Posts Made By: Tom Lacovik

what do people use for camping lanterns when camping at a star party.
you still want to turn the lights on when you get in your tent, read a bit before going to sleep and generally see what you're doing in your tent without flooding out with white lights.

any red lantern ideas out there?

thanks.

Hi All. I am building a 13.1" dob. My rocker box is about 21" square.
The bearing sides of it are 3/4" BB ply. and the non bearing sides are 1/2" BB ply.

a) the real question:
What should the bottom be? I don't want to overbuild it, but don't want crappy performance either.


---
b) the theoretical rumination going on in the back of my mind:
Will 1/2" be fine? I was wondering since the az bearings press on 3 points and define a plane, if any sag imperceptible or perceptible really matters? Even if it does sag, does it matter since the scope will spin in az on those 3 points, period.

HI all,
I've been inactive in the hobby for a while. Coming back into it now, and looking around for something to add to my very nice trio of Pentax XLs (7, 10.5, 14) where the 10.5 is the only one I would really not give up. But also not necessarily wanting to continue the habbint of paying absolute top dollar for the last 10% performance.

So now I look around and see claims of 90% the performance of a nagler for $100 in the 2" 30mm ish range. With several... gee, lets see if I remember them all.

Orion Q70 2" EPs claiming 70° at 32mm for $100
And I believe the exact same EP from Eclipse SWA2 for $90
Meade QX 2" 30mm is also 70° selling for around $90

and finally, this kind of blows my mind:
Agena UWA 30mm 80° AFOV $80

In short, are there any suprises now adays for WIDE field of views in the 30mm range? Or does the addage you get what you pay for still apply? Or does the 80/20 rule apply: 20% of the cost will get you 80% of the performance of the premium EPs (of which I have half a set as mentioned above, but nor am I a EP snob who could not stoop to have a cheap good bang for your buck wide field ep for binocular like feeling through a scope...)

Thanks for catching me up and offering any suggestions. Even if your suggestion is bite the bullet and add another pentax in that range, well, so be it.

TomL.

Hi.

Given the same eyepiece is at focus in a scope at the middle of the focusser's travel (let's just say we're talking about a pentax 10.5mm XL in my f4.5 dob).

What would happen if I add a paracorr? Would I need to rack the focuser in (toward the secondary) or out (toward my eye) when I put that same eyepiece back in the chain?

do you need to rack 1/2" in? out? 1"? parfocal? approximations are all i'm looking for.

Thanks.
TomL

(the reason I'm asking is i am building a f4.5 dob right now and just measured the distance between cage and mirror box to 35.75" apart in order to bring my EPs to focus in the middle of the focusers travel. knowing this is going to be a fast dob, i want to plan for a paracorr and if i need to round that 35.75 up or down that would be the deciding factor).

Any opinions on the Oberwerk 20x80 Lightweights?

is the 3.6 lb weight light enough to be comfortable to be hand holdable. that's close to the nikon 7x50 weight, so it sounds astounding. does it feel astounding?

is the 20x too much magnification to be handholdable?

if these aren't hand holdable, and i pretty much have to mount them, then i wouldn't limit myself to just these... weight/size won't matter that much if mounting them anyway.

thanks.

Is it just me? or does anyone else find the PST to be gaudy? Gold bling goes so bad with the plastic bits. And that it's a straight tube looks very much like plumbing not like a tapered refractor. The black box it screws into seems like a mis-shapen or elongated diagonal, and then there's the ol' glory sticker on there too ?! finished off by a fake rubber stamp effect P--S--T stomped on there in faux diagonal, like someone was in a hurry (on purpose) or like a cartoon "FRAGILE" stamp on an package.

As gaudy as that is is dwarfed by the largest logo-to-telescope proportion you'll likely ever see. CORONADO, fully 1/3 the length of the OTA-and-diagonal bit. No proportion. No color, finish and material harmony, and no respect for typography. Blech!

Lucky it's WONDERFUL to look through and an amazing deal for the money!!

