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Barlow or eyepiece (with specifics)


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Hi everyone,

First off, I understand that there are lots of topics out there very similar to this, but for whatever reason getting people replying specifically to my queries makes me feel a lot more comfortable (I’m sure some of you understand)

Anyway, I’m a new 8” dob owner (1200mm fl) and have just got a set of 8, 12, 18, 25mm BST Starguiders. Living in London, I feel as though planetary and lunar will make up a lot of my observing so I think I would like a 6mm for 200x. Would you guys recommend any specific 6mm? Alternatively there is a BST Barlow for a good price. The barlow would also give me 300x for lunar and maybe planetary on exceptional occasions. Might I add, I’m really not looking to spend much; £40 new or used is about my limit (already spent the cost of the scope in EPs, cleaner fluid, collimation tools, chair etc). 

Essentially, is the barlow (with the additional 300x) or a 6mm eyepiece on its own going to be better, and what are the recommendations for either? 
 

Thanks ever so much!

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Hello: the least amount of glass between the image and your eye is better. But a Barlow multiply your eye pieces. 
It's always a question of compromise.

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I used to have 8 and 12mm Starguiders to use with my 8" dob. A 2x barlow and the 8mm worked well for showing Neptune and Uranus as disks but I recall that for Jupiter and Saturn a 7mm X-Cel LX was usually the sweet spot over the 8mm Starguider or the barlowed 12mm. Unfortunately, although I sold that 7mm for about £40, prices have gone up so even second hand it is probably over budget. The barlow option is more cost effective because it gives you two new magnifications, but the 300x magnification is something you will rarely use as Jupiter and Saturn are by far the most interesting planets to observe. If you do choose a barlow the there is nothing wrong optically with the Astro Essentials barlow at £25. The Starguider barlow gets you a more solid build quality and a compression ring instead of just a set screw for clamping the eyepieces. 

The 58° "Planetary" eye pieces are probably the most comfortable budget option at 6-7mm. The 6mm Baader Classic Ortho will be optically better at £49 but the eye relief is very tight. The eyepiece now sold as the Stellalyra 55° LER was the intended 6mm option in my original plan but I never got around to buying one and have since moved on to binoviewers for lunar and planetary. 

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A 2x Barlow would suit your set up. Modern Barlows don't really interfere with the image so much; they can actually reduce aberrations in 'lesser' eyepieces due to the light cone being more shallow.

An 8" Dob is worthy of better eyepieces than the BSTs though. If you are ok at pushing at high magnifications (or have an EQ platform), then the Vixen SLV range gives orthoscopic like views with 20mm eye relief. 
For planetary in my 12" Dob I use the 6mm, 5mm and 4mm, which gives x253, x304 and x380 - all usable in a 12". Those three would scale nicely for an 8" though - x200, x240 and x300. That would be my route.

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The OP has just bought the dob and BST eyepieces so is probably not looking to change just yet. I’ve not used them but all the reviews the BSTs get are very positive; excellent performance for a great price so @sorrimen I think you’ve chosen well so far.

Astronomy is not all about the highest powers, and depends a lot on what you like observing. The Moon can take very high powers under good conditions, x300 or more, but a lot of the time conditions mean that using less gives better results.

Double stars can similarly need a lot of power to split the very tight ones, but beyond those you don’t need crazy powers; the Double Double for instance will split with x100 or even less and it has splits of just over 2”.

Mars tends to respond to, or rather need high powers to get the best out of, x250 or more when conditions allow.

Saturn tends to be lower, x200 to x220 ish, whilst Jupiter is lower contrast and can be best at x150 to x180 for example.

Globular clusters will be great in your scope and often look good at mid and high powers, say x100 to x150.

All other objects will be a wide range depending on their type and size, but often low and mid powers.

One thing you will also find is that you need relatively small increments at the shorter focal lengths to give you manageable steps to match the seeing. I tend to agree that a 7mm will be useful at x171, whilst the Barlow would be an option for getting to those higher powers. Barlows got a bad reputation from the cheap ones bundled with entry level scopes, but most modern decent ones now don’t degrade the image and can be quite useful, even if it just helps you decide which fixed focal lengths you want in future.

In summary (thank goodness he says 🤣), the BST Barlow is not expensive so may make some sense to let you experiment with higher powers for not much money, but a 7mm will also get some good use on the planets, Moon and other targets.

