Affordable low power eyepiece

[jackce]

About a month ago I got a Celestron 6" Advanced VX Series Go-To Equatorial Refractor. Of course nowadays when you buy a decent telescope they only provide you with one EP to get started, so in this case it is a 20mm Plossl that gives me 60x magnification which is too much to see the entire sun or moon's disc. Yes I would like to get a 4 or 5mm to achieve the maximum acceptable 300x magnification (1200mm focal length) for planetary and moon viewing, but I would probably get me a lot more use out of a 35mm or higher eyepiece. I have been looking at many of them online, but being relatively new to Astronomy at my age of 60, I don't want to spend a lot on one eyepiece which I have found is very easy to do. I won't mind spending a few dollars more than a 100 to get the EP, but I am somewhat overwhelmed by the many types, not brands I can choose from. I do know that I want the EP to be a 2" for more eye relief and wider field of view. I guess the most important features to the one I choose would be long eye relief as I wear glasses. 20mm eye relief or greater sounds like it would be sufficient. The 20mm Plossl that came with the scope has very, very little eye relief if any and no roll down eye cup either. If someone could please make some recommendations as to what may be an acceptable EP for me to purchase I would be very appreciative for the help.

Thank You

Jack   

[Cosmic Geoff]

Be aware that however much you spend or how long the focal length of the eyepiece, the field is ultimately limited by the diameter of the 1 1/4" barrel.

2" eyepieces will give a wider actual field - if you have a 2" focuser. A long focal length Plossl will have long eye relief (it is what they call a scaled design.)

[nightfisher]

Look at the Revelation 32mm plossl in 1.25 barrel, or if you have a 2" diagonal look at the Revelation 2" 42mm ep

[Alfian]

3 minutes ago, nightfisher said:

Look at the Revelation 32mm plossl in 1.25 barrel, or if you have a 2" diagonal look at the Revelation 2" 42mm ep

Agreed, you'd be hard pushed to find a better wide field EP for the money. It would seem a shame not to go for a 2" eyepiece given the wider possible fov and at F8, something around a 40mm with a 65-70 degree afov is going to give you something like 2.2 degrees, whereas a 1.25" EP is going to be almost a degree less. Another reasonably cheap alternative would be the Skywatcher 38mm/70 degree Panaview. I think these may be the same as the Agena 2" SWAs. The Revelation EPs will be the same as the GSOs.

[rwilkey]

Hi Jack, the Sky Watcher 2" 32mm PanaView would be a good choice at a reasonable price hopefully in the States.

[ronin]

The 20mm plossl you have  - is it a plossl ?? - will deliver around 13 to 14mm of eye relief, so in effect you are considering something that is a bit more.

Forget the 300x idea. At 6" 150mm and 1200mm focal length that f/8. Really you will get 180x I would expect fairly easy, 200x is likely towards the real limit and above that the gods of astronomy are smiling on you. Unfortuantely they seem not to smile often.

Budget is all important, and I tend to stick to 1.25" eyepieces. The swapping between 1.25" and 2" is a pain.

There the Paradigm's in the US that are good, 5mm to 25mm and they have 1-17mm of eye relief, so may be a bit close.

The Celestron X-Cels are a similar performing set and for planets the lower focal lengths are better suited to planets as the steps are closer. They have 17-18mm eye relief.

Plossl eyepieces are out of the question. The eye relief of a plossl is about 2/3 of the focal length.

ES 68's next but they appear to have short eye relief at some of the eye pieces.

The ES82's again seem to have eye relief that only manage 15mm.

The TV eye pieces Delites and Delos are both 20 mm eye relief but they are a significant jump in cost. Delites = $250, Delos = $340.

There are Meade 5000 series eyepieces at a 60 degree field, these have 17mm eye relief, that are generally reported as good, $90.

I have the equivalent of the Paradigms and I wear glasses and get along with them fine, only moan being I would have liked a 6mm also, just to fill the gap of 5mm to 8mm. Without too great a cost then the Meade 5000's.

Would be tempted to say consider the Meades, thay go to 25mm and the shorter lengths look useful.

Any clubs to visit? http://www.go-astronomy.com/

Texas: http://www.go-astronomy.com/astro-clubs-state.php?State=TX

[LukeSkywatcher]

32mm GSO?

Fantastic EP.

[Ricochet]

On 09/09/2017 at 09:15, jackce said:

a 20mm Plossl that gives me 60x magnification which is too much to see the entire sun or moon's disc

I'm surprised no-one has really picked up on this yet, but a 20mm Plossl giving 60x will show about 0.85° of sky whilst the Sun and Moon are about 0.5° in diameter. Your problem here must be that because you are wearing glasses to observe you cannot get your eye close enough to see the whole image. As such I think you need to replace your 20mm as well as adding additional eyepieces. I would guess that something like a Celestron X-Cel LX or Vixen SLV with long eye relief and twist-up eyecups that can be left fully retracted would be your best bet. I don't think a standard Plossl for lower power, where most of the eye relief is taken up by recessing the lens is going to better than the Plossl you already have.

[Stub Mandrel]

@Ricochet has a point. I have a 1200mm and 1250mm scope and they both comfortable show a full disk with a stock 25mm EP.

If you wear glasses, try taking them off and refocussing!

