Posts Made By: Tom Lacovik

So many ways to make a 12V Dob battery pack. I've done our battery shopping for us! But...which option to choose and why?

My research has shown that rechargeable alkalines, though 1.5V per cell are probably a bad choice, since they don't deep cycle.

It would take TEN C or D NiMH cells tied together in series to make 12V. Energizer D NiMH are 2200 mAh, and sell for about $8 per pair or $40 for ten.

No name ones here rated 2500 mAh for both C & D (why not get smaller Cs then?)
http://www.merchantamerica.com/neotec/index.php?ba=view_category&category=4385
cost only $2.50 per pair or $12.50 for ten (price is right anyway)

Then there's these high capacity 9.5Ah ones...this seems like a good deal with charger...(or check out the many combos and permus at the left menu)
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=46


Panasonic 12V lead-acid 7.2Ah for $26 here:
http://www.mdsbattery.com/shop/productprofile.asp?ProductGroupID=1065

how do you recharge these suckers anyway?

the lead acid one weighs 5.45 pounds (or 1.4 pounds for the 2500mAh Version there) . How much to 10 D cells weigh anyway?

Decisions, decisions.... what's a boy to do?

Thanks.
TomL

p.s. what the heck? a 12v battery the size of an AA cell!? for alarms. Weird:
http://www.mdsbattery.co.uk/shop/productprofile.asp?ProductGroupID=593

A couple weeks ago there was a thread on a good budget widefield 2" EP for a 13.1" f/4.5 newt. It seemed that the result of that thread was that there really wasn't a good bang-for-your buck surprise EP in there, unlike say planetary EPs where you find a lot of surprises (for the dollar).

So of the remaining high-end widefield EPs, including Naglers and Pentax, I was wondering about the Pentax XLs and if they would require a paracorr for a f/4.5 13.1" newt (build in progress)? Or is the effect not too bad if you are not an absolute purist? Or maybe anybody would be annoyed by it it's so bad. In which case I'll buy a paracorr.

PS. I have the pentax xl 7, 10.5 and 14 and was eyeing the 28 or 40mm ones...whichever will be better suited to my dob-to-be.

C is for coupe. which I still don't get as there's a big trunk. I wanted a 2 door and perhaps a 1969-1971 280 since those have the double stacked headlights I love so much, but the 73 sill has vertical headlight assembly (I lost interest in the design after about 1975 when they all looked like 240D), and a lot of style.

This one was the FILTHIEST car i'd ever seen, BUT... I could tell it had a good coat of paint under it all and most of the crud could be addressed. The chrome was so good and there was lots of it.

I especially like cars before 1973. The following year, the US forced these huge rubber bumpers to be 'stuck' on to Benzes, BMWs, and Bugs alike. The 'perfect' design on the bug has those 'plumers dream' crhome pipes for bumpers. After 73 or so, they were forced to ruin the lines (imo) by ripping of those bubbly bumpers and sticking on standard, big, american looking mostly rubber bumpers in the interests of safety.

Anyhoo, this one polished up nice and I put in new upholstery, hunted down all manner of missing doo dads, now completely original. Even found an original becker radio and secretly wired my iPod to it from a hidden location (modified ashtray) and tuned the engine and it's now a great daily driver.

The engine is strong straight 6 2.8L single carb. Here are some before and afters.

Enjoy.
TomL

I thought the meade 497 WAS LED (the letters/numbers ARE red lights). I have a celestron nexstar 8 and it's definitely LCD grey screen with black letters/numbers lit by a red light. The letters/digits themselves are not luminous. but I belive the meade ones ARE. The "497" autostar is newer. I think I know the bigger boxier, and older LCD meade version you are talking about with the older lx200s but if that's what you have maybe a newer 497 which has surplanted those older lcd ones...if compatible with your scope, might just be the ticket for your eyes.

TomL

I will be in Florida for a week (june 1 to 8 or so). Flying into Orlando and house (and car) sitting for a friend on Sattelite Beach an hour from Orlando on the coast and next to Coco Beach and Cape Canaveral.

What space stuff should I do there?

Thanks.
TomL

I really want to eliminate 'fuss' from the scope I'm building (I have computers to fuss with all day so I don't need more at night and besides, I have a goto Intes on a Nextar mount if I didn't get enough computer grief at work and want more at home!

So I don't really want to make a control panel where I'm fine tuning everything from fan speeds to heater output either. Actually I am thinking about putting all my heaters on a single pole single throw switch to really simplify.

But if I do that, I should pick power values that are suited for a dew-fight when on, otherwise I switch it off if dew is a non-issue that night. I live in Portland, OR which is wet 4 months a year but I don't observe while it's raining anyway The other 8 months I don't find humidity or sudden temp drops to be a huge problem, and I bet one could 'keep up' with the temp changes without much heat to the optics needed to fight the good fight.

So does 1.5W for the 2.6" secondary sound good? What about .75W for the telrad?
Also, do you find there is any need to switch one on and the other off. I would think that 99% of the time, they are either both heating or both off.

Thanks.
TomL

p.s. I think I will skip making an EP heater unless people here really pipe up in their favor. Those just seem to dangle unused on most people's scopes I've seen and who wants to fuss with that every time they change EPs (I don't even bother with my focuser set screws cause I change EPs frequently).

