Posts Made By: Greg Nowell

I forgot to share this with someone. For many years I have enjoyed hiking along the Mohawk trail which which has been pretty peaceful and a fairly safe area for a gringo to walk solo, since the Iroquois Confederation was annihilated in 1779. This appears to have been rather decisive as there are many hundreds of people who use this pathway every day and I have not heard any recent reports of scalpings or tomahawk attacks. Nonetheless, after recent discussions of the need to wear a firearm while observing on Yahoo! Refractors, I do find myself thinking that for a walk along the Mohawk at dusk I might need more firepower.

Apart from these musings, I have caught a number of views of Great Blue Herons.

In binoculars, the Great Blue typically presents this aspect: a giant prehistoric body on two long sticks, motionless, staring at the water. I have spent fairly long periods of time watching these birds do their thing. Sometimes they up and fly away.

Well about four weeks ago I was out with my Pentax 8x43s and decided to take in a view of a Great Blue that was out about 100 yards. So there I was motionless watching him being motionless. Just as I was about to give up he made this

Szzzzwaaaap!

And came up with a 12 inch fish, looked like a carp, that was struggling and flopping quite helplessly. He took a few walks to shore, as if he preferred to eat the thing over dry land where it couldn't get away if he dropped it, then ended up stopping in very shallow water and swallowing the whole thing. It's hard to believe that they can get a whole fish down their gullet in one gulp.

Well I decided I would keep watching him for a bit and I was particularly focusing on his chest because I wanted to see if I could see any pulsing from a thrashing fish.

He ambled back out into the water and then, in some kind of posture I didn't know they could do, lowered himself close to the water with his neck out long and horizontally flat. In this position he made some rapid strides in a very purposeful direction and then

Szzwaaap!

Up he came with another fish, this time he actually did walk all the way to the shoreline before swallowing it whole. I kept thinking that had to be enough food for now but he came right back out and resumed a motionless posture.

Anyhow, maybe it's a routine thing for people who bird a lot, but after many years of watching Great Blues, it was something of a treat finally to see one catch something, and two fish within ten minutes was all the more extraordinary.

Greg N

Televue gives 46mm for the field stop of the Pan 41 (an eyepiece I really like)
Pentax gives 46.5mm for the field stop of the XW40

For a c14, 3910mm fl

Pan 41--
57.3*46=2635.8
2635.8/3910=.674 degrees afov
or .674 * 60 = 40.4 arc minutes tfov

XW 40
57.3*46.5=2664.5
2664.5/3910=.681 degrees afov
.681 * 60 = 40.86 degrees

Both companies publish the field stop specs

TV claims they are offering the largest possible fov in a two inch eyepiece barrel, but they are edged out. They do however claim 68 degrees for their eyepiece, but it calculates to 67 (rounding the decimal down).

Pentax claims 70 degrees but publishes the field stop which gives 68 degrees.

Now, either both companies are fudging, TV by 1 degree and Pentax by 2, or perhaps there is some additional something to this formula that can be jiggered? The companies both publish their field stops so they're not going to be surprised that some anal retentive person will run the numbers. Using 57.29 for the radians isn't going to help.

Should the eyepieces just say "more or less what we put on the sticker on the side"??? Is the field stop calculation the "absolute last word"? Or does it have an approximative element?

Greg N

p.s. I can't believe my sacred XW40 got shoehorned down to a Pan Optic 68 degrees! I would rather believe the sticker.

Since I own a 10" Newt and am enjoying it, and own a 5" apo and love that too, I don't want people to think this video is saying that the C14 is the *only* or *best* choice. However, over the years I've read a lot of people posting that they think the C14 is too big to be portable, and I just thought I would make a demo video.

This was the hardest setup I've ever done due to the extremely high heat, and it wasn't that bad. It was 95 degrees and very humid.

http://www.youtube.com/watch?v=TBawz69qo_A

regards
Greg N

I've posted a number of articles here on A.M. (two on pentax eyeieces, one on super polaris mount, one on Losmandy G11/Ovision; if there are more I've forgoten) and was wondering whether any data is kept on how often articles posted here are actually looked at.

When I recently made a 6 minute youtube movie on the C14 I was quite tickled to see the number of hits and their worldwide distribution (which I think is viewable by the public). It's just amazing to think someone in Australia or India has been looking at my down-home video.

A "number of views" clicker on the articles would provide encouragement (assuming there is readership) to post new stuff.

thanks
Greg N

I recently purchased a 60mm "Circle T" 700mm (f11.7) refractor off Craig's list. I have been giving it a workout and am somewhat startled by it.

The main thing I'm pondering is why it is so hard to see chromatic aberration in this thing. I had thought that you needed to be at f/15 to f/18 to control CA in an achromat. I have *seen* chromatic aberration in other achromats including an f/7 80mm Antares that I used to own. I have seen purple hazes around bright objects and odd colors round the moon.

