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Eyepieces for SW Heritage 150P Dob


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Did you mean the Nirvana 16mm UWA?  If so, my understanding is that it is decent at f/5, but not outstanding.  Remember, these were selling here in the US under some brandings for about $65 6 or 7 years back.  Don't expect 16mm Nagler T5 performance in your scope.  Also, remember it only has about 10mm of usable eye relief; so you won't be able to use it with eyeglasses.

If you can pick up a used one for roughly 65% of new, I'd say it's a pretty good deal.

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6 hours ago, DhamR said:

Thoughts on the Nirvana 18mm?  I've seen a used one and thinking of snapping it up.

According to the various field of view visualisers it'll give a very similar field to my 25mm, but I assume it'll be a large step up in quality and ease of viewing

I use the Nirvana 16mm in the Heritage 150P and find it pretty good, although I've no experience against dearer glass. Mine's the older type with a twist-up cup, which I tend to use partway up. I don't wear glasses at the EP but I can see they would be an issue. I've also used it in the 114P (f/4.4) and it's still usable in that.

Edited by wulfrun
typo
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I don't tend to wear glasses when viewing, can't get close enough with my current EPs, so this won't change things from my perspective.

Are the edges notably poor?  I'm guessing I'd still see a huge improvement from the stock 25mm Super.

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2 hours ago, DhamR said:

Are the edges notably poor?  I'm guessing I'd still see a huge improvement from the stock 25mm Super.

No and yes, respectively. Stock 25mm gives x30 at about 1.7-degrees TFOV, the 16mm would give x37 & 1.75-degrees. I haven't noticed the edges to be noticeably poor but I don't have anything exotic to compare it to.

Edited by wulfrun
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Thank you, very much appreciated.  I like this field view, so whilst I was possibly going to go more mag first this will (with a barlow) be an upgrade on both my existing EPs.

Unless anyone can see anything obvious wrong with that approach.

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18 hours ago, Louis D said:

Did you mean the Nirvana 16mm UWA?  If so, my understanding is that it is decent at f/5, but not outstanding.  Remember, these were selling here in the US under some brandings for about $65 6 or 7 years back.  Don't expect 16mm Nagler T5 performance in your scope.  Also, remember it only has about 10mm of usable eye relief; so you won't be able to use it with eyeglasses.

If you can pick up a used one for roughly 65% of new, I'd say it's a pretty good deal.

Missed this earlier, is it only the edges that suffer at f/5 or across the range?

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28 minutes ago, DhamR said:

Missed this earlier, is it only the edges that suffer at f/5 or across the range?

From my reading of Ernest's tests coupled with user reports, it's quite sharp in the inner 70%, and then dropping off in the outer 30% at f/4 due to astigmatism and field curvature.  It would be slightly better at f/5.  If you keep an object centered and concentrate your attention on axis, you might never notice the aberrated edges.

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As an upgrade from stock EPs I'm sure you'll be happy with the Nirvana. You could get similar image improvements for less outlay with other eyepieces (BST Starguiders, etc.), but with a narrower FOV. If you really like the 82° experience, I think the Nirvana is good value.

I was lucky to pick up a 16mm second hand and I use it in an F/5 reflector. I'm very happy with it (and later added the 4mm on the strength of it). Just looking back on my observing notes, I see that I compared it favourably with my 10mm Celestron Ultima Edge (itself a decent EP) when used on M42; the view of the Perseus double cluster was very impressive - sharp, contrasty and wide; and it gave me my best views so far of M31 and M33 (OK, still very fuzzy with 150mm in Bortle 4). On the negative side: I did notice some edge effects, though only on some targets, and I couldn't decide if it was eyepiece astigmatism or scope coma; I saw a little edge field curvature, in a full field, when I looked for it (but it's not something I notice most of the time); the eye relief is only average - I do find it comfortable to use, but it wouldn't allow eyeglasses; and there is some kidney beaning, so you need to get used to positioning your eye correctly (I don't find it an issue).

No doubt a more experienced eye (and thicker wallet) would be able to tell you how much it is surpassed by premium competitors. The most expensive that I have to compare it with is an Explore Scientific 82° 6.7mm. I judge the Nirvana experience to be as good; in one respect I think it has the advantage - I find its views to be brighter than with the ES. It also weighs noticeably less.

And as a replacement for the stock eyepieces with respect to field, yes, you can get a similar TFOV to a longer EP having a narrower AFOV. That also has the advantage that you're getting that view with a narrower exit pupil, which can mitigate some of the effects of light pollution and improve the contrast. The only downside I can think of is that nebula filters often work better with larger exit pupils, so you may still end up getting a more direct replacement for the 25mm at some point down the road.