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10 hours ago, sorrimen said:

Hi everyone,

First off, I understand that there are lots of topics out there very similar to this, but for whatever reason getting people replying specifically to my queries makes me feel a lot more comfortable (I’m sure some of you understand)

Anyway, I’m a new 8” dob owner (1200mm fl) and have just got a set of 8, 12, 18, 25mm BST Starguiders. Living in London, I feel as though planetary and lunar will make up a lot of my observing so I think I would like a 6mm for 200x. Would you guys recommend any specific 6mm? Alternatively there is a BST Barlow for a good price. The barlow would also give me 300x for lunar and maybe planetary on exceptional occasions. Might I add, I’m really not looking to spend much; £40 new or used is about my limit (already spent the cost of the scope in EPs, cleaner fluid, collimation tools, chair etc). 

Essentially, is the barlow (with the additional 300x) or a 6mm eyepiece on its own going to be better, and what are the recommendations for either? 
 

Thanks ever so much!

I also think that you have made very good choices already.  I used an 8" Dob, 8mm, 12mm, 18mm Starguiders , and an inexpensive 2x barlow for a good couple of years, and that kept me enthralled.   I think you should just use and enjoy what you have already, with perhaps the addition of a barlow, for which your suggested budget is fine.  

Have a great time ..:smiley:

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Wow, thanks for all these great responses and in such a short time! I think I've settled on grabbing this BST barlow for £30. There happens to be a 7mm X-cel LX for £50 on ABS, but I'm just going to have to forget about bridging that gap for now so I don't spend £80 instead 🤣. Annoyingly, with a barlow my 12mm becomes redundant apart from the fact I need it for the 6mm, but even if all goes wrong I can sell any of what I've bought for little to no loss. Thanks again for all your help guys!

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17 minutes ago, sorrimen said:

Wow, thanks for all these great responses and in such a short time! I think I've settled on grabbing this BST barlow for £30. There happens to be a 7mm X-cel LX for £50 on ABS, but I'm just going to have to forget about bridging that gap for now so I don't spend £80 instead 🤣. Annoyingly, with a barlow my 12mm becomes redundant apart from the fact I need it for the 6mm, but even if all goes wrong I can sell any of what I've bought for little to no loss. Thanks again for all your help guys!

That's a sensible move. And if you mean by "redundant", that you'll be able to get 12.5mm by barlowing the 25, then do experiment and compare on different targets. The 12mm is possibly the best in the Starguider range, so you may prefer it anyway.

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16 minutes ago, sorrimen said:

Wow, thanks for all these great responses and in such a short time! I think I've settled on grabbing this BST barlow for £30. There happens to be a 7mm X-cel LX for £50 on ABS, but I'm just going to have to forget about bridging that gap for now so I don't spend £80 instead 🤣. Annoyingly, with a barlow my 12mm becomes redundant apart from the fact I need it for the 6mm, but even if all goes wrong I can sell any of what I've bought for little to no loss. Thanks again for all your help guys!

The 12mm BST is the best of the range (along with the 8mm). I'd hazard a guess that it would be better than the 25mm barlowed. But that is now for you to investigate.

With the 8" dob, I always found a 12mm EP gave a sweet-spot between magnification and contrast for bright-ish but diffuse targets. M13 (Hercules cluster) and M57 (Ring Nebula) were particular suited to it. An 8mm EP was usually a good option for both Jupiter and Saturn with standard UK seeing conditions.

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10 minutes ago, Pixies said:

The 12mm BST is the best of the range (along with the 8mm). I'd hazard a guess that it would be better than the 25mm barlowed. But that is now for you to investigate.

With the 8" dob, I always found a 12mm EP gave a sweet-spot between magnification and contrast for bright-ish but diffuse targets. M13 (Hercules cluster) and M57 (Ring Nebula) were particular suited to it. An 8mm EP was usually a good option for both Jupiter and Saturn with standard UK seeing conditions.

Totally agree. Apart from special cases like lunar viewing and splitting tight doubles, the EP I use nearly all the time in my 8" dob is a Morpheus 12.5mm. It seems to hit a sweet spot for definition, contrast and FOV and often, after using a 5mm XW for example, I'll go back to the Morph for a more comfortable view.

 

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5 hours ago, Pixies said:

The 12mm BST is the best of the range (along with the 8mm). I'd hazard a guess that it would be better than the 25mm barlowed. But that is now for you to investigate.

With the 8" dob, I always found a 12mm EP gave a sweet-spot between magnification and contrast for bright-ish but diffuse targets. M13 (Hercules cluster) and M57 (Ring Nebula) were particular suited to it. An 8mm EP was usually a good option for both Jupiter and Saturn with standard UK seeing conditions.

Yeah that's a great point actually. Seen plenty of people saying avoid overlaps with barlows but for the price I'm paying I might as well have the eyepiece on its own, knowing it's likely better. 

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That's why I've always liked the idea of a x3 Barlow - fewer duplicates. You could have a 25mm, 18mm and 12mm only, with the x3 giving you 8.33mm, 6mm and 4mm. A really nice spread.

