Eye piece explanations

[TwistedRider]

I'm looking around for some eyepiece upgrades, and rather confused by all the names etc. :shrug:

Is there a page or reference covering differences between types and also the intended or common use.

Things like plossl, Nagler, orthos etc.
Have no idea why one is preferable to others, or what I'd expect to be different between different types at same focal length.

Additionally, any recommendations for EP's I should check out ould be great.
My main topics are moon and deep sky objects.
Mainly because I've had fairly sub average luck with planets so far

For reference
10" dob Goto
1200mm f.l.
F4.7

Current EP's
SkyWatcher OEM plossl
6, 10, 15, 25
2x barlow

20, 12,9mm 50 deg Vixen NLV

26mm UWA 70 deg 2". (rather in love with the moon view through this)

5mm TV Radian (to much for my scope?)

[Renato1]

Hi Drew,
If your telescope doesn't give good views of the planets after you've given it a couple of hours to cool down outside, you probably either have a collimation problem, or you are looking over someone's house with their heater going.

Before they developed multicoatings, Huygens and Kellners were popular because they had fewer glass elements and less internal reflections.

Orthoscopic eyepieces give very sharp views, but have a narrow field (around 43 degrees)

Plossls have a wider field (around 52 degrees).

Erfles - the first generation of wider angle eyepieces. They distort at the edges.

Naglers have an 82 degree field and are sharp across the field. Other brands of 82 degree eyepieces may be on par, or get soft towards the edges, or distort a lot at the edges (and where I mention distortion at the edges, the distortion is always worse in an f/4.7 telescope)

For observing DSOs at a dark site, especially galaxies, an exit pupil of 2mm is often the most recommended (and I agree). In your telescope that means f4.7X2= 9.4mm eyepiece.

Especially for a dob that one is pushing around, I suggest getting an eyepiece as close to 9.4mm as you can get, with either a wide angle or ultra wide angle field of view, as it makes it much easier to track the object manually.

Anyhow, you have a good array of eyepieces already, and you can check out the views of DSOs in them before deciding whether you want a wider field of view eyepiece.

Your 5mm Radian gives 240X in your telescope. That is not a high power under good conditions (when the stars aren't twinkling). You should be able to go much higher than that (though that's where another ultra wide angle eyepiece would be handy when pushing a dob around).
Regards,
Renato

[TwistedRider]

Thanks Renato,

That was a really good into to eyepieces.

From what you have written, I think I'll look at trying some orthos and naglers.

Will have to ask nicely at the next Star party. :campfire:
Was some impressive hand grenades at the last one. :)

Cheers,
Drew

[astro744]

Plenty of information here http://www.televue.com/engine/TV3b_page.asp?id=154


Note too for an eyepiece such as 5mm Radian, it has 20mm eye relief with adjustable eye cup. It is much easier to view an object at 240x with a short focal length eyepiece that has a good size eye lens and plenty of eye relief than a Plossl or Ortho with a small peep hole and short eye relief.

Note too for an undriven DOB an eyepiece with 82 deg. apparent field such as a Tele Vue Nagler is desireable to keep the object in the field longer. Note the Nagler is highly corrected and will do well in your telescope (and any other telescope you choose to use it in) but you will still see primary mirror coma which can be corrected with a Paracorr. At least with a Nagler you wont see any eyepiece introduced aberrations that show themselves with cheaper options.

[TwistedRider]

Yes, I forgot to mention that I wear glasses, so eye relief is important to consider.

Oh and my Dob is a Goto, so very nice for tracking objects over time.

I had coma explained to me the other night... Paracorr added to my shopping list as well.

I'd better save my pennies,. Some of the big EP's are not budget items

If I was to consider another scope some time, I'm assuming I just plug and play with the eyepieces?
Something for light Astro photography is piquing my interest, but still a long way off

[Ukastronomer]

https://en.wikipedia.org/wiki/Eyepiece

http://www.quadibloc.com/science/opt04.htm


Have fun :) :)

[TwistedRider]

Thanks Jeremy,
Some good reading there.

