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25 mm BST or something else?


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Posted (edited)

I have owned by SW 8" Dob for just over 6 months (I am a beginner in the field)  and I am thinking of upgrading the standard 25mm EP that came with it; it does deliver decent views. I currently have 8mm and 15 mm BST EPs and I really like them. I also have a Celestron 32mm Plossl. My interests are DSOs (mostly nebulas) and I have found that I am particularly using my 15mm and 25mm EPs the most; 8mm when viewing allows. Would you recommend the 25mm BST or are other brands that might deliver better than the standard one? Or shall I keep the current 25mm and look at a different size? My budget is around £50-70 (maybe stretched a bit more).

Edited by Kon
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The 25mm BST performance is well below that of the 8mm and 15mm version.  However, anything that performs better at 60 degrees around 24mm to 25mm is much more expensive.

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17 minutes ago, Louis D said:

The 25mm BST performance is well below that of the 8mm and 15mm version.  However, anything that performs better at 60 degrees around 24mm to 25mm is much more expensive.

Thanks. Which one would be considered a decent EP if in the higher price bracket? It does not have to be 60 degrees since my current 25mm is probably less.

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Posted (edited)

I have the 25mm BST that I use as a DSO finder in my 200p. It does suffer some outer edge aberration in a f5.9 system but it’s still a great eyepiece for the money. There’s the 68° 24mm ES which is probably about the widest field you’ll get for 1.25” but costs over 3x the BST.

Edited by IB20
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Check the BST 25mm page on FLO

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-25mm-ed-eyepiece.html

if you scroll down it, you will see an image which shows you the field of view of an eyepiece, you can change the telescope, and delete / add any eyepiece views as you wish. Try using it to compare the view of a 25mm BST to that of a 32mm plossl , they are very similar ! I have both, and in my f5 dob, I actually prefer the view in my 32mm plossl, and use it rather than the 25mm BST . The BST shows some aberration around the edge of the view. The BST 25mm is fine in my less picky f11 .mak though.

From what I can see (and I've looked around a fair bit !) to get an eyepiece significantly better than the (under £50) BST, I'd need to spend at least 3x that, and the gains would be marginal. Explore scientific get recommended a lot ,

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

or folk mention liking the Baader Mortpheus for about £180

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

I'd suggest you buy a BST 25mm, and see how you get on with it : buying online means you can return an item as unsuitable , FLO or Alan at Sky's the Limit https://skys-the-limit-108154.square.site/shop/1-25-bst-starguider-ed/8  are sellers I'd trust to do the right thing.

Heather

 

 

 

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Posted (edited)

There is the ES 52 degree range which I imagine is far greater than the std kit eyepiece and cheapish too.

Alan

Edited by Alien 13
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3 hours ago, Kon said:

Thanks. Which one would be considered a decent EP if in the higher price bracket? It does not have to be 60 degrees since my current 25mm is probably less.

Well, if you like longer eye relief, the 24mm APM UFF and its equivalents (Orion USA, Celestron, Meade, Altair Astro all have their own) is very good.

If you're willing to move up to 2" eyepieces, the 30mm APM UFF is just about pure perfection.

There are just too many variables to be able to make a recommendation without a hard upper limit on price.

Here's my comparison image of all the BST Starguiders (Paradigms) stacked up against the Meade HD-60s (discontinued) and a table of measured dimensions.  If you click on the through the eyepiece image and enlarge it, you can get some idea of the edge falloff in sharpness of each eyepiece.

1633438738_MeadeHD-60Astro-TechParadigm5.thumb.jpg.113800f121fcd599abb8e75f05b6711b.jpg967372736_MeadeHD-60vsAstroTechParadigm.thumb.jpg.42441146f3ad3b2b31c2b578cb14aab2.jpg2014834196_MeadeHD-60vsAstroTechParadigmData.JPG.a8023468e8992fa9b6421b18f8cb6ea7.JPG

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20 minutes ago, Louis D said:

Here's my comparison image of all the BST Starguiders (Paradigms) stacked up against the Meade HD-60s (discontinued) and a table of measured dimensions.  If you click on the through the eyepiece image and enlarge it, you can get some idea of the edge falloff in sharpness of each eyepiece.

