Posts Made By: Milton Wilcox

Hi Larry,



In theory yes, because the aperture restriction is ahead of the focal plane where the diameter of the light cone is larger. Thus a larger clear aperture (note, CA also stands for chromatic aberration) will improve the illumination of edge objects in your 27mm field stop ep's. I highly recommend Rick Shaffer's excellent diagram in his tutorial on exit pupils, 'Wild Card 001' in the articles section of Astromart to see why this happens.

How noticeable it will be is a separate question given to some debate...

Milt

Howard,

I have been using 9mm Nagler T6's for 231x on my Baader and they look white to me although I haven't done a back-to-back comparison with plossls. You would expect the image to darken when doubling the power.

Although floaters are much less intrusive when using both eyes, they still will become more apparent as you reduce the exit pupil diameter. You are already below 1mm at 180x and would be about 0.6mm at 250x. When using high powers I periodically shut one eye at a time to make sure both are properly aligned on the exit pupils. Also, the diopter adjustment becomes more critical at higher powers.

I agree that the additional FOV is worthwhile in a non-tracking setup.

Clear skies, Milt

Hi Rich,

Gene hit the nail on the head. I too found that a binoviewer has to be "transparent" to enjoy two-eyed observing, the primary benefit being comfort for me. Any reduction in image quality, and I quickly forget the comfort. So I went from bino back to mono and just recently back to bino (I had already doubled up ep's, so had an incentive to find something that works :S) It turned out to be a matter of finding the right one for my scope:

http://www.astromart.com/articles/article.asp?article_id=150

This discussion raged on the binoviewer forum earlier this year. Note, SCT's are much more forgiving on back-focus than Newt's.

Milt

My 15 Pan's also have 10mm eye relief and work fine for me, again without eyeglasses. I agree with Paul this is a very handy f.l.

I also have T6's but find I cannot fully use the 82° AFOV when bino'ing. When I look straight ahead center, the field edges are so far out there in peripheral vision that unless something bright is at the field edge I miss it. Turning my eyes far enough to resolve the field stop in both is uncomfortable (in mono mode, I simply turn my head slightly).

So for me, Plossl's are too narrow, Nagler's overkill and Panoptics perfect. Others seem to do better utilizing 82°, so it may just be my 58 yr. old eyes. 8O If you have never bino'ed with Naglers you might want to give it a try before spending the big bucks.

Milt

Congratulations, Marc! That would be just about everybody's dream scope (and mount). But where are you in the photo?

Hi Dan,

The only true 2" eyepiece I own is the 31NT5 (and you can pry it out of my cold dead fingers). Everything else I need to do I can do with 1-1/4" eps up to the 24Pan.

My TV101 f/5.4 has a flat field and my Newtonian a coma corrector so I have not yet had to face the field flatness issue. You might want to check with TMB and find out at what diameter the field will be acceptable visually and then choose your ep field stop accordingly. In my case, going from the 24Pan to the 31NT5 gives me a 56% increase in f.s. dia.

Like Nils, I also own a 12NT4 and it is my most used ep in the TV101 both with and without Barlow. I no longer think of it as a 2" ep because I use the 1-1/4" barrel to keep the focus close to parfocal with my other TV ep's. (I would be embarrassed to admit how long I used the 12NT4 in 2" mode and had to rack the focuser way out and back in...)

Were I doing it today, I would probably just go for an 11 or 13 Nagler type 6. They weren't even available when I ordered the 12NT4 five years ago.

Clear skies,
Milt

Hi Don,

After reading your profile (too many telescopes, too little time) I would suggest acquiring a copy of H.R. Suiter's book Star Testing Astronomical Telescopes, which should have the answers you need. Assuming your diffraction rings are concentric, your unbalance could be caused by spherical aberration. It certainly doesn't sound good.

Milt

Hi Nils,

>>Aside from the slight dimming of the views, any bino will necessarily make the perfect star images in a high quality refractor seem a bit less sharp, partially negating one of the reasons for having the refractor in the first place.<<

Maybe, but there are degrees. It was views through an A-P/Baader in a Starfire 180EDT that convinced me to spend the extra $$$. I would be surprised if you could detect any degradation in your TMB using the Baader Planetarium, providing you have Mr. Christen's Glaspath compensator in place.

After living with both a Denk II and Baader, my thumbnail assessment is that the Denk offers value and versatility while the Baader offers superior optical quality at a commensurate cost. Why did you spend over 3x on your TMB what a very good Orion 100ED would have cost?

Milt

>>So I purchased three scopes with excellent reputations: a 9.25 Celestron SCT, a 15" Obsession reflector and a 5" Takahashi refractor.<<

So, Tom, this would be the "shotgun" approach. I would say that you made excellent choices in your scopes and your wife (no three at a time around here...)

Milt

Hi Rick,

Yours was a very thoughtful post. I hadn't heard about it, but I'm glad that telescope makers are being held accountable for the outrageous pictures some show along side their scopes.

Since you already have been observing, you now have an idea of what we all see through the eyepiece. But there are different kinds of challenges in astronomy, and seeing visual detail is only one. Sometimes just finding an object gives immense gratification even though it may only be an averted vision smear in the eyepiece. Those with larger scopes simply take this challenge to fainter magnitudes. I get a big kick out of finding objects in my small scope or binoculars that would be easy in a large scope.

In general, the purpose of astrophotos is not to show us what we can already see visually, but what we can't. I happen to be one of those who would rather look at the faint smear in the eyepiece than the detailed color astrophoto, but everyone is different.

Regarding objects for you to try for in an urban setting, I believe the Astro League maintains a list of such objects at http://www.astroleague.org/index.html but I was unable to access their website just now. Also, please consider taking your refractor out to a dark site once in awhile - not only will you be able to see fainter objects, they will be easier to find because of the increased number of naked-eye field stars.

Clear skies,
Milt