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upgrading eyepiece for wide field views in light pollution

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#1 Willarkin

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Posted 07 December 2021 - 05:16 PM

I've bought a 90mm Astroview refractor and I am enjoying learning to star walk. I have suburban light pollution of Bortle 7. I'm looking to upgrade the 25mm eyepiece for a better wide field view- ideally, an eyepiece which would make the background sky darker and bring out more stars if that's possible, with more contrast and sharpness in the images. I'm also interested in a wider-looking field, more immersive.

 

I'm looking at the BST Starguider 60 degree 25mm - I can get it for £45. Then there's the Explore Scientific 68 24mm - at £155, over three times the price. Beyond that are eyepieces like Tele Vue which are intriguing but look well beyond my price range. 

 

Money is the issue - should I go for the BST - or wait and save up for something 3 times more expensive? Is it worth the bigger investment? For the price of one ES eyepiece, I could get 3 BSTs. Any advice from anyone who has used the eyepieces gratefully received!

 

Thanks


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#2 Tony Flanders

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Posted 07 December 2021 - 05:45 PM

I've bought a 90mm Astroview refractor and I am enjoying learning to star walk. I have suburban light pollution of Bortle 7. I'm looking to upgrade the 25mm eyepiece for a better wide field view- ideally, an eyepiece which would make the background sky darker and bring out more stars if that's possible, with more contrast and sharpness in the images. I'm also interested in a wider-looking field, more immersive.


The 25-mm Sirius Plossl that is packaged with the Orion Astroview 90-mm EQ Refractor is quite a respectable eyepiece; improving on it significantly isn't all that easy. In particular, no 25-mm eyepiece is going to show a significantly darker sky background -- for that you need to travel to a darker location.

A higher-power eyepiece would indeed show a darker background and fainter stars, as I'm sure you can verify by comparing the same star field through your 25-mm eyepiece and your 10-mm eyepiece. The downside of higher magnification, of course, is that it's hard to achieve without getting a significantly smaller true field of view.

 

I hesitate to recommend specific eyepieces, because eyepiece preferences are so individual. For instance my own eyes don't take kindly to the Explore Scientific 68-degree 24-mm eyepiece -- nor, for that matter, the 24-mm Panoptic. It's not that they're bad eyepieces; quite the contrary. But I find their eye relief annoyingly short; I cannot really see the full field of view even with my eyeglasses off, and certainly not with my glasses on. By contrast my eyes immediately made friends with the Explore Scientific 62-degree 26-mm, and my 27-mm Panoptic is perhaps my single favorite eyepiece. Moral being that brand names prove nothing!

 

So the only truly reliable way to know if you will like an eyepiece is to look through it yourself. For what it's worth I find the difference between a 50-degree field of view and a 60-degree field of view to be much more significant than the difference between a 60-degree field of view and a 68-degree field of view. But even that depends on the specific eyepieces in question; not all 60-degree fields of view are made alike.


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#3 CowTipton

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Posted 07 December 2021 - 06:09 PM

Tony covered it I think.

 

-Darker background will come from darker skies or more magnification

 

I believe your scope is 1.25" focuser only so maybe something like a 20mm 70° eyepiece.  That should be a little darker and a little wider than your 25mm plossl.

At F10 or so it shouldn't be too expensive to get good performance at an affordable price since that is a fairly forgiving focal ratio.


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#4 SeattleScott

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Posted 07 December 2021 - 07:13 PM

Yes to get darker background sky, bring out more stars, you need a shorter focal length eyepiece. That being said your 25mm already has a rather small exit pupil for F10 so I’m not sure how much higher power it really makes sense to go. Low power is about finding targets and framing the big stuff. Normally you locate something and then you increase magnification to resolve it better. So I wouldn’t worry about more magnification for low power. You could get a bit wider view with the BST or Xcel LX 25mm. Then switch to medium or high power to resolve more stars.

Scott
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#5 sevenofnine

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Posted 07 December 2021 - 10:55 PM

Welcome to C/N! welcome.gif

 

I recommend taking a different approach. Build a small collection of good quality eyepieces and plan for trips to a dark location. Study a dark sky map of your local area and see if Bortle 3-4 (or better) is doable. In your Bortle 7 skies you will have to settle for bright objects like the Moon, planets and the bright DSO's. At your dark site, you will see the wonders. Good luck! waytogo.gif


Edited by sevenofnine, 07 December 2021 - 10:57 PM.


#6 Mr.Furley

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Posted 08 December 2021 - 11:49 AM

If you are set on getting a new EP my vote is on ES68 20mm, you will get a slightly larger fov than the 25mm 52* while darkening the background sky and providing higher magnification. I really enjoy this EP although I'm using it in much different scope.