Well right now I only have the comes-with 4mm and 23mm so I am limited to 30x and 175x. But I have done all the standard tests on this thing. I have looked at branches against bright blue sky at 175x and I have looked at the moon at 175x.

The bottom line is that it is *very hard* to make this scope show chromatic aberration. One must go considerably out of focus: many more cranks than, for example, my F/6.5 102mm ED Vixen.

Bottom line is that at 73x per inch this scope is much closer to the color control of the FS128 and the Vixen ED then it is to any of the more recent achromats I've used.

Obviously the focal length has a lot to do with it, but I'm wondering whether the small objective is also a factor. I guess I'm picturing in my head that a larger objective might put more rays in front of and behind the focus plane because the larger objective would have more of a curve.

Anyhow I'd appreciate some edification.....

thanks
Greg N

http://www.youtube.com/watch?v=IwVg1M6bURI

This is a much-needed follow on to my world famous "C14 is a small scope" video. It demonstrates the side mounting technique and shows that there is an easy way to get the C14 into the GEM saddle, which minimizes back strain to practically zero.

regards
Greg N

My FS128 is equipped with a Moonlite focuser. Last night on the moon some folks were "egging me on" to jack the power up beyond any reasonable expectation. It was fine at 300x with the 3.5mm XW. There appear to be 4 ways to use the Barcon:

ANYHOW, I gave in to the pressure and (1) put the AP Barcon in "the usual way": Barcon into the top of the diagonal, eyepiece into the Barcon. If I read AP's web site right that's about 1.6x or 480x power. The view was good, and I *could* focus.

Then I tried (still under pressure from three onlookers) for 600x by (2) putting the Barcon into the drawtube and then putting the diagonal into the Barcon and the eyepiece up top. The distance between the Barcon and the eyepiece gets bigger, leading to more magnification.

I couldn't reach focus.

Then I said, well, we can reduce the distance a bit. (3) I screwed the Barcon lens on to the mirror diagonal, inserted the diagonal in the drawtube, stuck an eyepiece in, and could not reach focus.

Then I said well I hear about people needing longer and shorter tubes depending on what they're trying to do so maybe this isn't going to work when it occured to me I had option (4), which was to insert the AP Barcon's lens-less extension tube into the refractor drawtube, and then put the diagonal, to which the Barcon lens was screwed on, into the *top side* of the Barcon extender (it's not screwed on in the usual way here).

That actually worked! I could reach focus, but have no idea of what the effective magnifying ratio of the Barcon lens was in this unusual position. It *definitely* seemed to be higher magnification than the 480x achieved in (1).

Anyhow there's a lot of ways to use a Barcon.

I was wondering what exactly is going on with the positions that "work" and the positions that don't work and what my effective magnification was when I hit paydirt with position (4).

FWIW, the views at 300x and 480x were excellent, and the view in position (4) was pretty good, but beginning to take on that "excess magnification feel". I think the optical limit of the FS128 is really as a practical matter 300x, maybe 400x under some circumstances.

regards
Greg N

I'm currently running an auction in REFRACTORS and am encountering some interesting questions from people who perhaps have not thought through "the theory of auctions" and also how it relates to classified advertising. In particular I'm going to talk about the opening bid price, the reserve price, and the buy it now price.

The opening bid price is designed to keep people in the right market for them. In my particular auction, if one wants a $30 finder, an auction for a Stellarvue F80 is probably the wrong place to begin (though hope springs eternal, I know). People who are in the market for an inexpensive Corolla to be sold at auction for $10 to $12k shouldn't really be bidding for a slightly used $300k Lamborghini which happens to be on the same lot. The opening bid limit encourages people to stay in the market for which they have the right funds and expectations.

One sets the opening bid price below one's reserve price to get a sense of the "spread" of interested buyers below the price at which one is willing to part with the item. This is useful to know if the auction fails.

The "buy it now" price may represent one's best guess as to actual value or one's most optimistic hope. Personally I think too high a buy it now price turns off potential bidders and makes them think that the reserve is higher than it may in fact be. I'm not sure why one would use the "buy it now" price since one can run a classified at that price and sell. When you get two dozen queries on an a classified you know you probably have priced too low but by then you've sold it and made a mental note that next time--why not try AUCTIONS? With a classified, the ideal pricing strategy is to get three or four motivated queries from people at the top of the price range (from the seller's point of view: the risk to buyers is that by waiting for the classified advertiser to list at a lower price, they lose the item to someone else). I had a rather stunning experience selling a Tak focuser a couple of years ago which went for double what I thought it was worth: but I think I was not taking into account how "cheap" dollar products looked at that time (in Europe). Anyhow I tend to look at the value of things in terms of next-available-substitutes and sometimes this gives a very different pricing result than one would think, because one's bidders in fact have tried the next-available and they don't like it, which is why they are bidding on your item. Or any number of other hypotheses....often times, neither you, nor they, have in fact arrived at a definitive valuation.

