The Perfect Number of Eypieces?

[Paul73]

So what is the perfect number for a single scope?? I say 7. What do you think?

If you browse through the "Show Me Your Eyepiece Case" you will see collections ranging from 3 to 33+!!! How much is down to personal taste/obsessive behaviour?

There are plenty of threads about which order to buy. But this is about the "finnished"

[michael.h.f.wilkinson]

42

In my C8 I use the 42mm LVW occasionally, Nagler 31T5 "Panzerfaust", Naglers 22T4, 17T4, 12T4, Pentax XWs 10mm and 7mm, and Delos 8mm regularly, and occasionally the Vixen SLV 5mm. That makes 9, but I do feel a Morpheus 14mm might slide in there somewhere

[Mrbloke]

Well I'm only using 2 of my 4 at the moment. A 20mm and an 8mm. The 20mm is in the scope 90% of the time. My next purchase will likely be a 6mm for planetry and double stars followed by a ~13-14mm for mid range. That may be it.

I'll go for 4 on that basis.

[swamp thing]

I use three and a 2x powermate.

31, 20, & 12mm.

[Mike73]

I keep my EP's in my coat pocket so just use four.

I guess a lot comes down to just how well you want to see each object. A decent collection of high power EP's is nice to have for planetary viewing to match seeing conditions and the same goes for galaxy season when trying to match exit pupil to surface brightness to try and see as much detail as possible with galaxies.

At the end of the day though an eyepiece is just tool we use, its what we see and enjoy when we look through one that counts. 

(Mike73 takes a big step down off his soap box  )

[rockystar]

As I'm only just (really) starting out, and about to start a proper collection, I was think that 4 or 5 ( 5 or 8, 13,17,22-25, >25) would make a reasonably good ranged collection. But in a couple of years time (when I've replenished the gold stock pile) I may be persuaded to get more. 

[laudropb]

Normally just 2. A 24mm Wide angle and a 8 -24mm zoom. Cheating a bit I suppose.

[Macavity]

The terminally nerdy (oops) will find only the *Fibonacci* series:

5, 8, 13, 21mm (Vixen LVWs, Baader Hyperions)... satisfying?

I think there is a *genuine* wisdom in the ratio of about 1.6x ...

But I'm not primarily a visual astronomer, so went for a cheaper

 "root three" (approximately) series: 10mm, 17mm, 31mm... 

(There has to be some kind of "logic", when I do such things!)

I think I will (re)buy some "planetary" eyepieces at 3.5 & 6mm

to compete the series, at some stage... In keeping with above!

[scarp15]

Currently I am just one over that number therefore eight, though seven as you indicate is likely a good round number for most circumstances. Two of these are low power plossls primarily for use for faint nebula hunting for circumstances when a narrow field would be beneficial, the rest are wide or ultra wide field. During my last session on Saturday I used a 21mm, 13mm, 8mm and 6mm, so tend to use four of five on average within a session. Perhaps the Show me your eyepiece case, can determine the amount of e.p,s to collect, before it can turn into Show me your eyepiece cases.

[triton1]

As many as you can fit in your ep case.I think I can only fit one more so that would make 7

[Moonshane]

my formula is :

if current number of eyepieces = x

perfect number of eyepieces = x+1

[Moonshane]

but seriously, it depends which scope. e.g. with a long focal length scope, differences in eyepiece focal length create bigger differences in field and magnification than in a short focal length scope.

with my 80mm f6 frac, I could happily just use my 26mm Nagler (18x) and my 6-3mm Nagler zoom (80-160x).

In my 6" f11 dob, I use this mainly for planetary and double stars and find a closely knit set of eyepieces works best (26mm Nagler, 17mm Delos, 12mm Nagler, 11mm Plossl, 9mm Nagler 7mm Nagler and 6-3mm zoom covering a range from 61x-533x).

[michael.h.f.wilkinson]

Of course, the smallest perfect number is 6

[triton1]

And the next perfect number is 28 mmmmmm

[Roy Challen]

I can get away with just 2, maybe 3, with any of my scopes, but I like having a few 'in reserve'. So at the moment the reserves (CZJ orthos, for when I absolutely, positively gotta split that double) outnumber the regulars 4-3.

