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Posts Made By: Milton Wilcox

September 9, 2005 11:12 PM Forum: Astro Binoculars

big binos, porro prism rotation

Posted By Milton Wilcox

Hi Jess,

My Astromeccanica/Borg 100ED binoscope had completely independent rotation of the two sides. This instrument used mirrors instead of prisms but the principle is the same. There were many times that they were not precisely symmetric about the center line and it had no effect on the merging of the images at powers <50x. Of course both eyes should see the same image orientation regardless of what angle your head is to the instrument, because both eyes move together as you rotate your head to accomodate the asymmetry.

As magnification was increased to 100x or more, I began to see the images move around a little as I rotated the two sides to change i.p.d., even when they remained symmetric. Simply changing eyepieces or the diopter adjustment if it rotates the eyepiece can cause this as well. It then becomes absolutely critical that there is an easy field adjustment for bionocular collimation, which Astromeccanica provides. At star parties I normally kept the bino at 27x so the images would merge for everyone regardless of i.p.d. or symmetry of the two sides.

Clear skies, Milt

September 18, 2005 02:40 PM Forum: Deep Sky Observing

Star Magnitudes

Posted By Milton Wilcox

Hi Lou,

Warren is exactly right when he says this isn't easy. Here is a link that was given me some time ago when I was wrestling with the question:

http://adsabs.harvard.edu//full/seri/PASP./0102//0000212.000.html

If this is too much too fast for you, just hold onto it for future reference.

Clear skies,
Milt

November 22, 2005 08:02 PM Forum: Astro Binoculars

Question from a novice

Posted By Milton Wilcox

Hi Inge,

It's hard to think of you as a novice at anything astronomical!

Most observers use binoculars as a very comfortable low-power adjunct to their larger telescopes. Low power binoculars can be handheld, but I've found that anything above 10x has to be mounted for serious work. You will find a wealth of information in the CloudyNights binocular forum (see links at top), but much of it is oriented toward beginners which, despite the title of this thread, you are not.

Since you are starting as a very experienced observer, it's less likely that you would put up with the optical defects of lower price binoculars that a beginning amateur would. These defects often include both CA and SA, causing color fringing and a loss in limiting magnitude. Because binocular objectives are so fast, field curvature in even the best ones also leads to fuzzy astigmatic edges.

I don't know your budget, but I have found that I am better off to get something good and keep it than to keep selling and buying what I have not been satisfied with. This led me ultimately to the Kowa Highlander 32x82 fluorite, which is so good it is replacing my 4" Apo for low power work. The price for the Highlander is between an NP101 and TMB115, and in my opinion worth every penny (see my CN review). Lower-priced alternatives that have received good reviews are the Fujinon 16x70 and Nikon 18x70.

Of course no binocular will have the versatility that a small Apo has in being able to cover high powers as well as low. The principal reason for this is the difficulty in keeping two parallel light paths collimated to each other at high magnification.

As you know, many extended objects require raw light gathering along with TFOV, so binoculars may not meet your expectations here either. Also, binoculars are typically not nebula filter friendly. In my skies, I can glimpse brighter nebulae like the NA and Veil in the 32x82 Kowa without a filter. For dim PN's, I blink an OIII in front of one eyepiece.

That said, you can do serious astronomy with something like a Highlander. In my mag 5.7 skies it will capture stars to about mag 12.5, galaxies around mag 10, split <6" doubles and give nice views of Jupiter and Saturn. I did the Messier Marathon with mine this year and got 106/110. It was by far the most pleasurable Marathon of the three I have attempted.

Good luck,
Milt

November 28, 2005 01:18 AM Forum: Eyepieces

High power help!!!

Posted By Milton Wilcox

Mike,

I may get some argument from Mark, who has owned a TEC140, but I would say save your money and enjoy the view at 294x. As good as the 140 is, I just doubt that there is much to be gained by going from 300x to 400x. Your own statement that 500x was "way too much" would seem to confirm this.

I will also add to Mark's reply that at <0.5mm exit pupil eye alignment is critical in the bino, particularly when your own entrance pupil is stopped down by a bright object. I would recommend periodically closing one eye at a time to ensure that you are actually catching both exit pupils.