This is a great tool to compare eyepieces, play around with it a bit.

https://astronomy.to.../field_of_view/

#7 vtornado

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Posted 08 December 2021 - 08:13 PM

There is an expanse 20mm eyepiece with a 66 degree field of view.

I have not used one, and I know they are maligned in fast scopes

If you have an f/10 scope it may perform acceptably.

If you can find a used one here, you could resell for about what you pay if you don't like it.

 

VT.


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#8 Dave Mitsky

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Posted 09 December 2021 - 01:18 AM

How about an 18mm APM UFF, 18mm Meade Series UHD, or Celestron 18mm Ultima Edge?  These are all fundamentally the same eyepiece with a 65-degree AFOV and ample eye relief.  Any one of them will produce a TFOV similar to the 25mm Plössl that you have but at higher magnification and with a darker background field. 

The 20mm Explore Scientific 68-degree will better them all in TFOV but not eye relief and has become pretty expensive of late.


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#9 Paul Sweeney

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Posted 11 December 2021 - 02:12 PM

Try the 23mm Aspheric eyepiece. I have one and it works well in long focus scopes. It has a 63° fov and only costs about $10, delivered direct from China.

#10 aeajr

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Posted 12 December 2021 - 09:32 AM

I've bought a 90mm Astroview refractor and I am enjoying learning to star walk. I have suburban light pollution of Bortle 7. I'm looking to upgrade the 25mm eyepiece for a better wide field view- ideally, an eyepiece which would make the background sky darker and bring out more stars if that's possible, with more contrast and sharpness in the images. I'm also interested in a wider-looking field, more immersive.

 

I'm looking at the BST Starguider 60 degree 25mm - I can get it for £45. Then there's the Explore Scientific 68 24mm - at £155, over three times the price. Beyond that are eyepieces like Tele Vue which are intriguing but look well beyond my price range. 

 

Money is the issue - should I go for the BST - or wait and save up for something 3 times more expensive? Is it worth the bigger investment? For the price of one ES eyepiece, I could get 3 BSTs. Any advice from anyone who has used the eyepieces gratefully received!

 

Thanks

 

Since you are asking about eyepieces, these will provide good background.

 

Understanding Telescope Eyepieces- There are recommendations, based on budget,
but the meat of the article is about understanding the considerations and specifications
to know when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

Understanding and using a Barlow Lens
https://telescopicwa...ens-and-how-to/

 

 

The BST Starguider 60 degree is known in the USA as the AT Paradigm (Sold by Astronomics) and the Agena Astro Starguider, all very respected eyepieces.

 

Discussion about Paradigm eyepieces
https://www.cloudyni...s/#entry8229760

Plossls are very good eyepieces  – Good discussion
https://www.cloudyni...s/#entry8285208

 

 

Since you are starting with an Orion Sirius Plossl, a good eyepiece, the benefit of going to the BST Starguider would be a wider field of view, not a darker background.  For that you will need to go to a higher magnification.

 

If you want to maximize the field of view of your scope, a 32 mm Plossl, such as the 32 mm Sirius Plossl, would be about the widest FOV you can get in a 1.25" focuser.


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#11 JOEinCO

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Posted 12 December 2021 - 10:24 AM

....Moral being that brand names prove nothing!

 

waytogo.gif waytogo.gif waytogo.gif


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#12 SeattleScott

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Posted 12 December 2021 - 04:47 PM

waytogo.gifwaytogo.gifwaytogo.gif

Brand name usually (not always) means well corrected in fast scopes. Tony didn’t say his 24 Panoptic exhibited a lot of astigmatism. He said the eye relief, ease of taking in the whole view didn’t agree with him (which is quite personal). So yeah just because an eyepiece costs $300 doesn’t mean it is for you. Each person needs to figure out their own preferences for AFOV, ER, size/weight of eyepieces, etc. Fortunately there are lots of options.
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#13 JOEinCO

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Posted 12 December 2021 - 04:55 PM

....So yeah just because an eyepiece costs $300 doesn’t mean it is for you. Each person needs to figure out their own preferences for AFOV, ER, size/weight of eyepieces, etc. Fortunately there are lots of options.

 

waytogo.gif waytogo.gif waytogo.gif



#14 Napp

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Posted 12 December 2021 - 05:00 PM

Contact your local astronomy club to see if it has resumed group observing sessions.  If so take your scope to one.  Ask members if they would put some candidate eyepieces in your scope to try out.  Best way to see what eyepieces work for you.


