Which BST Starguiders to get?

[dieg00]

Hi,

I’m new to astronomy and bought a Heritage 130p recently. I’ve seen the BST Starguiders to be highly regarded here and I was looking to buy a few. I found someone selling a used 25mm locally and I bought it. I’ve tried it today for the first time and I’m mesmerized! The views feel far better than the 25mm included with the scope.

My budget allows me to buy 2 new BST Starguider right now. Which ones should I get?

Note that I want versatility to observe both planets and DSOs, so I have to cover different magnifications. Also, My current non-BST eyepieces are the 10mm and 25mm included with the telescope, and a 4mm 58° HR Planetary Clone from a Chinese seller.

Thank you for reading, and thanks in advance for your answers!

[globular]

Hi and welcome to SGL.

When choosing eyepieces I like to

• have fairly equal magnification steps between eyepieces
• have exit pupil between 1mm and 5mm (but this varies from person to person and how dark your skies are)
• have a wide field eyepiece giving at least 1 degree true field... more if possible.
• have an eyepiece close to 2mm exit pupil. This is often a sweet spot for DSOs.

Your 25mm is giving you 26x mag, 2.3° tfov and 5mm exit pupil.  Nice wide field views from a dark site.

Stepping down to a 2mm exit pupil for the next EP would require a 10mm one but they are not available in this EP line.
Instead I’d pick the 8mm giving 81x mag, 0.7° tfov and 1.6mm exit pupil.

That is a mag difference of 55x from your 1st EP, so I’d go for about 136x for the next EP.
The 5mm gives 130x mag, 0.5° tfov and 1mm exit pupil. This seem to fit the bill nicely.

In summary 25mm, 8mm and 5mm.
Giving mags of 26x, 81x and 130x.
Exit pupils of 5mm, 1.6mm and 1mm.
True field of view of 2.3, 0.7 and 0.5 degrees.

[dieg00]

6 hours ago, globular said:

Hi and welcome to SGL.

When choosing eyepieces I like to

• have fairly equal magnification steps between eyepieces
• have exit pupil between 1mm and 5mm (but this varies from person to person and how dark your skies are)
• have a wide field eyepiece giving at least 1 degree true field... more if possible.
• have an eyepiece close to 2mm exit pupil. This is often a sweet spot for DSOs.

Your 25mm is giving you 26x mag, 2.3° tfov and 5mm exit pupil.  Nice wide field views from a dark site.

Stepping down to a 2mm exit pupil for the next EP would require a 10mm one but they are not available in this EP line.
Instead I’d pick the 8mm giving 81x mag, 0.7° tfov and 1.6mm exit pupil.

That is a mag difference of 55x from your 1st EP, so I’d go for about 136x for the next EP.
The 5mm gives 130x mag, 0.5° tfov and 1mm exit pupil. This seem to fit the bill nicely.

In summary 25mm, 8mm and 5mm.
Giving mags of 26x, 81x and 130x.
Exit pupils of 5mm, 1.6mm and 1mm.
True field of view of 2.3, 0.7 and 0.5 degrees.

Thanks for your answer! Great explanation for a beginner like me.

I have one question: what made you decide between the 8mm and 12mm? They are both “equally” away from the 10mm. Will the 8mm serve well for DSOs, even if it’s exit pupil is a bit lower than the 2mm you said to be the sweet spot?

[globular]

With a remit for 3 EPs and a "bit of everything" viewing I went for a low power a medium power and a high power.
The 12mm gives mag of 54x which is still quite low power - and you already have a low power EP with the 25mm (26x).
The 8mm is 81x which is getting into the medium range (for your scope).

Eventually you might want to add the 12mm and the 3.2mm too for higher power - but I'd recommend you get more experienced with the equipment you have, learn their capabilities and form your own view on what you enjoy observing before adding more.

