Posts Made By: Floyd Blue

I once again ask this question. Is the color seen with or without a filter?

Just recieved the 40mm Meade 5000 SP in trade for the 32mm 5000 SP, and MY GOD this thing is huge. It weighs 1 lb 9 oz and is enormous!. 8O
I will test it tonight on three fast Dobs and see how it goes.

Mike,
I too had a NS8GPS 8" SCT and on rare occasions I could see some spiral features in M51, but normally just a shape of gray color. My wife called them faint fuzzies. The Sombrero would show it's dark lane a little.
It was not until I got to 12.5" that I began to see details clearly, though now the 10" Zambuto seems to bring out the details too, so maybe this is the break point for this.
The larger the aperture the more detailed the galaxy and globular clusters will be.

Wow, I went the club meeting tonight and the club was getting rid of the S&T collection. It was grab and go and I got the 1961,1962,1964,1966 issues. This should make for some interesting reading.

Well, I just made a deal on the Pentax 20mm XW for the collection. This is my first XW though I still have 3 XLs in the case. I Really like the Pentax and the XW seem to be pretty nice. My Nagler 20mm T-2 is a bit heavy for my 10" scopes, so this might be the right one for them. 70° FOV should be nice for them too.
Hopefully the weather will clear up in time to use it this month so I can report on it.

I have been having a long discussion with another person concerning the claims being made about the 6% difference between Enhanced coatings and Standard coatings. Some people are making claims of great differences in effective aperture and the ability to see object that are not seen with standard coatings.
What is bothering me about these claims it this.
If a 14" mirror was coated with 90% reflective coatings and has a surface area of 154 square inches, then a 6% increase in reflectivity would add 6% to the effective surface area ( according to the math) for a total of 9 square inches. This would equal a 14.4" mirror in surface area.
Now even if this were true, the effective gain would be less than .1 magnitude in light grasp.( Doubling the surface area of a 14" scope requires a 19.8" mirror and that only gives you .7 mag increase in light grasp. ) It is my understanding that this would not be perceptible by most observers. Even if it was, .1 mag would not make much difference in what objects would be visible. General rule, a star is 2.512 times brighter than a star one magnitude less. But .1 magnitude is very difficult to judge when looking at two stars, one mag 5 and one 5.1 mag, don't you agree?
So how is it possible for people to state that they are seeing mag 15 and 16 stars under light polluted skies after the Enhanced coatings were applied if the increase in light grasp is no more than .1 mag?
I can not see any real difference between a 14.5" scope and a 15" scope, can you?
I am a bit miffed about this because I believe that there is a lot of hype being distributed concerning this. It seems to me that there just can not be evidence to support the increase in effective aperture and light grasp making visual differences that are being claimed.
What do you think about all of this? :S

When you outbid someone with less than one minute left on the auction, why does it add 10 minutes to the auction? This seems a bit strange to me. I have never seen an auction work like this. :S

Ok, I had a chance to try out the 20mm XW.
The EP is very nice, but it does have the one trait that I have found common of all the Pentax line above 10mm, field curvature. It is not as prevalent as the 14mm XL that I tried, but it does have it in the outer 15% or so of the FOV. Not really unpleasant but it is there non the less.
The good part is, the rest of the FOV is quite good with excellent clarity and good contrast. With the 70 degree FOV, you have about 60-62 degrees of flat field I would estimate.
I did not get a chance to really wring it out, but I did get a good look through it. I hope to get a little more time later. The clouds moved in as I ate dinner, so I only got about 25 minutes at the EP.
Truely, there are few EPs over 60 degrees FOV that don't show a little something at the outer edge, so I would not state that this is not a pretty nice EP.
More about it later when I get more time at the scope.

I am interested in your impressions for the 34-36mm Siebert Observatory EPs.

Well after Dave Bonandrini mentioned an article in Photonics Spectra magazine concerning cleaning of optical mirrors and their stating that alcohol was not to be used, I contact them and asked for a copy.
I have the magazine and article now and have read it. The article was well written and by a professional optician and the cleaning methods were well described and did correspond to what I had learned in the past. Including the information on alcohol and aluminum. Their statement is "Because alcohol reacts with aluminum, it should never be used on protected or bare aluminum- coated mirrors.
Now this goes along with everything I have ever been told about alcohol. I do not use it on mirrors, but use Acetone instead or sometimes MEK. There are people that are still advocating the use of alcohol as a rinse for our mirrors, and this is why I am writing this thread.
Dave Bonandrini already mentioned this. I am just confirming his statements.