Edited by Zermelo
added "Edge"
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I recently have the Virtuoso heritage 150p and after some research and valuable recommendations i added the svbony 7-21mm and  then the BST StarGuider 60º 5mm ED for close ups of Jupiter and Saturn 

I'm really happy with that combo so far along with the stock 25mm

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This Angle/FoV business ontop of the magnification factor is making my head hurt.

I'm using https://astronomy.tools/calculators/field_of_view/?fov[]=10054|67|||1||&fov[]=10054|68|||1||&fov[]=10054|806|||2||&fov[]=10054|105|||1||&fov[]=10054|806|||1||&fov[]=10054|122|||1||&solar_system=moon to get a feel for the range I'm looking at.

 

16mm Nirvana

Even if the edges are a bit iffy, it'll help finding things, and I feel like the immersion factor is pretty cool. FOV-wise it seems to replace the 25mm that came with the scope, which is my most used EP.

Next decision is based on things I'm seeing available second hand really, thinking being I'm not sure how I'll get on with them, so if I buy second hand I shouldn't lose too much cash if I dislike them.

 

Barlow the 16mm Nirvana

This (in my head at least) will reduce edge iffiness, and concentrate on the central portion of the EP where it's good, at the cost of light collection, maybe a bit of vignetting.  Will it mess up my idea of parfocality? Will I need to rack the focus back in to use the barlow?

 

8mm Starguider

Alternative option - well loved EPs from what I can see, would be a slightly higher power replacement of the 10mm, but mag (ignoring angle of view) sits bang on the barlowed mag of the 16mm Nirvana.

 

You'll also see a 40mm Plossl on there, but only because I've seen one going and wonder what that size exit pupil and light-catching ability would be like.

 

Edited by DhamR
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The Barlow will likely cleanup the edges of the 16mm Nirvana.

The Barlow will likely require refocusing unless you get a telecentric magnifier like a TV Powermate.  There may also be vignetting, but you won't know until you try them together.  A telecentric magnifier will not vignette.

A 2x Barlow may not really be 2x, and certainly won't be for all eyepieces.  Even those that are bang-on 2x when the eyepiece focal plane is right at the reference plane (eyepiece shoulder) will be some other power if the eyepiece focal plane is above or below the reference plane.  Thus, it's not a foregone conclusion that you will get exactly an 8mm equivalent with the combination.

Swapping in a Barlow and refocusing is a pain in the dark.  I prefer to leave the Barlow in all night if I am using one and work at elevated powers across all eyepieces.

A 40mm Plossl in a 1.25" barrel yields a fairly narrow apparent field of view with very long eye relief but nets you a slightly larger exit pupil in the process.

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Struggling for responses from the seller on the Nirvana I've been looking at. 

Someone else is selling the Celestron X-Cel LX 25mm for a good price though, which is appealing. The UFF was mentioned in here but not the x-cel range. Any thoughts? 

Edited by DhamR
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On 31/01/2022 at 23:57, DhamR said:

Struggling for responses from the seller on the Nirvana I've been looking at. 

Someone else is selling the Celestron X-Cel LX 25mm for a good price though, which is appealing. The UFF was mentioned in here but not the x-cel range. Any thoughts? 

I have had the x cel 25, i liked it as i remember but i had far less experience back then (10 years since) and i was more planetary then as they were easier to find 🤣

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If the 25mm X-Cel LX is the same as the 25mm Meade HD-60 which I do have, it should be a decent eyepiece.  It's better corrected at f/6 than the 25mm BST Starguider, but it has a slightly smaller true field of view.

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9 hours ago, cajen2 said:

@Louis D , would you expect any significant improvement in EOF aberrations for the Nirvana in an F/6 scope?

That's a loaded question.  Over the same ~60° field of view, I would expect the Nirvana to be better since that's still within the 75% inner area of Nirvana.  Over the entire field of view, I would expect the X-Cel LX to be better since 60° is easier to correct than 80° while on a budget.

There's a lot more at play here, though.  At 60° and a lower power, you'll be more easily able to appreciate the view in one glance.  The eye relief will be much longer, making the view more relaxing.  However, the background sky will be brighter making nebula and globular clusters less contrasty.  At 80° and higher power, you'll have to move your gaze around the field to take it all in in more detail.  This will be made harder by the shorter eye relief as you have to move your head to maintain exit/entrance pupil alignment.  On the plus side, the background sky will be darker, improving contrast on fuzzy objects.

I would get the XCel LX if it's available for a good price at the current time.  Just ask about black flecks in the field of view.  There have been multiple reports of blackening paint flaking off onto interior lenses, messing up the view of the moon and the sun (observed with a proper solar filter, of course).

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Having owned the full set of Xcel- LXs I can say they were nice eyepieces for the money although lately they have shot up in price a lot and not such a good buy anymore. Can be found cheap second hand though.

