture Baader solar film filter.

With the planned future purchases, I am quite comfortable that this is the complete set for me. Buy only what you need and quality counts.

A horsehead EP for me would be a 24mm Pan, but I tried one of those and didn't like it

[Pig]

Its a pity I cant just reach in and take them from the picture Your collection would be down to zero very quickly

[John]

...26.5mm, 32.5mm and 37.5mm would all be 'Horsehead' eyepieces for you John, but I don't think you can get any of those focal lengths exactly.

My research seems to suggest me that I should be aiming for low glass, a 4.5mm - 5mm exit pupil and a standard FoV (to keep nearby bright stars out of the field). So a decent quality 25mm / 26mm plossl would seem OK.

And some very dark, transparent skies of course !

[RikM]

My research seems to suggest me that I should be aiming for low glass, a 4.5mm - 5mm exit pupil and a standard FoV (to keep nearby bright stars out of the field). So a decent quality 25mm / 26mm plossl would seem OK.

And some very dark, transparent skies of course !

I've got a 21mm TV Plossl (4.4mm exit pupil in my scope) do you think that is close enough to be worth a trip out to the country in the autumn?

[bomberbaz]

Some good reasoning for differing EP's at a range of focal lengths. Wonder if I can think of a reason to add another EP to my already planned purchases, hehe. Nice thread shane mate

[John]

I've got a 21mm TV Plossl (4.4mm exit pupil in my scope) do you think that is close enough to be worth a trip out to the country in the autumn?

If you have an H-Beta filter it should be worth a shot. I've heard that a UHC filter such as the Orion Ultrablock can work as well. Personally I think the chances of seeing it without a suitable filter are very, very slim. I'd love to be proved wrong though.

[estwing]

that's not a show off thread...that should be a sticky,great read mate and should help a lot of people out.

[Stu]

http://observing.skyhound.com/archives/jan/IC_434.html

Might be useful for HH?

Stu

[John]

http://observing.sky...jan/IC_434.html

Might be useful for HH?

Stu

Thanks Stu.

I don't want to divert this thread away from it's main thrust which is Shane's rationale behind eyepiece selection which is very worthy of consideration even if your budget does not extend to Tele Vue and similar premium eyepieces.

[L8-Nite]

A great thread, thanks for posting.

[jetstream]

Great logic behind telescope and eyepiece selection.As a new astronomer this guide will help a lot & make the learning curve shorter,easier and cheaper.

Thank You

[swamp thing]

Great thread Shane, with good explanations on your choices.

My eyepieces set really consists of three eyepieces and a Barlow. I have one more to buy (an 8mm Ethos) then I'm done. Only the possible need to one day wear specs would then force any changes.

I would like another UHC one day and a H-beta too, but I am not in any hurry. Don't think I'll be changing scopes again now either. I'll always have a 10" Dob in my line up & the 20" f/4 is big enough (at last ). Although there may be room for a "Dobfractor" at some point

[Donkeiller]

Did you rob a bank- or are you a banker? (much the same!)

Seriously through, I could buy my whole eyepiece collection with what you have spent on one of the above.

[Moonshane]

Did you rob a bank- or are you a banker? (much the same!)

Seriously through, I could buy my whole eyepiece collection with what you have spent on one of the above.

what for £60? that's the cost of most of my eyepieces (or less).

[stevepeverall]

My eyepieces set really consists of three eyepieces and a Barlow

It's really refreshing to hear you say that Steve. The Backyard Astronomers Guide recommends the same thing and that's the basis on which I set my EP case up as a new astronomer. I appreciate that having two similar scopes simplifies things. However, as the OP asks though, is the jump from 10mm to 17mm too big a jump? The way I rationalised things was by drawing concentric circles (representing TFOV) on a piece of paper showing the step down (about x1.7 in my case) from 34mm to 24mm to 14mm to 8mm to 4.8 to 2.8 and there appears to be some pretty big gaps here when simply looking at the numbers.

However, on obseving the concentric circles the perceived gaps are diminished - an object which slightly overfills one EP is reasonable well framed in the longer focal length EP.

I do appreciate however that the situation is complicated for people with multiple scopes and with preferences of AFOV on different objects but it is still refreshing to hear that some seasoned astronomers still only use a few EPs.

[stevepeverall]

However, as the OP asks though, is the jump from 10mm to 17mm too big a jump?

Sorry, this OP was on another thread.