Posts Made By: Rod Kaufman

Originally Posted by Andrew Dies

Does anyone know the AFOV for the Meade WA 18mm eyepiece?

Depends which model you're referring to as they differ:

Meade Series 4000 Super Wide Angle (SWA) 18mm: 67° AFOV

Meade Series 5000 Ultra Wide Angle (UWA) 18mm: 82°

Meade Series 5000 HD-60 18mm: 60°

Originally Posted by Andrew Dies

I think it's before those because it only states Meade WA 18mm Multi-coated.

It's likely the 4000 series with a 67 AFOV. I have the 16mm Meade WA --original series--and it's the same AFOV but manufacturers frequently overstate the fields of view anyway. You're likely looking at 65 to a maximum 68 AFOV with the 18mm original series considering its 19.7mm field stop.

While I'm awaiting the arrival of an Antares 6" F6.5 refractor purchased via the AM classifieds, I've checked reviews of filters designed to reduce chromatic aberration inherent with achromatic refractors.
I've found an interesting review published in SkyNews, a Canadian journal for amateur astronomers. The authors utilized an 120mm f 8.3 skywatcher and an 150mm f 8 skywatcher for their tests of six filters: Lumicon minus violet, Celestron-Baader contrast booster, Baader fringe killer, Orion v-block, William Optics VR1 and the Sirius Optics PC1.
To make a long story short, the Lumicon minus violet filter is the one you want. With the 120mm on Jupiter, for example, the review states, "The Lumicon filter presented the brightest and most detailed image of Jupiter." "Although chromatic aberration was still present, the Red Spot and other surface details were more easily observed." "The Orion and William Optics filters slightly enhanced the visibilty of the spot, but it could hardly be seen in the Sirius Optics and Baader Fringe Killer filters and was not visible at all in the Celestron-Baader."
In addition, with the exception of the Lumicon, all of the filters imparted a yellow hue to Jupiter.
Similar results were noted with the 150mm refractor: "subtle details in Jupiter's equatorial bands and polar regions, not visible without a filter, jumped out when using the Lumicon, Orion and William Optics filters." "The Lumicon filter revealed the most detail and kept Jupiter in a relatively natural hue..."
I called Anacortes to order the Lumicon filter but they don't stock it so I called a local scope city store and I plan on buying one in a day or two.
If anybody has any other tips on improving achromatic performance, please share them. I'm not considering a chromacorr at this point, due to the added cost, but if there are other alternatives to improving achromatic refractor performance let me know. The scope I'm getting is said to have excellent star tests and adding a filter that provides for significant reduction in chromatic aberration while preserving the natural hue of the object being viewed seems to be optimum in meeting my expectations.

I've recently received an antares 6" f6.5 refractor from a seller in the AM and the collimation is need correction. I'm using a chesire eyepiece and I can see the collimation needs to be improved just a bit. I've emailed the seller about it as he may have some tips. The lens cell is adjustable and it has a total of six screws, two pairs per adjustment point. One screw at each point juts out while the other is indented towards the lens cell. I'm not sure of which one to tighten or loosen.

I'm interested if anyone has received shipment on this meade scope or if a review is available on this particular model. Adorama appears to have the OTA in stock with free shipping.

Robert,
I don't know if John Pons is going to want to mess with shipping and packing and what not. If you were within driving distance, it might be another story. I'll try talking with him and see what he's willing to do.
The astronomy shoppe does this kind of work and you might want to try contacting them as well.

I purchased an antares 6" f6.5 refractor from the AM awhile ago. It was sold with a twin at the same time from the same seller. I paid a 100.00 more for the scope than it's twin because it was advertised as having "excellent star tests and incredible images." It was also adverised as being compatible with a GC-5 mount which I had also purchased from through the AM.
When the scope arrived, I placed it upon the mount and it appeared to be stable but as soon as I moved the scope, the tube dislodged and it hit the floor like a B-24. I immediately emailed the seller who told me "sorry" but he may have mismounted the dovetail plate upside down on the tube! Fortunately, the lens was unscathed but a lens spacer was dislodged so I had a friend check out the scope. It turns out that other spacers were missing and a lens element was also flipped in the objective. This was the way I received the scope and the fall onto a carpeted surface couldn't possibly have flipped the lens in its cell. I emailed the seller because there was no way the scope could have produced excellent star tests and incredible images with a flipped element. The seller denied any responsibility for the problem and threatened to give me a bad rating if I did the same to him. Additionally, the thirty day period expired during the time I tried to correct the problem with the scope and the seller also deleted his ad. I contacted the buyer of the second scope and his arrived with no lens spacers!
My scope had a terrible diffraction pattern with third order coma evident in the image. My friend Jake worked very hard on the scope and the image was fairly sharp but the third order coma persisted. After contacting a lot of people, I was recommended to see John Pons whom Daniel Mounsey has described as an "optical guru."
John worked on the scope today and replaced lens spacers, shimmed the cell, replaced screws and collimated it with a beam splitter of his own making and the result is a beautiful diffraction pattern without any comatic flare.
Visiting with John Pons is like visiting with history, He's got the second 6" (actually 6.25") unitron refractor lens made back in the '50s. He's got a huge 9" achromatic zeiss refractor in his garage along with massive mounts, a 12.5" planetary optimized newt with a huge mount and so much stuff that it's truly incredible to see.
I spent most of today (Sunday) working on my scope with John, looking at sunspots through a wedge filter of his own making and drooling over his beautiful refractors.
What a day!

Rod Kaufman said:

How would these elements do for a scope?
http://www.owlastronomy.com/specials.htm

No opinions? Or did you guys buy 'em out already? 8O

How would these elements do for a scope?
http://www.owlastronomy.com/specials.htm

Anybody else catch the review of the explore scientific 5" apo in Astronomy magazine? The author of the review is a dean at a liberal arts/sciences university and he appeared adept at putting the scope through its paces. He felt his most demanding test for chromatic aberration at night was to train the scope on the full moon and then look for the latter at both in-focus and out of focus views and he found none. The performance seemed pretty impressive and the lens is supposed to be a three element job with one or more components being made from Hoya low dispersion glass.
The scope and its mechanicals at f7.5 looked quite nice. Anybody else have any experience with one of these models?