Wider FOV 68 Vs 82 Degree for a fast scope

[badhex]

I'm also generally very happy with 65-80ish FOV in terms of eye placement, so in that AFOV range I would give plus one over here for the 24mm UFF for lowest power/widest field in 1.25". I have the APM version but they are all the same optically (and the StellaLyra is the least expensive - top marks FLO). 

At a slightly higher power I would also strongly recommend the Morpheus 17.5mm which is nominally 76° -  absolutely top notch EP and pretty much my favourite EP ever. I can't speak for the Nirvanas as I don't have one, but if you do plump for the 16mm I'd certainly be interested to hear how it pans out, roughly the same TFOV as the Morpheus with a very slightly smaller exit pupil. 

 

[bosun21]

14 hours ago, Louis D said:

No SAEP in the SVBONY Redline 20mm, if that's what you're alluding  to.  Notice there's no significant shadowing in it's AFOV image in the third row, far right.

It is a poor performer in the outer field below f/8 for certain.  However, at f/18 in my binoviewer, they are terrific as a binoviewing pair for eyeglass wearers.

Here's my write-up on it:

 

That’s not my experience with the 20mm SVbony 68 degrees. I found it extremely difficult to keep the full FOV in view and the slightest movement caused kidney beaning. I gave it and the 9mm away to a scouts group. Maybe it’s how I observe differs from yours, but it was definitely not suited to me. PS I don’t wear glasses and have no astigmatism.

[Ratlet]

37 minutes ago, badhex said:

I'm also generally very happy with 65-80ish FOV in terms of eye placement, so in that AFOV range I would give plus one over here for the 24mm UFF for lowest power/widest field in 1.25". I have the APM version but they are all the same optically (and the StellaLyra is the least expensive - top marks FLO). 

At a slightly higher power I would also strongly recommend the Morpheus 17.5mm which is nominally 76° -  absolutely top notch EP and pretty much my favourite EP ever. I can't speak for the Nirvanas as I don't have one, but if you do plump for the 16mm I'd certainly be interested to hear how it pans out, roughly the same TFOV as the Morpheus with a very slightly smaller exit pupil. 

 

Hmmm.

I hadn't spotted the Stellalyra.  That would be a better fit in terms of my current magnifications as it is very close to the middle between the 32mm and 12mm... 

I will add that one to my list.  I'm not trying to grow my ep collection (deliberately) but it is nice to see the differences so I can understand the equipment.

I will update the thread once I get the nirvana.  I'm really wanting to get an observing chair and the low cost of the geoptik nadira has freed up the cash to make it affordable, unfortunately it is not in stock.

[bosun21]

1 minute ago, Ratlet said:

Hmmm.

I hadn't spotted the Stellalyra.  That would be a better fit in terms of my current magnifications as it is very close to the middle between the 32mm and 12mm... 

I will add that one to my list.  I'm not trying to grow my ep collection (deliberately) but it is nice to see the differences so I can understand the equipment.

I will update the thread once I get the nirvana.  I'm really wanting to get an observing chair and the low cost of the geoptik nadira has freed up the cash to make it affordable, unfortunately it is not in stock.

Try RVO

[Ratlet]

3 minutes ago, bosun21 said:

Try RVO

Unfortunately they are oos.  

I'd rather build one tbh, but the financial controller has required me to decorate the bairns bedroom prior to the release of funds so don't have the time to do it myself.

Edited January 28, 2023 by Ratlet

[Don Pensack]

18 hours ago, Louis D said:

The 6mm and 9mm versions certainly do suffer from SAEP.  Both also perform fairly well in faster scopes.  The reason for both results is the 6 and 9 employ a Smyth lens group to amplify the focal length.  This slows down the light cone, improving edge performance.  However, the matching of the Smyth and image forming groups was poorly done, leading to SAEP.

The 15mm and 20mm versions have no Smyth group.  They are purely positive designs which rarely suffer from SAEP.

Barlows tend to push out the eye relief and induce SAEP in my experience.  Both make holding the exit pupil more difficult.  This may be what you're experiencing with the Barlowed 32mm.  If you used a telemagnifier like a TV PowerMate instead, you would not experience either issue.