[Zermelo]

If you're interested in some longer threads on the topic, you can try:

https://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

https://stargazerslounge.com/topic/251506-a-guide-for-choosing-a-sensible-eyepiece-collection-using-the-exit-pupil/?tab=comments#comment-2740683

but I think @globular has effectively summarised the mag-centric and pupil-centric approaches for you in their post above.

I use the Starguider 5mm, 8mm and 12mm in my 150mm F/5 Skywatcher and all three perform well.

Have you considered a barlow or zoom, or are you just looking for single, fixed eyepieces?

(oh, and as you've mentioned both a Heritage dob and BSTs in the same post, expect a response from @Tiny Clanger - it's astro catnip)

[Pixies]

Whatever you get, bear in mind that the 8mm and 12mm BSTs are considered the best of the range. The 18mm is a bit soft at the edges. I've not used the 15mm or 25mm.

[Tiny Clanger]

11 minutes ago, Zermelo said:

If you're interested in some longer threads on the topic, you can try:

https://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

https://stargazerslounge.com/topic/251506-a-guide-for-choosing-a-sensible-eyepiece-collection-using-the-exit-pupil/?tab=comments#comment-2740683

but I think @globular has effectively summarised the mag-centric and pupil-centric approaches for you in their post above.

I use the Starguider 5mm, 8mm and 12mm in my 150mm F/5 Skywatcher and all three perform well.

Have you considered a barlow or zoom, or are you just looking for single, fixed eyepieces?

(oh, and as you've mentioned both a Heritage dob and BSTs in the same post, expect a response from @Tiny Clanger - it's astro catnip)

Hey, you callin' me a cat ?

I'd be flattered, actually.

Back  to the  topic in hand . Yes, I love my heritage dob , and have BSTs . My dob is the slightly bigger 150mm , which has a focal  length of 750mm and a focal ratio of f5 , while the heritage 130 is, I believe focal length 650mm (also therefore f5) So your 130 will  get slightly less magnification with a given eyepiece than the 150  does. 

The greatest magnification BST eyepiece I own is the 8mm, which I would recommend unreservedly, it is great for views of the Moon and planets.  The 12mm is just  as good. My absolute favourite for faint fuzzy stuff is the 18mm . I have the 15mm, it is fine, but gets less use.

I have not bought a 5mm BST, for a number of  reasons.  I tried the 8mm and 12mm with a 2x barlow when looking at Mars, and found the planet zipped across my field of  view so fast that I was constantly nudging the 'scope to keep up with it. So , for me, the 5mm would be a step too far in that 'scope. My (expensive) solution was to buy a 127 mak on and AZ5  alt az mount. This is twice the focal length of the dob, so gets me that big magnification along with slo mo controls to  ease keeping the planet in view.

In my 150 the 8mm BST gives 93.7x , in your 130 , 81.5x. Both 'scopes being f5, the exit pupil is the same, 1.6mm

The 12mm BST gives me 62.5x , you 54.4x , exit pupil 2.4mm

The 15mm BST in my 150 50x , in the  130 43.3  exit pupil 3.0

to me the 18mm BST 41.6x , to you 36.1x  exit pupil 3.6mm

for completeness, the 25mm we both already have is me 30x, you 26x exit pupil 5.0

And a 5mm would give you 130x and an exit pupil of 1mm

While the 5mm looks good on paper, I am concerned that you would get less use from it because of the difficulties of keeping the Moon and Planets in view by nudging the dob base. It's not impossible, but it takes a lot of patience and is not ideal. I'd suggest the 8mm as your high power EP. Then where you go for a mid range depends ... if you go on exit pupil, then the 15mm looks like a good mid point, if you look  for a mid way magnification maybe the 12mm,  but from a light polluted suburban fringe location I've found the 18mm is the ideal exit pupil for me to perceive the faint fuzzies against the night glow infested sky.

Here's a random thought : how about an 8mm BST and 2x barlow ? The Barlow would give you the option of using it with the 25mm to  give you 12.5mm , and the 8mm to give a (probably seldom used) 4mm . Some Barlows allow you to unscrew the lens part and use just that minus the tube to get 1.5x mag over that of the eyepiece alone, so the 25mm becomes a 16mm , the 8mm becomes effectively 5.3mm.

