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High power lunar binoviewing


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What’s everyone’s preferred set up for high power lunar/planetary binoviewing? I’m thinking of 150x up to 250x. What combination of eyepieces and barlows works best? 

The accepted view is that barlowing longer focal length eyepieces is preferable to using more powerful EPs on their own. But to reach 200x in my 4” refractor with 18.2mm Delites, for example, I need to use two ‘barlows’ (a 2.6x Baader GPC and AP Barcon in front of the diagonal). That’s a significant amount of glass.

Is there an optimum arrangement that delivers the crispest views at high magnification?

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What scope are you using Mark?  A 2X barlow attached to the nose of a binoviewer should amplify approximately 4X because of the increased light path, so a 14mm pair in a barlowed binoviewer would give in the region of 211X in an F7.4 refractor. I can use 7.5mm eyepieces with a barlowed bv in my FC100DZ F8 quite comfortably, which gives me around over 400X. A 10mm pair gives me 320X and 12.5mm around 256X. I don't need to wear glasses while observing and so can get away with minimal eye relief if need be, so no need for complex eyepieces.

Pic shows my 10mm Ultrscopic pair in a revelation bv, with 2X Ultima barlow after the prism diagonal

1593503157101_20200427_144347.jpg.85413cae96c5c4a0f951dcbff68ddf0b.thumb.jpg.81156a198ba42220b780e972bd586646.jpg

Edited by mikeDnight
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Hi Mike - I’m using Tak FC-100 DC.
Must say I find working out BV magnifications a little brainfrying at the best of times. Haven’t tried the two barlow combination yet on the Moon, so maybe my calculations are some way off, but I thought the standard 2x barlow screwed onto the nose of the Chinese BVs actually delivered that same increase in power. At least that’s what I recall with my old WO. Could be wrong. Maybe the Revelation is different?


My current (Baader) set up is more complicated, as I have 1.7x and 2.6x GPCs in the BV nose (which definitely don’t provide more than their stated magnification factors, in fact the 1.7x gives just 1.5x. Why Baader doesn’t call it a 1.5x GPC remains a mystery). But then placing a further barlow (Barcon) in front of the diagonal is supposed to provide another 2x leap in power - at least that’s what I read on CN. If correct this would mean Delites 18.2 would give about 200x in the F/7.4 Tak. Of course if I wanted more then I just add spacers to move the second barlow further from the eyepiece.

Would love to try a pair of pseudo Masuyamas one day. Interesting that you can use 7.5mm EPs comfortably in the Revelation. It is clearly a well collimated binoviewer - and a well collimated observer to be able to merge images at such high powers......😁

 

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I must admit I find the images above about 200x start to get rather dark and I enjoy much more the views at 109-150x. E.g using my 120mm Equinox, the Baader Maxbrights and the 1.7x GPC I get (I assumed) 117x and 156x with the 20mm (TV Plossl) and 15mm (Panoptic) pairs. I find if I go to the 11mm pair (212x) it starts to darken a lot.

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13 hours ago, Highburymark said:

The accepted view is that barlowing longer focal length eyepieces is preferable to using more powerful EPs on their own

This is true when using a normal barlow in front of the binoviewer and when using scaled eyepieces with short eye relief on the short focal length eyepieces. I would hope that a Baader GPC has been designed to correct aberrations from the binoviewer prisms such that further narrowing of the light cone is unnecessary for better correction. Additionally, if you can afford to binoview with Delites, I think that you could happily use short focal length Delites too.

11 hours ago, Highburymark said:

I thought the standard 2x barlow screwed onto the nose of the Chinese BVs actually delivered that same increase in power

It will depend on the focal length of the barlow compared to the light path of the binoviewer. Different barlows will give different magnification factors when used with a binoviewer. With my binoviewer I use the nosepieces two "2X" barlows. One gives 2.1X, and the other gives 3.1X when threaded to the nose of the binoviewer.

