# 42mm Orion lanthanum EP use?

• 03-01-2017, 12:19 AM
BrokeStarGazer
42mm Orion lanthanum EP use?
Club has a 42mm Orion 2" Lanthanum EP for sale for \$40. Seems like a good deal. Scope is 1200mm though so that would only get me 28x.....smallest I have now is 25mm. Question is....Is there a use at 28x and what might those be?? Mostly hunt DSO but never know might venture out.
• 03-01-2017, 12:35 AM
BrokeStarGazer
Re: 42mm Orion lanthanum EP use?
• 03-01-2017, 01:43 AM
Re: 42mm Orion lanthanum EP use?
I think you might want to calculate the exit pupil on that one, Doug. Too big an exit pupil is gonna let the secondary mirror shadow show up as a dark splotch on brighter stuff and otherwise offer a little light loss.

Exit pupil is aperture (in mm) divided by your magnification.

If that eyepiece gets you above 6mm exit pupil, might want to take a pass on it.

A good calculator is here: N.A.A. Telescope Math Calculator
• 03-01-2017, 01:46 AM
BrokeStarGazer
Re: 42mm Orion lanthanum EP use?
• 03-01-2017, 01:50 AM
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by BrokeStarGazer

Good article here, buddy: A Pupil Primer - Sky & Telescope :)
• 03-01-2017, 02:23 AM
Gabby76
Re: 42mm Orion lanthanum EP use?
A good eyepiece for a longer focal length refractor or SCT/ Mak, not so good for most reflectors though.
• 03-01-2017, 03:56 PM
BrokeStarGazer
Re: 42mm Orion lanthanum EP use?
Quote:

I think you might want to calculate the exit pupil on that one, Doug. Too big an exit pupil is gonna let the secondary mirror shadow show up as a dark splotch on brighter stuff and otherwise offer a little light loss.

Exit pupil is aperture (in mm) divided by your magnification.

If that eyepiece gets you above 6mm exit pupil, might want to take a pass on it.

A good calculator is here: N.A.A. Telescope Math Calculator

Well just when you think you kinda know something about telescopes this comes out of left field and makes you realize you know nothing.

According to the calculator
Optimum mag 63x - 133x
19mm - 9mm EP's
Min mag 37x which is a 32mm EP.

Some good info to know

Thanks
• 03-01-2017, 09:47 PM
Bigzmey
Re: 42mm Orion lanthanum EP use?
This is a very good quality EP, and price is a steal. If you ever consider getting a good refractor you should grab it. I would :)

Not very useful for your DOBs as Gabby and Bryan indicated, since the exit pupil will be over 7mm.
• 03-08-2017, 02:29 AM
Johnny J.
Re: 42mm Orion lanthanum EP use?
I had this same EP in the Vixen version, the 42mm Vixen LVW. It is a sleeper EP that has very good performance even in fast F5 optics. In a shoot out I did using a 25" Obsession F5 classic the Vixen beat out a Meade 40mm Series 4000 SWA and a custom made Seibert optics 38mm 2" Obsevatory EP. I owned all 3 and only one was going to be the keeper. The vixen was the clear winner with the Seibert coming in a very close second. The Meade Series 4000 SWA was in no way a "slouch" of an EP and in it's time held high regard. I sold the Meade and donated the Seibert to a local college. The Vixen was my wide field sweeper EP used for low power viewing. From dark sites the so called secondary shadow was not noticeable in my F5 equipment. Even with the large exit pupil when using F5 equipment contrast was very good. Well corrected to the field edge which is the field stop or actually the 2" barrel of this EP.
For the price you cannot go wrong. I sold mine to fund astrophotography ventures and wish I hadn't. Get it and try it..if you don't like it PM me I'll take it.
JJ
• 03-08-2017, 07:57 AM
jerryTheC
Just a reminder - although the form factor of the Vixen LVWs, Baader Hyperions, and some of the Orion eyepieces (stratus? - not sure) are very similar, the optics are DIFFERENT - this isn't a case where the same eyepieces are sold under different brands.
• 03-09-2017, 04:01 AM
Bigzmey
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by jerryTheC
Just a reminder - although the form factor of the Vixen LVWs, Baader Hyperions, and some of the Orion eyepieces (stratus? - not sure) are very similar, the optics are DIFFERENT - this isn't a case where the same eyepieces are sold under different brands.