Thank you very much, that's very useful! It makes a very good point from your earlier comment about its performance.  How do the ES 52 degree EP compare as suggested by @Alien 13?

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50 minutes ago, Tiny Clanger said:

Check the BST 25mm page on FLO

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-25mm-ed-eyepiece.html

if you scroll down it, you will see an image which shows you the field of view of an eyepiece, you can change the telescope, and delete / add any eyepiece views as you wish. Try using it to compare the view of a 25mm BST to that of a 32mm plossl , they are very similar ! I have both, and in my f5 dob, I actually prefer the view in my 32mm plossl, and use it rather than the 25mm BST . The BST shows some aberration around the edge of the view. The BST 25mm is fine in my less picky f11 .mak though.

From what I can see (and I've looked around a fair bit !) to get an eyepiece significantly better than the (under £50) BST, I'd need to spend at least 3x that, and the gains would be marginal. Explore scientific get recommended a lot ,

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

or folk mention liking the Baader Mortpheus for about £180

https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

I'd suggest you buy a BST 25mm, and see how you get on with it : buying online means you can return an item as unsuitable , FLO or Alan at Sky's the Limit https://skys-the-limit-108154.square.site/shop/1-25-bst-starguider-ed/8  are sellers I'd trust to do the right thing.

Heather

Thanks Heather. Due to the FOV comparison at FLO, I went for the 32mm plossl but somehow I do not get along with it very well. Nothing wrong with the EP but i find my basic 25mm better(?), I suppose it a personal preference?.

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2 minutes ago, Kon said:

Thanks Heather. Due to the FOV comparison at FLO, I went for the 32mm plossl but somehow I do not get along with it very well. Nothing wrong with the EP but i find my basic 25mm better(?), I suppose it a personal preference?.

I too have a 32mm plossl and its fine if you can clamp your head in a vice otherwise a few mm off center and the image is gone 😋

Alan

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6 minutes ago, Alien 13 said:

I too have a 32mm plossl and its fine if you can clamp your head in a vice otherwise a few mm off center and the image is gone

Exactly! It's the reason i use it a lot  less than the 25mm one.

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1 hour ago, Kon said:

Thank you very much, that's very useful! It makes a very good point from your earlier comment about its performance.  How do the ES 52 degree EP compare as suggested by @Alien 13?

It seems a bit overpriced for what it is.  If you want to go down the ~50 degree route for premium money, there's also the 25mm Vixen SLV.

However, since you have a 2" focuser, I would recommend the 22mm Omegon Redline SW, Technosky Superwide HD, TS-Optics Expanse WA, etc.  I have the discontinued Astro Tech AF70 version and prefer it to the 24mm APM UFF for about the same true field of view when I have a 2" focuser available.  The stiff eye cup screws completely off and can be replaced with the Morpheus one if you want a more pliable eye cup.  I only retired it after acquiring a 22mm Nagler T4.

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I found that in my 8" f6 dob the maximum field of view from a 1.25" isn't quite wide enough so I think that rather than spending £70 on an eyepiece that turns out to be slightly too narrow, you should save up for a good eyepiece with a wider field. Personally, I would be looking for something at least as wide as a 28mm 68° eyepiece. If you're in no rush then taking your time also gives you the opportunity to see if anything suitable turns up on the second hand market, which could also help in terms of the budget.

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14 hours ago, Kon said:

Thanks Heather. Due to the FOV comparison at FLO, I went for the 32mm plossl but somehow I do not get along with it very well. Nothing wrong with the EP but i find my basic 25mm better(?), I suppose it a personal preference?.

Funny isn't it, of the 3 EPs you mention (SW  bundled 25mm, 32mm plossl, 25mm BST) I can see there is an improvement in quality at each step up in price , but am not happy with the edge image in the BST, therefore find the plossl preferable (but only in my f5 dob) and for me the plossl is very esy to use.  But you prefer the bundled SW to the plossl ! It shows that while statistics will tell you a certain amount,  these things are very subjective

I've never actually seen anyone discuss or review the ES 52 degree EPs mentioned by Alan, which is slightly strange, but I guess as they are in the same approximate price range as the BSTs but a bit more expensive they may be seen as less of a bargain. There certainly is a tendency towards quality EPs being wider, which means they are necessarily bigger, heavier and inevitably more expensive. The one thing you can guarantee about suggestions on what eyepieces you should buy, is that many suggestions will blithely stretch or totally ignore any budget you mention !

