Hey guys! wow, i've been gone a while...anyways...
For my birthday my boyfriend and I are building me a telescope (he surprised me with a tool and had me guess what it was...it didn't take long) i was wondering if you guys would have any suggestions/hints/tips...anything. neither of us have ever really built a telescope before (well...i worked on one at astronomy camp one year but mostly just drilled holes and assembled the exterior). We've got a 10" blank, i was thinking f/8 would be good (i know, it'll be a REALLY long tube 7'-ish? but i think we can handle it). I was wondering if you guys had any input on suppliers, aluminizers, general building tips etc. any and all input would be great! (and yes, i know, we're crazy for starting with a 10" but i think we can handle it. we've got a crazy prof at our school that i'm sure would LOVE to give us a hand if we asked for it in exchange for telling us a few stories).
Thanks guys!!!

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Cold be hand and heart and bone
Cold be travellers far from home
They do not see what lies ahead
When sun has failed and moon is dead

My first mirror was a 12.5" f/6. It was a bit of a steep learning curve but I did it with out any help other than a good book. One book that I feel is a must is "How to Make a Telescope" by Jean Texereau. You could go with a f/6 or f/7 without much trouble. This is a fun hobby so you should enjoy it very much. Its not as hard to make a good mirror as one might think. When you are ready to have it aluminized just let us know and we can tell you of some good places to have it done. So, "get er done".

You may be surprised at just how troublesome a seven-foot-long solid OTA can be.

Dave Mitsky

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De gustibus non est disputandum.
Never attribute to malice that which can be adequately explained by stupidity.

I have a 16" f/4.5. It's total length is around 6 feet. I can move it my myself, but it sucks. It won't fit through the front door unless I lean way over backwards (think caber toss). The van I used to haul it around in was a full size model and it was just big enough for the tube and base. What do you plan to use to take it from place to place?

I would suggest putting soome sort of reinforcement on the tube where the alt bearings are, then mounting handles of some sort there. Actually, I would first suggest getting a 7 foot dowel and try moving around the house, shed, garage, whatever. 7 feet it bigger than it sounds.

Check out this program as well. It will help you get your figures.

Here is the place I was going to go for my secondary mirror when I was going to rebuild my 16". Protostar

The other places I had linked have moved on. Too bad too. I had a design that would let me fit that 16 in the trunk of a Dodge Neon.

__________________
A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek with think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

I had an 8" f10.5 which was just a dynamite scope. I built that one into a two pole truss so the moving was easy. But it was a bit like tinker toys to put it together.

Balance the OTA and carry it like a suitcase. On a long tube you need a door opener ahead of you.

There are many great web sites now that deal with making a scope. Go to Mel Bartels site at http://www.bbastrodesigns.com for way more links that you would think possible. The ATM list at http://www.atmlist.net is the home page of a good old fashion email list server on telescope making. Least I forget it, the web site for Stellafane http://www.stellafane.com has many good atm links.

I use a coater called alcoat down by San Francisco. I have used others including Clausing back east. But alcoat has always been fast and he did a good job for me.

David Davis
Toledo, OR 97391

I also forgot to mention the ATM web ring at

http://www.crickrock.com/cgi-bin/web...ing;siteid=sl1

So many designs, so little glass.

David Davis
Toledo, OR 97391

There is an excellent telescope making forum at http://www.cloudynights.com/ubbthrea...at/0/Board/atm

There are some excellent mirror makers there that are very helpful.

(I hope posting this link is allowed. If not, I apologize, please remove it!)

Randy D.

Thanks guys! you're awesome. when i get back to school we'll probably reconsider focal length. My brothers are 6'5" and generally have little trouble making it through doorways. though...i'm 5'8" and usually am not trying to manuver them through doorways either so we'll talk about it. We probably won't actually start building for at least another few weeks so if you think of any other helpful hints, they would be greatly appreciated.
i THINK the "How to Build a Telescope" book is the one our library at school has, i'll have to check that out and i'll definitely visit those sites as soon as i get home (yay my internship is almost over!)
Thanks guys! you've been a big help! i appreciate it!

__________________
Cold be hand and heart and bone
Cold be travellers far from home
They do not see what lies ahead
When sun has failed and moon is dead

There is also the three book series "Amateur Telescope Making" edited by Albert Ingals and published by Scientific American from Sky and Telescope articles back in the 1930s. They've been re-edited and reprinted by Whitmann-Bell. Some of the materials used back when the books were first written are, shall we say, somewhat hard to come by these days.

