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Posts Made By: John Finnan

March 12, 2003 07:15 PM Forum: Zeiss

15 x 60 B/GA T ClassiC Binoculars

Posted By John Finnan

The April 2003 issue of Astronomy magazine has a review 10 giant size binoculars (in the 60mm - 80mm size range) by Phil Harrington. He ended up rating this model as # 1 for viewing the heavens. Since some of the ones he was comparing it to were the 16 x 70 Fujinons and 18 x 70 Nikons that's quite an accomplishment for a 15 x 60mm binocular.

Has anyone else had any experience using these binoculars? And if yes have you had a chance to compare them to 16 x 70 Fujinons in particular? Also, has anyone ever had a chance to compare these agaist the 15 x 60 Zeiss Jena (now Doctor Optics) Nobilems? If yes, how do those two stack up against one another?

John Finnan

March 27, 2003 11:34 PM Forum: Astro Binoculars

30 x 80 or 40 x 80 Doctor Aspectums

Posted By John Finnan

Does anyone have any experience using either or both of these binoculars for Astronomy? If yes, do they have good contrast and are they as sharp and is the glass as clear as you usually find of smaller aperture Zeiss Jena products (e.g., the Nobilem series)?

April 8, 2003 08:40 PM Forum: Astro Binoculars

Zeiss 10 x 56 Victories

Posted By John Finnan

Does anyone have any experience using these for astronomy? If yes, what were your impressions. And also, did you get a change to compare them to any good 10 x 50s?

April 8, 2003 08:41 PM Forum: Zeiss

Zeiss 10 x 56 Victories

Posted By John Finnan

Has anyone on this forum had a change to try these for astronomy? If yes, what were your impressions? Also, did you get a change to compare them to any good 10 x 50s and how do they compare to those?

April 12, 2003 03:56 PM Forum: Astro Binoculars

Exit Pupil Size and Binocular Performance

Posted By John Finnan

Ed Zarenski wrote: "My own experience with binoculars in more than one side by side, all 80mm and less, is that a higher quality binocular at higher magnification but a smaller or equal aperture, will outperform the larger aperture that has a lower magnification".

Ed - This has been my experience as well. About 10 years ago I bought a pair of 10 x 70 Fujinons because they were highly recommended in The Backyard Astronomer's Guide. They were very sharp and clear and overall an excellent binocular. However, a few months later I got a chance to try a pair of 12 x 50 Aus Jena Nobilems and was amazed to find that on 19 out of 20 objects that I compared them on, the 12 x 50s gave me better views than the 10 x 70s.

Obviously, magnification plays a role in this. But, what about exit pupil size? The Adler Index for a pair of 12 x 50s is 85 and it is 84 for the 10 x 70s. But I found the difference between those two to be much more significant. If I was told the 12 x 50s had a Adler Index of 85 and was then asked to guess what it was for the 10 x 70s were I would have estimated around a 75.

But the other factor that plays a role in this is exit pupil size. The 10 x 70s exit pupil is 7.00mm, the 12 x 50s is 4.17mm. And my own personal entrance pupil at that time was around 5.00 - 5.50mm. Now it has further shrunk to about 4.25 - 4.50mm (I use Sky & Telescope's Pupil Guide to estimate this). Anyway, for purpose of making the example clearer, let's say that my entrance pupil was 5.00. That means when I'm using the 10 x 70s (with their 7.00mm exit pupil) half of the light that is being collected by the binocular objectives is not reaching my eye. So my smaller entrance pupil is functioning like an aperture stop on a telescope. And, when you cut the amount of delivered light by half, those 10 x 70s should be performing (for someone like me) like a pair of 10 x 50s. And, if that is the case, then it is clear why the 12 x 50s are delivering 100% of the light that they are collecting (and at a higher magnification) should be outperforming the 10 x 70s.

Anyway, what I just wrote was "conventional wisdom" 10 years ago. Do you know of any reason why that type of user entrance pupil/binocular exit pupil type of analysis should not be taken into consideration when trying to numerically estimate how well one binocular should perform in comparison to another when used by a particular observer?

September 29, 2003 08:56 PM Forum: TeleVue

Re: TV 102 and a new Astro-Physics 130

Posted By John Finnan

Robert, I recently upgraded my NP-101 for an NP-127 which I've had an opportunity to use quite a lot over the past month. Naturally, I would not have made that expensive upgrade unless I thought that I would gain a significant performance boost from it.

In most respects the NP-127 performs the way that I expected it would. That is, nebulas are both brighter and show more nebulosity. Globular Clusters like M5, M13 & M22 show many more individual stars but are not really well resolved not would I expect them to be in a 5-inch scope. On the moon and the planets I can go to higher powers while retaining a sharper image. However, most of the objects that great in the NP-127 also look pretty nice in the NP-101. To use an analogy, I'd say the NP-101 is like a Porsche 911 sports car and the NP-127 is a like a 911 turbo. There is a significant and noticeable difference in performance but it is not a radical difference. Nevertheless, I'm pleased with the NP-127. But, knowing what I know now, if I still had a NP-101 and I did not have a set of Nagler eyepieces or a Bino Vue, that is where I'd invest me money before upgrading to a NP-127. But, since I already had the Naglers and Bino Vue upgrading the OTA was the only thing left I could do to improve the overall performance on my system. I fairly certain the NP-127 will be the end of the line for me.

The category in which I noticed the greatest difference was when using a binoviewer. Some of the brighter DSOs look good/great in a NP-101 but not many. Those same objects look better in the NP-127 but more importantly (for me anyway), is that many objects that don't look so good (or so-so at best) in the NP-101 look good/very good in the NP-127. To me this was the most important (and desired) performance gain that I've got with the NP-127.

