Choosing eyepieces

[enigma]

Would any of the following eyepiece types make a better choice than the rest for general use with a f/5 Newtonian?

BST Explorer Dual ED

Circle-T Abbe Orthos

GSO Super Plossls

TS Planetary HR

Any other suggestions would be welcomed.

[great_bear]

- You can't really go wrong with Circle-T Orthos - except at very short lengths

- GSOs are too astigmatic for my liking at F5 (but excellent in slower scopes)

- Many people find the TS Planetaries are very comfortable eyepieces with good views

- The BSTs look like they're the same as Paradigms - which are also well-liked

So in summary, there's no "duds" in the list, although I'd (personally) rule out the GSOs at F5

[Later] In [this review] Tom Trussock says at the end that the TS [TMB] Planetaries and BSTs [Paradigms] Can be used together to span the range of focal lengths (eg the Planetaries at the shortest lengths) (and that's assuming that Paradigms==BSTs)

[John]

"for general use" I'd probably go for the TS Planetary HR. The eye relief plus the 60 degree FoV make it comfortable to use and the ones I've tried worked pretty well in fast scopes as well.

[enigma]

How do the TS Planetary HR perform near the edge of the field of view compared to the BST Explorer Dual ED? Would either work well with a Barlow at the longer focal lengths? Does anyone have experience with the 25mm, 20mm and 15mm TS Planetary HR?

[Doc]

F5 is pretty fast and I have no doubt your primary mirror will show coma in all but the expensive eyepieces.

It's all down to budget and how bothered you are by those little comet tailed stars.

[enigma]

I would like to get the best eyepieces for the price (under £50 each) and these might not be the most expensive ones in my list.

[russ]

How do the TS Planetary HR perform near the edge of the field of view compared to the BST Explorer Dual ED? Would either work well with a Barlow at the longer focal lengths? Does anyone have experience with the 25mm, 20mm and 15mm TS Planetary HR?

I hadn't noticed a 15mm, 20mm and 25mm had been added to the range. I wonder if these are what would have been the TMB Stellar range?

[enigma]

I don't see any indication that the 25mm, 20mm and 15mm are different than the rest of the TS Planetary HR.

http://www.modernastronomy.com/eyepieces.html

[russ]

I can't find a picture of the 15,20,25, not even on the TS website. The original plan by Burgess TMB was to release a set of planetary eyepieces ranging from 2.5mm to 9mm. And then release another set of eyepieces called the Stellar range, which would be 15mm to 25mm. The only Stellar that made it to production was the 20mm. I just wonder if TS had the factory make the other models and pad out their own HR all the way up to 25mm. Very interesting indeed, always fancied a lower powered Planetary.

[enigma]

There are photos of the 25mm, 20mm and 15mm on the TS Online Shop and they all look alike and have the same specifications:

http://www.teleskop-express.de/shop/index.php/cat/c70.html

[russ]

So there is, nicely done. Quite fancy the 15mm or 20mm, would make a good workhorse eyepiece.

[John]

Coma is inherant in fast newtonians. Really well corrected eyepieces show it. Lower cost eyepieces show the edge of field abberations they they introduce - masking the scopes coma in fact !.

I've used the TMB Planetaries down to F/6 and they seemed pretty sharp to the edge to me.

The main drawback with the series was off-axis flaring caused by poor internal baffling, notably the design of the retaining ring for the lower group of lenses. I believe this has been fixed with later issues of the eyepiece although I did have to modify one example that I tried (an unbranded 6mm) myself to address this.

[enigma]

Having in mind that the TS Planetary HR have 6 elements, would it be a good idea to use the longer focal length eyepieces with a Barlow?

[John]

Having in mind that the TS Planetary HR have 6 elements, would it be a good idea to use the longer focal length eyepieces with a Barlow?

The optical design of the TS Planetary HR's (at least the 9mm and shorter focal length ones) employ a barlow-type lens set mounted in the chrome barrel:

http://www.svenwienstein.de/Pics/ed_schema.gif

So they are already a "barlowed" design (as are Naglers for that matter).

Despite that I seem to recall they barlow pretty well. It's possible that the new longer FL ones are a different optical design of course.

[enigma]

Has anyone done a comparison between the BST Explorer Dual ED and the TS Planetary HR? Both types of eyepieces have similar specifications.