Edited by Ricochet
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3 hours ago, Highburymark said:

Hi Mike - I’m using Tak FC-100 DC.
Must say I find working out BV magnifications a little brainfrying at the best of times. Haven’t tried the two barlow combination yet on the Moon, so maybe my calculations are some way off, but I thought the standard 2x barlow screwed onto the nose of the Chinese BVs actually delivered that same increase in power. At least that’s what I recall with my old WO. Could be wrong. Maybe the Revelation is different?


My current (Baader) set up is more complicated, as I have 1.7x and 2.6x GPCs in the BV nose (which definitely don’t provide more than their stated magnification factors, in fact the 1.7x gives just 1.5x. Why Baader doesn’t call it a 1.5x GPC remains a mystery). But then placing a further barlow (Barcon) in front of the diagonal is supposed to provide another 2x leap in power - at least that’s what I read on CN. If correct this would mean Delites 18.2 would give about 200x in the F/7.4 Tak. Of course if I wanted more then I just add spacers to move the second barlow further from the eyepiece.

Would love to try a pair of pseudo Masuyamas one day. Interesting that you can use 7.5mm EPs comfortably in the Revelation. It is clearly a well collimated binoviewer - and a well collimated observer to be able to merge images at such high powers......😁

 

Hi Mark,

As I use a prism, I prefer to use a full barlow body so as not to let the barlow lens cell touch the prism surface, which can occur if I screw the lens directly into the bv nose. The increased distance, though only a few centimetres, is enough to make a noticeable power increase. I've never tried to measure the magnifications with any degree of accuracy, but just went off what I was told by Peter Drew a number of years ago. And comparing the bv view with a single eyepiece of the same power seems to lead me to believe the 4X amplification to be reasonably accurate with a full barlow attached to the viewer.

The 7.5mm Pseudo Masuyama's may not be everyone's first choice in a binoviewer, as the eye relief is ok but starting to get tight. The view does start to dim as Shane said above, but with the Moon there's still a long way to go before its too dim. To be honest, at such high powers I much prefer the lunar views through my Vixen HR's, as there's less glass, they are more comfortable and sharp.

One thing I did with my FC100DC was to use a Tak 1.6X extender-Q and a 2X barlow. On the Moon the views were nothing short of jaw dropping through the binoviewer!

Edited by mikeDnight
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It never twigged to me the extra distance barlowing the bino's would increase the magnification ratio. Good point and thanks, Always learning.

Glad I got a 2x tele-extender. Although still have a 2x barlow. 

Steve

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13 hours ago, Highburymark said:

Hi Mike - I’m using Tak FC-100 DC.
Must say I find working out BV magnifications a little brainfrying at the best of times. Haven’t tried the two barlow combination yet on the Moon, so maybe my calculations are some way off, but I thought the standard 2x barlow screwed onto the nose of the Chinese BVs actually delivered that same increase in power. At least that’s what I recall with my old WO. Could be wrong. Maybe the Revelation is different?


My current (Baader) set up is more complicated, as I have 1.7x and 2.6x GPCs in the BV nose (which definitely don’t provide more than their stated magnification factors, in fact the 1.7x gives just 1.5x. Why Baader doesn’t call it a 1.5x GPC remains a mystery). But then placing a further barlow (Barcon) in front of the diagonal is supposed to provide another 2x leap in power - at least that’s what I read on CN. If correct this would mean Delites 18.2 would give about 200x in the F/7.4 Tak. Of course if I wanted more then I just add spacers to move the second barlow further from the eyepiece.

Would love to try a pair of pseudo Masuyamas one day. Interesting that you can use 7.5mm EPs comfortably in the Revelation. It is clearly a well collimated binoviewer - and a well collimated observer to be able to merge images at such high powers......😁

 

I use a bino with GPCs on a 100DC as well :). I like 7 and 9 mm Delites the most in combination with a 1.7x GPC. I also have ADC with an lightpath of 48mm, that I need to accomodate, so the 2.6x GPC and longer FL eyepieces are used - something like 25 mm X-cels or 17.5mm Morphei. 

