Maximum focal length eyepiece for ED80

[pluton]

Hello,

Anyone to know what is the max. magnification with a ED80 refractor?

I have a 6.7mm eyepiece and the view is fantastic, for lunar and planets, a 3mm can be OK?

Thank you very much.

Paul

[nmoushon]

On my ED80 I find that my 3mm usually pushes it too much. Especially on planets and the moon. Things tend to get more fuzzy than more resolved. At least for me and my location anyways.

[russ.will]

I know it's not an ED80, but in my 80mm Apo I could occasionally use the 3mm end (160x) of my TV Nag zoom, once the scope and the Diagonal had been professionally collimated and only on some subjects. Before and more generally after, 4mm (120x) was always doable on pretty much anything. In other words, exactly what the rule of thumb would lead you to believe on 50x per inch of aperture as a maximum.

I wish I hadn't sold that Nag zoom....

Russell

[osbourne one-nil]

It's going to give you a very small exit pupil, 0.4mm, which you might not find very useful. It's not just magnification, as I've learnt over the years. 

[Stu]

I agree that around a 0.5mm exit pupil is probably as far as you want to go on this. I find that with my nag zoom I rarely go below the 4mm setting, although occasionally 3.5mm works well. I have tried a 3.5mm Nagler and even a 3.7mm Ethos, both of which work well as a high power.

I would say that a 4mm would be the best option though. Perhaps a used Radian?

[Charic]

osbourne one-nil makes the point. As you further increase the magnification, you will reduce the exit pupil. Going less than 1mm ( 7.5mm EP,  the same as the focal ratio! ) is not the best option / direction  for extracting  more detail?

A 4mm EP would give about 0.53mm exit pupil, half as much again. 

I only use my shortest focal lengths on the Moon( Large, plenty to see, and bright enough to view )  Not much fun on the Planets or DSOs.

[Stu]

osbourne one-nil makes the point. As you further increase the magnification, you will reduce the exit pupil. Going less than 1mm ( 7.5mm EP, the same as the focal ratio! ) is not the best option / direction for extracting more detail?

A 4mm EP would give about 0.53mm exit pupil, half as much again.

I only use my shortest focal lengths on the Moon( Large, plenty to see, and bright enough to view ) Not much fun on the Planets or DSOs.

Charic, with small, high quality refractors then smaller exit pupils are certainly worth using. You do risk floaters showing up more but there is more detail to be had by going to higher mags.

I've used a number of these types of scopes, namely William Optic SD 66mm, Tak FS-60C, FC-76SC, Stellarvue 80ED, Televue 76 and 85. The 'worst' of these was the WO 66, but even this would take x120 and show GRS and shadow transits on Jupiter, not easily but they are observable. I used up to x155 but this just added image scale, no further detail.

The TV85 will take x160, and even more on good nights and on double stars.

I tend to treat 0.5mm as my minimum exit pupil, you really do need to use this in order to get the most out of the optics in these high quality, small aperture scopes.

[Charic]

ok.... I was under the impression that the formula / system works for both types of telescope?

learning all the time

[Stu]

No probs. I think it is fairly specific to small Apo refractors. They are capable of high mags but obviously being of small aperture the exit pupil by definition ends up being small.

To me, sticking to x85 on my TV85 would miss a lot of the capabilities of the scope. Yes, it is lovely on low power, Widefield stuff but also very capable on tight doubles and planets.

[osbourne one-nil]

That is interesting as I've been thinking my 9mm Nagler in my f7.4 Tak refractor would be about the maximum (1.2mm exit pupil) but you're suggesting I could push it to a 4mm eyepiece which would give an exit pupil of 0.5mm and a magnification of x185. 

Time to sell something else to fund that!

[Moonshane]

I managed a clean split of 32 & 52 Ori the other night using my 120ed f7.5 at 300x using my nagler zoom at 3mm and a 0.4mm exit pupil so these sorts of ratios are feasible.

[Stu]

That is interesting as I've been thinking my 9mm Nagler in my f7.4 Tak refractor would be about the maximum (1.2mm exit pupil) but you're suggesting I could push it to a 4mm eyepiece which would give an exit pupil of 0.5mm and a magnification of x185.

Time to sell something else to fund that!