Enjoy, Milt


December 16, 2005 02:53 AM Forum: Takahashi

NOW we're talking !!!

Posted By Milton Wilcox

Mike Clemens said:

I bought the FS128 to tide me over until my TEC160 arrives, but I'm honestly getting pretty attached to it.

Hi Mike,

I likewise acquired an AP130/8 to "tide me over," but there is no way it's going to be sold now. Very nice job on the pictures - I'm sure they will be of interest to other Tak owners. I have had several very impressive views through an FS128.

Milt

January 3, 2006 11:36 PM Forum: Takahashi

Transit/Storage Case

Posted By Milton Wilcox

Dear Hans,

I can tell you one that I would not recommend anymore. Based on Dave Novoselsky's CN recommendation of Thermodyne cases in 2003, I called Josh Ackerman recently and he expressed an interest in doing my semi-custom case. I sent him detailed dimensions of my scope and never heard from him again. He didn't answer multiple phone calls or emails, even to say "sorry, we can't take the job." I had told him that I would need two more cases if this one worked out, but apparently that wasn't of sufficient interest.

Bottom line is I went back to Scopeguard. Don Holcombe replied promptly, quoted a fair price and is now building my case.

Best Regards,
Milt

February 1, 2006 09:26 PM Forum: Astro Binoculars

Wide Angle Finder for 20x125s

Posted By Milton Wilcox

David, great job!

Milt

March 15, 2006 08:07 PM Forum: Refractors

TEC 140 pricing

Posted By Milton Wilcox

How does Yuri produce a 140mm f7 oil spaced triplet apo with 3.5" Feathertouch for $4750?

I suspect volume has something to do with it. TEC produces the APO140 in much higher quantities than their other apo models, which are priced more in line with competitors. Yuri found a real sweet spot with the 140ED.

July 29, 2006 08:14 PM Forum: Astro Binoculars

Surveyor Tripod, UA or Oberwerk

Posted By Milton Wilcox

Steve,

Ed's advice is right on - you need to chose your tripod based on total weight. You will probably need both 5 lb. CW's on the T-Mount, so the total weight carried by the tripod will be over 30 lbs. Another aspect is that you may wish to mount significantly heavier binoculars at some point in the future, which would still be well within the capablilty of your T-Mount.

For these reasons, I believe the HD surveyor tripod would be the best bet. The UA version has a carry handle built into one leg, and you should also check with Larry about options for a more convenient leg spreader.

Don't throw away the stability of the mount with an undersized tripod!

Good luck,
Milt

August 22, 2006 02:15 AM Forum: Binoviewers

question on correctors

Posted By Milton Wilcox

I see some units come with different size correctors; Williams Optics has a 1.6X Siebert has the 1.8X TV 2x ..is this for fast and slow scopes?

John, the quick answer is no. How much magnification you will have to accept to make the binoviewer focus is a function of how much in-focus your scope has in reserve. The optical path length through a binoviewer is on the order of 110mm. Assuming that you use the same diagonal as you use for mono, the scope's focuser would need to be racked in over 4" on your TV to come to focus without any corrector!

The less in-focus you have in reserve, the more you have to move the focal plane back, which means more magnification. Often Cassegrains like your MN66 don't need any correction at all because the motion of the primary when focusing is magnified by the secondary. Also, there are other ways to skin the cat. Denkmeier and Siebert both offer a clever dual lens system that effectively reaches out and grabs the light cone forward of the focuser and brings it back to the binoviewer. The very expensive A-P Baader binoviewer uses a very compact prism diagonal to reduce path length compared to a mirror diagonal.

On your TV you can measure the in-focus available, but the actual calculation for what rated magnification corrector you would need is complicated (for me, anyway). To give you an idea of the relationship between corrector mag and in-focus required, go to the A-P website at
http://www.astro-physics.com/index.htm
select 'accessories' then 'visual accessories' and finally 'Mark V Binocular Viewer.' Scroll down to the bottom of that page and it gives the required in-focus for several configurations.

Good luck,
Milt