I believe there is a BST barlow available on FLO , for a bit less than the price of a BST eyepiece, although I've not looked recently.  The good thing about Barlows is that they instantly double (or triple if you can unscrew the lens) the number of focal lengths available to you. The bad thing is that they are a faff , and cheap ones can be poor. I bought a skywatcher one ( I believe it is their 'super' model ) and I just don't like using it . But, it is an option, and could show you what focal lengths you are likely to find useful.

Heather

[Tiny Clanger]

Oh, and by the by, the 25mm BST is, to my eyes,  the least good of the set, and the only one I would like to upgrade. So as you were impressed by the improvement over the stock  EP of that one, you should be blown away by the others in the range !

[dieg00]

2 hours ago, globular said:

With a remit for 3 EPs and a "bit of everything" viewing I went for a low power a medium power and a high power.
The 12mm gives mag of 54x which is still quite low power - and you already have a low power EP with the 25mm (26x).
The 8mm is 81x which is getting into the medium range (for your scope).

Eventually you might want to add the 12mm and the 3.2mm too for higher power - but I'd recommend you get more experienced with the equipment you have, learn their capabilities and form your own view on what you enjoy observing before adding more.

Oh I see. Thanks for clearing up what higher, medium and lower magnification means; I’m still trying to get around the numbers and magnitudes in my head.

[Stu1smartcookie]

Good info there Heather ... 

i had put the 25mm in my basket but have now changed it to the 18mm .  

[Zermelo]

1 minute ago, Stu1smartcookie said:

Good info there Heather ... 

i had put the 25mm in my basket but have now changed it to the 18mm .  

The BST 25mm was the subject of this recent thread.

[dieg00]

2 hours ago, Zermelo said:

If you're interested in some longer threads on the topic, you can try:

https://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

https://stargazerslounge.com/topic/251506-a-guide-for-choosing-a-sensible-eyepiece-collection-using-the-exit-pupil/?tab=comments#comment-2740683

but I think @globular has effectively summarised the mag-centric and pupil-centric approaches for you in their post above.

I use the Starguider 5mm, 8mm and 12mm in my 150mm F/5 Skywatcher and all three perform well.

Have you considered a barlow or zoom, or are you just looking for single, fixed eyepieces?

(oh, and as you've mentioned both a Heritage dob and BSTs in the same post, expect a response from @Tiny Clanger - it's astro catnip)

Really interesting threads, thank you for linking them.

They have allowed me to fully understand @globular reasoning behind his explanation better. 

I have considered the barlow, not so much the zoom as I'm afraid a "do it all" eyepiece would require a significant investment to be worth it.

The thing with the barlow is that, being such an important eyepiece of the collection, I'd rather "buy it once and forget" by searching for the optimal price-performance option. 

To avoid having to choose now, I wanted to buy a few eyepieces to get me going and then deciding what amount would be reasonable to spend.

Hahaha, I see that you were right about @Tiny Clanger

[dieg00]

2 hours ago, Pixies said:

Whatever you get, bear in mind that the 8mm and 12mm BSTs are considered the best of the range. The 18mm is a bit soft at the edges. I've not used the 15mm or 25mm.

Yeah I can see some sort of fuzziness in the edges of the fov of the 25mm, so I guess the problem goes away in lower focal distances.

[Tiny Clanger]

56 minutes ago, Stu1smartcookie said:

Good info there Heather ... 

i had put the 25mm in my basket but have now changed it to the 18mm .  

I'm by no means an expert on EPs, all I've used is the stock ones, plossls and BSTs , but I just don't much like the 25mm  in the dob , the f5 focal ratio shows it's flaws up . It's fine in the mak which is , er, f12 ish , but I actually use a skywatcher 32mm plossl in preference when using the dob. , and it has a very similar field of view.

