new eye pieces

[kmce]

Hi i am wanting a new lense for better magnification, but really i have no idea what i am looking for is this one right (in the link)

Skywatcher - Skywatcher SP Plossl eyepieces

if so can you tell me if its good or if its the wrong thing can you point me towards the correct one

[cootuk]

The eyepiece depends on the focal length of your scope and your budget.

Magnification = focal length / eyepiece size

Depends what scope you have, what eyepieces you already have, and what you want - more or less magnification...up to the limits of seeing for your site.

[kmce]

I have a Skywatcher Skyliner 150P Dobsonian, i want better mag like for things to be bigger, i think i got a 10mm one with the scope

[michael.h.f.wilkinson]

This depends on your scope, your budget and your interests. Plossls are generally decent to very good eyepieces, depending on the manufacturer. The Skywatchers are probably good value for money, but the key point is what magnification you are looking for.

If you want to look at planets, you will need an eyepiece that gives a magnification somewhere between 1x-1.6x the diameter of your objective in mm (or 50-80x the diameter in inches). For a telescope with a focal ratio of 10 (F/10 indication is frequently used) this means an EP with focal length of 7-10 mm. For an F/5 scope just halve these values. Going to even shorter focal lengths (higher magnification) is not a good idea, in general.

The problem with the Plossl design is that they have an eye relief (distance between rear lens and optimal position of your pupil) about 0.8 times the focal length. This means that if you wear glasses you are constantly banging them against the scope, which is not good for viewing comfort. Special "planetary" eyepieces do not suffer from this drawback (but they are more expensive).

To get more detailed advice, it is best to tell us what scope (and eyepieces) you have, and what you want to observe.

Cheers

Michael

[kmce]

I have a Skywatcher Skyliner 150P Dobsonian, i want better mag like for things to be bigger, i think i got a 10mm one with the scope

[cootuk]

Your scope has a 1200mm focal length, so your 10mm eyepiece gives a magnification of x120.

I would look for something around x170-x200 (around 7-6mm).

Higher than x200 would depends on how good the 'seeing' is in your area.

[michael.h.f.wilkinson]

I did use a 5 mm orthoscopic EP on my old 6"F/8 Newtonian (very similar to the dob you have), but had little use for it. A 6-7mm Plossl suggested by cootuk should work, but remember the eye relief is tight (4-5mm). If you do not wear glasses, thats OK, otherwise consider a long-eye-relief design, like the TMB Planetary. A 25-26mm Plossl should be a very good addition to your collection for viewing more extended objects like the Orion Nebula. I had a 25mm in the focuser of my Newtonian more than any other eyepiece. A Plossl design has about 20mm eye relief at 25mm focal length, so that is very comfortable.

[cootuk]

CGolder has a 6mm long eye relief ultra wide Skywatcher on sale in the sales section for around your target price - these retail new at 30 quid.

You could always drop him a pm if that suits what you need.

6mm (14.8mm Eye Relief) Multi-Coated, 66º apparent field of view

[Doug]

Thank a look at this site it hads a eyepiece chart and you can work out what you need

www.buy-telescope.com/telescope-power

Doug

Essex

[michael.h.f.wilkinson]

Thank a look at this site it hads a eyepiece chart and you can work out what you need

www.buy-telescope.com/telescope-power

Doug

Essex

Nice link, but note that in the "maximum EP section" it assumes that your eyes dilate to a 7mm pupil, which is true only for younger observers (<35 y, roughly). As you grow older, the pupil is limited to about 5mm, so 5 x the focal ratio is a better equation to use. For an F/8 scope that means 40mm rather than 56mm as a maximum focal length for an EP. At those focal lengths you would probably need a 2" focuser.

[kmce]

Buying lenses is hard lol, didnt know they are so many things i have to take in to account like what age i am for pupil dilation .

Well i am 23 so quite good eyesight and do not wear glasses, my gazing buddy does , but he will just have to settle for the lenses we have. The lense i want is for seeing the objects bigger like i stated earlier, since jupiter is really small with the lens i have.

