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Kusanagi

choosing eyepieces for a 250 PDS

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Hi I was wondering if someone could give a little advice on choosing some eyepieces for my new scope ( 250 PDS on a dob ).

At the moment all I have got eyepiece wise is the stock 28mm LET which comes with the scope ( not impressed with ), a Meade 40mm SWA ( japan ) ( gives lovely clear images ) and a explore scientific 2" 2x focal extender, what advice I need is on some shorter focal length eyepieces.

I will be using this scope for a mixture of looking at planets and DSO.

I have been looking around and a couple of eyepieces have caught my eye, SW Nirvana-ES 16mm and 7mm eyepieces, I was wondering if anybody has any opinions or experience on these lenses particularly on a 10" F4.7 scope, another range of eyepieces was the BST Starguider lenses but with these lenses being only 60 degree will require more nudging of the dob to stay on target plus I have read that these lenses are a bit marginal on a fast scope, again I would like any advice on these lenses would be helpful as they might be useful for looking at the moon and planets.

I would like the explore scientific 82 degree lenses but most of them are a little out of my price range ( I might look at the Opticstar 82 degree range ).

If I stayed at 82 degree lenses I was thinking of eventually ending up with this range of lenses ( but it might take a year or so )

40mm Meade SWA ( 68 degree )

28mm Nirvana 82 Degree or ES or Opticstar 24mm 82 degree

16mm Nirvana-ES

11mm ES or Opticstar 82 Degree

7mm Nirvana-ES

4mm Nirvana-ES

plus a ES 2" 2x focal extender

Any thoughts on this line up or any other recommendations would be appreciated.

Thanks in advance.

Karl.

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Hi! since my first recommendation would be the ES 82 degree's (check my signature:icon_biggrin:) I'm going to recommend some other ones since you mention they're out of your price range. What about the 68 degree Explore scientific then:-)? I've heard many good things about them, and they're not as expensive as the 82 degrees. I don't know if it's just me but I prefer to stick to one type and brand of eyepieces.

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General thoughts on your initial selection are:

- I'm not sure that the 40mm eyepiece will get much use in the 250 dob, especially if you opt for the 28mm Nirvana. The amount of sky that the 40mm will show is not much more than the 82 degree Nirvana will show and the exit pupil will be rather large with the F/4.7 optics of the scope. It you like the 40mm then perhaps opt for the 24mm 82 ES instead of the Nirvana ?

- You might find that the 2x Telextender is not used often with the 7mm or 4mm eyepieces (too much power).

- I might be tempted to squeeze a 6mm eyepiece in and change the 7mm to an 8mm to get a more versatile set of high powers.

 

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TS' version of the 82° eyepieces in 4mm, 7mm and 16mm are on sale between 92€ and 102€. I have the older 4mm and it's quite sharp all over the field; it doesn't flare and eye relief is adequate for me (not an eyeglass wearer). My scopes' f/ratio are between 5 and 10, and it retains good edge sharpness with all.

The newer versions are fogproof as well as waterproof, and TS announces they contain a new optical design. In any case my 4mm is very good and the other focal lengths always get nice reviews. Beware that the older versions and the Nirvana or William clones cost a few euros more, but more importantly, they are not waterproof.

Currently the TS 82° are THE bargain in widefield eyepieces. Many 68° cost more.

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p8989_TS-Optics-Optics-1-25--Ultra-Weitwinkel-Okular-UWAN-4mm--82--Gesichtsfeld.html

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26 minutes ago, Ben the Ignorant said:

.... Beware that the older versions and the Nirvana or William clones cost a few euros more, but more importantly, they are not waterproof.

I agree that these TS branded 82 degree eyepieces seem good value for money, assuming that their performance is on par with the earlier versions of the UWAN / Nirvana's.

Is being waterproof and gas purged much of a big deal though ?

Tele Vue seem to be highly regarded despite not sharing those attributes :icon_scratch:

 

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1 hour ago, Ben the Ignorant said:

TS announces they contain a new optical design

Where do they say that? All the other sellers of this eyepiece state that they are the same as the old version. 

Having said that, I have the 28mm and as such would recommend the range. If I was in need of an eyepiece in those focal lengths I would happily buy one. However, a 4mm will give 300x, which probably won't see a great deal of use under UK skies. 

With regards to the BST Starguiders, which have also been mentioned, I think the 12mm and shorter will be fine in an f5 scope. 

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3 hours ago, John said:

Is being waterproof and gas purged much of a big deal though ?

One night someone from my club forgot the observatory's Hyperion case in a steel locker that is prone to condensation (and rust) when it's cold. The next morning we were kinda shocked and a bit scared to see all the Hyperions fogged up. We left them outside in the sunlight, taking care to orient the lenses away from the Sun, and luckily after a couple hours the fog went away. But I suspect some residue remains that would show up as nasty spots if they fog up again. Never happened to my personal non-waterproof eyepieces, but now I buy only sealed eyepieces if the focal/field I want is not too expensive.

After that mishap the club's management agreed to buy ventilated PVC lockers for the observatory.

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3 hours ago, Ricochet said:

Where do they say that? All the other sellers of this eyepiece state that they are the same as the old version. 

To the right of the eyepiece photo, in the gray area:

82° field of view - very well accessible through new design

Not sure if it refers to the whole set of lenses, or only the eyelens group, or maybe just the top of the frame that might be redesigned to let the eye come closer?

