Posts Made By: Floyd Blue

Dang Michael,
Sorry to hear that, but I understand the cost and all. See you on Yahoo! 8)

Well, It is another one of those unanswered questions. Do you rely on Foucault or do you only trust an interferometer?
Are results derived from any other testing but Interferometer to be dismissed as inadequate?
Seems like Carl Zambuto produces some mighty fine figures and smooth finishes based on Foucault tests.
Do other manufacturers have better figures because they test by machine?
Makes one wonder doesn't it?
For my money the proof is in the eyepiece. Nothing can convince me a bad mirror is good but nothing can convince me a good mirror is bad either.
If the mirror is great the images will also be great. If the mirror is poor the views will also be poor. If the finish is rough the contrast will suffer. If the figure is poor then the images will suffer. Seems simple to me. Maybe I am just simple? 8)

Well, with the comments about the inability to distinguish between 1/4 wave and 1/40 wave optics, it would seem that we are wasting our money buying premium optics.
I would have to suppose that the visual difference between one scope and another of the same aperture is just my imagination! 8O I seem to suffer from some kind of optical illusion of sorts, because I can see a real difference between optics of various qualities. I can see a real difference between my 15" Swayze and my 14.5" Zambuto for instance. Both have very good secondary mirrors and used the same EPs, yet the difference was dramatic and real. I can not say that I have looked at 3-4 18" scopes side by side, but I have looked though 4 15" scopes side by side and there was a definite difference between two Discovery, Nova and a Swayze mirrors. If I had the Zambuto at the time, I am sure there would have been a big difference there too, but it came later.
You might have to examine the object carefully or it might be immediately obvious depending on the object.
I think that those opticians that produce fine quality mirrors would argue the idea that you can not see the difference between 1/4 wave and 1/40 wave.
Maybe I am just seeing what I expect to see? Not sure, but I can say that I do see a difference between lessor and better optics. Perhaps this is just me?

Hello all,
Because of a comment made about the results I posted of Interferograms by Antares about possible manipulation or masking of edges or defective areas. I thought I would post part of a correspondence I had with Antares about these comments.
The following is an excerpt from this letter for you to read and make your own judgment about the validity of their testing and documentation.
"We measure all of our mirrors at 100% aperture. No Mask data manipulation what so ever. We only trim the outside perimeter to 5 points as shown on the interferogram. True a 1/50 wave PV optic is a rare & prized piece of work; It does happen enough, "here", that I can say it is almost a weekly event.
As I explained in our earlier phone conversation, we produce 4" and 6" transmission Flats for "EDIT" itself. Producing a 6" 1/25 wave PV TF is much more difficult than finding 1/40 or 1/50 wave mirror on a block of twelve or more 1.83" secondary mirrors.
We use these secondary mirror blocks as a testing platform to measure the performance of our 52" & 60" Continuous Polishers. After these blocks have polished on a daily basis for a week or two, we test these mirror blocks on a Zygo GPI. When we see the test exceeds a 1/20 wave PV, we retire that mirror block and start a new one.
There is no pressure to produce these mirrors. They're finished when they're finished. Why wait a week or two you ask?
(The first few days, in the life of a mirror block) If you leave a mirror block set up on the interferometer overnight, the next morning, you will see that the test has changed from what was seen night before. We wait until we see no change in a 24 hour period. After a week or more, most, if not all of the blocking stresses have dissipated, so when we de block, the mirrors change very little. Some change, or "spring" in the wrong direction and some spring in the right direction! That is what you have there. A mirror that corrected itself in the right direction. Yes, I like to take credit for all of our fine mirrors but sometimes I have to say I just got lucky with a few of them. If you do a few thousand of these mirrors, you will have plenty of rejects, and on the inverse, a few exceptional pieces to show for your time.
We've been contracted once again by a major customer, to correct a problem that "EDIT" could not remedy."
I hope that this resolves the issue of testing done and quality statements concerning these flats.

I just got a chance to test a 30MM GSO Superview EP for a distributor. I found a lot of off color in all scopes from f/10-f/8-f/5-f/4.3. Has anyone else had this problem or was this an isolated incidence with one EP?

