I always recommend that you post a link to the scope, or any equipment you are asking about, so we are all sure we are talking about the same things.
How do you plan your eyepieces?
I am going to outline a strategy for you. Whether you have a Mak, SCT, refractor or Newtonian, the strategy is the same. I have done this example based on my Meade ETX 125. This is a 127 mm Maksutov–Cassegrain with a 1900 mm FL for an F15 focal ratio. This is a good example of a scope with a 1.25” focuser that can’t accept 2” eyepieces. For this reason I have left 2” eyepieces out of the discussion. Just redo the calculations for your focal length to get the eyepiece sizes that work for you.
If you have a scope that can accept 1.25" and 2" eyepieces, let us know.
Watch the Video - First, some background on selecting an eyepiece - Orion telescope video
This is a very general video discussion of eyepieces and why there are a variety of designs
EYEPIECE STRATEGY SUMMARY
- One or two low power wide view eyepieces
- One or two midrange eyepieces
- Two to four high power eyepieces
- Or, Zoom plus barlow to cover mid range and high power
- Planning to use a barlow can save you money
A 127 mm scope will have a maximum mag of around 254X, though many nights you may not be able to reach that magnification level due to atmospheric conditions. More on that later. I estimated that based on 2X the aperture in mm. 127 X 2 = 254X
This scope has a 1.25” diagonal/focuser. The best low power/widest view eyepiece would be a 32 mm Plossl eyepiece. In my scope that provides 59.4X and .84 degree FOV. That is about as wide as this scope will go. If your scope has a different focal length than you can redo the calculations for your scope with a 32 mm Plossl that typically has a 50 degree AFOV.
Focal length scope ( FLS) / Focal Length eyepiece ( FLE) = Magnification
Apparent Field of View of eyepiece (AFOV) / Magnification = Field of View (FOV)
( this is a simplified calculation that offers a very close approximation of FOV)
Based on a 32 mm for the low power wide view and 254X as the top mag target, here is a sample range of eyepieces and magnifications for my scope.
59X = 32 mm ( low power)
95X = 20 mm (medium power)
127X = 15 mm (medium power)
158X = 12 mm (high power)
The above mags should work almost any night.
Below are mags for this 127 mm scope that would need good seeing and transparency to be useful
190X = 10 mm (Some nights I can’t go this high. This could be the 20 mm in a 2X barlow)
237X = 8 mm ( Fewer nights I am able to reach this mag. )
256X = 7.5 mm (15 mm in 2X barlow could provide this which is likely to be infrequently used)
317X = 6 mm ( Might work on the moon on good nights.)
Since I have a 12, I can easily 2X barlow that to give 6 mm to try it without having to buy an eyepiece I would rarely use.
Nothing rigid about these mag targets, I am just using them as an illustration of a range of magnifications to work toward. And there is nothing to stop you from trying to go higher than 2X aperture, as I illustrate. Do the calculations for your scope. Note that I have selected eyepiece spacing that would work well if I wanted to use a 2X barlow to help me cover some of the higher powers if I didn’t want to spend the money on magnifications that I might not be able to use often.
How high you can go depends on transparency, the clarity of the air, and "seeing".
What is SEEING and why it can be bad. How it will limit how high you can go.
This is not a problem with your telescope or your eyepiece.
Barlow Lens – I mentioned using a 2X barlow lens. A barlow is an intermediate optical device that goes between the eyepiece and the objective lens or primary mirror. It effectively gives each eyepiece two magnifications, one with and one without the barlow. For visual use, barlows ranging from 1.5X to 3X are common. So, if you have 4 eyepieces properly spaced and add a barlow, you now have 8 magnifications with only 4 eyepieces. You can read more about barlows at this link: http://www.telescope...rlows/99807.uts
The alternative method to multiple eyepieces is to use a zoom eyepiece. This is my primary approach. An 8-24 mm zoom, in my ETX 125 scope, provides 79X to 237X, and everything in between. Most nights this is all the range I need based on atmospheric conditions, so the zoom is all I use. If I want to push higher, I can drop the zoom in my barlow and probe those higher magnifications. If this were my ETX 80, 400 mm FL, then a 2X or 3X barlow would be in use frequently.
