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Which planetary eyepiece should I buy?

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#1 Callumf97

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Posted 23 May 2020 - 01:36 AM

I’ve got a 130mm F7 newtonian telescope with a 900mm focal length and I’m thinking of buying a speciality planetary eyepiece, however I can’t decide on an eyepiece focal length as my options are 2.5mm, 4mm, 5mm, 6mm, 7mm and 9mm - whcich one do you guys think I should go for? My main planets I observe are Jupiter, Saturn, Venus and Mars

#2 sg6

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Posted 23 May 2020 - 02:57 AM

Personally I would try a 6mm.

You have 910mm focal length, I would not consider 2.5mm or 4mm as delivering a usable result (certainly not the 2.5 364x).

 

5mm eyepieces seems to like f/5 scopes, they might work or they might not. Find that everything needs to be good = eyepiece, scope, setup, luck. Rarely do you get all 4.

 

Will say to an extent drop Mars, Mars tends to be difficult even with all 4 of the previous on your side. It needs 250x and preferably 300x.

 

6mm would give around 150x. If a good image then adaquate for Saturn, and if Saturn then covers Jupiter, likely find Jupiter better at 80x even if smaller or just the same size as Saturn @150x.

 

My thoughts are work on what is necessary for Saturn and aim for that, put Mars a little to one side - you might be able to borrow a shorter eyepiece for Mars just to try out if you are in/at a club.

 

Eyepieces for planets means you can have from 3mm to 12mm in 1mm steps - I am only missing (I think) a 7mm, have the rest.

 

Which eyepiece is I suppose next. See what ES offer in their 52 degree line, cannot recall if they do a 5.5mm or a 6mm. WO used to do a 6mm planetary (have that one) also around as an Altair Lightwave so maybe others brands. Slight warning about the Altair - they do, or did, 2 eyepieces called Lightwave, one is about 3x the cost of the other. Never understood that.

 

Was once asked on CN What use is a 4mm eyepiece?

As I recall putting it on the ground, pushing it down a bit, putting a golf ball on top and using it as a tee come top.



#3 mikeDnight

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Posted 23 May 2020 - 03:34 AM

Hi Callum,

 

I find that Jupiter is best observed at around 180X give or take a little. The other planets you mention can also be observed well at around that magnification, including Mars when its at its best later in the year. I'm more inclined towards a 9mm orthoscopic and a 2X barlow which will give you 156X, yet it will be quite comfortable to use. ENS Optical have a number of old volcano top ortho's for sale, so it might be worth checking them out. Some cheap short focal length eyepieces can be uncomfortable to use and not very good performance wise, but these old orthoscopics are very sharp and at 9mm, very comfortable.


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#4 StarAlert

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Posted 23 May 2020 - 03:54 AM

What EPs do you currently have? 



#5 Shorty Barlow

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Posted 23 May 2020 - 03:59 AM

I have a 130mm, f/7 Newtonian.

 

med_gallery_249298_5348_5411.jpg

 

I found the most used three planetary eyepiece focal lengths were 6mm, 5mm and 4mm. These gave 150x, 180x and 225x respectively. Later I added a 4.5mm (200x).

 

med_gallery_249298_10131_73777.jpg

 

These Vixens are the same focal length. 

 

med_gallery_249298_10131_172933.jpg

 

These also work well in my 150mm, f/6 Newtonian. Occasionally I can use a 3.2mm StarGuider on the Moon 281.25x.


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#6 Shorty Barlow

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Posted 23 May 2020 - 04:02 AM

Oh yeah, I forgot these:

 

med_gallery_249298_10131_1189619.jpg

 

https://www.firstlig...-eyepieces.html

 

Good for the money.


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#7 Riccardo_italy

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Posted 23 May 2020 - 04:20 AM

May I suggest a 5.5mm eyepiece?

 

This one: https://explorescien...oducts/62-5-5mm

 

165x it's the right magnification, and that eyepiece is sharp.

 

EDIT: given your scope, whatever you choose do not go above 6mm or below 5mm if you plan to have a single planetary eyepiece.


Edited by Riccardo_italy, 23 May 2020 - 04:23 AM.

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#8 izar187

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Posted 23 May 2020 - 08:23 AM

I’ve got a 130mm F7 newtonian telescope with a 900mm focal length and I’m thinking of buying a speciality planetary eyepiece, however I can’t decide on an eyepiece focal length as my options are 2.5mm, 4mm, 5mm, 6mm, 7mm and 9mm - whcich one do you guys think I should go for? My main planets I observe are Jupiter, Saturn, Venus and Mars

My vote is also for 5mm to 6mm.

The 5mm will work best at it's approximate 182x, when the planet is high in the sky as possible, crossing your meridian.

When the scope is cooled, after setting out for a little while, which can be when you are looking at other stuff.