0.5mm exit pupil should be x200 so x185 will be comfortable, particularly with Tak optics. Not all the time, needs good seeing but worth having. Perhaps a nag zoom?

[Stu]

I managed a clean split of 32 & 52 Ori the other night using my 120ed f7.5 at 300x using my nagler zoom at 3mm and a 0.4mm exit pupil so these sorts of ratios are feasible.

Nice one Shane. The 120ED is lovely on doubles isn't it!!

[Moonshane]

Indeed mate. Really happy with it.

[Stu]

Indeed mate. Really happy with it.

I don't know, what's happening. You with your fracs and me with my dobs. Who'da thunk it! [emoji6]

[Moonshane]

Finally found a frac that gives Newtonian like views.

[John]

I find that 300x is really quite useful with the ED120 on tight doubles. 3mm Radian in my case. Darn fine scopes as I've been saying for some time

With an ED80 I'd reckon 200x would be useable in the same way.

[Stu]

Finally found a frac that gives Newtonian like views.

Or is it that your newts give decent apo Frac views [emoji12][emoji12][emoji12][emoji6][emoji6][emoji6]

[Moonshane]

who cares LOL

[chiltonstar]

A good magnification with my Orion ED80 (fl = 600mm) is about x160, using an orion 3.7mm EP. This is still tack sharp with Jupiter and Saturn (shows Cassini nicely) and will resolve doubles down to about 1.4 arcsec apart. I have used x300 to show the Airy disk size and sep better, but as others have opined, floaters can break out....

Chris

[mikeDnight]

I often use my 3.5mm Pentax XW on my Equinox 80 while observing the Moon. However the way to get the best views of the moon and planets, at least in my experience, is to use a bino viewer and a couple of cheapish orthos or plossl's. Even though I feel the Pentax XWs are the best single eyepieces I've ever used, the bino viewer and orthos deliver a consistently superior view.

The orthos in my bino viewer are 16.8mm fl and the viewer has a X2 Barlow screwed to its nose piece. I'm not certain of the exact magnification as I've never measured the exit pupil accurately enough, but the resultant image is plenty large enough to reveal detail in the cloud belts of Jupiter and superb views of the moon. Also, this little scope with its bino viewer installed seems to cut through poor seeing like a knife through butter.

Mike

[Stu]

I often use my 3.5mm Pentax XW on my Equinox 80 while observing the Moon. However the way to get the best views of the moon and planets, at least in my experience, is to use a bino viewer and a couple of cheapish orthos or plossl's. Even though I feel the Pentax XWs are the best single eyepieces I've ever used, the bino viewer and orthos deliver a consistently superior view.

The orthos in my bino viewer are 16.8mm fl and the viewer has a X2 Barlow screwed to its nose piece. I'm not certain of the exact magnification as I've never measured the exit pupil accurately enough, but the resultant image is plenty large enough to reveal detail in the cloud belts of Jupiter and superb views of the moon. Also, this little scope with its bino viewer installed seems to cut through poor seeing like a knife through butter.

Mike

Must give that a go Mike

[Pig]

I have gone as far as the 2.5 SLV when the seeing allows, fine focus option is a must if you want crisp views

[Charic]

Regarding the ED80, my Skyliner will no doubt go into its Summer hibernation soon, due to the longer, brighter nights, therefore not so good for a scope dedigned for DSO.

The Skyliner has been tagged as being the UKs most popular Dobsonian?

I have seen many references to the ED80, and it has been on one of my wanted lists, for some time!

What is considered as the UKs most popular Refractor telescope, and how much will the image scale differ between the two scopes. If I were to purchase a Refractor, I want the image to be bigger in the eyepiece than my Skyliner offers.

[Stu]

Regarding the ED80, my Skyliner will no doubt go into its Summer hibernation soon, due to the longer, brighter nights, therefore not so good for a scope dedigned for DSO.

The Skyliner has been tagged as being the UKs most popular Dobsonian?

I have seen many references to the ED80, and it has been on one of my wanted lists, for some time!

What is considered as the UKs most popular Refractor telescope, and how much will the image scale differ between the two scopes. If I were to purchase a Refractor, I want the image to be bigger in the eyepiece than my Skyliner offers.

Not sure I get your last sentence Charic? Unless you get a very long focal length refractor, it is unlikely your image scale will rival the skyliner?