The EP I really  loved instantly was my 17mm plossl ,  turns out that 17mm focal length , giving a 3,4mm exit pupil (with the dob) is , to my eyes, from my back garden, the best. I held off buying the BST 18mm because I so liked the plossl it seemed pointless to replace it, but when one came up for sale second hand at a decent price I went for it , and have found the BST (exit pupil 3,6mm) is even better for me. The 17mm plossl has been shifted over to my ST80 where it does a lovely job too !

I'd think a more forgiving than f5 'scope might not be a problem for the 25mm BST, but I'm not sure where you'd draw the line of acceptability !

Heather

[Stu1smartcookie]

Just now, Tiny Clanger said:

I'm by no means an expert on EPs, all I've used is the stock ones, plossls and BSTs , but I just don't much like the 25mm  in the dob , the f5 focal ratio shows it's flaws up . It's fine in the mak which is , er, f12 ish , but I actually use a skywatcher 32mm plossl in preference when using the dob. , and it has a very similar field of view.

The EP I really  loved instantly was my 17mm plossl ,  turns out that 17mm focal length , giving a 3,4mm exit pupil (with the dob) is , to my eyes, from my back garden, the best. I held off buying the BST 18mm because I so liked the plossl it seemed pointless to replace it, but when one came up for sale second hand at a decent price I went for it , and have found the BST (exit pupil 3,6mm) is even better for me. The 17mm plossl has been shifted over to my ST80 where it does a lovely job too !

I'd think a more forgiving than f5 'scope might not be a problem for the 25mm BST, but I'm not sure where you'd draw the line of acceptability !

Heather

Yes , i already have a more than acceptable 25mm anyway . But reading your comments ( expert or not ) and others on the forum i think the BST EP's are some of the best out there , for value .  

[Tiny Clanger]

1 minute ago, Stu1smartcookie said:

Yes , i already have a more than acceptable 25mm anyway . But reading your comments ( expert or not ) and others on the forum i think the BST EP's are some of the best out there , for value .  

Yep,  you can always spend more ,  but the improvements per £ are marginal  :  the ES I'd rather like to replace the  25mm BST i with would be 3x the cost of the BST, but no way would it be 3x better !

[dieg00]

1 hour ago, Tiny Clanger said:

Hey, you callin' me a cat ?

I'd be flattered, actually.

Back  to the  topic in hand . Yes, I love my heritage dob , and have BSTs . My dob is the slightly bigger 150mm , which has a focal  length of 750mm and a focal ratio of f5 , while the heritage 130 is, I believe focal length 650mm (also therefore f5) So your 130 will  get slightly less magnification with a given eyepiece than the 150  does. 

The greatest magnification BST eyepiece I own is the 8mm, which I would recommend unreservedly, it is great for views of the Moon and planets.  The 12mm is just  as good. My absolute favourite for faint fuzzy stuff is the 18mm . I have the 15mm, it is fine, but gets less use.

I have not bought a 5mm BST, for a number of  reasons.  I tried the 8mm and 12mm with a 2x barlow when looking at Mars, and found the planet zipped across my field of  view so fast that I was constantly nudging the 'scope to keep up with it. So , for me, the 5mm would be a step too far in that 'scope. My (expensive) solution was to buy a 127 mak on and AZ5  alt az mount. This is twice the focal length of the dob, so gets me that big magnification along with slo mo controls to  ease keeping the planet in view.

