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Posts Made By: Ed Zarenski

August 31, 2005 09:07 PM Forum: Astro Binoculars

StellarVue 15x63

Posted By Ed Zarenski

I've heard some others comment the same about the SV 15x63. I have not had a chance to try a pair of these.

Isn't this one of the models that has a 70mm objective with a masking ring to knock it down to 63mm. If that is the case, that in itself would help improve edge sharpness, at least to a small degree. Although it gets a 10% gain in edge sharpness at a 19% loss of light, a big expense to pay.

edz

September 2, 2005 05:13 PM Forum: Equipment Talk

Field of View

Posted By Ed Zarenski

have a look at the double star 95 Herc. it's 6.3 arcsec. And then look at Rho Herc, it's 4.1 arcseconds.

edz

September 16, 2005 11:35 AM Forum: Astro Binoculars

Thoughts on mounts

Posted By Ed Zarenski

For versatility, YES. But for stability, well maybe.

A Pgram mount like the newer model UA Unimount Light would handle an 8# binocular and really give you a wide range of viewing, even for different height people, and even for seated viewing. But you'll have a little movement in the binocs. The base tripod you put it on will have an affect on the overall stability. A tripod/head combo like the Bogen 501 on a 3246 legs would be rock solid and would still provide vertical adjustment.

I use both. And both work well.

edz

December 13, 2005 05:09 PM Forum: Deep Sky Observing

sky atlas companion, what's it good for?

Posted By Ed Zarenski

Of all the deep sky references, I think Sy Atlas Companion is one of the least well organized. You neveer know when they are goingg to list an item by it's name rather than it's designation. For instance, you're going along alphabetically thru the M objects and thru the NGCs, but when you can't find an object you will need to know if it is a Ki or a Do or Cd or St or has a proper name.

Personally, I find Lginbuhl and Skiff Deep Sky Objects a much better DSO reference.

edz

December 13, 2005 05:21 PM Forum: Deep Sky Observing

Rosette/2237 question

Posted By Ed Zarenski

I've seeen it maybe twice in my life, once with 100mm binoculars under mmag 5.7 skies. But, you probably won't see in if you have mag 5.5 skies. I've never seen it in mag 5.5 skies with any instrument.

edz

January 19, 2006 05:51 PM Forum: Astro Binoculars

Nikon 8X40 Action Extreme

Posted By Ed Zarenski

john shea said:

Anyone use this binocular? Is it true that most of the binoculars one purchases online instead of a store that they need to be sent back to the company to have it collimated?

I used it and it is a pretty nice binocular. I paid $129 new for the 8x40 AE.

No that is not true. To this day, I have not had to adjust any of the htree Nikon AEs I bought online.

edz

April 12, 2006 01:30 AM Forum: Telescope Making

2 refractor OTA's side by side with 2 diagonals??

Posted By Ed Zarenski

Do you not own a single refractor that you can set up, and then with a switch sides with the tilt of the diagonal and move the stool to the other side? Pretty simple really.

Your only reqirement for this test is to keep your body orientation the same to the direction the scope is pointing. When sitting on the left side of the scope, you would view with your right eye. When sitting on the right side of the scope you would view with your left eye.

edz

April 12, 2006 12:54 PM Forum: Beginning Astronomy?

SCT Collimation with an Artificial Star

Posted By Ed Zarenski

The final adjustments for collimation are made on and IN FOCUS image.

The artificial star must not be larger than the Rayleigh Limit, or the Airy disk size for your scope. You have an 8" scope. The radius of the Airy disk for your scope is 5.45/8 = 0.68 arcseconds. For a very bright light, the central visible disk within the Airy disk will be larger than that.

You would want the test point source light to form an angular image smaller than the Airy disk. I think your light source is too large, or you are too close.

However, there are some parameters to take into consiideration based on the f# of the scope. there is an appendix section in the back of Suiter's book "Star Testing Astronomical Telescopes" that gives all the parameters.

edz

edz

April 12, 2006 01:28 PM Forum: Astro Binoculars

25x100 choice and an idea.

Posted By Ed Zarenski

I have not seen a skywindow mount that has the capability to carry the load of a 10# 25x100.

If you could get past that, the mounting requirements for the combination load of a 25x100 with the extra load of a mirror would be substantial. Just roughly I would estimate you'd need a mount up in the $500 range.

edz

April 20, 2006 12:14 AM Forum: Refractors

Resolution Limit

Posted By Ed Zarenski

Seeing (detecting) a thin line is a special condition for resolution. It is resonable to consider that a thin black line against a white background will be seen at R/5 to R/10. So it may be possible to see the thin line of Encke with a scope that has a resolution limit of 0.6 arcseconds. That's a 9" scope.

That will not resolve the line. But it may allow you to detect the line.

edz