Plus when man-made heat sinks, like roofs, pavement and chimneys, are not under your line of sight to the planet, radiating off their thermal load into your view of the planet.

My best planets with my modest sized newts, have all been when I've taken counter measures for as much of the seeing as is possible. Then they always do better. Planet high in the sky(yup, set an alarm and get up for it), scope cooled, viewing on and over grass.

 

In truth, if many of the above are simply not in your control, as is very much sometimes the case, then seek closer to the 6mm (approx, 150x), and enjoy. Sketch what you can see, and you'll automatically start to see more anyway.


Edited by izar187, 23 May 2020 - 08:32 AM.


#9 BillP

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Posted 23 May 2020 - 09:46 AM

Over the years, for planetary with scopes with apertures of 10" and less, I have found that a good rule of thumb is to keep the working magnification up to whatever eyepiece produces about a 0.7mm exit pupil.  Going smaller than that certainly works, but the planet dims enough that you will start losing visibility of low contrast features, so most important for Jupiter with the festoons often being like that.  Mars can tolerate a bit of a smaller exit pupil if you don't mind losing some edge definition to the Planetia regions (darker plains note the 1st and 2nd Mars sketches, the 1st is with a wide field and 2nd with a planetary specialty eyepiece, you can see how the planet some fine details off the dark Planteria are not visible like in the 2nd sketch, so both the smaller exit pupil and more scatter complex glass eyepiece contributes to that loss).  Saturn can take smaller exit pupils well unless you are hunting for the ethereal storms sometimes visible in its bands (recommend a 10" for that though).

 

You calculate what the exit pupil will be by taking the focal length of the eyepiece and dividing it by the focal ratio of the telescope.  So for your scope a 5mm eyepiece would be: 5mm / Focal Ratio 7 = 5/7 = 0.714.  Once you do this then you need to make sure the magnification is not so high that your local seeing would not support it.  For where I live it is very easy to get to 150x with a steady planetary view, and then less frequently 200x, and then less often when 250x works well.  So in your scope a 5mm will produce 180x which should be usable often.  However, if it were me I would probably get a 6mm also for when the seeing is not so good as it will produce an easier 150x.

 

Now about the magnification, do not worry so much about that.  At about 20x/inch of aperture magnification for any scope, your eye will be able to see all the details available produced my the main objective.  So in your scope that is believe it or not just 100x!  Yup.  Even though the planet will be small at 100x if you study the image critically and train your eye to get used to hunting for and picking out the smallest details, you will find that as you magnify more than no net details will be revealed (unless they were masked by an overly bright image at the lower magnification).  FWIW I routinely do most of my planetary observing at about 135x and below are some examples of the details I can see with my 4" scope (images are not to scale relative to the FOV boundaries FYI as had to draw them larger to represent all the detail I was seeing).

 

So I recommend a 5mm and a 6mm eyepiece with your particular scope for planetary.  Best of luck with whatever you decide to get and enjoy!!

 

6175546-Mars4.JPG
6175521-4077350-Juppiter2.jpg
6173840-Jupiter in TSA.jpg

Edited by BillP, 23 May 2020 - 07:18 PM.

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#10 BillP

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Posted 23 May 2020 - 02:25 PM

So I recommend a 5mm and a 6mm eyepiece with your particular scope for planetary.  Best of luck with whatever you decide to get and enjoy!!

 

As far as what eyepieces to get it all just depends.  For the most part a good wider field is still going to show you a great planetary view even though more complex design.  But if you wanted to be a traditionalist and go with a minimum glass design with tight eye relief then the new (and inexpensive) Takahashi Starbase Ortho in 6mm is an exceptional little eyepiece.  It is $56.  https://www.astronom...o-eyepiece.html

 

Finding an affordable 5mm will be a little more difficult.  As example, the Fujiyama 5mm Abbe Ortho is probably the best-in-class for Abbe Orthos still in current production.  It is $95.  They also have a 6mm so could get two as a matching set.  If you have the money and want the traditional planetary then this is what I would do with these two matching Fujiyamas.

 

Otherwise, you will get great views with just about any more complex wider AFOV out there.  So don't feel like it is neessaary to go for these traditional planetaries to get a good view of a planet.  And don't be afraid to use a 2x Barlow to get to 5mm and 6mm if you currently have a 10mm and 12mm eyepiece as you will get good views. 

 

Finally, if you want more comfortable eye relief and wider AFOV, then things like the Astro-Tech Paradigm Dual-ED or Agena BST Starguider in 5mm, and then one in 12mm with a 2X Barlow to get to 6mm would be very good also.  Not going to get the rock hard crisp view the little Fujiyama Abbe Ortho can give with its minimum glass and excellent coatings, but will be close enough for all but the purists.  I have almost a full set of the BST Starguiders and enjoy them very much being both inexpensive ($60), comfortable, wider 60 degree AFOV, and good performers.