Eyepieces are a tool that you will want to add over time. Above is just a strategy for where and how to add them. Below are some eyepiece examples for your consideration. The good news is that eyepieces are standard sized. Any brand of 1.25" eyepiece will fit in almost any telescope. So if you plan to upgrade your telescope some day, or add a larger scope, the eyepieces you buy today will fit.
32 mm Plossl - I find most of them all to be good. Celestron, Meade, Orion, GSO are all quite good. Televue has an excellent reputation, at a higher price.
Lower Cost Single FL eyepieces - AT Paradigm line has an excellent reputation and offers a 60 degree AFOV, wider than Plossl eyepieces. I don’t have these but I read so many good reports about them, especially in scopes of F5 or higher focal ratios.
The Agena Astro Dual ED are the same eyepieces under a different label.
Discussion about Paradigm eyepieces
Medium Priced Single FL Eyepieces – Explore Scientific 68 degree, 82 degree and Meade 82 degree
Premium single FL eyepieces – TeleVue – I don’t have any Tele Vue but they are considered, by many, to be among the best available, but they are expensive.
THE ZOOM EYEPIECE
This is my favorite eyepiece. Like a zoom lens on a camera, this single eyepiece effectively replaces a range of eyepieces. Sounds great, but there is a trade-off. The apparent field of view of the zoom runs from a narrower AFOV at the 24 mm range to a wider FOV at the 8 mm range. So, like any approach, the zoom is a compromise. I find that compromise quite acceptable when weighed against the benefits. I find I tend to use it mostly in the 18 mm to 8 mm part of the range.
Lower cost zoom – Celestron 8-24 – This was my first zoom and still use it from time to time in my scopes – $66
Higher priced Zoom – Baader Hyperion 8-24 mm – Now my main eyepiece in my Orion XT8i, Apertura AD12 and frequently in my other scopes – $290
- I never expected the zoom eyepiece to become my primary eyepiece, but it has.
- With a zoom, the eyepiece seems to disappear as you just move in and out at will, no swapping, no thinking about eyepiece changes
- The Celestron 8-24 zoom is good and comparable to my Plossl eyepieces
- The Baader Hyperion is great and comparable to my Explore Scientific eyepieces
- Watching doubles split as I rotate the barrel is wonderful
- One filter serves over a wide range of magnifications, no screwing and unscrewing to try other eyepieces
- Moving smoothly from and between small changes in magnification helps when seeing is not the best
- I am always working at the optimum magnification for this target.
- Sharing the view with others is easier, especially in my manual tracking Dob - I hand it over at low mag so it stays in the view longer. They zoom back in to whatever magnification works best for them.
- My eyepiece case has been greatly simplified
- Kids love the zoom
In my 127 mm Mak, when I observe, 90% of the time, I use the 32 mm Plossl and then the 8-24 zoom and that is all I use. But if conditions are really good, I will probe higher with the barlow and zoom.
With my ETX 80, 400 mm FL, the 32 mm Plossl, the zoom and the barlow are all used each evening.
In my Orion XT8i and Apertura AD12 Dobsonians, which have a 2” focuser, I use 38 and 20 mm 2”, 8-24 zoom and may go to a 2X barlow. Same strategy for each scope.
Zoom eyepiece review including the Celestron
An older view, and the Celestron specs have changed, but the discussion matches well to my experience with my Celestron zoom
Baader Hyperian Mark IV Zoom review - The current model -
Baader Zoom User Discussion
Explore Scientific 82 degree Vs. Meade series 5000 Ultra Wide 82 degree eyepieces
A very good discussion, by Al Nagler, about eyepieces and magnification for those who want to go a little deeper. He discusses our eyes, our telescopes, focal ratios, exit pupils, the atmosphere and things related to choosing magnification. A good read and not too technical. It is a general discussion and not specific to any eyepiece or any brand of eyepiece.
Eyepiece Designs - This is the one I turn to when I am trying to understand or explain the differences between the various designs. There are many different designs, Many are named
for their original designer, such as Huyghens, Ramsden, Kellner, Plossl, Konig, Erfle, Branden and Nagler.