I just got a AP Baradv (Barcon successor). However, I am having a hard time achieving focus when putting in front of the ADC/diagonal/bino combo :(. This yields something beyond 3x magnifaction and gives some much back focus, that large extensions are necessary. At the moment I am also not convinced by the image this combination delivers. I did some extensive tests just yesterday on back focus added depending on the distance of the barlow to the eyepiece and also tried to measure magnification factor. If you are interested I can post these results.

best wishes

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3 hours ago, fate187 said:

I use a bino with GPCs on a 100DC as well :). I like 7 and 9 mm Delites the most in combination with a 1.7x GPC. I also have ADC with an lightpath of 48mm, that I need to accomodate, so the 2.6x GPC and longer FL eyepieces are used - something like 25 mm X-cels or 17.5mm Morphei. 

I just got a AP Baradv (Barcon successor). However, I am having a hard time achieving focus when putting in front of the ADC/diagonal/bino combo :(. This yields something beyond 3x magnifaction and gives some much back focus, that large extensions are necessary. At the moment I am also not convinced by the image this combination delivers. I did some extensive tests just yesterday on back focus added depending on the distance of the barlow to the eyepiece and also tried to measure magnification factor. If you are interested I can post these results.

best wishes

Hi Michael - I’d be very interested in your results. Presume Baradv is same power factor as the earlier Barcon?

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19 hours ago, Highburymark said:

Hi Mike - I’m using Tak FC-100 DC.
Must say I find working out BV magnifications a little brainfrying at the best of times. Haven’t tried the two barlow combination yet on the Moon, so maybe my calculations are some way off, but I thought the standard 2x barlow screwed onto the nose of the Chinese BVs actually delivered that same increase in power. At least that’s what I recall with my old WO. Could be wrong. Maybe the Revelation is different?


My current (Baader) set up is more complicated, as I have 1.7x and 2.6x GPCs in the BV nose (which definitely don’t provide more than their stated magnification factors, in fact the 1.7x gives just 1.5x. Why Baader doesn’t call it a 1.5x GPC remains a mystery). But then placing a further barlow (Barcon) in front of the diagonal is supposed to provide another 2x leap in power - at least that’s what I read on CN. If correct this would mean Delites 18.2 would give about 200x in the F/7.4 Tak. Of course if I wanted more then I just add spacers to move the second barlow further from the eyepiece.

Would love to try a pair of pseudo Masuyamas one day. Interesting that you can use 7.5mm EPs comfortably in the Revelation. It is clearly a well collimated binoviewer - and a well collimated observer to be able to merge images at such high powers......😁

 

Not sure how you screw 2.6x into bino nose, unless I am missing something it either gets screwed into the 1.25 or 2in nose which is then attached to bino, or into the T2 diagonal in front of the bino. Alternatively, if you have T2 diagonal you can screw 2.6x in front and it gives around 3.13x if I remember. This would also allow stacking with other two GPCs in the bino nose. Baader says you should not do it because it introduces abberations, others report that they stack GPCs with no problem whatsoever.

I tried binoviewing with FC100DF on the Moon at around 150x (12.5orthos and 2.6GPC). It 'feels' like 200x mono in terms of brightness and detectable detail. I might try putting 2.6 in front which would give around 185x next time, not sure if it will work.

 

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58 minutes ago, BGazing said:

Not sure how you screw 2.6x into bino nose, unless I am missing something it either gets screwed into the 1.25 or 2in nose which is then attached to bino, or into the T2 diagonal in front of the bino. 

 

No - you’re right - the 2.6x gpc does go into the diagonal, unlike the other two GPCs - I was generalising rather than getting into the confusing world of Baader bits. 
 

Thanks for all your contributions. Really useful to see different approaches.

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4 hours ago, Highburymark said:

Hi Michael - I’d be very interested in your results. Presume Baradv is same power factor as the earlier Barcon?