[Louis D]

On 9/10/2017 at 13:19, Stub Mandrel said:

@Ricochet has a point. I have a 1200mm and 1250mm scope and they both comfortable show a full disk with a stock 25mm EP.

If you wear glasses, try taking them off and refocussing!

I'm guessing the OP has severe enough astigmatism that refocussing without glasses is simply not an option.  It would be delightful if some manufacturer would create a variable power/variable angle astigmatism corrector for focusers to address this issue.  The TV DIOPTRX are nice, but hardly a universal solution.

The OP's new scope does come with a 2" focuser, but I think only a 1.25" diagonal is included, so they'll need a 2" diagonal to move up to 2" eyepieces.  That's a $100 or so expense to be considered as well.

A cheap 2" eyepiece with long eye relief would be the Meade 56mm Plossl.  The exit pupil will be a tad large at 7mm, but it will deliver a widest field possible with fewer aberrations at the edge compared to cheap 70 degree 38 to 42mm eyepieces.  Given it's an unobstructed telescope, there shouldn't be any shadowing issues in the center of the field of view to deal with.

[Stub Mandrel]

The 25mm that came with my Skywatcher 150PL is apparently the same as the Celestron design and has lots of eye relief. The 32 that came with my C90 Mak has HUGE eye relief, both work well with my glasses.

These are both cheap entry-level EPs, but I find them OK.

[jackce]

Ok, I guess I'm not sure I know what eye relief is. I thought it was the distance from the glass to the top of the EP barrel where your orbit would come in contact, but now I'm not sure I am right about that at all! I included a picture of the 20mm Plossl that came with my scope and somebody here said it should have about 13mm eye relief. Looking at the picture I barely see 1mm at most! Somebody please tell me where the 13mm shows in the picture!

 

[Stub Mandrel]

Eye relief is how far your eye needs to be from the upper glass surface of the eyepiece.

With my 32mm EP this is probably about 20mm so it took a bit of getting used to as I can't rest my glasses/eye against the eyepiece and have to 'hover' behind it.

Funnily enough once I have found the right spot I find this EP easier to use than most, I struggle to stay at an EP for long.

[Louis D]

3 hours ago, jackce said:

Ok, I guess I'm not sure I know what eye relief is. I thought it was the distance from the glass to the top of the EP barrel where your orbit would come in contact, but now I'm not sure I am right about that at all!

The eye relief point is where the image forms for the eye to refocus on the retina.  You generally place you cornea/internal eye lens at that point.  It is easiest to see and measure by shining a flashlight backward through the eyepiece from the barrel end that inserts in the focuser.  Now, if you move the eyepiece's eye lens end toward a wall, table top, or piece of card stock, you should see a projected circle of light that gets smaller the closer the surface and eyepiece get to each other, to a point.  Beyond that point, it gets bigger again until the two touch.  It is that point of smallest circle of light that is the eye relief point.  If you measure the distance from the top of the housing to the projection surface, that is the usable eye relief.  If you add in the distance from the center of the eye lens to the top of the housing, that is the design eye relief.  Give it a try and let us know what you find out for your stock eyepiece.

[Mr niall]

I've got a vixen NPL 30mm, has a twist up cup so lots of eye relief. Definitely my favourite eyepiece. I think they're still on sale at FLO?

[Louis D]

1 hour ago, Mr niall said:

I've got a vixen NPL 30mm, has a twist up cup so lots of eye relief. Definitely my favourite eyepiece. I think they're still on sale at FLO?

Given the OP is in Texas, it would be about $30 cheaper (shipped) to order local to the US.

[Mr niall]

2 hours ago, Louis D said:

Given the OP is in Texas, it would be about $30 cheaper (shipped) to order local to the US.

Good point, apologies!

[jackce]

14 hours ago, Stub Mandrel said:

Eye relief is how far your eye needs to be from the upper glass surface of the eyepiece.

With my 32mm EP this is probably about 20mm so it took a bit of getting used to as I can't rest my glasses/eye against the eyepiece and have to 'hover' behind it.

Funnily enough once I have found the right spot I find this EP easier to use than most, I struggle to stay at an EP for long.

Thank you for clearing that up for me! I used a flash light that is pretty much the same diameter as the barrel of the EP and held it right up against the EP barrel end and although it is hard to get an EXACT measurement, the eye relief appears to be about 15 to 20. Thank you for your help in clearing that up! I can see where the fold out eyecups make it easier to get that far from the glass.

[JOC]

I'm only a beginner, but how about a Celestron Omni Plossl 32mm?   I've got one here and it gives 22mm eye relief (I wear specs), it also shouldn't break the bank https://www.celestron.com/products/omni-32-mm-eyepiece FLO seem to knock them out for £25 which doesn't seem a bad price.

FLO says that Celestron's LX range are better suited if you want higher powers at good eye relief, but that at lower powers the Omni plossls are fine.

[Louis D]

2 hours ago, JOC said:

I've got one here and it gives 22mm eye relief (I wear specs)

I've measured mine at 15mm (usable), which is just enough to use with specs, but not comfortably compared to eyepieces with the eye lens flush mounted to the top of the housing.  The problem is they recessed the eye lens about 7mm (22mm-7mm=15mm).  If you watch the classifieds, you might be able to find a vintage 32mm Meade 4000 Plossl smoothie with the eye lens nearly flush mounted.