Note that the presence or absence of a negative lens below the positive section is not what leads to SAEP.

Many all-positive designs also have that, as your own images reveal.

Many all-positive designs have it because it was not a characteristic looked at by the designers.

That does not mean many negative/positive designs don't have it, because they do, but carefully-designed ones have little or none, also as some of your images reveal.

 

Edited January 28, 2023 by Don Pensack

[Don Pensack]

4 hours ago, Ratlet said:

Hmmm.

I hadn't spotted the Stellalyra.  That would be a better fit in terms of my current magnifications as it is very close to the middle between the 32mm and 12mm... 

I will add that one to my list.  I'm not trying to grow my ep collection (deliberately) but it is nice to see the differences so I can understand the equipment.

I will update the thread once I get the nirvana.  I'm really wanting to get an observing chair and the low cost of the geoptik nadira has freed up the cash to make it affordable, unfortunately it is not in stock.

Look at the Berlebach Charon--it has a wider range of adjustment and works with more scopes.

[Ratlet]

1 hour ago, Don Pensack said:

Look at the Berlebach Charon--it has a wider range of adjustment and works with more scopes.

That was my original pick but the Nadira seemed to have it's own fans and at almost half the cost of the Charon.  It looks like it will be good for binocular astronomy too as the strap can be adjusted for an almost lying back position.  My only concern is that the rear support leg looks quite narrow and I'm a little concerned that it might sink in the soft grass in my back garden and become unstable.  Could be easily modified with a bit of wood if it is the case.  I do like the idea of owning something Berlebach though.

This is technically a treat for myself and the wife is getting a mobile phone which will far exceed the value of my humble purchases (so long as you don't look at the previous 12 months) so perhaps a treat is in order...

[PeterC65]

13 minutes ago, Ratlet said:

That was my original pick but the Nadira seemed to have it's own fans and at almost half the cost of the Charon.  It looks like it will be good for binocular astronomy too as the strap can be adjusted for an almost lying back position.  My only concern is that the rear support leg looks quite narrow and I'm a little concerned that it might sink in the soft grass in my back garden and become unstable.  Could be easily modified with a bit of wood if it is the case.  I do like the idea of owning something Berlebach though.

This is technically a treat for myself and the wife is getting a mobile phone which will far exceed the value of my humble purchases (so long as you don't look at the previous 12 months) so perhaps a treat is in order...

I have the Nadira. It's a good chair but the back and seat are quite narrow. Because the adjustment slots span about 2/3rds of the width of the back, and because I'm fat (18.5 stone), I found that the back flexed in a rather unnerving way, particularly when the seat was in the higher positions. The seat is also narrow, sufficient, but not that comfortable.

So I've pimped mine ...

 

 

[Don Pensack]

22 hours ago, PeterC65 said:

I have the Nadira. It's a good chair but the back and seat are quite narrow. Because the adjustment slots span about 2/3rds of the width of the back, and because I'm fat (18.5 stone), I found that the back flexed in a rather unnerving way, particularly when the seat was in the higher positions. The seat is also narrow, sufficient, but not that comfortable.

So I've pimped mine ...

 

 

Nice wood work!!

[Ratlet]

22 hours ago, PeterC65 said:

I have the Nadira. It's a good chair but the back and seat are quite narrow. Because the adjustment slots span about 2/3rds of the width of the back, and because I'm fat (18.5 stone), I found that the back flexed in a rather unnerving way, particularly when the seat was in the higher positions. The seat is also narrow, sufficient, but not that comfortable.

So I've pimped mine ...

 

 

That's fantastic!  Curious as to how it fits together at the back

[PeterC65]

1 hour ago, Don Pensack said:

Nice wood work!!

It's now very sturdy, but also very heavy!

[PeterC65]

1 hour ago, Ratlet said:

That's fantastic!  Curious as to how it fits together at the back

Here's the view from behind ...

and from under the seat ...

The seat still slots in to its storage space at the top of the back as I re-used the original seat (actually I made it slightly narrower) and the side rails extend beyond the original back by the width of the original seat. Quite a lot of thinking went in to the re-design!

