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Posts Made By: Milton Wilcox

March 10, 2003 02:45 AM Forum: Astro Binoculars

Oberwerk 100mm Binocular Scope

Posted By Milton Wilcox

Hi David,

I will echo what Kenny just said to Chas - it's great to hear enthusiastic reports on new binos.

In the case of your binoscope, I'll bet you saw a big improvement in the Trapezium going from 25x to 62x. Speaking of multiple stars, have you tried Polaris, Mizar, Rigel and Eta Cassiopeiae just to name a few doubles that should be easily split at that magnification?

And if you like O.C.'s, have you tried for NGC2158 next to M35 yet? That should also benefit from the higher mag. And the Virgo galaxy group is on the rise...

Happy two-eyed hunting, Milt

April 18, 2003 02:20 AM Forum: Astro Binoculars

Oberwerk 100mm Binocular Telecope

Posted By Milton Wilcox

Hi Dan,

Congratulations on your great selection, and thanks for sharing the picture. I completely agree that in this price range you would want to have the flexibility to use whatever EP's and filters you want. As Ed keeps telling us, most binocular objectives are underutilized, but yours won't be! It sounds like you already have some favorite EP's from your scope, so you can just double up on them. I have heard good things about the Meade 24.5 SWA EP's for bino applications.

Keep the reports coming,

Milt

April 24, 2003 07:49 PM Forum: Astro Binoculars

Good seeing last night

Posted By Milton Wilcox

Hi Daryl,

Congratulations on a great night with your 15x70's. I have been kicking myself for not recording all the M's I have viewed with my binos (With the scope, I very diligently took notes as I went through the Messier list the first time). I guess I just get too caught up in enjoying the view with two eyes.

A Messier Marathon with binoculars would be fun, too. Did anyone try it this year?

Clear skies, Milt

May 18, 2003 04:21 PM Forum: Astro Binoculars

FOV Calculation

Posted By Milton Wilcox

Hi Eric,

Since I happpened to be reading when you posted your question, I'll have a go at it.

The simplified calculation for true field of view (TFOV) is to divide the apparent field of view (AFOV) of the eyepiece by the magnification (the exact calculation requires knowing the field stop diameter). Thus, a 90° AFOV eyepiece would be required at 30x to achieve 3° TFOV (90/30=3). To my knowledge this is at the absolute maximum of what has ever been done. The popular TeleVue Nagler EP's are 82°. I believe there was a report of one binocular (Docter?) that achieved 90°.

The focal ratio merely determines the required focal length of the eyepiece to achieve your 30x. For example, f/6 100mm binoculars would have a 600mm focal length (6x100=600), meaning that you would require 20mm EP's to achieve a magnification of 30 (600/20=30). The focal ratio only becomes a limitation when it is so large (called a "slow" focal ratio) that the resulting long focal length of the EP does not allow the desired AFOV due to design constraints.

Hope this helps - Ed Zarenski please feel free to expand.

Clear Skies,
Milt

July 3, 2003 02:29 AM Forum: Astro Binoculars

Rare night in New England! 15x70Oberwerk2003

Posted By Milton Wilcox

Hi Ed,

Thanks for the great report. I, too have been viewing many of the same objects and a review is imminent on my new binoscope. However, due to space limitations I'm afraid it will have to stay home during our upcoming autumn trip - to New England, as it happens.

Therefore, I am in the market for a lightweight tripod that I can mount my Canon's on for the trip (I know they have IS, but we've danced that dance before). I previously researched all the heavy-duty Bogen stuff, which obviously would be overkill.

Can you, Erik or others please recommend the appropriate Bogen P/N's for a tripod and fluid pan head with 5 lb. or so ratings?

Thanks,
Milt

July 6, 2003 06:29 PM Forum: Binoviewers

First light with 16mm Nagler Type 5's (2)

Posted By Milton Wilcox

Hi Tom,

That pretty much agrees with the experience I have had with my 9NT6's (71x, 1.15°) with one exception. I cannot see the full 82° AFOV with direct vision in two-eyed mode, while I can see it in "cyclops" mode because I can turn my head that extra bit relative to the EP.