 

https://agenaastro.c...epiece-5mm.html

https://www.astronom...gm-dual-ed.html


Edited by BillP, 23 May 2020 - 02:33 PM.

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#11 cimar

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Posted 23 May 2020 - 03:16 PM

Hi,

I guess I would use a 5mm, 6mm or 7mm eyepiece most for planetary observing with your scope.

A 6mm Delos would be great.



#12 Riccardo_italy

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Posted 23 May 2020 - 04:12 PM

A 5-6mm Ortho might be a bit uncomfortable to use. A 12mm + a good barlow is a nice option. But in a manual scope a super-small AFOV should be avoided.


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#13 Bataleon

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Posted 23 May 2020 - 08:18 PM

If you can get to a dark site, Uranus and Neptune are nothing to sleep on either. They're tiny, but resolving them as a sharp blue orb is more satisfying than you might think.

Sent from my SM-N960F using Tapatalk
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#14 AJK 547

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Posted 23 May 2020 - 09:17 PM

If you can get to a dark site, Uranus and Neptune are nothing to sleep on either. They're tiny, but resolving them as a sharp blue orb is more satisfying than you might think.

Sent from my SM-N960F using Tapatalk

So true Bataleon.  If Uranus or Neptune are ‘up’ during a visual session, I’ll certainly spend time just taking in the blue-grey Uranus or striking med-blue of Neptune...

 

I’ll usually be using one of my 5,4 or 3DL’s based on seeing.

Attached Thumbnails

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Edited by AJK 547, 24 May 2020 - 06:59 AM.

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#15 grzesznypl

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Posted 23 May 2020 - 09:21 PM

It would help to know how much money OP wants to spend. Baader Mark IV Zoom with 2x barlow would give him 4mm-12mm range that can be adjusted in real time without swapping eyepieces which would also allows to find optimal magnification for the night. I use BZ on moon and planets and IMHO its fantastic.


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#16 Bataleon

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Posted 23 May 2020 - 09:22 PM

So true Bataleon. If Uranus or Neptune is ‘up’ during a visual session, I’ll certainly spend time just taking in the blue-grey Uranus or striking med-blue of Neptune...

Nice! That's not far off from what I saw last time I got my C8 under a dark sky site. I *definitely* saw Titania since it resolved as an orb within the field of Uranus. Looked very much like Titan in the field of Saturn. Possibly saw Oberon, but hard to tell if moon or dim star. I think I may have seen Triton, but also hard to confirm. The position matched where it's supposed to be everything looks so small that far out.

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#17 izar187

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Posted 24 May 2020 - 07:01 AM

It would help to know how much money OP wants to spend. Baader Mark IV Zoom with 2x barlow would give him 4mm-12mm range that can be adjusted in real time without swapping eyepieces which would also allows to find optimal magnification for the night. I use BZ on moon and planets and IMHO its fantastic.

Too many folks have shared positive agreement with that to doubt it. I believe it.

Yet in my modest sized newts a heavy ep and barlow combination is much less fun then a lighter weight ep or 2.

After decades of barlowing, I switched to a specific ep, and then another, just for planets in a couple short scopes.

 

As others have mentioned, if hand tracking, then something wider field is easier.

However, if slow motion controls are there, then this also helps greatly for when with modest field ep's.



#18 SteveG

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Posted 24 May 2020 - 12:31 PM

The eyepiece will work well on planets and everything else. Tons of positive reviews on this site:

 

https://optcorp.com/...dxoCFqQQAvD_BwE


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#19 SandyHouTex

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Posted 25 May 2020 - 07:33 PM

Over the years, for planetary with scopes with apertures of 10" and less, I have found that a good rule of thumb is to keep the working magnification up to whatever eyepiece produces about a 0.7mm exit pupil.  Going smaller than that certainly works, but the planet dims enough that you will start losing visibility of low contrast features, so most important for Jupiter with the festoons often being like that.  Mars can tolerate a bit of a smaller exit pupil if you don't mind losing some edge definition to the Planetia regions (darker plains note the 1st and 2nd Mars sketches, the 1st is with a wide field and 2nd with a planetary specialty eyepiece, you can see how the planet some fine details off the dark Planteria are not visible like in the 2nd sketch, so both the smaller exit pupil and more scatter complex glass eyepiece contributes to that loss).  Saturn can take smaller exit pupils well unless you are hunting for the ethereal storms sometimes visible in its bands (recommend a 10" for that though).

 

You calculate what the exit pupil will be by taking the focal length of the eyepiece and dividing it by the focal ratio of the telescope.  So for your scope a 5mm eyepiece would be: 5mm / Focal Ratio 7 = 5/7 = 0.714.  Once you do this then you need to make sure the magnification is not so high that your local seeing would not support it.  For where I live it is very easy to get to 150x with a steady planetary view, and then less frequently 200x, and then less often when 250x works well.  So in your scope a 5mm will produce 180x which should be usable often.  However, if it were me I would probably get a 6mm also for when the seeing is not so good as it will produce an easier 150x.