I think they changed some things regarding flattnes of the field when doing photography...

So some numbers: Column A ist the distance from of were the drawtube goes into the scope. Column B is distance of the backside of the Baradv to the eyepiece. C is magnification measured by drift.

A--------------B----------------C

188------------xx------------1 (no Baradv)

204------------15------------1.4x

212------------31------------...

221------------48------------...

244------------75------------2x (this is the Baradv with the standard extention it comes with)

286-----------119-----------2.64x

397-----------226-----------... (case were Barlow is in front of ADC followed by prism/bino).

All dimensions of length in mm. I did not measure the magnification in all cases.

Especially the last case is problematic. Its too much magnification (I estimate >3x) and too much backfocus added. I wanted to use to this Barlow to get best results with the ADC/bino combo. Guess this is a dead end. Not that the ADC/bino performance is bad in case though.

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Late to the party here Mark, but as you probably know I use a similar approach to you which works well for me. I use 25mm Ortho eyepieces, a x1.7 GPC and then an AP Barcon, varying the mag by using extension tubes. I also struggle to calculate the magnification this gives, suffice to say I find it to be enough at the high end for the best conditions in the Tak.

I use exactly the same setup in my CoolWedge and find it gives excellent results, despite the extra glass. Comparing the Baader with binoviewer in the Tak vs Lunt wedge with an ortho eyepiece in the optically very similar Vixen FL102S gave a clear advantage to the Tak setup, with much clearer granulation; the variables being the wedges and the binoviewer etc so I suspect it was incremental differences coming from each element with the scopes being the same.

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This is something that has been scrambling my brain recently too, i found a helpful article on Baaders website relating to calculating the magnifications as the extension distance changed for the VIP barlow.

Theres a pdf under the downloads tab:

https://www.baader-planetarium.com/en/accessories/optical-accessories/barlow-lenses-coma-and-glaspathcorrectors/vip-2x-modular-barlow-lens-visual-and-photographic.html

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2 hours ago, Stu said:

Late to the party here Mark, but as you probably know I use a similar approach to you which works well for me. I use 25mm Ortho eyepieces, a x1.7 GPC and then an AP Barcon, varying the mag by using extension tubes. I also struggle to calculate the magnification this gives, suffice to say I find it to be enough at the high end for the best conditions in the Tak.

I use exactly the same setup in my CoolWedge and find it gives excellent results, despite the extra glass. Comparing the Baader with binoviewer in the Tak vs Lunt wedge with an ortho eyepiece in the optically very similar Vixen FL102S gave a clear advantage to the Tak setup, with much clearer granulation; the variables being the wedges and the binoviewer etc so I suspect it was incremental differences coming from each element with the scopes being the same.

Hi Stu,

I am not sure I understand this fully. You are using a GPC in combination with a Barcon in mono mode? Isn't that too much magnification? ~1.5x from the GPC and 1.4x from the Barcon (no extension), you could just use the Barcon with extension. MAybe I misunderstood you there.

 

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2 hours ago, fate187 said:

Hi Stu,

I am not sure I understand this fully. You are using a GPC in combination with a Barcon in mono mode? Isn't that too much magnification? ~1.5x from the GPC and 1.4x from the Barcon (no extension), you could just use the Barcon with extension. MAybe I misunderstood you there.

 

This is with binoviewers, a similar setup to Marks I believe.

I use the GPC as I understand it corrects for CA in the binoviewers, and adding the Barcon gets me to the kinds of powers I enjoy. The eyepieces are 25mm, so I need a lot of barlowing in a 740mm scope to get the mag. Does that make sense? It’s a slightly off the wall setup in Congress but having compared a range of different kit I find this gives me the best results. I also have a preference for the x1.7 GPC over the x2.6, I just seem to get better results with it.

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This is a very interesting thread if I can interject a little. Stu you said :

10 minutes ago, Stu said:

I use the GPC as I understand it corrects for CA in the binoviewers, 

Does this mean that CA in a std achromat frac will be reduced.