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20 hours ago, sorrimen said:

Hi everyone,

First off, I understand that there are lots of topics out there very similar to this, but for whatever reason getting people replying specifically to my queries makes me feel a lot more comfortable (I’m sure some of you understand)

Anyway, I’m a new 8” dob owner (1200mm fl) and have just got a set of 8, 12, 18, 25mm BST Starguiders. Living in London, I feel as though planetary and lunar will make up a lot of my observing so I think I would like a 6mm for 200x. Would you guys recommend any specific 6mm? Alternatively there is a BST Barlow for a good price. The barlow would also give me 300x for lunar and maybe planetary on exceptional occasions. Might I add, I’m really not looking to spend much; £40 new or used is about my limit (already spent the cost of the scope in EPs, cleaner fluid, collimation tools, chair etc). 

Essentially, is the barlow (with the additional 300x) or a 6mm eyepiece on its own going to be better, and what are the recommendations for either? 
 

Thanks ever so much!

Your choice of a 2X Barlow was a good one.

With the eyepieces you have (also good ones), you now also have 9mm, 6mm, and 4mm.  The jump from 200-300x might seem large, but here is the thing:

on the nights when a 200x image is clean and sharp and not scintillating, it is likely 300x will be usable too (Moon, double stars, Mars at opposition, Neptune, Uranus).

And on a night where 200x is really pushing the limits imposed by Seeing conditions, even 250x won't be usable.  So the 100x jump a the high end is likely to be fine.

It's the same reason why, in my 12.5", I have smaller steps to 300x, then jump to 400x and 500x.  On the nights when 300x is clean and sharp and still, 400x and 500x are usually usable.

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Posted (edited)

Eyepeices come and go, but a good Barlow is forever.   I have a 2 inch 4 element Barlow that I positively love.  With the new 20mm 80 degree it has given me some lovely views.  I am waiting to see how it does on Saturn and Jupiter when they come back around   

Edited by Mike Q
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1 hour ago, Mr Spock said:

That's why I've always liked the idea of a x3 Barlow - fewer duplicates. You could have a 25mm, 18mm and 12mm only, with the x3 giving you 8.33mm, 6mm and 4mm. A really nice spread.

Hadn't even considered that it gave me such a good split. Perhaps I'll look into that, definitely when I look to upgrade in the years to come.  Thanks for your comments!

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1 hour ago, Don Pensack said:

Your choice of a 2X Barlow was a good one.

With the eyepieces you have (also good ones), you now also have 9mm, 6mm, and 4mm.  The jump from 200-300x might seem large, but here is the thing:

on the nights when a 200x image is clean and sharp and not scintillating, it is likely 300x will be usable too (Moon, double stars, Mars at opposition, Neptune, Uranus).

And on a night where 200x is really pushing the limits imposed by Seeing conditions, even 250x won't be usable.  So the 100x jump a the high end is likely to be fine.

It's the same reason why, in my 12.5", I have smaller steps to 300x, then jump to 400x and 500x.  On the nights when 300x is clean and sharp and still, 400x and 500x are usually usable.

'Your choice of a 2X Barlow was a good one', best words I could've heard. Always nice to have someone directly agree when there's so much personal preference in this hobby. All that makes sense too, can't imagine if I'm able to get to 300x I'd be craving the 250x so badly. Thanks for your help!

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1 hour ago, Mike Q said:

Eyepeices come and go, but a good Barlow is forever.   I have a 2 inch 4 element Barlow that I positively love.  With the new 20mm 80 degree it has given me some lovely views.  I am waiting to see how it does on Saturn and Jupiter when they come back around   

4 element?! Haven't even heard of that, must be a pretty nice piece of kit. Yeah can't wait for Saturn and Jupiter to be a bit earlier on, staying up all night has been a bit taxing haha

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6 minutes ago, sorrimen said:

4 element?! Haven't even heard of that, must be a pretty nice piece of kit. Yeah can't wait for Saturn and Jupiter to be a bit earlier on, staying up all night has been a bit taxing haha

I got mine from Orion on this side of the pond.  I am sure they are sold elsewhere under a different branding.  This is a personal choice but I am really preferring 2 inch to 1.25 inch eyepieces and using the Barlow to achieve the desired image.  I can't really use much more then 300x here most of the year and I am usually at no more then 200x.  Attached is an image of my 2 inch 4 element Barlow.  It has an insert that will allow the use of 1.25 inch eyepieces

IMG_20220329_120554.jpg

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I get it, I really do.  To me, Barlows is one place to spend money.  You will always swap out eyepieces, but a good Barlow you will have for years.  

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I have the StellaLyra 2" 2x one that I linked to and an Explore Scientific 1.25" 2x focal extender. Both excellent.

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