 

Now about the magnification, do not worry so much about that.  At about 20x/inch of aperture magnification for any scope, your eye will be able to see all the details available produced my the main objective.  So in your scope that is believe it or not just 100x!  Yup.  Even though the planet will be small at 100x if you study the image critically and train your eye to get used to hunting for and picking out the smallest details, you will find that as you magnify more than no net details will be revealed (unless they were masked by an overly bright image at the lower magnification).  FWIW I routinely do most of my planetary observing at about 135x and below are some examples of the details I can see with my 4" scope (images are not to scale relative to the FOV boundaries FYI as had to draw them larger to represent all the detail I was seeing).

 

So I recommend a 5mm and a 6mm eyepiece with your particular scope for planetary.  Best of luck with whatever you decide to get and enjoy!!

 

So this was a great discussion on the exit pupil, which I was unaware of.  0.7mm is pretty small, is there a physical reason for this number, or is it something you derived based on all of your observations?



#20 Riccardo_italy

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Posted 26 May 2020 - 01:16 AM

The diameter of the scope matters a lot!

 

In a 200mm scope, 0.7mm e.p. = 285x, often above what the seeing allows.

 

In a 300mm scope, 0.7mm e.p. = 428x, usable a few nights and way above what I would purchase as a single planetary eyepiece in that scope.

 

On the other side, in a 100mm refractor, 0.7mm e.p. = 142x. For a single planetary eyepiece, in that scope I prefer 160x-180x even if the e.p. is smaller than 0.7mm.



#21 RichA

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Posted 26 May 2020 - 03:39 AM

I have a 130mm, f/7 Newtonian.

 

med_gallery_249298_5348_5411.jpg

 

I found the most used three planetary eyepiece focal lengths were 6mm, 5mm and 4mm. These gave 150x, 180x and 225x respectively. Later I added a 4.5mm (200x).

 

med_gallery_249298_10131_73777.jpg

 

These Vixens are the same focal length. 

 

med_gallery_249298_10131_172933.jpg

 

These also work well in my 150mm, f/6 Newtonian. Occasionally I can use a 3.2mm StarGuider on the Moon 281.25x.

The TMB designs are very good, and incredibly affordable.  It's possible to fractionate focal lengths by 0.5mm divisions since there appear to be that many for sale on Ebay.



#22 ValhallaObserver

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Posted 26 May 2020 - 01:37 PM

Has anyone tried the Stellarvue planetary eyepieces? They seem interesting but have more elements but that does bring some benefits of course.

 

https://www.highpoin...-1-25inch-ep061

 

https://www.highpoin...-1-25inch-ep049

 

Opinions and Thoughts?

 

VO



#23 BillP

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Posted 26 May 2020 - 07:23 PM

So this was a great discussion on the exit pupil, which I was unaware of.  0.7mm is pretty small, is there a physical reason for this number, or is it something you derived based on all of your observations?

Based on observations so empirical.  Whenever I got below .65mm, then low contrast features on Mars and Jupiter would no longer be visible.  So I bump it up to 0.7mm to be safe as a rule-of-thumb.  Of course, given all the variables in an optical chain, including one's own eyes, I would expect this to vary a bit.  But the cool thing about it is that it is easy enough for everyone to experiment for themselves to find out the exact number that works for them.  Just start with a .8mm exit pupil and start decreasing.  Of course one would need great seeing conditions and use only Mars and Jupiter as these are really the best for a lot of low contrast stuff.


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#24 BillP

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Posted 26 May 2020 - 07:29 PM

Has anyone tried the Stellarvue planetary eyepieces? They seem interesting but have more elements but that does bring some benefits of course.

 

https://www.highpoin...-1-25inch-ep061

 

https://www.highpoin...-1-25inch-ep049

 

Opinions and Thoughts?

 

VO

These look like a re-badge of the discontinued Zhumell Z Planetaries.  As I recall, people liked them pretty much and they were strong performers.

 

https://cdn.shopify....eg?v=1571277557



#25 russell23

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Posted 26 May 2020 - 07:40 PM

These look like a re-badge of the discontinued Zhumell Z Planetaries.  As I recall, people liked them pretty much and they were strong performers.

 

https://cdn.shopify....eg?v=1571277557

The 6mm and 5mm versions have some issues with blackouts and glare from bright stars just outside the fov.   The 9mm is the best of that series in my opinion, but the 12.5mm and 14.5mm are also pretty good.  Stellarvue did not have them made in those focal lengths but you can still get them from Orion as the "Edge on" series.  I still have my 9mm Astrotech branded version.  I don't use it often but every time I do I enjoy it. 




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