The Right Eyepieces

aaronsadler · #1 10-09-2005, 04:08 AM

Anyone know which is the perfect eyepiece for viewing planets like jupiter.

I've got a Televue Genesis and heard that a televue 3mm Radian was my best bet
any comments

iceman (Mike) · #2 10-09-2005, 06:02 AM

What's the focal length and objective diameter in the TV Genesis?

What is it mounted on?

davidpretorius · #3 10-09-2005, 08:58 AM

Welcome to the site Aaron and also welcome to the inner sanctum of cool members who use their name as their username!

aaronsadler · #4 10-09-2005, 09:13 AM

Tv Genesis -focal lenght= 500mm
-objective diametre=102mm

Mounted on EQ5

Since yesterday i've had a look around and found the televue nagler type 6 3.5mm and 2.5mm, these could also be good.

Prices for eyepieces up to about $500 tops.

davidpretorius · #5 10-09-2005, 09:54 AM

can i borrow one? if you get one?

[1ponders] (Paul) · #6 10-09-2005, 10:26 AM

Hmmmmm...you might be pushing it a bit with those short eyepieces. Given the objective fo your scope then your max usable mag is around 200X (50X per Inch of objective. you can go more but resolution will suffer) So with a 2.5mm eyepiece that will give you 200X. All then depends on your seeing conditions. Anything less than above average seeing conditions will more than likely make viewing less than pleasing. The 3.5 would be ok giving a mag of about 145X. I don't know those particular eyepieces personally though, I've just giveing you a bit of the theory

Maybe consider the 3.5 or slightly longer and a good longer FL eyepiece (16 mm nag or slightly longer) for widefield viewing which your scope (at such a short FL) would be better suited for. It will still certainly do planets, but doesn't have the longer focal length for serious magnification in good seeing.

aaronsadler · #7 10-09-2005, 10:41 AM

Thanks for that, I might have a look at a 5mm Version and then I can always stick a 2x barlow in for more mag.

Below, some info on nagler type 6's

Nagler Type 6
The 7-element, Nagler Type 6 design is based on the original patented Nagler design. This new 7-element design update for the short focal length Nagler deserves its own designation. Using different exotic materials, coating processes and design ingenuity, Al has massaged more eye-relief, contrast, and true field of view into the shorter focal length Naglers, while maintaining the absolute sharpness of the originals. Eye-relief is 12mm on each model, and all are sized about the same as the original 7mm! Weight about 0.4 to 0.5 lbs. Available in 13mm, 11mm, 9mm, 7mm, 5mm, 3.5, and 2.5mm focal lengths.
In recognition of the cost increase of the new 7mm and 5mm models over the originals, we intend to continue offering the original 7mm and 4.8mm Naglers. NOTE: The goal we set designing these new eyepieces was to increase contrast, maintain or increase eye-relief, reduce size and weight, and maintain the sharpness of the originals. They are all parfocal and great with the Bino Vue. We are confident we’ve succeeded on all accounts and look forward to your comments.
The 11mm Nagler Type 6 slots in perfectly between the 13mm and 9mm Type 6s and makes a perfect companion to the 7mm.
The 3.5mm Nagler Type 6 is a natural progression of 1.4x power steps from 7mm and 5mm Naglers.
The 2.5 is also a 1.4x step from the 3.5mm. You don't have to sacrifice field in order to gain sharpness and power. And, you're not limited to slow scopes, or have to squint through pinhead lenses. These are the lunar and "planetary" eyepieces with field to spare.

ving (David) · #8 10-09-2005, 10:56 AM

hi aaron

ausastronomer (John Bambury) · #9 10-09-2005, 02:13 PM

Quote:

Originally Posted by aaronsadler

Tv Genesis -focal lenght= 500mm
-objective diametre=102mm

Mounted on EQ5

Since yesterday i've had a look around and found the televue nagler type 6 3.5mm and 2.5mm, these could also be good.

Prices for eyepieces up to about $500 tops.

Aaron,

You must own 1 of the original TV Genesis models, the original version was a 101mm F5 APO, with the later version known as the Genesis SDF being a 101mm F5.4 APO (540mm fl). A very fine scope using a rear end doublet to reshape the F12 light cone from the primary doublet.

What eyepieces/barlow combinations do you already own ? You may already own something that can barlow nicely for great planetary views. If not there are several very good options for use as a planetary eyepiece in this scope.

Owning a top quality scope makes it easy to match eyepieces to.

CS-John B

ausastronomer (John Bambury) · #10 10-09-2005, 02:30 PM

Quote:

Originally Posted by [1ponders]

Hmmmmm...you might be pushing it a bit with those short eyepieces. Given the objective fo your scope then your max usable mag is around 200X (50X per Inch of objective. you can go more but resolution will suffer) So with a 2.5mm eyepiece that will give you 200X.

Paul,

50X per inch of aperture is a general rule of thumb that usually can be applied to most general designs of telescope. In many cases it can easily be exceeded when atmospheric conditions are favourable. The telescope designs most able to exceed 50X per inch are 3" to 6" high quality apochromatic refractors, The Russian 5" and 6" Maksutov Newtonians and high quality reflectors with premium hand figured mirrors. In many cases these scopes can run to 65X or 70X per inch of aperture without image breakdown. Carl Zambuto "guarantees" his mirrors to "exceed" 50X per inch of aperture under favourable conditions as does Bob Royce.