TomL, Portland, OR

ps. Didn't somebody here put a beautiful automotive-quality takahashi paint job on their home made refractor?

Anybody tried these? 82 degrees at a full range of FLs. Wonder how it compares to my Pentax XL (68 deg).

It's nice that they also have a 2" ep at the 19mm point. something you don't see too often.

Price is good too. Can't find any reviews or opinions though.

Where to begin? I just searched the forums for my first posting to the ATM group and it is from April 2004, almost 4 years ago! But reading those posts I had clearly already started several months before.

In 2003, I saw a wonderful string scope made by a wonderful person (doug tanaka) who wound up mentoring me through thick and thin. He showed me how he made a carbon fiber curved spider and strings, served archer style. It nested into itself collapsing like russian dolls, and he encouraged me to build my own... and that's when it began.

I acquired a very good 13" f4.5 mirror from a coulter that tested very well at Steve Swayze's shop, and he said it doesn't need refiguring, but I had him perfect it just the same. (and it is perfect).

I started on the cage, learning to route in the process, learning to mold carbon fiber in the process, learning to cut tubes in the process, learning to forstner drill pockets for struts... everything was new to me.

I used nylon screws everywhere i could and shaved every ounce I could on the cage knowing that a pound saved up top is 5 saved below (so 6 total if you can shave a pound off the top).

I felt a bit let down when the rocker posed fewer learning opportunities being pretty much a box, so I challenged myself to learn some joinery at least. That added many months and failures (was trying to learn dovetailing which is not for the beginner, but I tried just the same). Finally I decided to simplify my goal a little bit and learn to cut box joints. Almost as beautiful, and very strong. I learned a lot about how not to chip out plywood on a table saw (hint: use wood backing for every hole, every cut).

I had a 8" dob that I traded in for a 6" mak on a Nexstar mount to keep me equipped during this long learning process (made longer by my self-challenges).

Then something very difficult happened about 2 years into my atm-ing. My marriage broke up and it took all my strength to recalibrate, recreate, resurrect myself. Naturally, such luxuries as ATMing took a distant back seat to rebuilding my life and spending lots of time with friends, family and not so much solitary time in the basement. I emerged positive, uncynical, and with the perspective that it must have been for the best if we are happier now, and I am truly happy again!

With a good attitude, it's a lot easier to attract the right mate the second time around, and that's what happened. My new girlfriend encouraged me to pick up the project again, and with some stops and starts, I did just that. Any of you reading this that can relate to the joy of having someone you love share your interests, and then you get to share the sky with them, and essentially rejoice (pardon the hyperbole, but what word describes this better) together over the sight of saturn's rings, jupiter's cloud bands, the trapezeum, albeiro, the ring. All the show stoppers shared with someone who really appreciates it. Wonderful. Well all this on the 6" mak, the 13" dob was back underway.

I built the ground board in no time. I also made friends with Dan Gray who is equally amazing as an ATM and as a person, and who gave me a lot of good advice, and had his welder weld my cell. He showed me how to use a tap and die and metal lathe. I made all my metal parts in his shop and am very much in his debt. I wish I met him earlier since he is so radical in his design opinions, he's opened my eyes to questioning a lot of the received wisdom from the K-B book, and his designs prove that K-B tends to promote an overbuild strategy. Some of which I am saddled with though I did cut corners wherever my skepticism seemed valid (a lot this discussion on this very forum).

Back to the shop: I CAD-ed up my scope with F/L in order to determine the angles my poles would have to incline. This was a totally unexpected hurdle. It was very difficult to figure out how to make pole-holes in corner blocks at a 7° compound angle. My new job has a shop adjacent to it, so I made friends with the shop guy of course. A case of beer later and he had machined those 7° holes into some solid ren-shape.