[hgjevans]

I'm finding my eyepiece use is much the same as my use of photographic lenses used to be - I like to have a wide choice available, but on any given occasion I'll usually settle down to working with just two. Which two is probably down to the sky conditions and the kind of objects I'm trying to observe.

[Mr Spock]

The perfect number is one...

...one for every occasion

[michael.h.f.wilkinson]

And the next perfect number is 28 mmmmmm

I like your line of thought. My bank account doesn't

[Floater]

The revered Al Nagler wrote a seminal article on eyepieces (pretty sure it's on the Televue website) in which he states that one needs only three - for low, medium and high power viewing.

I didn't follow his advice either! Just saying ...

[michael.h.f.wilkinson]

The revered Al Nagler wrote a seminal article on eyepieces (pretty sure it's on the Televue website) in which he states that one needs only three - for low, medium and high power viewing.

I didn't follow his advice either! Just saying ...

That is a bit rich from the man who has enticed to buy more EPs us with all those brilliant designs of his

[Piero]

My main "night" set has 4 eps + powermate 2.5x: Panoptic 24, Nagler 13mm, Nagler 7mm, Nagler 3.5mm. 

I am very happy with it and I find it usable under different seeing / transparency condition as well as different target brightness.

With the TV-60, the combinations N13+PM (=N5.2mm) and N7+PM (=N2.8mm) are also used quite a lot. 

With a future dob 10" F5, I also expect to use the combination Pan24+PM (=N9.6mm) quite a lot.

I also have two 50 degrees eyepieces (TV Plossl 20, Vixen 5SLV) and a Bresser 2x SA which I now use for solar observation only. I could use the main set for solar too, but I have a feeling that these 50deg eyepieces show the Sun a bit better. This set is also my "ultra-light grab and go set". I could sell the Bresser 2x and just use the PM also for this set, but I prefer to wait and see for now. 

Until some time ago I used the Vixen 5mm for night. It is a lovely eyepiece, but swapping between 50 and 82 degrees distracted me every time. Since I like large fields, I decided to opt for a PM2.5x and replace the vixen 5mm with a gained "Nagler 5.2mm". 68-82 degrees afov match my taste nicely! :-)

In conclusion, I would say that 3 eyepieces are enough (exit pupils of: 4-5mm, 2mm, and 0.8-1.2mm). Despite this, I am pleased to have some eyepieces in between to cover the gaps and to see better (or just spot!) certain targets. 

[RikM]

Well I have 7 eyepieces: 3.5, 5, 7, 10, 14, 20 & 28mm. But I could make do quite happily with 4 of them 5, 7, 14 & 28mm. the only change that I could imaging would be dropping the 20 and 28 in exchange for big 21mm! That's not likely to happen anytime soon but I could see it happen.

[Paul73]

I guess that it is a personal thing. So the perfect number is when the experienced observer says "My collection is complete"

.... And actually means it.

Paul

[Lorne]

I,m downsizing my present case of 6, last week I was planning to reduce to 4. From my signature, my 28mm Nirvana and WO zoom (my 2 most frequent used) are being kept. I planned on moving on the 7mm Nirvana, the 6mm SPL & 12.5mm SPL - seldom used,  and buying a 9mm SW Myriad. On a session last weekend I had a look through a mate's 9mm ES100 in my scope and was blown away. That got me thinking that if I get the same effect with the 14mm ES100 I could move on the 16mm Nirvana too. That would leave me with 28mm, 14mm 2" wide FOV's and my zoom to let me up the mag when seeing allows (although narrow FOV's) when viewing the planets. On the other hand, that will leave a lot of exposed foam in my EP case...... 

[michael.h.f.wilkinson]

I guess that it is a personal thing. So the perfect number is when the experienced observer says "My collection is complete"

.... And actually means it.

Paul

Even if they mean it at the time, they always change their mind later