In this case it is the case! :D. This particular Orion lanthanum series was made by Vixen for Orion.
• 03-09-2017, 04:41 AM
12richardk
Re: 42mm Orion lanthanum EP use?
I have a 22mm version of this eyepiece it's really good wish I could get this 42 for my Bosma Mak especially at that price
• 03-09-2017, 05:02 AM
Johnny J.
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by 12richardk
I have a 22mm version of this eyepiece it's really good wish I could get this 42 for my Bosma Mak especially at that price

Vixen still makes them though they are spendy at about \$380 US, but well worth it. Don't know where you would get one in your neck of the woods though.
AGENA ASTRO VIXEN LVW 42mm
JJ
• 04-19-2017, 03:21 AM
Johnny J.
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by BrokeStarGazer
Club has a 42mm Orion 2" Lanthanum EP for sale for \$40. Seems like a good deal. Scope is 1200mm though so that would only get me 28x.....smallest I have now is 25mm. Question is....Is there a use at 28x and what might those be?? Mostly hunt DSO but never know might venture out.

BSG
Did you ever pick up this EP and if you did what are your experiences with it?
JJ
• 04-19-2017, 06:14 AM
tomjones
Re: 42mm Orion lanthanum EP use?
Exit Pupil, that's a Red Herring if ever there was one. has very little application in the real world. I use outlandish long focal length eyepieces with good results in all my scopes. Great for comets and big clusters. Russell Optics on ebay sells an 85mm one. I have 65,56,45mm ones to get lowest powers and big chunks of sky without resorting to impossibly expensive wide fields like Naglers and their ilk. Doesn't seem to matter if the scopes exit pupil is bigger than your eyeball, you are still seeing large stuff very well indeed.
• 04-19-2017, 09:39 AM
not_Fritz_Argelander
Re: 42mm Orion lanthanum EP use?
Exit pupil is no "red herring" at all. It's a better guide to contrast discernment effects on DSOs than magnification. With a refractor you can get away with large exit pupils but you're effectively stopping down the scope. If your eye accommodates a 6mm exit pupil and you use a 10mm exit pupil eyepiece you've just stopped down your aperture to 60%. On obstructed telescopes you start seeing the central obstruction which many find unpleasant.

If you've seen a DSO in a larger scope and want to try for it in a smaller one exit pupil is a much better guide than magnification.

So exit pupils very useful if you know how to use it. Those Russell long focus eyepieces are OK in a refractor and a slow Mak but on a Newt? If you like looking at an illuminated doughnut with a dark central hole, maybe.
• 04-19-2017, 07:51 PM
Bigzmey
Re: 42mm Orion lanthanum EP use?
Here is a paper form Al Nagler on choosing EPs. Exit pupil is an impotent parameter to consider, however in refractors you could still use extra low power, albeit loosing some aperture as nFA indicated

Tele Vue Optics: Choosing Your Telescope's Magnification
• 04-23-2017, 12:57 AM
not_Fritz_Argelander
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by Bigzmey
Here is a paper form Al Nagler on choosing EPs. Exit pupil is an impotent parameter to consider, however in refractors you could still use extra low power, albeit loosing some aperture as nFA indicated

Tele Vue Optics: Choosing Your Telescope's Magnification

I think you meant "important" not "impotent". I think an impotent eyepiece would be one with a magnification of 1, much like the eyepieces supplied with TP rolls. ;)
• 05-05-2017, 07:12 PM
Bigzmey
Re: 42mm Orion lanthanum EP use?
Quote:

Originally Posted by not_Fritz_Argelander
I think you meant "important" not "impotent". I think an impotent eyepiece would be one with a magnification of 1, much like the eyepieces supplied with TP rolls. ;)

"Important" - "impotent", "tometoes" - "tomatoes" ;)