[Ukastronomer]

There are more eyepiece types than most people like me ever knew existed ;)

As a side, is it "twistedrider" 'cos you are a cyclist ?

[Startrek]

For my previous 10” dob and my new 12” Goto dob I think the best all round eye piece for DSO’s ( in particular large emission nebula ) is my Televue Panoptic 27mm and a close second would be my Televue Ethos 21mm

My 2cents.......

Cheers

[TwistedRider]

Yes, there does seem to be a plethora of different options. I have some study to do I think.

And you are almost correct, Motorcyclist. :)

[TwistedRider]

Sooo many to try.
I can see myself attending a few gatherings to try and see what some of these do for my scope

[Renato1]

Hi Drew,
To be honest, I have Orthos - they are good - but I rarely use them. The narrow field annoys me. And way back then I later bought Meade 5-element Series 4000 Superplossls, which gave me sharp images across the entire field (not just in the centre) and I used them a lot. Unfortunately, Meade then changed their series 4000 SuperPlossls to lesser 4-element ones, and one can't tell them apart.

My high power Orthos, plossls and Ultrawides all have shallow eye relief, but at high power it doesn't really matter much whether you use eyeglasses of not. If you are long or short sighted, you adjust the focus. If you have astigmatism, it doesn't show up much at all with 1mm or smaller exit pupils (I start seeing the astigmatism at around 2.5mm exit pupil). I did find that buying even cheap GSO very low power eyepiece (26, 32, 40, 50mm) were useful in my dob when I put them in a Barlow, as I could then wear eyeglasses, since their long eye relief remained the same.

The hand grenade eyepieces are good, but weigh a lot. I had to figure out a way to add lead pieces to the back of my dob to balance them.

If you have a computerised dob that tracks objects, then an UltraWide (82 degree) or Megawide (100degree) eyepiece is certainly nice to have - but not really essential, as your eye can only ever see 65 or 70 degrees in it without moving your eye around. Superwide eyepieces with 65 to 70 degrees will give a pleasant view.

Before buying a coma corrector, see if you can borrow one and check it out. I wasn't overly impressed with my TeleVue Parracor Type 1 - the improvement at the edges wasn't all that great, and it added weight and 1.15X magnification.

Basically there are two types of amateurs - those who hate distortion at the edges of the field of view, and those who don't mind some because they focus on the central area most of the time. I'm the latter type, but you need to find out what type you are - which will determine whether you aim for very expensive premium eyepieces, or whether they are overkill for you and cheaper ones would have been very satisfactory.
Regards,
Renato

[astro744]

If you are contemplating a Paracorr, I recommend trying one before buying one. If your telescope is Skywatcher and the focuser is anything like mine then the Tele Vue Paracorr Type 1 with tuneable top will simply not fit as the Skywatcher focuser has a stop inside the draw tube and this prevents full insertion of the Paracorr and as a result focus cannot be achieved at least not on the telescope I have.

This compromise focuser design is to allow the upper section to be replaced with a lower profile T2 adaptor but it has not been thought through and has resulted in a poor design for visual use if one wants to use a Paracorr. I bought this 'scope for the kids so priority at present is low as they are not going to observe with a Paracorr which is a great accessory when combined with great eyepieces for pinpoint views for those that appreciate them but not essential for general observing for most observers. I do use my Paracorr in the other 'scopes I have if I want the sharpest off axis views but I also enjoy my 'scopes without the Paracorr and as with many the choice is a personal one.

Get some better eyepieces first and then you will see pure primary mirror coma only and it may not bother you and you may not ever need a Paracorr.

[Startrek]

The Televue Paracorr Type 2 fits perfectly in the focuser of my Skywatcher 12” Goto dob and is a must for wide field high end eye pieces at F4.9
It’s a superb coma corrector and compliments all my Televue eye pieces
My scope is 12 months old

[TwistedRider]

Thanks all for the info.


Once i've tried a few things i'll look at EP's 1st, then the paracorr if needed.


Thanks Martin, about the same age as my scope, to maybe the same focuser...although a dual speed would be nice.
I feel a case of equipment-mania trying to take hold :)


Looks like my collimation is out so that's the 1st job, before trying any new toys.