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Posts Made By: Jeff Verona

July 24, 2002 07:06 PM Forum: Telescope Making

Solar filter

Posted By Jeff Verona

I've got a piece of Baader AstroSolar film, and I want to make a filter for my refractor. I figure I can mount the film between two sheets of cardboard, but what's the best way to attach the filter to the dew shield? I'm worried that tape would fall off. I recall someone using an embroidery hoop, but I have a small scope, and I'm also afraid to put the film under too much tension. Suggestions?

Jeff Verona

September 21, 2002 06:20 PM Forum: Equipment Talk

William Optics diagonal

Posted By Jeff Verona

Anyone encountered one of the new 2" William Optics diagonals? It's a mirror diagonal; they claim 1/6th wave and 96% reflectivity, which should put it on par with the upper end of the mirror diagonals but not the dielectrics. I was wondering if anybody owns one and can discuss performance. The price looks right.


Jeff Verona

November 19, 2002 08:21 AM Forum: Deep Sky Observing

Leonids in rural Iowa

Posted By Jeff Verona

LEONIDS -- 2002

I watched the Leonids from 1000-1100 UT on 19 November 2002. From my backyard, the skies were exceptionally transparent, but the seeing was a bit off (not that it mattered, with meteors). Despite the full moon, stars were visible down to the 5th magnitude, and I could distinguish Praesepe between Leo and Gemini. Early on, the radiant was closer to Gemini, but it shifted toward Leo during the shower. My spot was in the shadows, and eventually the moon dropped behind the house, so seeing improved slightly. I saw 200-300 meteors during the hour. Most were about mag. 2 to 0. The brightest came out of the sickle of Leo and flared just below Jupiter, at about mag. -2. The vast majority showed green trails, although the brightest were white, and I detected many vapor trails. The longest-lived arced over 10° of sky; about a third were simple flares. The shower had a definite peak, when 2 or 3 meteors were visible simultaneously. Once I saw four go off in short order in the same small patch of sky. At that peak, I counted as many as 8 meteors in 20 seconds.

Jeff Verona

December 27, 2002 03:20 PM Forum: Equipment Talk

Fully-illuminated field

Posted By Jeff Verona

I know that long focal-length scopes have a smaller fully-illuminated FOV, but I don't have an exact formula. Does anyone have an equation where I can plug in aperture and focal length to get the size of the fully-illuminated FOV? Thanks.

February 21, 2003 11:15 AM Forum: Chinese Optics Imports

Optics source

Posted By Jeff Verona

I've looked at the Burgess website and Yahoo group, but I can't find any information on where he sources the optics, or if they're matched or tested. Anybody have any info? The mechanics on the scopes are undoubtedly superb, and the price is fantastic, but I don't want to play Chinese roulette.


Jeff

April 2, 2003 11:57 AM Forum: Telescope Making

Linearity in optics

Posted By Jeff Verona

This may be a dumb question, but...

Say you have a 6" f10 lens. At the objective, the light path is 6" in diamter; 60" away, at the focus, it's an infinitely small point. My question: is the relationship between diameter of the light path and distance from the objective linear? For example, at 30" from the objective, will the light path be 3" in diameter? At 20" from the objective, will it be 4" in diameter?

I'm working on a folded refractor project, and I need to figure the size of the flat and the distance from the objective. Haven't decided on the size and f-ratio of the objective yet, so I was hoping for the theory, rather than the specific practical application.


Jeff Verona

April 4, 2003 06:27 PM Forum: Telescope Making

Link for lenses

Posted By Jeff Verona

I'm looking for a few links that will give an overview of different lens types and some 2-element lenses. For example, what happens to the image when you combine a double-concave lens and a plano convex lens? I've tried general searches on optics tutorials, but I can't seem to find what I'm looking for. Thanks.

Jeff Verona

April 8, 2003 09:41 AM Forum: Telescope Making

Working lenses

Posted By Jeff Verona

Most of the traffic in this forum has been concerned with grinding and polishing mirrors. Does anyone have experience with working achromatic lenses? Newport Glass offers some achromatic lens kits, with machined blanks and tools. Has anyone here used them?

Jeff Verona

April 20, 2003 12:29 PM Forum: Telescope Making

A baffling question

Posted By Jeff Verona

Are there any general rules on baffling the OTA of a refractor, such as "X number of baffles for Y focal length" or the like? If somebody could point me to a website, I'd appreciate it.

Jeff

July 30, 2002 06:08 PM Forum: Eyepieces

Panoptic or not?

Posted By Jeff Verona

I have a Gary Russell 19mm Konig ep (1.25", tho he also makes a 2" model). I'm quite pleased with it. I've compared it head-to-head with the 19 Pan. The Russell's not as good, but it's 1/5 the price and delivers 70% of the performance. I use it in an f6 scope. There's some internal reflection and ghosting on bright objects (mag. 0 or better), but it's just fine for DSO, and the ghosting problems vanish if it's barlowed (yielding f12). Hope that helps.


Jeff