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15 hours ago, Ben the Ignorant said:

To the right of the eyepiece photo, in the gray area:

82° field of view - very well accessible through new design

Not sure if it refers to the whole set of lenses, or only the eyelens group, or maybe just the top of the frame that might be redesigned to let the eye come closer?

I'm pretty confident they're just talking about the tapered top, not a change to the lenses. 

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Well I finally got around to ordering the first of the eyepieces that I wanted, a Nirvana-ES 16mm UWA.

 Quite nice looking and very light, had look though it on the scope during the day, nice and clear views ( apart from the murky sky and the moment I got concerned that I could not get the eyepiece to focus with the focal extender on it ( forgot to put the 2" spacer back on ?)) and I managed to get 10 minutes viewing in tonight and was quite impressed with what I could see.

 When I do get to put some serious viewing in with this eyepiece I will try to do a proper review.

P1010115a.jpg

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Interesting to see the branding "Helios" on the box. Synta (who own and make Skywatcher stuff) used to use the Helios branding before the name Skywatcher was used.

Hope you enjoy the views !

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Interesting thread. From all I have heard, the Nirvana eyepieces were touted as Nagler-killers (back when Naglers were seen as being more awesome) and work well even in fast scopes. I prefer the new mechanical design, less blocky and bulky than the original.

Edited by Ags

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On 12/12/2018 at 15:27, Kusanagi said:

BST Starguider lenses but with these lenses being only 60 degree will require more nudging of the dob to stay on target plus I have read that these lenses are a bit marginal on a fast scope.........

There's a few folk using the Starguiders to good effect on their  f/5 (f/4.7) scopes, and  if you chose  between a  Starguider  or  Delos, you'd be hard pushed to see much wrong with the view on axis.
What happens at the edge of the view should be of no real concern  for visual observers,  on a manual setup, it's all part of the process, as long as they  track smoothly.
Nudging infers some force to overcome the 'stiction'? .......My scope glides, there's no  real effort and stays where I leave it. 
The often quoted 'requires more nudging' seems like a chore for some folk?

I'm not digging at you, but if you had a tracking mount, then the issue dos not arise, but how long do you want to allow the target to drift across your field of view!

That said, the Starguiders work well down to f/5 and  (for example) the Tele Vue Delos EP's are tested at f/4 so, unless you try  for yourself,  you may not appreciate how little difference there could be between the two eyepieces, considering what they are and what you pay for them.  I found  little or no real  benefit with  72° afov,  over my 60° afov, and my eyes actually prefer the present afov. The only downside for me was by having too much field, and with more field, the target object is infinitely smaller, whereas I want my Jupiter to look as large as possible with little space/field. around it.

It takes time to find what suits and what you feel is the best. Of all the eyepieces the have passed through my hands, I still favour the BST's on my f/6 and have had no regrets selling ANY of the other eyepieces or those waiting to be sold ?

You will at some stage, find what's right and will build up from there! 

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1 hour ago, Charic said:

.... The only downside for me was by having too much field, and with more field, the target object is infinitely smaller, whereas I want my Jupiter to look as large as possible with little space/field. around it....

I respect your choice / preferences in eyepieces Charic but I feel that I ought to point out when you view a target with an eyepiece of a certain focal length, the actual linear size of the target in the field of view remains the same regardless of the apparent field of view. It does not get smaller (infinitely or otherwise!) just because the apparent field of view is larger.

What does change is the extent of background sky framing the target and folks have varying preferences on that I know.

I think this illustration shows what happens when eyepieces of the same focal length, but different apparent fields of view are used on the same target (in this case M31, the Andromeda Galaxy):

 

post-208787-0-16816800-1440090662.jpg

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This is true, and I think a good analogy is when looking at the moon when I it's near the horizon, it looks much bigger than when it's high in the sky.

High in the sky it is isolated in an open void of space, whilst on the horizon it is framed by close objects like distant trees or buildings that it dwarfs.

Just an optical illusion.

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2 hours ago, John said:

I think this illustration shows what happens when eyepieces of the same focal length, but different apparent fields of view are used on the same target (in this case M31, the Andromeda Galaxy):

 

Can't argue with that!

As Geoff puts it, I must be suffering from the 'optical illusion' ......that the image appears smaller, but it's clearly not, just the field is wider.

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On 12/12/2018 at 11:22, John said:

opt for the 24mm 82 ES instead of the Nirvana ?

vg suggestion John, an eyepiece such as the 24Es 82 is just right for so many things in the 10" f4.7 scope. My 10" is cooled, waiting for me out there and I wish I had one!

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Well  had my new 16mm lens out last night, did not  get  much stargazing  in because of bad seeing but  I did manage to get some views of the Orion nebula ( very good but hazy due to fine cloud ) and got some wonderful views of the moon ( I need a moon filter badly as I nearly went blind ). With this eyepiece the moon was fantastic, bright and detailed and absolutely no signs of CA or any other distortion ( it was even more detailed with my Tele extender ) and once I had got used to the eye positioning there was no problem with blackouts and I could see very well to the edge of the image.

 If this eyepiece works just as well when I get a good night viewing of the stars ( and a few galaxy's plus nebula's ) I will be buying the 7mm version as well. I will  report back  again when I get some more viewing in with this eyepiece.

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