The Nirvanas are sharper though and find the views very good in a f/6 scope. Great eyepieces for the money.👍🏻

 

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I can get two xcels second hand for the price of two bst's brand new, warranty, box etc. Plus if I go with the starguiders I have my pick of focal lengths. That's the only thing stopping me really. 

BSTs feel like the unimaginative option though 😂 

Edited by DhamR
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I've received a used Nirvana-ES UWA 16mm today from the classifieds here and it's lovely thing (thank you seller).

Have tested it out on a neighbour's roof and the field of view is similar to the 25mm as expected, but so much bigger, much better contrast and colour, and it appears crisper too although hard to tell as I wasn't being too picky about focus when swapping from one to the other.

I struggled with what I assume is pupil constriction in daylight though, getting black patches in the opposite side of the view if I moved my eye off-centre or even looked towards the edge of the field (is this what's called kidney-beaning?).  Assuming this won't be so bad in the dark, but it was avoidable even if it is, just might not be very good for showing family/friends.

Can't wait to get out and use it.  Thursday night looks good 🤞 

Edited by DhamR
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I'm sure it will perform as well in the dark.

I did say above that I experience some kidney beaning with mine. I've just searched on this and others have reported the same with that EP, though I also found this thread that distinguishes between kidney beaning and similar effects. Kidney beaning, unsurprisingly, shows as a kidney bean shape:

435932447_kidneybeaning.jpg.33c58230fc5998ad1e74dbc03a50033a.jpg

I think the effect will be more jarring on daytime use, because of the brightness difference.

I have gotten used to mine. It does mean you have to train yourself to keep your eye reasonably steady so, as you say, it might not be the ideal EP for sharing with a complete novice. Being seated rather than standing makes it much easier (apart from the advantages to observing in general).

 

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Have done a bit of research and found a post on "some website" that explains it really well visually.

Also explains that it should be less of an issue when the eye is dark-adapted, as your eye aperture is bigger:

 

 

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So, I've read through this thread (a couple of times now) and it's been really good in helping me think about a decent (but not too pricey) low power eyepiece for my Skywatcher 8" f6 dob. I've just invested in a zoom lens (Celestron 8-24mm) and think that between this and my 2x Barlow I have the high-medium power range covered, so I'm looking to fill the gap at the "DSO/ wide-field/ first EP to slot in the scope at the start of a session" range.

@BomberBaz had me hooked at the idea of a ES 26mm 62degree purchase (£99) and I loved his logic, but the Vixen NPL 30mm 50 degree option at £49 sounded great value, both of which seemed to trump my initial thinking that the BST Starguider 25mm at 60 degrees and £49 was the best first dabble in the 'upgrading my eyepiece' journey. I'm still undecided, can anyone help, especially as I had nearly clicked the 'buy now' button on a TeleVue 32mm Plossl with 50 degree afov for £149 (about as far as I'd be prepared to invest at this stage and I'm sure there's a bit of brand attraction pulling me to that green logo from all of the TeleVue love I've read on here)?

I know it's not the biggest investment and that there is probably no right or wrong answer, but I think the quality of my stock 25mm is decent and have no idea what difference this will make to my visual enjoyment or, indeed, whether spending a bit more to get an even wider afov is what makes better sense, given that I am still very new, but loving this hobby and see myself doing it for years to come. 

Of my options would you say there is much to choose from, any I should steer clear of or if my afov ambition should go wider than 62?

Jim

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The first thing is that the stock 25mm/26mm plossl is usually not that bad to start out with, and some people don't prioritize its replacement. But that depends on your wallet.

Second, and I may take some flack for this, but a TeleVue plossl is not a TeleVue Ethos, even if it is green and black. I've never used one, but I wouldn't pay a £100+ premium over other decent equivalents, as a beginner. There are better places to put your pennies.

I do use the 30mm NPL and it's a nice eyepiece. The longest BST Starguider is 25mm, and that one has been reported by a few people as perhaps the weakest in that series, because of edge performance. So I went for the NPL over the BST, but otherwise I like the Starguiders.

On the widefield question, only you can decide whether you want 50, 60, 82 degrees for your long eyepiece. And until you've tried it, you really won't know. Some people just don't get on with anything over 70 degrees. If you can borrow an eyepiece or two, or get someone at a local club to let you try before you buy, that would be worth doing.

There are different factors that you're trading off in that decision. The longer the EP focal length, the larger the exit pupil. That's good if you're using a nebula filter, but otherwise it makes the sky lighter and reduces contrast. Uncorrected eye astigmatism can also show up worse. A wider apparent field of view allows you to get a larger true field of view with a shorter focal length than you would otherwise achieve (reducing the previous effects) - useful for a "finder" eyepiece. But those wider eyepieces, if they're any good, will also be more expensive than your regular 32mm plossl.

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