I think this is an interesting thread, I've not looked up  the focal ratio of your 'scope, which is an important factor , but this deals with a query related to a fast (low number) ratio device :

 

 

Heather

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Actually, the SW stock 25mm (modified achromat) isn't horribly bad. I used it with my F/5 for a while and it was OK (and you're closer to F/6?). I think most people look to ditch the 10mm first if they're on a budget.

The Vixen NPL 25mm (not stocked by FLO) has also been suggested as slightly superior in the Starguider price bracket, though the AFOV is only 50 degrees. I have the 30mm, which does well at F/5, though the body feels a bit insubstantial.

On the ES 52 degree range, Ernest Maratovich has some opinions here. A well-known translation engine renders some of the comments as follows:

"These eyepieces have appeared relatively recently and rather unexpectedly. Eyepieces with a 52 ° field of view (typical for Super-Plosswords) are already very far from the mainstream in the modern astro gadgets market. However, among Explore Scientific eyepiece rulers, there were no comparatively simple eyepieces with a small field of view and a minimum of optical elements. Explore Scientific engineers took the well-proven Plössl as a base scheme, added a prefocal element (a kind of Barlow lens) to it at short-focus denominations, so that the observer did not have problems with the extension of the exit pupil and his usual "chip" - a sealed design with a nitrogen purge / argon. Perhaps in this form, these eyepieces will be able to compete with both Plösslam (and especially from TeleVue) due to the already built-in Barlow - on the one hand, and numerous Paradigm clones - on the other. The peculiarity of the line is that, unlike Plosslov, it has a short-focus end (3 and 4.5 mm), and unlike Paradigms, it has a long-focus end (30 and 40 mm). If we add to this the multilayer antireflection coatings and the quality of the workmanship of the mechanics, then the chances of a niche at 52-degree Explore Scientific seem to exist.

Judging by the plate (which is built on the basis of the data at the link https://explorescientificusa.com/collec ... -eyepieces), 15 mm eyepieces and shorter focus ones are built according to the Plossl + Barlow scheme with compensation, 20 mm - Kellner + Barlow with compensation , 25 mm and longer focal lengths - the traditional non-binding Plossl.

In another thread I wrote: Mechanically well made, as are all ES eyepieces. Hermetically sealed. Optical design: Plossl + Barlow. The increase in the prefocal component is of the order of 7x. In the center and in the wide center area, the image quality is close to ideal. Closer to the edge in the high-aperture instrument, astigmatism and magnification chromatism become noticeable, but their effect on image quality is small. The curvature of the image is well corrected (in contrast to the single Plössl). The field is equal to the declared one; the pupil is comfortable - you can even observe with glasses, if someone does not like them without them. The enlightenment is typical for the Chinese - green. It is interesting that the outer surfaces (both for the eye lens and for the field lens) give a slightly different tone of flare - they seem to be made with protection, this indicates a serious attitude to the matter. Light scattering and glare is negligible - when a bright object enters the field of view, it has a ghostly double reduced in half in half of the field of view. It seems to me that the eyepiece is quite suitable for observing planets at magnifications close to the limiting one."

... although the quantitative review information on that page (and also, apparently, a response from ES) is specifically for the 3mm version. Ernest does not seem to have reviewed the 52 degree range in his survey of eyepiece defects (though he does include the 68 degree 24mm, 82 degree 24mm and 100 degree 25mm, the last two being 2").

Some further recent discussion of the BST 25mm, including some fans, appears here:
https://stargazerslounge.com/topic/369290-ep-advice/?tab=comments#comment-4011972

and an SGL thread on the ES 52 degree here:
https://stargazerslounge.com/topic/357276-what-are-people’s-views-on-explore-scientific-52°-eyepieces/?tab=comments#comment-3891472

and more on the ES from Another Place:
https://www.cloudynights.com/topic/646853-my-honest-review-of-the-52-degree-from-explore-scientific/?hl= es 52 degree

https://www.cloudynights.com/topic/756395-es-52°-series-25mm-vs-televue-plossl-25mm/?hl=%2Bes+%2B52+%2Bdegree#entry10891109

https://www.cloudynights.com/topic/638504-comparative-trial-run-of-the-es-3052/

 

 

 

 

 

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Posted (edited)

@Tiny Clanger and @Zermelo thank you for your suggestions. I thought the SGL forum was meant to help me make a decision, not scrabble my head 😖....joking aside a lot of interesting links to read and help me decide on an EP, thank you!