The reason that I was willing to pay big bucks for a 5-inch rather than using that money to get a Tak, TEC or TMB 6-incher was because I prefer the shorter focal length and rich field options of the NP-101/NP-127 type of scope and the fact that they are small and light enough to use with a Gibraltar Mount.

On the color issue with your AP-130, have you had a chance to use it with Saturn yet and have you seen any false color with it? I don't know how to account for your 40x splitting on the double-double with the TV-102. The lowest power that I've seen in split at (in another friend's TV-102) is 98x. The 87x split you got with the AP-130 sounds about right to me, not 40x with a TV-102. Do you have any other astronomer friends who have seen it split at that power through your TV-102?

Anyway, I hope my post gives you some idea of what to expect with respect to a performance gain between a four-inch apo and a 5-inch. If you're looking for a bigger boost than that perhaps you’d be happier with a 6-incher. One of the many good things about your AP-130 is that is should be easy to resell.

December 21, 2003 09:39 PM Forum: TeleVue

Re: TV85 Maximum FOV

Posted By John Finnan

I agree with you that a 22mm or 26mm Nagler would give you more than enough of a field of view for a TV-85. Plus their smaller exit pupils will darken the sky background and increase the contrast. Another advantage that these two eyepieces have over the 31mm Nagler and 41mm Panoptic is that they are much smaller and lighter.

I have an NP-127 with a 660mm focal lenght and I use the 26mm Nagler as my low power eyepiece on it. It gives me a 3.04 degree true field at 25x with a 5.00mm exit pupil. On your scope it would give you a 3.35 degree true field at 23x and a 3.7mm exit pupil.

July 17, 2004 07:28 PM Forum: Eyepieces

Re: 5mm and smaller

Posted By John Finnan

The Radians all have a very long 20mm of eye relief and a fairly wide eye lens and they all are very comfortable/easy to observe with. However,some users do not care for their click stop eyeguards.

The newer high power Type 6 Naglers are also a big improvement (with respect to eye relief and the size of their eye lens over the older 4.8mm Type 1 Nagler). I just got the 2.5mm, 3.5mm & 5mm Type 6 Naglers and I'm very pleased with them.

I do not have any experience using any of the higher power Pentax eyepieces.

January 28, 2005 08:31 PM Forum: Astro Binoculars

Why so many 16x70's for sale?

Posted By John Finnan

I've noticed that in Astromart's Classified Ad section (for binoculars) there seems to be quite a few Fujinon 16 x 70 FMT-SX binoculars up for sale. This binocular has an excellent (and well deserved) reputation for both its optical quality and reasonable cost (relative to its competition). So I'm kind of curious as to why they are offered up for sale fairly often. Does anyone have any knowledge or thoughts about this.

February 2, 2003 12:39 AM Forum: Binoviewers

Qs on using Denkmeier OCS with TV Binovue

Posted By John Finnan

John, like you I also have a NP-101 and a Tele Vue Bino Vue. I got a Denkmeier OCS last month and have been able to use it a few times. It definately works well with the TV Bino Vue. With a pair of 24mm Panoptics I'm now able to binoview at 29x. That gives me a field that is 55% wider and a field area that is 137% larger than what I can get using that same eyepiece with Tele Vue's 2.0x corrector.

This extra large field (especially for a binoviewer) comes in handy for both locating objects and for observing rich star field areas like the summer Milky Way or Saggitarius. It is also great for the larger Messier objects like M7, M24, M31, M44 & M45. However, many of the other M objects that look good in a binoviewer (e.g., M8, M35, M42, the Double Cluster, Alberio, etc.) will look better at 45x using the regular TV Bino Vue than they will at 29x using the Denkmeier OCS. Which one will work best depends on what object you plan to use it with.

I also reconfigured the Denkmeier OCS to see if it would work at a higher magnification and it did. I not sure of what the increase was but I'd estimate that it was somewhere between 3.0 and 3.5x. However, I don't plan to use that option very much because my Tele Vue Bino Vue (at 2.0x) gives me more than enough high power options (using the 9mm or 7mm Type 6 Naglers) that I don't need the Denkmeier OCS to provide that option for. However, depending upon which eyepieces you currently own that Denkmeier high power option might come in handy.

Is the Denkmeier OCS easy to use? I'd have to answer both yes and no. Once you get it setup it works just as easy at the Tele Vue 2.0x corrector provided that you remain in binoview observing mode. However, if you want to switch back to single eyepiece mode to view and object then you mustsad1) Remove the diagonal from the OTA. (2) Unscrew the Denkmeier OCS from the front side of the diagonal. (3) Reattach the diagonal to the OTA. (4) Put you single eyepiece in the diagonal and then start observing. Then, in order to go back binoview mode you must reverse the process. In this respect I don't find the Denkmeier OCS easy to use. With the Tele Vue 2.0x corrector switching between single eyepiece and binoview modes is as easy as switching from one eyepiece to another to change the magnification.

Another thing to keep in mind that that you will need to switch back and forth (between modes) quite often. While many deep sky objects look great in a binoviewer, in my opinion the majority don't look as good due to the light loss. Hence, I tend to do about 75% of my telescope observing in single eyepiece mode and 25% in binoview mode.

Nevertheless, the Denkmeier OCS can do some things for you that the Tele Vue Bino Vue alone cannot. For that reason I
can recommend it to you. I'm glad I got one and look forward to using it a lot more next summer.

John Finnan