Have you accurately measured the fields you are seeing? I used both the drift method and pairs of objects spaced just inside my calculated TFOV. In both cases I had to be looking straight ahead and use peripheral vision to pick up objects at the field edges when using both eyes.

This has also been discussed over on the Astro Binoculars forum, and the general consensus seems to be that most two-eyed observers can only see 65°-70° with direct vision.

Still love those Naglers,

Milt

July 31, 2003 01:34 AM Forum: Astro Binoculars

Affordable 20x120??

Posted By Milton Wilcox

Mike,

The back ends of these binos look like the Matsumoto units that I mentioned in my report. These are very high quality and very expensive. Seeing them on the back of achromatic OTA'a is a bit surprising, but it definitely gives the owner room for improvement as his budget allows.

Here is the link to Tatsuro Matsumoto's website if you haven't seen it:

http://www.page.sannet.ne.jp/mazmoto/index-e.htm

Good luck,

Milt

August 4, 2003 03:14 AM Forum: Astro Binoculars

TFOV and 1.25"/2" eyepieces.

Posted By Milton Wilcox

Hi Eric,

You have pretty much summed up the tradeoffs, and touched on a frustration of mine. There are very few conventional binoculars that can take standard 1-1/4" eyepieces, let alone 2". The only ones that come to mind are the Vixen BT80 and one Oberwerk model.

The additional factor for TFOV is of course the focal length of the objective system. Shorter f.l.'s will produce wider true fields of view, but generally at the expense of chromatic aberration. I believe it would be hard to come up with much more than 3° TFOV in 80mm binos or 2.5° in 100mm binos using 1-1/4" eyepieces.

Some observers have reported being able to use 2" eyepieces, which, as you point out, open up the field stop significantly. You might try posing this question on the binoviewer forum, where all manner of standard eyepieces are used. It is possible that some 2" eyepieces might fit you, and others not.

The next problem would be actually finding binos that could take the 2" EP's. The only ones I am aware of are binoscopes made by Matsumoto or Astromeccanica using dual telescope OTA's.

Good luck,

Milt

January 15, 2004 01:34 AM Forum: Astro Binoculars

Canon IS binos

Posted By Milton Wilcox

Hi Ivan,

I have owned the Canon 18x50IS for 2-1/2 years.

Regarding eye relief, I do not wear eye glasses when I observe but I checked my owner's manual and both the 15x and 18x are spec'd at 15mm. This may not be enough. However, if you already have a telescope and can use EP's with 15mm eye relief, then it would probably be OK with the eye cups folded back.

The bigger issue on these binoculars is whether the image stabilization is really worth the added cost. Because the contrast and image quality are quite good, I have been pushing my 18x50's pretty deep, and have come to believe that the cost of IS would have been better put into larger apertures (assuming the image quality was maintained).

I say this because I have not even turned on my IS since I acquired the Manfrotto 3011BN tripod and 3130 micro fluid head that Erik Lin and Ed Zarenski recommended on this forum. Yes, after spending all the extra $$ for IS, I ended up mounting them anyway.

AS you probably know, serious observing often involves finding objects that can only be located with the help of star charts. IS does not help you regain the exact same area of sky after you have consulted a star chart - only mounting will do that. Furthermore, as good as the IS is, for studying an object in detail it is not steady enough. For example, I have split alpha Delphini (9.6") mounted, but cannot do it using the IS.

For a non-IS, high image quality, larger aperture alternative in this price range you might consider the Fujinon 16x70. I don't know what the eye relief is, but someone else will. Or you could go for lower cost binos and put the difference into a good mount. There will be many others with good ideas on this forum.

Good Luck, Milt


April 8, 2004 01:58 AM Forum: Binoviewers

Do these count as binoviewers?

Posted By Milton Wilcox

Tom,

They are potentially better than an equivalent binoviewer on an OTA of 1.414x diameter aperture because the two sides are non correlated. Any minor aberration existing in only one OTA will tend to be rejected by the brain in the magical mystical process of two-eyed comprehension.

Nice Bino's - Miya 77's?

Milt