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#15 kongqk

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Posted 12 December 2021 - 11:58 PM

Let me just offer my 2cents opinion. I have both the Paradigm 25 mm (same as BST Starguider, but different brand) and the ES68 24 mm. They are both good eyepieces, I like the ES68 24 mm more, and it is my first major upgraded eyepiece, and after I looked through it, I found that, I have to buy more good quality eyepieces :)

 

The 25 mm Paradigm eyepiece on my telescopes (f/5 or f/6.7) do not show the sharp stars near the edge as ES68 24 mm, but since you have a relatively slow scope (f/10.1), it maybe perform better on your scope, but hope someone with a similar slow scope can comment on that. If this is the case, I think you can get it for cheaper. 

 

But if you plan to get fast scopes in the future, maybe ES68 24 mm is a better choice, which works better on fast scopes. As others mentioned, it has a short eye relief, maybe not good if you wear glasses. But other than that, I really love mine, and it gives the widest FOV on my 1.25" focuser telescopes, and due to higher magnification, it has a darker background than 32 mm plossl, and easier to see objects, therefore, it gets more time in the focuser. 


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#16 Dave Mitsky

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Posted 13 December 2021 - 12:04 AM

I also own a 24mm ES 68-degree eyepiece and have no issues with using it in any of my telescopes.  It's my preferred wide-field eyepiece for my 6" Celestron NexStar Evolution SCT.

 

I also have a 19mm Tele Vue Panoptic which has even less eye relief than the 24mm Panoptic (13mm versus 15mm) and for many years it was one of my two favorite eyepieces.


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#17 gnowellsct

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Posted 14 December 2021 - 05:07 PM

The pursuit of wide field views in a light polluted area in a small aperture scope strikes me as a sad undertaking.  The glory of the wide field view needs a good sky.  In urban areas chase planets, the moon.  Do solar h-alpha during the day.  Greg N


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#18 MartinPond

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Posted 20 December 2021 - 03:41 AM

This or that eyepiece just gives you a close-up or wide-angle view of a smoke bomb.

 

The advice is often to go to higher powers,

but when the haze is bad enough to diffuse the peak/point brightness,

you just get a fuzzy jelly bean.  Headlights in the fog, you see?

 

Sometimes a green filter will help clean things up a bit.  With a medium-power eyepiece.

 

People who use NIR image intensifier eyepieces are fanatical about them in the haze.

They are, however, a bit expensive. 

 

I take the radical step of using an eyepiece that separates colors in its scattering.

   (instead of scattering all colors the same)

I make high-index 50 degree Ramsdens, but Kellner eyepieces also produce 

   an odd intense red 'high-lighter line'  around diffused objects.   I can see  cormorants,

   sailboats, and seals through the fog, and  nebulae through haze when a Plossl,

   Paradigm, or   DeLite sees nothing.  It's peculiar, and fun.   Anyways....there are few

   higher-quality Kellners made, but trying one is fairly cheap.

   The cheapest Ramsdens are horrible....you would need to make your own for quality.

 

Just an out-of-the-box observation   


Edited by MartinPond, 20 December 2021 - 03:43 AM.


#19 isolli

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Posted 20 December 2021 - 08:27 AM

Side question: many here are commenting on how the long focal length of OP's scope will make it easier to use cheaper eyepieces. I would like to understand that better.

 

As I understand it, short focal ratios create spherical aberration (for refractors) and coma (for reflectors) at the edge of the image. Do expensive eypieces correct for that? Or is some other physical property of long focal ratios involved here?



#20 rhetfield

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Posted 20 December 2021 - 08:59 AM

Side question: many here are commenting on how the long focal length of OP's scope will make it easier to use cheaper eyepieces. I would like to understand that better.

 

As I understand it, short focal ratios create spherical aberration (for refractors) and coma (for reflectors) at the edge of the image. Do expensive eypieces correct for that? Or is some other physical property of long focal ratios involved here?

Yes, the more expensive eyepieces often do a better job of correcting the coma and spherical aberration in faster scopes.  It really does depend on the eyepiece though and price is only one factor.  Many more expensive eyepieces are designed to get wider FOV or longer eye relief.  Others are all about getter better color correction, glare reduction, and contrast.  You really have to do your research to see which ones work with any given scope, any given target, and any given eye.


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#21 BostonBoySU55

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Posted 20 December 2021 - 09:05 AM

The pursuit of wide field views in a light polluted area in a small aperture scope strikes me as a sad undertaking.  The glory of the wide field view needs a good sky.  In urban areas chase planets, the moon.  Do solar h-alpha during the day.  Greg N

I tend to agree with what Greg said here - aperture is king in the suburbs.  Now - I have a 68 degree ES 16mm eyepiece that I LOVE.  The eye relief is perfect for me and it's solid quality.  Not high end, but certainly a big difference over what came with my telescope (Orion).  Not saying Orion eyepieces are bad, they're just merely "capable".