The TV Genesis is a high quality 4" APO which uses an F12 primary doublet and another doublet at the rear of the OTA to reshape the light cone. It "should" do 50X per inch "on its ear" under reasonable conditions. The 2.5mm Vixen Lanthanum is one of the more popular planetary eyepieces in the TV Genesis giving 200X @ 50X per inch.

CS-John B

aaronsadler · #11 10-09-2005, 03:48 PM

Tv Genesis is original version 101mm F5 APO,

already own -20mm Southern Cross Wide scan type III 84 degree
-Orion shorty-plus 2x barlow
-5mm Orion Ultrascopic (very poor optics, am replacing with televue or similar)

Have heard about pentax eyepieces, can u reccomend any?

aaronsadler · #12 11-09-2005, 10:57 AM

any comments

Starkler (Geoff) · #13 11-09-2005, 11:20 AM

I own 10.5mm and 14mm Pentax XL's which Im very pleased with. The only issue with a small refractor is the size and weight of them compared to plossls, which I beleive is about 500g, or close to a pound.
I use mine in my ED80 and get pinpoint stars in good seeing.

ausastronomer (John Bambury) · #14 11-09-2005, 11:25 AM

Aaron,

I am somewhat surprised !!! The Widescans whilst an expensive eyepiece are not at their best in fast scopes of F5 focal ratio like your TV Genesis. They are based on a modified Erfle design and really are at their best in scopes of F9 and slower, like SCT's, MCT's or slow, long focus achomats. In a slow scope they work well, in a fast scope they leave something to be desired IMO. The Orion Ultrascopic on the other hand should be an outstanding performer optically in your scope. These work well at F5 and image quality is as good as any premium eyepiece from Televue and Pentax. The downside with the Orion Ultrascopic should be its short eye-relief and narrow field of view not the optical quality of the images it provides.

You say the issues with the Ultrascopic are optical, if that is the case I think you have
a faulty eyepiece or something is wrong with the telescope.

The 5mm eyepiece gives 100X in your scope and the Genesis should easily be able to go way past that, when conditions are favourable. Do you have any observing colleagues that can "lend" you a 5mm eyepiece of known high quality to compare the images with your own ? This is the least likely cause.

What has possibly happened is that over the years with constant transportation the scope has been knocked out of collimation !! You can test this yourself. Using your 5mm eyepiece, better stilll a borrowed one of 5mm to 8mm focal length, if you can get it in case the eyepiece also has issues, defocus on a bright star. The defocused pattern should appear perfectly circular and evenly illuminated, if it doesn't the scope is out of collimation and this will be causing the images in your 5mm eyepiece at 100X to appear poor.

This needs to be addressed before you consider buying another eyepiece, because the 5mm Ultrascopic used native or in conjunction with the 2X shorty plus barlow should give 1st class images, notwithstanding the short eye-relief and narrow FOV.

Check the scopes collimation, if its out come back to me either on list or with a PM and I will tell you where to send it to get it fixed. Unfortunately its not a DIY project unless you have experience in collimating a refractor.

CS-John B

[1ponders] (Paul) · #15 11-09-2005, 03:17 PM

Stand corrected John

aaronsadler · #16 13-09-2005, 12:23 AM

Quote:

Originally Posted by ausastronomer

You say the issues with the Ultrascopic are optical, if that is the case I think you have
a faulty eyepiece or something is wrong with the telescope.

CS-John B

Thanks for the advice john, found out the orion was faulty, will change for an eyepiece with better eye-relief and wider field of view definetly. When I bought the genesis the seller recomended the eyepiece so I went with it.

No problem with collimation, scope works great.

ausastronomer (John Bambury) · #17 13-09-2005, 12:33 PM

AAron,

Glad to hear you sorted the issues out and it was only the eyepiece. Chris Venter in Victoria is currently selling (or had) for sale a 5mm Vixen LVW eyepiece.

http://www.iceinspace.com.au/forum/s...ead.php?t=3593

This eyepiece is ideal for your needs. Native it would give you 100X and barlowed in your 2X Orion Shorty Plus would give you 200X. The eyepiece native would be excellent for medium power views of DSO's and also lunar and planets. This is an excellent quality eyepiece with very sharp views across the field and has 20mm of eye-relief. The differences between it and other premium eyepieces by Televue or Pentax would be difficult to detect. If money is not an issue then look at the 5mm Nagler T6 or the 5mm Pentax XW, these are both superb eyepieces with the Pentax offering 20mm of Eye-relief.

I would be looking hard at the Vixen LVW that Chris is selling, its a great eyepiece at a great price and perfect for your scope and needs, new these are over $400. Be aware however, that it is a large eyepiece for a 5mm, so your scope would need to be adequately mounted.

CS-John B

aaronsadler · #18 13-09-2005, 06:06 PM

I have finally decided to go the whole hog

I'm going to buy the 3.5 and 5mm Televue Nagler type 6's.

Should be plenty of choices in magnification with my 2x barlow.

Thanks for everyone's advice.

davidpretorius · #19 13-09-2005, 06:39 PM

well done aaron!

aaronsadler · #20 14-09-2005, 12:21 PM

Have decided to purchase the televue nagler type6 5mm and 2.5x powermate,
giving top magnifacation of 250x, this works out at 62.5x per inch.

Does anyone know how large in diametre Jupiter will physically appear at the eyepiece and what quality of view should be expected.

Sorry for changing my mind so much.

Thanks for every1's advice so far.