I replaced the extending leg partly for aesthetic reasons and partly to make it a little thicker.

Since I took these photos I've also make a foot rest. It's like the seat but only extends from the back by 3". I've found it very useful when the seat is at the top of its adjustment which is how I mostly use it.

 

[Guest]

On 28/01/2023 at 12:10, PeterC65 said:

I have the Nadira. It's a good chair but the back and seat are quite narrow. Because the adjustment slots span about 2/3rds of the width of the back, and because I'm fat (18.5 stone), I found that the back flexed in a rather unnerving way, particularly when the seat was in the higher positions. The seat is also narrow, sufficient, but not that comfortable.

So I've pimped mine ...

 

 

Now that is cool. 

[Louis D]

Did you use mahogany wood?  It looks beautiful.

[PeterC65]

5 hours ago, Louis D said:

Did you use mahogany wood?  It looks beautiful.

I did use mahogany, reclaimed when next doors replaced their French doors, so no (further) damage to the Rain Forrest.

 

[bomberbaz]

I have only read a few of the posts so sorry if I am repeating others.

I have actually been looking at eyepieces tonight potentially for an F5.5 frac and so could be right in the bolt hole with what I am commenting.

These are something new but are a clone of APM UFF's:  StellaLyra Telescope Eyepieces for Sale Online | First Light Optics, the ultra flat field versions. 

I am drawn to the 30mm for my needs but I already own the APM 24,18 & 10 versions which get used in an F4.7 pair of bins. (I also use a 24mm in my F4.8 dob)

They are simply superb to use but the only downside is the FOV isn't giving you a lot more than you already have, nothing in the case of the 10mm.

However what they are superb and will give you pretty much a flat, well correct image across the entire fov.

Something a lot of people overlook is that a well corrected eyepiece with a narrower FOV (65 degree in this case)  is actually giving you a better return than a poorly corrected UWA type eyepiece. EG 100% performance of 65 degree is 65, 75% of 80 is 60. 

Given you are using an F5  OTA then consideration of performance needs to be top next to price.

[Ratlet]

1 hour ago, bomberbaz said:

I have only read a few of the posts so sorry if I am repeating others.

I have actually been looking at eyepieces tonight potentially for an F5.5 frac and so could be right in the bolt hole with what I am commenting.

These are something new but are a clone of APM UFF's:  StellaLyra Telescope Eyepieces for Sale Online | First Light Optics, the ultra flat field versions. 

I am drawn to the 30mm for my needs but I already own the APM 24,18 & 10 versions which get used in an F4.7 pair of bins. (I also use a 24mm in my F4.8 dob)

They are simply superb to use but the only downside is the FOV isn't giving you a lot more than you already have, nothing in the case of the 10mm.

However what they are superb and will give you pretty much a flat, well correct image across the entire fov.

Something a lot of people overlook is that a well corrected eyepiece with a narrower FOV (65 degree in this case)  is actually giving you a better return than a poorly corrected UWA type eyepiece. EG 100% performance of 65 degree is 65, 75% of 80 is 60. 

Given you are using an F5  OTA then consideration of performance needs to be top next to price.

Cheers baz, this ties in with part of what I'm looking to do with getting the wide angle.  I'm trying to figure out what works best for me.  I'm absolutely satisfied with my 60° FOV at the moment and I'm stepping up to 82° purely out of curiosity and dip my toe in. 

Chances are in a couple of months a flat field will be on the cards.  Never tried a flat field before so it'll be interesting to see what difference it makes and if that's what I'm looking for. 

I'm enjoying the learning process immensely, even if my initial expectations are usually wrong.  But flat field is definitely something I'm wanting to look into.

[Ratlet]

So having bedded in with the Nirvana 16mm I'm finding that at the edge of view the image quality is quite poor and the stars are pretty out of focus/smeared with my 10" F5 dob.

Is this likely to be something I'm doing, such as my collimation or scope cooling? Or is it just the nature of the eyepiece?  Would it be helped if I tried focusing on a star midway on the FOV rather than dead centre?  I've got mild astigmatism (0.75 diopter) but I'm getting contact lenses to correct this but haven't had a chance to try them out yet so possibly that is a factor.