And as suggested 7mm-6mm so the 6.2mm should be ok and i have no idea what a possel is lol. im a newbie

[michael.h.f.wilkinson]

Selecting an EP is hard because there is so much choice!!

Plossl is a lens design. It is quite old, but a good workhorse. It has decent colour correction, good sharpness, and a good apparent field of view (about 50 degrees). This means that you see a reasonably sized piece of the sky, which makes finding things easier. Many scopes come with Plossl EPs.

You will hear phrases like "Erfle", Ortho(scopic), Monocentric, Nagler, Radian, Panoptic, SWA (super wide angle), SWAN (same), UWA (Ultra-Wide Angle), UWAN (guess), and Ethos pop up throughout the threads on EPs. These are all lens design types, all of which have pros and cons.

Rule of thumb is, the more optical pros, the more the financial cons.

Having said that, I started with a handful of cheap Plossls and Orthos, and had loads of fun with them. Then I got some better quality Plossl EPs, had fun with them until the small eye relief became annoying, and gradually replaced them by premium EPs. The biggest step in quality is moving from the ultra cheap Huygens and Huygens-Mittenzwey plastic crud that is supplied with some scopes (indicated by e.g. H-9 or HM-20, for Huygens 9mm and Huygens-Mittenzwey 20mm on the EP barrel) to the affordable Plossls, like the Skywatchers.

[Revs]

Just an FYI; I think CGolder still has a 6mm Sky watcher 66º eyepiece for £18 available here... http://stargazerslounge.com/sale/113181-bits-bobs.html

[michael.h.f.wilkinson]

That looks like a better deal than the Plossl

[cootuk]

Looks like the 6mm now sold.

[russ]

You can buy the Skywatcher Ultrawide 66º eyepieces new for £24.99 which includes delivery. Here's a link:

Sky Watcher Sky-Watcher Ultrawide Eyepieces (6mm to 20mm)

They are excellent eyepieces for the money. The only issue i had with my 6mm was a bit of light scatter with the moon.

[kmce]

i got one, it was me that bought the 6mm from CGolder

Thanks all for your help

[michael.h.f.wilkinson]

Have fun with it! Let us know how you like it.

Cheers

Michael

[rowan46]

some people don't like barlow lenses some people rate them but a 2x barlow lens will double magnification on all lenses this maybe another option for you

[cootuk]

A barlowed 10mm would be 5mm, so x240 for this scope.

A bit too much for a lot of nights unless 'seeing' good and a good quality barlow.

Better to have two eyepieces that work well the majority of time, and try the barlowed 10mm (if OP has a barlow) on the best nights.

The next buy should probably be a 30mm-ish eyepiece for widefield.

[michael.h.f.wilkinson]

A barlowed 10mm would be 5mm, so x240 for this scope.

A bit too much for a lot of nights unless 'seeing' good and a good quality barlow.

Better to have two eyepieces that work well the majority of time, and try the barlowed 10mm (if OP has a barlow) on the best nights.

The next buy should probably be a 30mm-ish eyepiece for widefield.

I would agree: having the 6mm means barlowing the 10 is rather unnecessary anyway, and barlowing the 6 is pointless. A 25-30mm would be the best addition to the set. A Plossl design is quite comfortable in that range (used a couple for years), but a wider-field design gives you more sky to look at. At 30mm a wide angle would require a 2" EP holder however.

[Chris H]

A good range of ep's to have for your scope are as follows.

A low power ep for wide field views and finding DSO's - 25 to 30mm

Medium/high power for a closer look at DSO's and planets - 10 to 13mm

High power ep for planets and small DSO's when conditions allow - 5 to 8mm

If you go for one of each with a 1200mm focul length you won't go far wrong.

[rowan46]

i agree with everybody else If you have bought the 6mm there is no point putting a barlow on it. ( i should read peoples replies before I post, my apologies)