Small eyepiece vs barlow and larger eyepiece ?

[SAW]

Hi,

Longer focal lengths are preferred for lunar/planetary for example, an example SW72ED with 8mm eyepiece vs 15mm eyepiece and x2 barlow gives me roughly the same FOV, so what's best to use ?

Thanks.

[Stu]

Shouldn't make too much difference. If the 8mm has decent eyerelief such as a Delos then I would think that would be the best option. If it is an ortho with tight eye relief then barlowing a longer focal length would be more comfortable.

I think if you had a fast achro such as an ST80 then using the Barlow option may help counter spherical aberration but I doubt the 72ED would show much benefit as the optics are already very good.

[bingevader]

Whilst at home I prefer using the individual EPs.

I'm sure it's marginal, but it's a little less glass without a barlow and a little less faff..

It's taken me a while to build up EPs in the focal lengths I like though, so in the interim, the barlow has helped fill the gaps.

However, a barlow can be good for cutting down on the number of EPs whilst on the go too.

[Louis D]

If it's a long barlow, you may not be able to rack the focuser in far enough to reach focus.  If it's a short barlow and you're able to reach focus, it may introduce aberrations of its own unless it's a high quality barlow.  I tend to prefer individual eyepieces in refractors (I have the AT72ED).  Newts are more forgiving of long barlows because it's a long way from the focuser to the secondary, so they can be inserted all the way into the focuser, unlike the situation with a refractor and diagonal.  If you used the refractor straight through without the diagonal, then the long barlow would not be an issue.  I keep coming back to long barlows because the older, affordable, Japanese made long barlows of the 90s tend to give better views than today's Chinese made short barlows for the same money (around $50 to $70 used vs. new).

[markse68]

17 hours ago, Stu said:

If it is an ortho with tight eye relief then barlowing a longer focal length would be more comfortable.

Yes- the other barmy  warm  night I was out looking at the moon and think I found a new favourite - a recently acquired vintage Celestron 25mm ortho barlowed 2x gave beautiful contrast and tack sharp right to field stop image with decent eye relief. I don’t have a 12.5mm ortho to compare but I prefer this combo to the BCO 10mm I now kinda regret buying. 

[Stu]

8 minutes ago, markse68 said:

Yes- the other barmy  warm  night I was out looking at the moon and think I found a new favourite - a recently acquired vintage Celestron 25mm ortho barlowed 2x gave beautiful contrast and tack sharp right to field stop image with decent eye relief. I don’t have a 12.5mm ortho to compare but I prefer this combo to the BCO 10mm I now kinda regret buying. 

I sometimes Barlow my 12.5mm BGO rather than use the shorter focal lengths.

I would give your 10mm BCO a chance, they have an excellent reputation.

[jetstream]

27 minutes ago, markse68 said:

BCO 10mm I now kinda regret buying. 

Can I ask why?

[markse68]

9 minutes ago, jetstream said:

Can I ask why?

Well it’s probably more a feel thing than its optical quality and I will spend more time with it but it just feels a bit cheap, I don’t really like the eyecup and when I have used it before it didn’t stay long in the focuser- unlike this barlowed combo that I couldn’t get enough of 🤷‍♂️

[markse68]

28 minutes ago, Stu said:

I sometimes Barlow my 12.5mm BGO rather than use the shorter focal lengths.

I would give your 10mm BCO a chance, they have an excellent reputation.

I will Stu. now the 12.5 BGO I’d love to get a hold of 😉

[jetstream]

1 minute ago, markse68 said:

Well it’s probably more a feel thing than its optical quality and I will spend more time with it but it just feels a bit cheap, I don’t really like the eyecup and when I have used it before it didn’t stay long in the focuser- unlike this barlowed combo that I couldn’t get enough of 🤷‍♂️

I respect your opinion for sure to each their own I say.

My visual experience might differ somewhat from yours and you might want to keep it, even if for later. The 10mm BCO is an extremely useful eyepiece IMHO. Are you an experienced astronomer and what do you observe with? No disrespect intended with the questions btw.

[markse68]

No I’m a complete noob- it is only personal “feeling” not even a proper opinion-  nothing more. Next time I get the chance I’ll spend some more time with it- I’m sure it’ll grow on me.