#22 aeajr

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Posted 20 December 2021 - 10:00 AM

I've bought a 90mm Astroview refractor and I am enjoying learning to star walk. I have suburban light pollution of Bortle 7. I'm looking to upgrade the 25mm eyepiece for a better wide field view- ideally, an eyepiece which would make the background sky darker and bring out more stars if that's possible, with more contrast and sharpness in the images. I'm also interested in a wider-looking field, more immersive.

 

I'm looking at the BST Starguider 60 degree 25mm - I can get it for £45. Then there's the Explore Scientific 68 24mm - at £155, over three times the price. Beyond that are eyepieces like Tele Vue which are intriguing but look well beyond my price range. 

 

Money is the issue - should I go for the BST - or wait and save up for something 3 times more expensive? Is it worth the bigger investment? For the price of one ES eyepiece, I could get 3 BSTs. Any advice from anyone who has used the eyepieces gratefully received!

 

Thanks

Willarkin,

 

We have not heard a word from you.  Are you reading and learning or have we lost you?

 

Let's summarize some of the points made above. 

 

 

Why go to a wide view?

 

  • If you are using a manual mount - this makes star hopping and using other finding techniques easier - Mostly useful at low powers
  • If you are viewing very large DSOs, such as the Pleiades, this let's you view the whole thing or the largest possible portion - mostly useful at low powers
  • If you are using a manual mount, this allows for more drift time - mostly valuable at medium to high powers.
  • Wide field eyepieces do provide an enjoyable immersive feel to the view as compared to narrower field of view eyepieces. 

 

A wider field of view at low power will not typically darken the sky or bring out more stars as compared to a narrower field of view eyepiece at the same mag.   If you want to darken the sky you go to higher power with narrow or wide field eyepieces.  This will usually bring out the dimmer stars, to a large extent. 

 

A narrower field of view eyepiece can often be useful in helping you to exclude bright areas outside of the object you are trying to view.  For example viewing something near the Moon.  Trying to view the moons of Mars while excluding the planet itself.   

 

Narrow field of view eyepieces are often sharper across the field specifically because they are narrow.   A good Plossl, 50 degree AFOV, can provide an excellent image across the field as compare to a poorly corrected 70 degree AFOV eyepiece.

 

If we look at all the DSOs we are likely to view, 90% or more of DSOs, planets and the Moon are all less than 1 degree wide so you don't need a wide field of view to enjoy them. The Moon is only 1/2 degree wide.

 

 

As stated by many, field of view is driven by the AFOV, apparent field of view of the eyepiece.   So you can have a 25 mm Kellner with an 40 degree AFOV and you can have a 25 mm 68 degree eyepiece.  Both provide the same mag and will present a similar background to the sky.  The 68 will show more sky.


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#23 vtornado

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Posted 20 December 2021 - 02:23 PM

 Yes, the more expensive eyepieces often do a better job of correcting the coma and spherical aberration in faster scopes.  --- rhetfield

 

It is the sharply converging light cone from fast optics that low element eyepieces cannot correct  that shows itself as astimgmatism. In this case spherical abberation is produced by the eyepiece. (assuming no SA in the objective)

 

Coma in the image comes from the mirror. it is not corrected by the eyepiece.

A coma corrector can be used to fix this.

 

Usually atigmatism of the eyepiece dominates coma, so coma is not noticed until

the eyepice astigmatism is removed.

 

I live in a grey zone.  I do some widefield observing, but not a lot.  The reason

being is most of the sky is washed out at low powers.  I would not buy an eyepiece

that produces a  greater than 5mm exit pupil.  it destroys my night vision.  There are some open clusters  that are very nice to view even in bright skies. (pleiades, double cluster, behive melotte ...)


Edited by vtornado, 20 December 2021 - 02:25 PM.

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#24 Anony

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Posted 20 December 2021 - 02:38 PM

As stated by many others here, what the OP seems to want is sort of impossible. As an example, I am in bortle 7ish if I had to guess, and I rarely use my 2" eyepiece. It'd provide a nice wide field view, but it's all washed out in grayness.

 

But a 32mm plossl might still be useful for as a finder eyepiece. But it certainly won't make the skies any darker.

 

And I wonder if he'd like a zoom. At the higher mags it should provide a greater fov vs a plossl, and he can dial it in and out to get the sky as dark (or slightly less gray) as he wants.


Edited by Anony, 20 December 2021 - 02:39 PM.

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#25 oldtimer

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Posted 20 December 2021 - 04:13 PM

IMNSHO 90mm from Bortle 7 skies isn't going to do much for DSO observing.  My 4" Mak even has trouble resolving the Auriga clusters. I think a nice 6" F5 reflector is a minimum requirement for DSOs from Bortle 7.




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