I dunno. I always admired Russel Porter's idea of using an engine block set in concrete for the polar axis.

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The Devil offered me power. I told him I preferred aperture.

How about Porters Folly, a complete equitorial mount made of concrete. ATM1 has it in there. I wonder of anyone responded tot he challenge?

David Davis
Toledo, OR 97391

One year my wife gave me the complete ATM set for a birthday present. Definitely a spouse who cares.

__________________
The Devil offered me power. I told him I preferred aperture.

This is the best thread ever made.

My wife and I are going to get into this. We're probably going to start low, around 4", and work up from there. By the time my daughter is old enough (she's 3), I want to make a huge one with her.

That OTA will need a very substantial mount. I would not think it would be a good choice for a Dobsonian mount, unless you don't mind standing on a ladder to observe. But its GEM needs would be steep.

Utwo, if I were you I'd start with a 6". It's still not much glass to push, and I feel the extra aperture would be worth it. I once made a 4" mirror and actually found it a bit too small in my hands for comfortable work. Just a personal opinion, though.

And like just about everyone else here suggests, find a copy of Texerau's book. I built my first scope using the original (haven't seen later edition) and it tells you just about everything you need to know.

__________________
The Devil offered me power. I told him I preferred aperture.

I built my 4 1/4 and then 8 inch using Thompson's book. I kind of followed Porter's design re a modified fork-mount, but found that having the north opening really weakened the structure. So I wound up with a mount similar to that of the 60 inch at Mt. Wilson.

BTW, having a couple of aluminum handles on the tube really helps re transportation.

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Probably the neatest design I've seen for a Dob was a home made one at a start party. The OTA was sold wood and square. It held a 6 inch mirror. Nothing really special so far. The cool bit was that he had placed counterweights on the top of the tube. 4 of them on long threaded shafts. The weights had a couple of inches of travel and were heavy enough to move the balance point right up to the location of the eye peice. The focuser came out of the side of the altitude bearing so no matter where you looked the ep was alway in the same place. It just happened to be the exact height of the owner while seated in a comfy little chair. On the "driver's" side was an accessory tray that held all the standard goodies. It was made out of stained oak and had a pretty small footprint.

Attached Images

Cool Dob.gif (3.1 KB, 21 views)

__________________
A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek with think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

I agree with Mike, start with a 6" or even an 8". Both are a good beginner size. Also if you make the mirror an f/8 or so, it will be a lot easier to figure than a faster f ratio of lets say a f/4 or f/5. Plus it will have more power for planets. Its when you take on a large mirror that the battle begins. The 20" f/5 I am currently working on is a real undertaking. The weight alone is enough to kill the back.

Take glasspusher's advice, don't go too deep on your first mirror. f/8 is where I started and looking back it was lucky I did.

Just a personal opinion, but figuring an f/4 or f/5 is hard. On the other hand, a decently spherical f/8 at low power will still give pleasing views.

__________________
The Devil offered me power. I told him I preferred aperture.

Thanks for the advice! I think I will start with a 6" or maybe an 8". I don't want the focal length to be too high, though, because I'm terrible with the low FOV's. Is it possible to get an eyepiece that produces a low power despite a high focal length? I heard that if I wanted a spherical mirror for a scope this size, the focal length would be over 2000mm, so I'd need an eyepiece that's 50mm or more. Do these exist?

I also have a couple slightly random questions:

1) Does any magnification happen at all without the eyepiece? What if I just looked directly at the secondary mirror? How does focal length relate to what I'd see in that case?

2) Do you think it'd be possible to increase aperture without increasing magnification? I always wondered what the sky would look like through a pair of 1x50 binoculars. It'd be extra awesome if they were thin enough to wear like glasses, and the resulting image wasn't vignetted. Also, if I could wear them while riding around the skies on my unicorn.

You would need an EP to view the image. 2000mm focal length isn't as much as you might think. My 12.5" f/6 in almost that long and the longest F/L EP I own is 40mm. But there are EPs that I've seen as long as 70mm. I'll have to scach my head for a while over your second question. I'm not sure.

If you were to make an 8" with a 1500mm F/L, it wouldn't take too much to figure the mirror, even for a beginner. You would need a Foucault tester to check the figure. And a Ronchi grating is also a must. I have even made Ronchi gratings using clear plastic, a straight edge and a Sharpi marker. They work better than one would think. Turns out when you draw a line on plastic with a Sharpi, it dosn't make just one line, it makes a bunch of very fine lines.