In my 150 the 8mm BST gives 93.7x , in your 130 , 81.5x. Both 'scopes being f5, the exit pupil is the same, 1.6mm

The 12mm BST gives me 62.5x , you 54.4x , exit pupil 2.4mm

The 15mm BST in my 150 50x , in the  130 43.3  exit pupil 3.0

to me the 18mm BST 41.6x , to you 36.1x  exit pupil 3.6mm

for completeness, the 25mm we both already have is me 30x, you 26x exit pupil 5.0

And a 5mm would give you 130x and an exit pupil of 1mm

While the 5mm looks good on paper, I am concerned that you would get less use from it because of the difficulties of keeping the Moon and Planets in view by nudging the dob base. It's not impossible, but it takes a lot of patience and is not ideal. I'd suggest the 8mm as your high power EP. Then where you go for a mid range depends ... if you go on exit pupil, then the 15mm looks like a good mid point, if you look  for a mid way magnification maybe the 12mm,  but from a light polluted suburban fringe location I've found the 18mm is the ideal exit pupil for me to perceive the faint fuzzies against the night glow infested sky.

Here's a random thought : how about an 8mm BST and 2x barlow ? The Barlow would give you the option of using it with the 25mm to  give you 12.5mm , and the 8mm to give a (probably seldom used) 4mm . Some Barlows allow you to unscrew the lens part and use just that minus the tube to get 1.5x mag over that of the eyepiece alone, so the 25mm becomes a 16mm , the 8mm becomes effectively 5.3mm.

I believe there is a BST barlow available on FLO , for a bit less than the price of a BST eyepiece, although I've not looked recently.  The good thing about Barlows is that they instantly double (or triple if you can unscrew the lens) the number of focal lengths available to you. The bad thing is that they are a faff , and cheap ones can be poor. I bought a skywatcher one ( I believe it is their 'super' model ) and I just don't like using it . But, it is an option, and could show you what focal lengths you are likely to find useful.

Heather

Your argument for the barlow is pretty convincing. I've checked FLO and sadly the price must have gone up as it's the same as a BST eyepiece. Is the BST Barlow worth it over other Barlows on it's price range? I'm asking because I'm buying the BST eyepieces in FLO as I can't find them on any local shops (I'm in Spain), however, if there are Barlow alternatives of the same quality I could try to buy them locally to avoid the extra shipping and tax duties that I'll face when buying from FLO (and only buy BST eyepieces from FLO). 

As an example, would these Barlows be any good compared to the BST?

https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

https://www.firstlightoptics.com/barlow-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

[Zermelo]

5 minutes ago, dieg00 said:

I'd rather "buy it once and forget"

Haha! You may say that now, but if the bug bites ... there are a few people on this forum who thought they had their "ideal" setup, until they saw that shiny new thing ... 😁

But there are different ways to approach this, yours is fine and you have clearly given it some thought.

There is some discussion on barlows and zooms for a heritage 150 here.

 

[Zermelo]

5 minutes ago, dieg00 said:

As an example, would these Barlows be any good compared to the BST?

https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

https://www.firstlightoptics.com/barlow-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

I have the Baader and it performs well for me (i.e. it's comparable with the quality of the scope and eyepieces that I use).  It's one of those that you can split to give two different magnifications (2.25 and 1.3) but note that you can only do that if the eyepiece you're using can accommodate it; some eyepieces, including some of the BSTs, don't have enough room at the end.

The Astro Essentials model is often recommended here as a decent first barlow.

I have no first hand experience of comparing either with the BST/ES versions, but I would be surprised if there was much difference.

The other thing to bear in mind with barlows is that you can certainly discuss their intrinsic quality, but it's also the case that specific eyepieces sometimes perform better or worse with specific barlows. Obviously there are thousands of possibles combinations, so it's hard to analyse in advance. Sometimes you'll see comments in this forum along the lines of "I find that X eyepiece barlows well with Y", but otherwise you'll just have to try and see. I don't think you can go seriously wrong.

 

 

[Tiny Clanger]

Just now, dieg00 said:

Your argument for the barlow is pretty convincing. I've checked FLO and sadly the price must have gone up as it's the same as a BST eyepiece. Is the BST Barlow worth it over other Barlows on it's price range? I'm asking because I'm buying the BST eyepieces in FLO as I can't find them on any local shops (I'm in Spain), however, if there are Barlow alternatives of the same quality I could try to buy them locally to avoid the extra shipping and tax duties that I'll face when buying from FLO (and only buy BST eyepieces from FLO). 