If the auction fails to sell the product one has the option of contacting bidders if one adjusts one expectations, or one might take note of the spread and place a classified "to see how it works that way." An auction that is listed for a week has less time to attract motivated buyers than a classified which lists for three weeks and catches more drop-in views. This is where the calculated risk comes in. The seller hopes that the item will eventually sell for more than the reserve, perhaps even more than one would list at in a classified. One can't be sure. The buyers have their say in this game too.

In any case one does not *share* the reserve price because that is a bit like a classified ad where one says "price $100 but I'll take $80." If you SAY that, then you will get $80.

Astronomy is a thinly traded market in many items. Markets can be thin on fairly inexpensive items (like the Stellarvue F80) and also on the pricey ones. It may be that someone out there is willing to pay $50,000 for a 10" AP Mak Newt, but that does not mean that there are *a lot of buyers* at that price. Some people might stop to consider that at that price they could get a 20" RCOS and keep a spare in the closet. We tend to think of "the value of the good" on the basis of "the last price paid." That's the way it works in the housing market. Or the stock market. But in a thinly traded market--which astronomy is--there may be one person willing to pay $50k and then a steep slope down to the next willing buyer at $20k. In thinly traded markets the low volume does not give reliable pricing because buyers are few and all over the place. The buyers are *also* unsure of the "market price" of the item.

When an auction is most favorable to the seller it is because the most highly motivated buyers are aware of and have been attracted to the auction. If they are absent the bidding will be less aggressive and the seller may not meet his minimum goal. So he thinks....hmmm, below this price, maybe I can find another use for this thing so I'll not sell it, or perhaps, I'll sell it in a different way. So the reserve is a bit of a safety net for the seller.

To conclude:

Dear bidders--
1. I am not interested in secretly disclosing my minimum (reserve) price!!!
2. The opening price is just "to get the game going" it is not the price at which I or most other people will in fact sell
3. An auction which fails to meet reserve price still discloses useful information to sellers and buyers
4. I must say that of the several dozen sales and purchases I have made on astromart, the most fun have been the two or three auctions.

Astromart auctions prohibit sniping (it is fascinating to me how many variations there are on auction design). Sniping is when you come in at the last minute to put in high bid and take the item from the people who have been plodding along. Astromart resets an additional five minutes after a very late bid to prevent this. Alternatively, ebay tolerates it: there are services which will snipe a bid in during the final six seconds of an auction.

Many people think this is unfair, but I am not so sure. Once one has been in the game a while there are certain names that attract attention. There are people here on AM, who, if they were bidding on something, might make me look at it real hard to see why they saw value where I did not.

So well known volume buyers can "attract price competition" which works against their own interest. This is why there are insider trading rules. And also why everyone wants to know what Warren Buffett is buying. Some people have a reputation for choosing well, so if word gets out that Mr. Buffett is picking up 100k shares of something that will make it attractive to others, who will assume he knows something they don't. And they trust Mr. Buffett's judgment more than their own (perhaps rightly so).

I have sniped (on that other site), I have been sniped, and I have been out-sniped (dueling bids in the last six seconds go to highest bidder of the two: but snipers will automatically lose to someone who simply has entered a higher maximum bid, even though he has not sniped). I have also listed here where the practice is seen as unfair. Works for me. There are thousands of different auction designs, this one works pretty well I think.


Auctions are a great deal of fun, but classifieds also have their place, and are the bread-and-butter technique for most of us, for buying and for selling.

And I hope you all forgive me for simply following the rules of the system here "as I have found it." I'm being mean spirited, I'm just letting the auction run its course as it was designed to run here. I'm sorry to say that one person got very angry when I refused to divulge the reserve price "off line." One can read more about auction designs here:

http://en.wikipedia.org/wiki/Auction

best wishes,

Greg N

39 minutes...not edited, not well shot...no script...

Pete doing a demo of the Obsession 15" with servoCAT and the Argo Navis. The AN is the last ten minutes. The video is essentially "crib notes" taken while he showed the unit to a buyer.

http://www.youtube.com/watch?v=EHP2gOFjHQc

Greg N

Another reason I dislike international orders. I told a guy I'd be happy to ship to him in Malaysia, found the perfect box for the pier (the box berlebach had shipped my tripod in), spent and hour getting it sealed up right and another hour taking it to the post office to find out what the charge would be.

Only to discover that although the box is fine for U.S., Canada, and Europe, it is 4 cm too long for Malaysia and would be rejected by their customs office.

I give up.

Greg N