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Posts Made By: Alan French

August 31, 2008 10:23 PM Forum: After Dark

FUJINON BINOCULAR 16X70

Posted By Alan French
Michel Roy said:

Hi

Somebody can tell me if Fujinon Binocular 16X70 are good
very good or excellent before I buy

Thank-you

Aquamamiya smile

The Fujinon 16x70s are generally considered first class. If you wear glasses, you may find the eye relief a bit sparse - and you really need your glasses if you have any correction for astigmatism.

I had the older 14x70s, and sold them because they did not have enough eye relief for use with my glasses, and my astigmatism greatly detracted from the view without my glasses.

Clear skies, Alan

September 12, 2008 10:22 PM Forum: Equipment Talk

SkyScout vs. MySky

Posted By Alan French
Gary Greenwald said:

I would like to buy my nephew and niece one of these for the holidays.

Any advice from users would be appreciated.

I Believe there were significant quality issues with the Meade (not a surprise), but I believe it is a much better design than the Celestron - and I think that Celestron may be redesigning the SkyScout and that is why they are down to $199.

Thanks

The SkyScout here works reliably and has had no problems. Rather low use, however, since it is not needed. A gentleman had a MySky at a club star party recently, and he had problems getting it to initialize.

IMHO, Meade has tried saving too many pennies on electronics and their QC has suffered for it.

Clear skies, Alan


September 17, 2008 05:35 PM Forum: Eyepieces

35 Pans (where are they?)

Posted By Alan French
John Meiners said:

Checking the Eyepiece cat. I have not seen a 35mm. Panoptic for sale in a longggggg time?? JM

Mine is a "keeper." Perhaps others feel the same way.

Clear skies, Alan

September 23, 2008 03:26 AM Forum: Deep Sky Observing

The benefits of aperture

Posted By Alan French
"By the way, I still never did see the 'color' with my 90mm f11 achro that all the Apo guys worry about."

A 90mm f/11 is too small and too slow to have a lot of secondary color, and it would only show on the brighter objects.

The advantage to a 90mm apochromat is versatility, providing low power, wide field views and arguably the best high power views for the aperture. It is also great for daytime viewing. The little 80mm f/6.3 achromat I had here for a few weeks showed secondary color only on the brightest celestial objects, but daytime viewing featured lots of annoying purplish fringing on high contrast borders.

I think you'll love your 8" telescope. There is a lot to see with 8" of aperture.

Clear skies, Alan

September 29, 2008 06:26 PM Forum: Equipment Talk

Polorized filter question?

Posted By Alan French
If the two pieces are really polarizing filters, rotating one relative to the other should certainly change the transmission. There should be a position where the light coming through them is quite noticeably attenuated.

Clear skies, Alan

October 27, 2008 07:54 PM Forum: Beginning Astronomy?

APO Scopes

Posted By Alan French
To me, the real advantage to the smaller apochromats, such as a 4", is their versatility. In the shorter focal lengths, they can show wide true fields, yet also provide fabulous high power viewing. With the longer focal lengths, you give up some of the wide field advantage.

While they can provide surprising lunar and planetary views for the aperture, they are still limited by their modest aperture. A 10" Newtonian with reasonable optics and proper cooling should provide considerably better lunar and planetary views.

Clear skies, Alan

November 11, 2008 11:31 PM Forum: Equipment Talk

Chromatic Abberration in eyeball

Posted By Alan French
On-axis or off-axis?

I've sometimes noted odd chromatic effects if I am tired or careless and my eye is not properly aligned with the eyepiece's exit pupil. They go away when I take care about the placement of my eye.

Clear skies, Alan

November 12, 2008 02:30 PM Forum: Equipment Talk

Chromatic Abberration in eyeball

Posted By Alan French
ATM book 2 has a brief section on "The Observer: Optical Qualities of the Eye" in the chapter on Atmosphere, Telescope, Observer.

Clear skies, Alan

November 15, 2008 06:19 PM Forum: Refractors

Can anybody identify this 5" lens

Posted By Alan French
I am not sure why so many folks are trying to make this into a Jaegars lens. The quality of their lenses varied. Some were excellent, and some were not good.

I'd say put the lens in a tube of some sort and see how it does. It may prove a nice rich field instrument.

Clear skies, Alan

November 18, 2008 10:19 PM Forum: Refractors

Collimation

Posted By Alan French
David Colton said:

One of the things that drew me to a quality refractor (TV102) was that it should not need collimation. So why is Astro-Tech making collimation a selling point in the advertisements for some of their refractors? It was my understanding that collimating a refractor is not something the average user should need or want to do.

If a refractor has an adjustable cell, allowing slight variations in the tip of the entire lens, then collimation is quite easy and something anyone can do. Normally, however, refractors hold their collimation well and adjustment is usually not required.

Some apparently have the ability to adjust the relation of the two lens elements. IMHO, this is a sign of poor cell design or tolerances that are set too low, either of which may be from a desire to keep the price low. I don't think it is something users should have to do - ever.

Clear skies, Alan

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