As an example, would these Barlows be any good compared to the BST?

https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

https://www.firstlightoptics.com/barlow-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

As I said, I have the skywatcher barlow , which looks identical to the FLO astro essentials one, a good feature of both is that if you have a DSLR and want to try taking photos through your 'scope, the barlow is threaded to take a t mount adaptor. I can't say you would love the barlow, because I don't but it is a cost effective way of extending your range of focal  lengths.

If you decide on a 2x barlow and 2 new EPs, try to have EPs which are not twice the focal length , eg your 25mm will become a 12.5mm with the barlow, so best not get a barlow + 12mm !

By the way, I believe FLO will remove the UK VAT  when you buy anything from the EU (so my S. Irish friends tell me 🙂 ) , and your local taxes ought to be paid as you import them ...

[scotty38]

31 minutes ago, dieg00 said:

Your argument for the barlow is pretty convincing. I've checked FLO and sadly the price must have gone up as it's the same as a BST eyepiece. Is the BST Barlow worth it over other Barlows on it's price range? I'm asking because I'm buying the BST eyepieces in FLO as I can't find them on any local shops (I'm in Spain), however, if there are Barlow alternatives of the same quality I could try to buy them locally to avoid the extra shipping and tax duties that I'll face when buying from FLO (and only buy BST eyepieces from FLO). 

As an example, would these Barlows be any good compared to the BST?

https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

https://www.firstlightoptics.com/barlow-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

The only thing I'd add but be aware I've not used any is the the ES is a focal extender and not a Barlow as such and behaves differently Some would say better and these are supposed to be pretty good. Think of the difference between a TV Powermate and their Barlows. If you read the TV blurb on the FLO site they explain the differences.

[Stu1smartcookie]

44 minutes ago, dieg00 said:

Your argument for the barlow is pretty convincing. I've checked FLO and sadly the price must have gone up as it's the same as a BST eyepiece. Is the BST Barlow worth it over other Barlows on it's price range? I'm asking because I'm buying the BST eyepieces in FLO as I can't find them on any local shops (I'm in Spain), however, if there are Barlow alternatives of the same quality I could try to buy them locally to avoid the extra shipping and tax duties that I'll face when buying from FLO (and only buy BST eyepieces from FLO). 

As an example, would these Barlows be any good compared to the BST?

https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

https://www.firstlightoptics.com/barlow-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

Check out other suppliers such as Rother valley optics and Widescreen Centre 

[Tiny Clanger]

1 hour ago, Zermelo said:

The other thing to bear in mind with barlows is that you can certainly discuss their intrinsic quality, but it's also the case that specific eyepieces sometimes perform better or worse with specific barlows. Obviously there are thousands of possibles combinations, so it's hard to analyse in advance. Sometimes you'll see comments in this forum along the lines of "I find that X eyepiece barlows well with Y", but otherwise you'll just have to try and see. I don't think you can go seriously wrong.

 

That's true : I dislike the barlow in my heritage dob, have never felt the need to even try it in my mak (which gives all the magnification my eye floaters allow with a 6mm ortho ) , but am quite happy to use the barlow in my little ST80 refractor , where it stays in a small case to make a lightweight grab & go kit, alongside a couple of plossls and the stock 25mm !

[dieg00]

4 hours ago, Zermelo said:

Haha! You may say that now, but if the bug bites ... there are a few people on this forum who thought they had their "ideal" setup, until they saw that shiny new thing ... 😁

But there are different ways to approach this, yours is fine and you have clearly given it some thought.

There is some discussion on barlows and zooms for a heritage 150 here.

 

Hahaha, yeah I know that it's easy to fall down the rabbit hole of searching for the optimal setup.

Thanks for the link! Checking it up now

[dieg00]

3 hours ago, Stu1smartcookie said:

Check out other suppliers such as Rother valley optics and Widescreen Centre 

As in, to check for other types of Barlows?