Edited by Kon
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Haven't tried the 25mm Vixen NPL, but I do have the 30mm and it is a vast improvement over standard EPs. I wouldn't say it was up to something like the 12mm BST, but the edge softness of the Vixen is very much less obvious than the lower powered BSTs. Also, the true FOV of the 25mm BST is pretty much equal to the 30mm Vixen NPL.

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I also have a Vixen 30mm npl and I find it to be a very good eyepiece, especially the twist up eye cup. I find eye placement much easier and do not struggle with kidney beaning etc as I did with a 32mm plossl.

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11 hours ago, Pixies said:

the true FOV of the 25mm BST is pretty much equal to the 30mm Vixen NPL

Yes, and close to the maximum for a 1.25" format, beaten only narrowly by the ES68°/24mm. A consideration is how much you really value the edge-to-edge sharpness, or just like the effect of a wider field. The ES is currently £155 new.

The 24/25mm EPs will have a narrower exit pupil for the same TFOV, though. I find the 30mm NPL can give quite light backgrounds in my skies, which may not be ideal for some targets (although the OP's scope will be better than mine in that respect, giving a 5mm pupil for the NPL 30mm and 4.2mm for the NPL 25mm). I also notice my own astigmatism (i.e. biological, not technical) with a 6mm exit pupil but not 5mm, though you're only going to find that out when you try.

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14 hours ago, Kon said:

@Tiny Clanger and @Zermelo thank you for your suggestions. I thought the SGL forum was meant to help me make a decision, not scrabble my head 😖....joking aside a lot of interesting links to read and help me decide on an EP, thank you!

Ask 10 different astronomers and you’ll get 10 different answers! 😈

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8 minutes ago, Knighty2112 said:

Ask 10 different astronomers and you’ll get 10 different answers! 😈

At least 11 answers, surely?

 

14 hours ago, Kon said:

I thought the SGL forum was meant to help me make a decision

The purpose is to show you that whenever you ask yourself "should I buy A or B?" the answer is "you should get A and B (and possibly C as well)"

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Posted (edited)

A used Celestron X-Cel LX 25mm saw a great deal of use over two years across several scopes including an 8" dob. Only just out of your budget new at around £73.

I'm very happy with my 24mm 68° Altair UFF (£135), but my current scopes are f7 and f12 so I don't know how well it will perform in faster instruments.

 

Edited by ScouseSpaceCadet
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I had a BST Starguider 25mm for a while - as an eyepiece to use with a travel scope.

It seemed to work pretty well with the travel scope (a 70mm F/6.8 refractor) showing mostly sharp stars across the field of view.

It was not well enough corrected towards the field edges to be fully satisfying with my F/5.3 12 inch dobsonian though. I think I would have preferred a good 25mm plossl over the Starguider in that scope. Luckily I have the 24mm Panoptic which is excellent.

Of the lower-than-Panoptic-cost wide angle eyepieces that I've owned and used around that focal length I think the Maxvision 24mm / 68 and the Explore Scientific 24mm / 68 were the nicest. The Maxvision is sadly now no longer in production but if you can find one they offer very good "max field in 1.25 inch" performance, even in quite fast scopes. The Explore Scientific 24mm / 68 is pretty much as good as the 24mm Panoptic in terms of performance but it a slightly bulkier package.

 

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Posted (edited)

Thank you all for the links, comparisons and personal experience with different EPs. After reading the links and careful consideration, I am thinking of going for the ES 24mm (68°) (ouch, that's a lot higher than my initial budget). Several of you suggested it.  I realise that I use my 25mm EP quite a lot so getting an EP that will deliver hopefully sharper images is worth it. I will try see if anything might come on second hand market otherwise I will be placing an order soon.

Edited by Kon
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