All that remained was for me to make strings. Dan said he just screwed two big screws into a bench and used that to wrap several windings of 450+ archer string tying the end in a crude, yet simple to execute square knot. Whereas Doug encouraged me to learn the art of sting serving. Curse and bless you Doug! This took longer still and about 20 emails, until finally I just met him in our mutual second hometown of Vancouver BC, where we spent the afternoon making my strings and he showed me how serving works which is an art form in itself. The idea is that since a knot is the weakest point in a string, you eliminate it, by not using a knot and rather winding a special serving string (with a special serving tool) around the strings several dozens of times each and back in on itself in a way that can never come undone, and distributes the load of the winding across maybe 3" of area. It's wonderful to have learned how that's done and even better to see the results as it looks very professional and very 'finished'.

I knocked out a mercedes-logo looking ground board with hockey pucks as its feet. A good vibration dampener. I learned a lot about wood finishing in this whole process as well (I like spar urethane).

I tried a few different springs until I got the right balance between too much tension to be able to insert the poles and too little to make the tube taught in compression/tension.

And that brings me to today. This day, March 11, 2008: I saw my telescope for the first time in its completed form! It almost brought a tear to my eye remembering the long journey above and all the happy and sad moments along the way. Almost.

I collimated it to within an inch of its life. I zip-tied on the first red-dot finder I could find in my shop and took it outside to align it on a distant tree. Having seen the tree through the scope in broad daylight, I realized, this is the first time in over 4 years that I'm actually looking through my telescope...it's first light. Let me ask you something, does 'first light' strictly apply to the night sky?

I took the pictures below, knowing I owed this forum a record of my completion: this forum that helped me through so many quandaries, with so much wisdom and camaraderie (THANK YOU ALL!).

I waited. waited. and then waited! Hoping clouds wouldn't set in (I live in Oregon so that's no mean feat in March). And at last. At long bloody last, night came. I hadn't had much ocassion to look up in the months since comet Holmes but a few days ago swore that red dot at zenith had to be Mars. So i pointed my scope there for first light and... and... oh yes! oh my! never did that tiny planet look so good as in first light. Over to M42, and oh yes... pinpoint, really pinpoint trapezeum and structure easily visible in the nebula even at 7:30pm. I was happy for the extra aperture, having lived with a 6" mak for a long time. then purely by recognition, that amber color, could it be? i hadn't checked a map but i could pick that out of a police lineup... it was! yes, it was... saturn. This flood of emotion hit me. How all the above had to happen and how I persevered even as I shelved my project to get myself back together, i didn't shelve it permanently, I did it!

And now, I am seeing these sights with my own naked eyes. Some question that, saying a telescope is cheating and it's not truly with your own natural senses. But when your senses, your hands, intellect, and perseverance made you an instrument that extends your senses, then arguably, what you are seeing is entirely EARNED. And that is the great thing about ATM. I made this with my own two hands so that my own two eyes could take in what I'm taking in and that our puny little ant brains are able to do this, are able to comprehend how to extend our senses, and what it is we're taking in though it is trillions of miles away and all but invisible, i am just so proud to be human. At this time. And to be FINISHED MY SCOPE!

Thank you to all here for your bottomless help with my project! Now, to get to know the sky without any batteries, computers, and that stupid goto I've wrestled with for years...

Very sincerely,
TomL
Portland, OR

If you missed my saga ("The Long Road To My First Light"), here are the pics for those that like images more than words.
Enjoy!
TomL

stupid question warning!

I just finished my first dob, and I know i should know this. think i did at one time but...took it for granted until I had a pop quiz today: a friend of mine asked me over a beer how my scope works. I drew the usual newt diagram showing incoming light, the primary parabola and the focussing property of that,, the reflection and the 45° secondary. then he asked the confounding question. Why doesn't the secondary block out the center of your view? I struggled to convince him that it doesn't, and ultimately couldn't prove it, or draw it out, but just left him with "trust me, it's not visible. it does impede contrast, but it's not a hole in the middle of your view. but i'll have to get back to you as to why exactly though."

so how do you explain this and/or is there a site you can point me to that explains this?

darn those "simple" questions!
Tom.