Posts Made By: Jeff Canar

Asked this over at sci.astro.amateur but didn't get any responses, so thought I'd try here. Ive just recently acquired 2 Hercules (model 4550) piers, on wheels with the telescoping center cylinder (So you can raise and lower it). They were used to hold television cameras (about 60lbs each) in a small production studio at a training facility (they were used in the production of training videos).

Anyway, these things have gotta be 30+ years old but are in perfect condition. I'm gonna keep one as a telescope mount, and then thought I'd sell the other one to recoup some of the costs from the telescope I'm building now (8" f4.8 reflector). The trouble is I can't find anything to give
me a sense of what a fair price would be. I checked Astromart, E-Bay, google, and some local (Chicagoland) classifieds, but can't seem to find anything like these. It's not technically a telescope pier, but sure could be used as one.

I really can't provide any more details cause I don't know much more about them. The center pier is about 30" high or so, resting on a four legged base. My guess is that the pier and base together weigh somewhere between 30-40 lbs. I have no idea how far the center cylinder telescopes up cause I got tired of cranking the handle ;-). They both have pan and tilt heads.

I'd prefer not to just list it as "offer me a price." I have no idea if these things are worth $5.00 or $500.00. Any thoughts about what a fair price for something like this would be? If I can figure one out, I'll be selling it here.

thx in advance,
jeff

I'm working on plans for my first scope. It's gonna be a variation of the Berry 6" DOB from chapter 5 of his book. I think I'd prefer a curved vein spider and was wondering if the following is feasible:

The inside dimension of my scope is gonna be 9.5 inches square. Could I...

1. Take a 9.5" square 1/2" piece of plywood
2. Cut out a 9" diameter circle
3. Mount a curved vein spider to the inside cut out of that square piece of plywood
4. Slide that square into the main tube assembly and secure it.

The 9" circle comes from the widest baffle that "Newt" computed, which would sit at the opening of the tube. I figured there was no harm in putting a 9" opened block of plywood inside as this exceeded the measurements of all other baffles inside the tube.

Is this a reasonable approach?

thx in advance,
jeff

I bought an 8" f4.8 mirror from Discovery Telescopes. I followed the direction in the Berry book about putting a flashligh into an index card, then moving the card until the flashlight beam comes into focus. I've done this a couple times, and am coming up with a focal length right around 72.5". So halving that, and dividing by 8" gives me a f-ratio of 4.5. So my questions are:

(1) Could this be right?

(2) When a mirror says 4.8, how much latitude is there in terms of how close it should be to 4.8. Is three tenths acceptable and reasonable?

(3) Any other methods to determine focal length?

Needless to say, there is a couple inch difference in where the focuser hole should go between an f4.8 and and f4.5 mirror. Any thoughts would be most appreciated.

thx in advance,
jeff

I just purchased a JMI 2" RCF. I noticed that when I rack the focuser all the way in, the bottom of the eyepiece tube of the focuser will project about 1/4" or so into my OTA. I'm using .5" plywood for my OTA. So, when I plug the value of the "fully racked in focuser height" into Newt, should I:

(1) use the height of the racked in tube when the tube crosses the outside plane of my OTA

(2) use the height of the racked in tube when the tube crosses the inside plane of my OTA

-or-

(3) simply the fully racked in height even though the tube dips into the OTA?

thx in advance,
jeff

I received the following email yesterday (04-07-04) about some piers I advertised (and sold) on Astromart over two months ago:

" hello, my name is jeff swain ,i saw your advert on the internet and i am highly interested in buying your (2 Hercules (model 4550) piers) pls get back to me with the present condict of the (2 Hercules (model 4550) piers) and also the picture to prove it that is a good condition and also the price and pics for it .about shipping arrangement i have a very solid arrangement for the shippment of the (2 Hercules (model 4550) piers) pls mail back as soon as u receive this mail.
thanks and hoping to hear from u
jeff swain"

I guess what makes me suspicious is that the item in questions is always appearing in "()." The grammer is terrible, and if you insert any item into the "()" the message still works. FWIW, the domain it came from was "movemail.com"

Don't know. And I'm perfectly happy to repost if "Jeff Swain" is indeed interested in these piers, but it does seem somewhat suspicious to me.

jeff

Although not entirely related,

These maps recently came out

http://www.astro.princeton.edu/~mjuric/universe/

that gives a pretty interesting 2D view of the mapped universe and also really shows just how vast things are. The best 2D map i've seen to date to demonstrate this.

jeff