It's still a great eyepiece, and has provided wonderful views, but sometimes it feels like the outer edge distortion is really apparent for some reason.

I'm currently just playing with eyepieces mostly to figure out what works for me and I was thinking the next would be an ultra flat, initially looking at the 30mm Stellalyra UFF to replace the 30mm superview.  I'm now thinking it might be an idea to try a 15 or 18mm ultraflat instead if anyone has experience of them.  I tend to mostly observe with the 16mm so it does kind of make more sense for comparative purposes.

Feedback greatly appreciated.

[Ags]

i owned a Nirvana 16, and found its edge performance very poor even at f13.

[bosun21]

12 minutes ago, Ratlet said:

So having bedded in with the Nirvana 16mm I'm finding that at the edge of view the image quality is quite poor and the stars are pretty out of focus/smeared with my 10" F5 dob.

Is this likely to be something I'm doing, such as my collimation or scope cooling? Or is it just the nature of the eyepiece?  Would it be helped if I tried focusing on a star midway on the FOV rather than dead centre?  I've got mild astigmatism (0.75 diopter) but I'm getting contact lenses to correct this but haven't had a chance to try them out yet so possibly that is a factor.

It's still a great eyepiece, and has provided wonderful views, but sometimes it feels like the outer edge distortion is really apparent for some reason.

I'm currently just playing with eyepieces mostly to figure out what works for me and I was thinking the next would be an ultra flat, initially looking at the 30mm Stellalyra UFF to replace the 30mm superview.  I'm now thinking it might be an idea to try a 15 or 18mm ultraflat instead if anyone has experience of them.  I tend to mostly observe with the 16mm so it does kind of make more sense for comparative purposes.

Feedback greatly appreciated.

The Morpheus 17.5mm is a better eyepiece than the UFF 18mm. I owned the later and sold it due to the lack of sharpness at the edges. The 30mm UFF is the best of that particular range.

[Mr Spock]

The Nirvana 16mm has field curvature - definitely the runt of the litter as the others are fine.

[Ratlet]

I had a look at some of the other posts discussing the uff eyepieces.  They are quite informative.  There was a link to Ernst's eyepiece reviews where he quantifies the amount of aberration in the eyepieces.  The 15mm seems to be a better performer than the 18mm, although the 17.5mm Morpheus is better than both. The 16mm nirvana is nowhere near as well corrected as any of the others.

I think I need to take my existing eyepieces out and get a feel for what I consider acceptable correction with what I've got already and try to relate that back to Ernst's tables.  I think the 15mm to 18mm would provide a decent framing for a lot of DSO in the dob.

Also need to get a better bead on how I feel about the wider FOV in general.  It's nice for panning about but I'm trying to make a push with my sketching and I found the 82° FOV was quite challenging, especially with the distortion.  I suspect that about 70° is about the sweet spot.

Quite enjoying this mucking about with eyepieces.  It's interesting to see the differences they make to the experience beyond magnification.  Really appreciate the help and feedback.

[John]

57 minutes ago, Ratlet said:

...Quite enjoying this mucking about with eyepieces.  It's interesting to see the differences they make to the experience beyond magnification.  Really appreciate the help and feedback.

I agree - because eyepiece preference is such a personal thing, if you can actually try a few alternatives out for yourself it really helps in working out what ticks your personal boxes. Thank goodness for the used equipment market ! 🙂

[johnturley]

11 hours ago, Ratlet said:

 

I'm currently just playing with eyepieces mostly to figure out what works for me and I was thinking the next would be an ultra flat, initially looking at the 30mm Stellalyra UFF to replace the 30mm superview.  I'm now thinking it might be an idea to try a 15 or 18mm ultraflat instead if anyone has experience of them.  I tend to mostly observe with the 16mm so it does kind of make more sense for comparative purposes.

Feedback greatly appreciated.

I can recommend the Stellalyra 30mm UFF, it works quite well in my f5 Newtonian, although the edge is not perfect, it is vastly superior to my 36mm Baader Hyperion Aspheric. 

John