Hey Kids.
A friend of mine who is not into astronomy (YET! but does like the views I force on him through my scopes and 10x50 Nikons), asked me to help him pick out a pair of binoculars for general use. I asked if astronomy was a consideration. He said, "Well, if I had em I'd probably look at this or that, but moreso for my upcoming road trip through California with my little nephew. Sea World, that sort of thing."

Ok so not giants, not opera glasses. I asked how much he was thinking of spending. He threw out $50 as a number. I frowned and said, "Well you get what you pay for in optics: the price is directly related to optical and mechanical quality, since there's no electronics or other features which makes judging quality by price not as superficial as it sounds: so $50 could get you okay 7x35s, $75 would get you good ones, and $125 would get you great ones and $150 and up will get you perfect ones (after that only the optical equivalent of audiophiles could either notice quality gains or even if you could be talked into noticing an imperfection, you wouldn't care). Also, since it's not electronics, it's never going to be obsolete, and if they are well made you're going to have them for the rest of your life, if they are not you'll need two pairs before you die so may as well go with getting one quality pair for the rest of your life "

"okay, let's make it $75 then."


So having pushed his budget as much as I could (a 50% gain was pretty good I thought) I know he and his nephew don't want to hold up 10x50s at concerts, on mini hikes, or at sea world, that leaves the following question (I know: FINALLY!!

What's a good pair (if not model, then brands at that price point) of general use 7x35s for about $75 or less?

Thanks
TomL

I have a different take on this from all the other replies. I mean sure, I agree, with your mathematical breakdown of your costs and markups and all (that's just called business and doesn't need further justification). I also can't argue with the usual supply/demand formulas.

Rather, it's an observation I have stepping back. First I think what that fellow probably should have said, was "$5k is way more money than I have. That is an outrageous amount of money for me to spend on anything" rather than "Michael's scopes are outrageously priced (ie. not worth it)" That's different. Putting aside that this fellow may not be able to afford a 30" scope that was $5000 if you get my drift, what is outrageous, what is truly outrageous is that we can, any of us, even have in our possession these precision scientific instruments at our homes. The dobsonian revoluion and decades of ATM toil and refinement have made possible having great instruments of large aperture within reach. What is amazing is that it doesn't have to cost $50,000 to own a large scientific instrument accurate to within a fraction of a wavelength of light in your home and not in a lab.

How the heck did we even get here, to the point of having 16", 20", or more, large observatories in our back yards? How come that is NOT $50,000. Dobson found a way to make affordable mountings for newtonians that were solid as all get up, and that were affordable to make yourself. These were heavy and you didn't really want to lift a 13" classical dob (like a Coulter Odyssey for example), but trusses and let us say, obsession style dobs, raised the bar. now ultralights are raising it further still. The limit to aperture now is really how much you can spend on buying an optician's time for a month at a time to grind and figure glass for you. If you build your own that is. If you have someone build it for you, then you better be prepared to buy their time and skills too. If you want a large instrument, that is a lot of people's time (are they doing it for fun? are they doing you a favor, and you'll pay em back with beer like a friend helping you move a couch?) and a lot of skill (Zammit with metal, Royce with glass) you are expecting to rent or have them work for you for what? fun? Subtracting the cost of all the materials alone like pyrex blanks and metal (or 3rd party add ons like focusers or telrads or whatever), you are buying Royce and Zammit for like a $100 to $200 an hour combined.

These aren't car detailers, they are opticians and machinists. Actually, come to think of it, I seriously think that a car detailer will bill you around $100 to $200 an hour as well, for labor and "materials".

Look, $5000 is a LOT of money to any of us, rich poor or in between right? Right. But what comments like that show is just a lack of knowlege and familiarity with the history of telescopes, and how amateur telescope making has brought the price DOWN to the $5000 range for large telescopes.

TomL

Anybody have or know a good place to get a 8" x 4.5" -ish
first-surface mirror? (it's for a bino box).

Yes, I've done my googling, but there are so many sources and apparently kinds, and for once I don't feel like shopping for this stuff, and was wondering if someone had a solid recommendation (price / availability).

Thanks.
TomL

If so, then I won't feel so bad asking you for a favor, but only if you really want to okay?

I am at my folks place in Vancouver, BC, and I just learned that a good friend of my father's is a welder and can make me a cell if I can supply the drawing or specs or something (I have none with me!). This is a great opportuniity if I can seize it. I've never designed one before and to be honest was a bit held up and mystified by plop (read: stuck).

SO away from home right now, I have the opportunity to have a welder do whatever I want him to, question is: what dimensions or drawing do I give him? can someone help draw or just dimensiont this out for me while I'm on the road away from all my 'tools'? I'd be everso grateful!

Here's the facts, my mirror box will be 20" square. I was planning on using the Kriege/Berry book throughout: steel tailgate, 3 triangles and sling on split bolts. I recall finding that 9point cell for my 13.1" Coulter/Swayze mirror which is 1.125" thick at the edge and 58.5" FL (f/4.47).

I would like to use steel tubing and have 9 points on 3 triangles, but am not equipped to calculate or spec the shapes, sizes and dimensions of the triangles and the 'ladder'.

Can someone help (again, only if you like that sort of thing)? If not, It'll have to wait til I get home, with a PC and more spare time this summer

Thanks either way guys, and I hope all is well with you all. Clear skies.

TomL