Posts Made By: John Holt

john shea said:

What are the differences between the Uranometria 2000 and the Night Sky Observers Guide? I have the Night Sky Observers Guide but when is it time to warrant the purchase of Uranometria 2000?

As the other guys said, Uranometria is an atlas. Very detailed map of the whole sky.

If you have access to some rural/darker sky (public or private) I highly recommend it, for just about any size scope. It is one very good non-electronic way to locate just about anything.

Consider Will Tirion and Brian Skiff's
BRIGHT STAR ATLAS.

It has the what and where (as in ngc# and coordinates) of many hundreds of the brightest and best that may be crossing your meridian at any time of night any where on our planet. Already listed and tabled. Perhaps 50% tables and 50% charts.
http://www.willbell.com/atlas/index.htm

Highly recommended!

I have no experience with any of these specific ep's. So I am not actually answering the question.

But it has been my experience that there is a direct connection between the retail price of any ep and it's performance, within a general eyepiece catagory. In this case 20mm ER with 50-ish Degree fov. The more expensive ones will out perform the less expensive. And there is a pretty significant difference in price from top to bottom between these three.

Bright Messier's, Luna and Saturn often look pretty cool in just about any scope/ep combo. Particularly at modest magnifications. Optical finish and coating differences show up on more difficult targets and at higher magnification. Like bright planets with subtle details or fine detail in fainter objects. More expensive ep's, again within a general type, have less issues with glare, internal reflections, sharpness on axis and light through put in my experience. They are priced higher because they cost more to make.

Sorry to sound preachy and repetetive. I've screwed around with budget ep's for years, and found this out for myself by trial and error. At retail price, the higher end plossls, orthos, konigs and various multi-element wide fields always out do the budget ones of similar advertized parameters. The used market is a little different. Seems to be less hype, and more supply driven. So it is sometimes helpful to look up retail prices as a judge of performance.

Anyway, I'd bet the Vixen will spank the Agena pretty soundly.

Bill Meyers said:

My interest for my urban observing is in double stars and wide field star asterisms.
Does it make sense to you to use an 80 or 90 or 100mm apo for this, or is this overkill and a small achro would do the job as well? This far I have used only larger Dobs, so I am quite unfamiliar with refractors in this range.
Thanks for your help,
Bill Meyers

A small newt also makes a good grab-n-go.

I confess to keeping almost no track of what I'm observing anymore. The non-astro parts of life, and the weather, leave me scope time in no predictable schedule. So I steal it where I can. Therefore I observe what ever is near the meridian at the hour available on any dark night.

Having a deep field atlas at hand, rather than an list of intended targets, has been one of the best methods to do this. All objects on the page in a given part of the sky are on the menu.

The down side is that you miss some of the seasonal wonders. But I was missing them anyway. The method of non-planning and just going to rural sky with the MSA or Uranometria really opens up the deep sky options. If it's faint and fuzzy and crossing the meridian, then it's in season.

As a non-sage owner of no Naglers nor Pentax's it has been my experience that premium ep's really do work well. Membership in astro clubs give even us tight wads the opportunity to see the difference well correct for fast focal ratio's, coma correction, and superior glass and coatings on those multi elements can actually do. And can't do.

I've never met a member of the NGC that could _only_ be seen in the most expensive ep of a given focal length. But well coated and decent field correction regardless of the size of that field, beats budget wide field every time.


Some valuble work arounds for lack of premium glass in the focuser are:

Fix the movements on the dang alt-az mount for smoother navigation.

Detailed diagrams of where one is looking.

Powered finder rather than unit finder.

Bill Barrett said:

All my observing is done in Seattle with refractors. I understand the impact of light pollution on observing DSO's. Do urban skies have a similar impact on observing the details on Jupiter, Saturn & Mars?

Light pollution does not. Heat sources do however. Roofs, parking lots, roadways large buildings...any thing that is radiating off it's thermal load collected during the day. So a work around is to keep such structures out of the line of view, by as large a margin as possible IME.

Floyd Blue said:

Every one has different needs for their scope or scopes. But I believe that most of us observe many object types with various focal length and types of scopes.
It seems that most all the newer EPs are at least 60° FOV and most seem to be longer eye relief. This seems to imply that the demand is for a wider FOV and longer eye relief and the manufacturers are responding with new designs.
Even Planetary EPs are 60° or more from many makers.
So the question is, [COLOR="Blue"]Do you feel that the wider FOV and longer eye relief is a necessity or a luxury that you can do without?[/COLOR]
Next question is, [COLOR="Blue"]If the FOV is wider, must it be all usable or is it ok for a percentage of the field to be soft or astigmatic?[/COLOR]
Finally, [COLOR="Blue"]Is it acceptable to have any color at the very edge of the FOV?[/COLOR]

Some muddled reflections:

Demand is somewhat determined my marketeers. Offering all kind of something for less. Folks often do not realize that the eye astigmastism that their glasses correct for is frequently simply not there in short focal length ep's. Placing an additional piece of plastic into the optical path is considered heresy for an ep or scope manufacturer, no matter how well it's supposedly anti-reflection coated. Yet scope owners do it all the time. Myself included. Perhaps necessary for low power. But often not for high power.

Well corrected beats wide field. Both together are luxury.

Lots of repackaged ep designs being recycled with new names. Still, after years and years, many selling ep's do not tell us that the number one determining factor for ep field performance is the focal ratio of the scope.

The more aperture one has, the less one is bothered by loss of light through-put in mondo multi element ep's. Or, if ones targets of are only brighter ones. Really really well made multi element ep's(and other in your focuser schtuff) with tip top coatings work very well on glare and internal reflections.

I visited 3C273 earlier this week with a 6", 2 plossl's and an ortho. A powered finder would have been help. But what made it possible to see it was the chart in S&T.

Gary Cunniff said:

Looking for guidance from frequenters of this forum - Could you recommend binoculars suitable for birding, sports and star-gazing that would have some of these features; rubber-clad, compact (similar to the reasonably nice Celestron 8x21 binocular I had), not made in China, and priced at under $75.
Feel free to let me know if my criteria is way out of line.
I generally spend my time on the TeleVue and refractor forums and have ventured here seeking new knowledge.
Thanks
Gary C.

No criteria is ever out of line.

IMHO 21mm and rubber coated are the two criteria that I would most likely pass on. It has been my experience that small aperture bino's can and do work well. Larger aperture just work significantly better. For birds, wildlife and night sky. More detail resovled, more color for those targets where color is an identifying parameter, and fainter fuzzies after dark.

It has also been my experience that within a given price range, one gets better optics without the rubber coating on the binos. The manufacturer has to make cost choices.

http://members.aol.com/billferris/h400.html

Very good work done here!