If this is the case would it work with or without binoviewers.

Excuse my naivety  but I have not come across a GPC before, are these a recent thing?

EDIT> Think I am missing something here, are these a Newt thing. 

Edited by bomberbaz
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2 minutes ago, bomberbaz said:

This is a very interesting thread if I can interject a little. Stu you said :

Does this mean that CA in a std achromat frac will be reduced.

If this is the case would it work with or without binoviewers.

Excuse my naivety  but I have not come across a GPC before, are these a recent thing?

No. A GPC is only good to tame aberrations due to prisms in a bino.

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Just now, fate187 said:

No. A GPC is only good to tame aberrations due to prisms in a bino.

Yes I think I am gathering this by some pretty fast reading. Maybe I should do this before posting, thanks. 

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I had another go on measurement and placing the Baradv in the optical train. Because placing the Baradv (and I think any other barlow?!) in front of the ADC/diagonal/bino gives way to much magnification, I now tried diagonal/baradv/ADC/bino. IT works, no GPC is necessary in this configuration. Coincidently, focus position is almost the same as when only using mono mode with ADC/diagonal/2"+1.25" Baader Clicklock adapter. This is very good, because in the other cases I always had to fiddle with extension. Seems the ADC/Bino just uses the backfocus yielded by the barlow. But I digress.

In bino I'll use a T2-Sitall mirror. I have to contact Martin Gutekunst again and ask if a mirror is considered a dispersive element as for example a prism... I don't think so.

See the attached image. The baradv barlow is now in the 2" Clicklock, followed by the ADC and bino. Optical length from the back of the barlow to eyepiece is around 190 mm. This gives 2.94x by drift timing and 3x magnification by using coordinates on my goto mount, respectively on a distant object. Consider those values the same. Viewing quality was fine using 35mm Eudiascopic eyepieces in the bino.

I think I will try this configuration the next time the weather is good to the situation without barlow.

2.jpg

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  • 4 weeks later...
On 17/07/2020 at 13:56, fate187 said:

I had another go on measurement and placing the Baradv in the optical train. Because placing the Baradv (and I think any other barlow?!) in front of the ADC/diagonal/bino gives way to much magnification, I now tried diagonal/baradv/ADC/bino. IT works, no GPC is necessary in this configuration. Coincidently, focus position is almost the same as when only using mono mode with ADC/diagonal/2"+1.25" Baader Clicklock adapter. This is very good, because in the other cases I always had to fiddle with extension. Seems the ADC/Bino just uses the backfocus yielded by the barlow. But I digress.

In bino I'll use a T2-Sitall mirror. I have to contact Martin Gutekunst again and ask if a mirror is considered a dispersive element as for example a prism... I don't think so.

See the attached image. The baradv barlow is now in the 2" Clicklock, followed by the ADC and bino. Optical length from the back of the barlow to eyepiece is around 190 mm. This gives 2.94x by drift timing and 3x magnification by using coordinates on my goto mount, respectively on a distant object. Consider those values the same. Viewing quality was fine using 35mm Eudiascopic eyepieces in the bino.

I think I will try this configuration the next time the weather is good to the situation without barlow.

2.jpg

Only just catching up with this thread - many thanks Michael for this useful  information. I don’t use an ADC myself, but by adding a few T2 spacers I can replicate your above set up with AP Barcon. 

Interesting to see you use Eudiascopics for binoviewing - how do you find they compare with orthos or high quality plossls? And do you use shorter focal lengths, or just barlow the 35mms (which seem to have an excellent reputation, as Mike can attest).

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Hi Mark,

The 35mm Eudiascopic is really the finder pair or for lower mag only. During the last days I used my TEC140, GPC1.7 for some cluster viewing, but with my 25mm Cel X-cels, because the 35mm need just a little more inward focus :(. For the 35 I would have to switch to the 2.6 GPC, pratically rendering the longer fl compared to the 25mm useless. This is for the TEC140.