I find it rather sad that a discussion on a forum such as this one can result is bad feelings, disrespect and emotional responses. This unfortunately is true of the last two threads that I started. In private messages I have been told that certain persons will no longer correspond with me or relate to me on this or any other forum. This is far from my intent in starting these or any other threads.
I am surprised by this response as well as saddened by them.
I would like to publicly state that I did not at any time mean to disrespect anyone or to make statements that would cause anyone grief or annoyance. This is not my nature. I can be argumentative and disagree with some one because I too am opinionated, but I try to stop short of making enemies of breaking of relationships.
Because of this unintentional outcome that arose from a perfectly innocent beginning, I intend to be much more careful when I start a thread or state my opinions on line.
Perhaps it is better to leave things unsaid, than to say what can not be withdrawn.
Any and all those that were effected by these last threads in any unpleasant way, I send my deepest apologies.
Now I think I will take a little break from these forums and try to recover from this ridiculous situation that I have created.

To all,
I first want to say thanks to those who feel that I have contributed to this and other forums. I have received a few private messages showing concern and support and I want to thank those that have done so.

I am also pleased to say that I have been able to patch things with those individuals that I had a problem with by having heart felt words with them.
It is more important that we express our opinions than agreeing with each others opinions.

In addition to Astronomy I also dabble in upholstery and making things with my commercial sewing machine. I find it very rewarding to take a thread and weave it into a fine cloth, making something of beauty with pride of accomplishment.

To me this is the same with a thread in a forum, it is just a thread if in the end it does not produce something beautiful and useful. I will try my best to pick my thread carefully and sew it with all the skill and imagination that I possess to produce a fine fabric of shared knowledge.

OK, so we now know that figure and polish and PV and RMS and even Strehl are all different characteristics.
We are also informed that Wavefront error is not the most important of these attributes.
It appears that figure and polish have the greatest effects on image quality.
It also appears to be fact that RMS is a fair indication of the smoothness of the surface and is figured into the equation for Strehl which determines how much of the light will remain within the Airey Disk.
Then we are to understand that the figure of the mirror including the edge as well as zones is important to producing a good Strehl rating which is considered to be very important for good optical quality and performance.
Now it sure seems to me that the only way to insure that all of these aspects of mirror performance are present is to have a mirror made by some one who is very skilled and then to have it coated by someone who is very skilled and finally to have it mounted in a structure that is designed and built by some one that is very skilled.
If I am understanding this correctly, then I must conclude that this means "Highest Quality in Optics and Construction" are the parameters required for the finest performing telescopes with the best images.
With this all out of the way, then I also must assume that this is all for nothing unless I am located in an area where the conditions and seeing allow these high quality components to function to their highest ability.
But does it still not follow that having these components will insure that on any given night you will have the best possible images that can be acquired in that evening under the prevailing conditions?
It still seems logical to me that if you are wanting your experiences as an amateur astronomy to be the most rewarding. Then it "IS" worth the extra expense to purchase the best.
Does this seem like a fair statement with the facts as we know them?
Did I do the right thing by purchasing the best that I could find or did I waste my money in my rush to excellence?
This was the intent of my latest set of threads, to determine the truth and wisdom of buying the best of the best.

Now that the equipment has been well covered I would like to tackle the next big question. What is the most important attribute in a site for observing?
There are many thoughts on this in our club and community. Some feel that it is altitude. Others say it is light pollution (dark skies). Still another train of thought is location, in relation to prevailing conditions.
I realize that all the above are important factors. I have my own ideas on this subject, but I would like to hear yours.
The reason for this thread is this. In recent years the conditions at many of the existing premier sites have deteriorated considerably. Light pollution has wreaked havoc on many. Others are lost from urban sprawl. Due to this loss we are faced with the need to find new sites or else we will just loss our ability to enjoy the night skies.
I have been actively searching for new sites over the last 3 years die to this problem. Mostly I have be concerned with dark skies as the main objective. The next priority for my search has be the amount of sky one could see from the respective site. I have looked at altitude but this seems even more elusive because of the lack of access. The location issue is still under investigation for me, as I am trying to learn more about recognizing what constitutes the "right location to find the best atmospheric conditions".
If you were looking for a new and great site, what would you look for in this site and where would you look?
I hope you find this subject interesting, because it is one of my biggest concerns at this time.

I am going to get the Feathertouch for my new scope the ZZ-10 and am trying to decide how much travel would be best, the 1.5" or the 2" for a 10" f/6.
What do you guys think?