Recommended Lenses

[dd999]

Hi All,

Since starting this astronomy journey around 15 years ago I have only ever used the standard come-with-telescope lenses. Usually the 10mm and the wide-angle 25mm. Crazy I know!

I have a birthday approaching that under almost every other circumstance I would have been happy to forget about, but with mounting pressure for gift ideas, the thought of upgrading my lenses to something 'better' just about has me excited about turning another year older.

In terms of magnification I am looking for around 8-10mm and as I have a SW 130pds, ideally I'd like a 2" lens. I quite like the 'comfort viewing' of the standard 28mm 2" eyepiece that came with my 130pds.

What would you recommend?

Thanks in advance!

[Dave Lloyd]

Not 2" but the BST starguider range is a useful step up from kit eyepieces. 

[turboscrew]

The BST Starguiders are meant for F/5 and slower.

 

[fozzybear]

The 130-PDS is F/5 so should not be a problem

[dd999]

Thanks - I'll take a look

[Louis D]

2" is only relevant at low powers and for heavy eyepieces.  There are plenty of 1.25" 8-10mm eyepieces out there with large eye lenses and loads of eye relief.  The 8mm BST is quite good as mentioned above, but a bit tight on usable eye relief compared to some more premium offerings.  The 9mm Morpheus is excellent as is the 10mm Delos.  It all depends on your budget which you didn't specify.

[Ruud]

Longer focal length eyepieces, like you 28mm, usually have enough eye relief to be comfortable.

That some eyepieces need to be two inch has to do with a combination of how wide the apparent view of the eyepiece is and how long the focal length is. These two determine how big a circle of the focal plane needs to be shown. 

Is that circle bigger that 1.25" then the eyepiece barrel needs to be bigger too.

Here's a diagram that shows which eyepieces can be made in 1.25" format, and which cannot:

The reason why retailers mention the barrel size is that not all eyepieces can be used in a 1.25" focuser.

Below the blue line is the domain of eyepieces that can be made in the 1.25" barrel format.

The BST starguider eyepieces recommended are good value indeed. Another amazing budget eyepiece is the 16mm 82° Nirvana (see here).

[Alan64]

As you go up in focal-length(eyepieces) -- 28mm, 30mm, 32mm, 38mm. 40mm -- that's where, and only, you'll find 2" eyepieces.  It takes that wider barrel to provide a wide view at those focal-lengths.  This is an example of the shortest focal-length with a 2" barrel...

http://www.televue.com/engine/TV3b_page.asp?id=20&Tab=EP_ETH-17.0

...and the AFOV at 100°; very wide indeed.

However, that eyepiece is an exception, due to its construction, and cost.  For us mere mortals, the vast majority of eyepieces at around that focal-length have 1.25" barrels.

There are no 6mm, 8mm, 10mm, or 12mm eyepieces with 2" barrels, as the wider barrel is not needed to provide a wide view at those focal-lengths.  There would be no benefit.

I would suggest what the others have, combine it with a barlow or two(2x and 3x) of better quality, and ramp up the power.  Telescopes, in the first place, are for seeing faraway objects up close, the closer the better.  Else, one may make do with binoculars. 

[Dantooine]

A good 8mm and barlow would be my advice. Magnifications of 81x and 162x or a 9mm giving 72x and 144x. I think you would see well with either of those in your 130pds. There are some nice optics around and quite a choice for good value. 

[Louis D]

On 10/09/2020 at 15:59, Alan64 said:

There are no 6mm, 8mm, 10mm, or 12mm eyepieces with 2" barrels

🤔 12mm ES-92 is 2" only.  There are also the 5.5mm, 9mm, and 14mm ES-100 eyepieces as well as the 9mm ES-120.  I can't think of any 6mm, 8mm, or 10mm 2"-only eyepieces, though, as you say.

[Alan64]

1 hour ago, Louis D said:

🤔 12mm ES-92 is 2" only.  There are also the 5.5mm, 9mm, and 14mm ES-100 eyepieces as well as the 9mm ES-120.  I can't think of any 6mm, 8mm, or 10mm 2"-only eyepieces, though, as you say.

That one would work quite well with the telescope in question, albeit after mortgaging something or other.

Edited September 15, 2020 by Alan64

[John]

Some eyepieces have 2 inch barrels simply because they are large and heavy and the manufacturer feels that they will be held more securely in a 2 inch draw tube or diagonal. Some have hybrid barrels to give you the option to use either size fitting.

 

 

 

[Dantooine]

8 minutes ago, John said:

Some eyepieces have 2 inch barrels simply because they are large and heavy and the manufacturer feels that they will be held more securely in a 2 inch draw tube or diagonal. Some have hybrid barrels to give you the option to use either size fitting.

 

 

 

I feel much happier using the 2” on the “double barrels”. Also saves me from standing on top toes. 

[Alan64]

1 hour ago, John said:

Some eyepieces have 2 inch barrels simply because they are large and heavy and the manufacturer feels that they will be held more securely in a 2 inch draw tube or diagonal. Some have hybrid barrels to give you the option to use either size fitting.

 

 

 

Indeed, for example...

https://www.firstlightoptics.com/tele-vue-eyepieces/tele-vue-ethos-100-110-degree-eyepieces.html

[Alan64]

But in my next breath, I'd prefer this, and a most useful ocular for a 130mm f/5 Newtonian...

https://www.firstlightoptics.com/tele-vue-eyepieces/tele-vue-3-6mm-nagler-50-degree-zoom-eyepiece.html

Yes, I would suggest that one.