Planetary eyepiece recommendation

[tramsden]

Hi..

I need recommendation on a good quality eyepiece to be use for planetary viewing with my Meade 80mm ED Triplet APO. I don't mind spending £'s if the extra quality is noticable.

Any advise on getting the best planetary viewing will be gratefully received.

..Tony

[GazOC]

I've used them and you can't go wrong with Baader or UO orthos, TMB planetarys also have a good reputation but I've never used them.

You don't have to spend a fortune on planetary eyepeices to get great results.

[tramsden]

Thanks, i've done a little reading and fancy a university optics ortho, but I can't find a UK retailer, can anyone give me a link to a seller..

.. Cheers

.. Tony

[GazOC]

I bought mine direct from UO with no problems.

[tramsden]

Thanks again I'll do just that..

May I ask another question, My focal length is only 680mm , but I would like to get x250 ish mag. Would I best with a really short ortho 2.5 /3.0mm or get a longer one and use a barlow. I have a televue powermate x5, I suppose that this is just to much is it not.. I value your suggestions .

.. Tony

[GazOC]

Most ranges of orthos only go down to 4mm, I think Takahashi make (made?) a 2.5 ortho but they are expensive. I'd guess a 6mm Barlowed would get you around x250 but that takes away of a strength of the orthos (good contrast due to few lens elements) and a decent barlow would double your outlay.

What scope have you got BTW Tony?

[tramsden]

I have a Meade 80mm ED Triplet APO..

[AndyH]

250x is, in my honest opinion, pushing it a little bit, for an 80mm scope. Maybe the max would be a 4mm, giving 170x. Seeing would need to be steady/good though. I have the U.O. 4,5,6,7,9 and 12.5mm. They are great, but I like the Burgess/TMB planetaries just as much(3.2 and 6). They have waaaay better eyerelief and a wider field of view. SCS Astro are the only ones who stock the burgess/tmb line. They do a 2.5, 3.2, 4 etc. Here's a link to them.

http://www.scsastro.co.uk/it120007.htm

Andy.

[GazOC]

I agree with Andy, X250 is pushing it a bit for a 80mm scope.

BTW, these are the same eyepiece rebadged..

http://www.telescope-service.com/eyepieces/start/eyepiecesstart.html#hr

They are getting very good write ups and in addtion to being good planetary eyepieces are def. of more alround use than orthos.

[KaStern_Former_Member]

Hi T.Ramsden,

so it is the new 80/480mm ED triplett?!

My focal length is only 680mm , but I would like to get x250 ish mag. Would I best with a really short ortho 2.5 /3.0mm or get a longer one and use a barlow.

- why do you want to get 250x mag?

- Is it your first scope?

I ask, because the useful max magnification is dependent on the aperture.

In the range of 0,7mm exit pupil you begin to see dthe airy disc as a tiny disc.

A star appears not as a non-dimensional point, it appears as a small disc, surrounded by rings.

As soon as the angular resolution is big enough you will see that.

It is dependent on your eyesight, some need only 0.9mm e.p. others 0,7mm

and some need 0,5mm e.p. to see the disc as a disc.

When you observe the moon you might magnifie up to 0,5mm exit pupil (D x 2),

because the moon is bright and Moon displays high contrasts at the terminator region.

So I propose the following:

Up to 160x for the Moon

up to 110x for Jupiter

Up to 120x for Saturn and Mars

(all planets at opposition)

Oh, a part of my post got lost is space...

A good eyepiece should work good with your f/6 Refractor and it should give you good contrast.

It should have low light scatter, no or at least low reflections.

All eyepieces with only few lens elements like Kellner, reversed Kellner, Monocentrics, Plössl,

Abbe orthoscopic, have short eyerelief, wich is only about 60% to 80% of the focal length.

So a 4mm Plössl or Ortho will have less than 4mm eyerelief.

You have to put your eye right onto the eyelens.

But a good Plössl or Ortho will give you very good views,

until the eyelens is covered with grease from your eyelashes.

You have to clean it frequently, the coating should be high quality.

The shortest Ortho and Plössl I know is 4mm, so if you want even

higher magnification than 120x you will have to do one of the following:

1) barlow a longer focal length eyepiece

2) use a modern multi-element eyepiece with long eyerelief and mostly a bigger apparent field of view

3) use a modified eyepiece with normal apparent field of view and internal barlow group / smyth group

3) Eyepieces like the Takahashi hi-ortho, the short focal length (3,8mm/5mm) Baader Eudiascopics

2) Modern eyepieces like the Pentax XW / XL, Vixen LVW, Televue Radian

1) take one of the very good Barlows wich are made for aplanatic telescopes (most of them),

and a good few-elements-eyepiece.

It is not easy to say what to do. It depends on things wich you cannot know now.

You will know this after some times of observing.

Regards, Karsten

Edit:

I would not recommend the TMB/Burgess / TS PLanetary / other brandnames eyepieces.

I could look through two of these and found that there was too much straylight,

especially when I looked at the Moon.

These eyepieces are discussed very controversly, some people like them, some do not liek them at all.

It is sayd that the second production run does not display straylight anymore, but as I could see, it is not solved.

Maybe the third, or the fourth, or... production run will have solved that issues.

[tramsden]

Karsten

Thank you for your in-depth reply, I've taken note of your advise and will make my eyepiece decision with this in mind. I really do appreciate the time taken to answer my question..

.. Tony

[GordonCopestake]

Tony, you might find this article of interest: http://www.cloudynights.com/item.php?item_id=272

Your 5x powermate isn't as useless as you think.