[jetstream]

3 minutes ago, markse68 said:

No I’m a complete noob- it is only personal “feeling” not even a proper opinion-  nothing more. Next time I get the chance I’ll spend some more time with it- I’m sure it’ll grow on me.

I think your opinion was fine, proper etc. I just wanted to convey some experience with this eyepiece- it is just as sharp as my Docter 12.5mm, sharper than my Delos, goes deeper than the 12.5mm Tak ortho (vg btw) and barlowed is becoming a favorite galaxy core eyepiece, up around 500x. It is one of my best eyepieces.

Eyepieces are a personal choice for sure and there are many good ones out there, have fun with your choices!

[John]

The 18mm and 10mm Baader Classic Orthos are really good eyepieces - far better than their <£50 price tag suggests. They come in a "plain wrapper" but optically beat top tier eyepieces that cost 5x as much.

 

[markse68]

Thank you for taking the time to pass on your experience Jetstream . I will definitely give it more time. I guess part of the problem is the seeing where I am (SE London) I think I really need to get out somewhere better as I’m pretty much stuck with moon and planets at the moment- I can only dream of high magnification like that but then my scope is only 8.5” so not sure it’s be physically possible anyway. But I don’t think conditions here allow really critical comparisons- it’s more about if conditions allow definition on Jupiter or it’s a mushy blur 😉

Apologies to SAW for derailing  this thread 😬

[markse68]

That’s better- liking it much more already 😉

[Piero]

With a short tube like the 72mm ed I would not barlow but get the eyepiece.

The 10mm BCO was good but didn't impress me. It wasn't on par with my Docter but it was close to the 9mm Vixen SLV I had. I believe that there is some variability between units.

[John]

1 hour ago, Piero said:

With a short tube like the 72mm ed I would not barlow but get the eyepiece.

The 10mm BCO was good but didn't impress me. It wasn't on par with my Docter but it was close to the 9mm Vixen SLV I had. I believe that there is some variability between units.

Just for clarity then, the £50 Baader Classic was not as good as the £700 Doctor 12.5mm but close to the £99. Vixen SLV 9mm ?

If that was a less-than-optium Baader Classic thats still quite an impressive performance !

[Piero]

4 hours ago, John said:

Just for clarity then, the £50 Baader Classic was not as good as the £700 Doctor 12.5mm but close to the £99. Vixen SLV 9mm ?

If that was a less-than-optium Baader Classic thats still quite an impressive performance !

Fair point, John. I should have been more precise. I didn't mean that the BCO is not good, but simply that the one I had was not at the level of my Docter UWA. As this similarly was detailed a few posts above, I simply infer that there could be some differences between BCO units. 

My previous SLV 9mm was close to the BCO I had. Between the two I prefer the SLV due to the larger frontal lens and longer eye relief.

[jetstream]

28 minutes ago, Piero said:

Fair point, John. I should have been more precise. I didn't mean that the BCO is not good, but simply that the one I had was not at the level of my Docter UWA. As this similarly was detailed a few posts above, I simply infer that there could be some differences between BCO units. 

My previous SLV 9mm was close to the BCO I had. Between the two I prefer the SLV due to the larger frontal lens and longer eye relief.

In which respects wans't it as good? The BCO series was designed to open up the field and shows edge distortion a bit whereas the Docter is better in this regard.

[Piero]

43 minutes ago, jetstream said:

In which respects wans't it as good? The BCO series was designed to open up the field and shows edge distortion a bit whereas the Docter is better in this regard.

Mine wasn't as sharp on-axis as the docter. Instead it was more similar to the SLV.

[Paz]

I prefer not to use barlows just for the simplicity, having less glass in the path, and keeping it easier to balance my scope by using smaller focal length eyepieces.

However I prefer long eye relief eyepieces and at short focal lengths not only are they more expensive but they also have more elements anyway.

 ABarlow plus longer focal length eyepieces would be the next best option for me if cost was more of a factor.

[SAW]

So if I was going to add a x2  is it best to go power mate over barlow for visual and/or imaging ?

Can't see me ever wanting a x5 one but I think I'd like to get a x2.

Edited August 3, 2019 by SAW