Nonetheless they are nice with the TAK or the CFF. Very sharp - obviously also due to the low magnification. For higher powers I use Morpheus 17.5 and 12.5, followed by 9 and 7mm Delites. The laast three get most usage during this planetary season in any of my scopes, combined with 1.7. Sometimes I also experiment w/o GPC in the CFF.

I will add another 5mm Delite to complete the pairs in my collection ;)

CS

Edited by fate187
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Mark,

I can't claim to understand most or even much of the above in terms of calculating which combinations give which magnifications - and, to be honest, some of the "stacks" being used seem distinctly unwieldy to me?

In fact, at one point it seemed to me to be so complicated that I almost gave up on binoviewing.

Thankfully, I didn't give up, but instead decided to go back to basics and try to keep everything as simple as possible. So I determined to see if I could find a way to use binoviewers just with eyepieces at native magnifications, without the need for Barlows or GPCs: (just as an aside, regarding GPCs, when I had a pair of Maxbrights, I used both ordinary Barlows and GPCs (not both at the same time), and found no difference in the levels of CA or any other aberrations as between barlows or GPCs).

I may have been just lucky, but with help from a couple of other kind members, I was able to find a combination of parts that enabled me to get my FS128 (F8 1040mm) scope to focus natively (chopping a few inches off the tube was never a consideration!).

I put up a thread on SGL which detailed how I did it, see link below if of interest..

https://stargazerslounge.com/topic/316218-binoviewing-with-a-tak-fs128/

This approach does need to be based on the T2 system and a Baader prism, as these components use up the least amount of back focus. I don't know if it will work with other Taks or not, or with other scope brands, but may be worth a try? 

Even if a Barlow or GPC is needed, it may avoid needing to mix and match other components and creating "big stacks"?😊

Dave

Edited by F15Rules
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51 minutes ago, F15Rules said:

Mark,

I can't claim to understand most or even much of the above in terms of calculating which combinations give which magnifications - and, to be honest, some of the "stacks" being used seem distinctly unwieldy to me?

In fact, at one point it seemed to me to be so complicated that I almost gave up on binoviewing.

Thankfully, I didn't give up, but instead decided to go back to basics and try to keep everything as simple as possible. So I determined to see if I could find a way to use binoviewers just with eyepieces at native magnifications, without the need for Barlows or GPCs: (just as an aside, regarding GPCs, when I had a pair of Maxbrights, I used both ordinary Barlows and GPCs (not both at the same time), and found no difference in the levels of CA or any other aberrations as between barlows or GPCs).

I may have been just lucky, but with help from a couple of other kind members, I was able to find a combination of parts that enabled me to get my FS128 (F8 1040mm) scope to focus natively (chopping a few inches off the tube was never a consideration!).

I put up a thread on SGL which detailed how I did it, see link below if of interest..

https://stargazerslounge.com/topic/316218-binoviewing-with-a-tak-fs128/

This approach does need to be based on the T2 system and a Baader prism, as these components use up the least amount of back focus. I don't know if it will work with other Taks or not, or with other scope brands, but may be worth a try? 

Even if a Barlow or GPC is needed, it may avoid needing to mix and match other components and creating "big stacks"?😊

Dave

Thanks Dave - and thanks for the link to that excellent thread. You’re absolutely right about the need for simplification. It seems to be part of the natural lifecycle of amateur astronomers that we feel the urge to decomplicate and declutter once we’ve gathered enough experience of different optics to realise that the differences between ‘very good’ and ‘excellent’ are often very slim.
Yours is one recipe for simple binoviewing. Stu’s is another - stick a decent barlow at the end of a stack of T2 spacers and just vary the stack size to reach ideal magnification. Unfortunately my problem stems from having three different BV set ups - solar ha and white light as well as high powered lunar/planetary, which require different scopes and many different eyepieces. I’ve sold off about ten eyepieces this year (and acquired a couple) but now in touching distance of achieving the zen-like calm of knowing I have all the EPs I need.

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