Amateur telescope making

Adding Autoguiding to a Classic C8

Oriontaage — Sun, 20 Sep 2009 19:52:44 GMT

Hi,

I have had a DSI Pro ccd camera for some time, but haven't had the time to try it out until this weekend. I was taking some unguided images of Jupiter with my C8 and decided to try building a RA axis autoguider for the C8. I had a spare Meade 492 motor and it only took a couple of hours to fabricate a simple system that sits inside the forks and rotates the RA adjustment knob. Below are a couple of photos of the prototype. This sytem seems to work pretty well. The Autostar motor can rotate the RA adjustment knob and move the telescope. There is a fair bit of backlash in this adjustment knob and this system wouldn't work for full goto operation, but for autoguiding it may be OK. A rough test with a guiding program and my webcam shows that the autoguider will drive the Autostar system. I need to adjust the friction wheel that contacts the C8 RA knob and will probably add a small belt or rubber strap for better contact and to reduce torque on the worm wheel axis. Otherwise the prototype works very well for only a 3 hour project, and was a pretty simple and quick way to add autoguiding (RA axis only) to an older SCT.

Bill

Diagonal replacement

inthedark — Wed, 18 Nov 2009 17:56:07 GMT

I am considering getting my diagonal recoated when I do my primary -- however I can't get the mirror out of the holder at all! If I have to, I will buy a new one. I have an extra holder, so my question is: I've seen references to spacers on the bottom. What is to be used for spacers and do instructions exist somewhere for how to do it? I saw one site that showed laying two toothpicks on the bottom of the mirror, then adding the silicone adhesive over that -- the toothpicks acting as spacers. Advice needed!

Making large homemade telescope

Zelliov345 — Sun, 01 Nov 2009 00:51:24 GMT

On this homemade telescope site, http://sites.google.com/site/telescope1999/ I see that the secondary cage for his telescope making project is made from a formica sheet and two wood rings. Has anyone else tried this?

Secondary Spiders?

Squatchmo — Mon, 25 Sep 2006 16:48:21 GMT

First of all, Hi! Nice to finally find a decent ATM Forum is still out there - seems like the web is devoid of any decent information on the subject, at least I'm having a hard time finding it.

I'm working on my first ATM project - incidentally, also my first woodworking project. It's an old 8" Starhopper dob (My first scope) converted into a truss tube configuration. So far it's going pretty well - I have the mirror box and secondary cage done, except for two little things...

1) Back panel cover/fan (Easy)
2) Secondary Spider (Hard, apparently)

Here's a pic.

So the old mid-90's Starfinder has a single-vane secondary. I'm not a fan of it; you can't control the secondary's position over the primary, and I want this thing to be one collimatable beast. So I tried to convert the four-vane mount from my C6-NGT into one wide enough to use; essentially I replaced the 3" vanes on the secondary mount to 5" ones. The metal was way too flimsy though.

So I just wanna see any suggestions on how I can mount up a secondary. I need its position to be adjustable, and preferably pretty strong. I understand many ATMs use pre-made spiders; I'd like to avoid using pre-fab parts as much as I can, otherwise I won't learn anything. Anybody got some innovative DIY Spider designs?

Thanks, and once again, nice to see this forum is out there!!!

Choosing a mirror

vintner — Tue, 18 Aug 2009 16:34:18 GMT

I got hooked on amature astronomy just over 2 years ago when my wife bought me a 4.7" department store newtonian. I made a dobs mount for it using Richard Berry's Build Your Own Telescope. I'm really pleased w/the results, & I'm determined to build a 10" Dobs from scratch next.

I don't understand all the math and science of light and how it's affected by mirrors... I do understand that a better quality mirror is one w/a short wave length, even though I don't understand what that means.

I'd like to get a mirror for general purpose veiwing. At the present time, I don't have the finances or inclination to get into astrophotography. I'm pretty tall, so a longer tube doesn't deter me.

I'm woundering how much difference I'd notice between an f/6, f/7, & f/8 mirror.

Any advice is appreciated.

Tracy

DIY Camera Backstop (Zero-shift focus)

Bloodhound31 — Mon, 10 Aug 2009 10:59:09 GMT

It's been a while since I got industrious and built something out in the shed! Gee I've missed it! I had a problem with my camera losing focus through the night as the weight shifted back on the telescope and camera, so I came up with an innovative way to fix it! Check it out! http://www.asignobservatory.com/index.php?option=com_content&view=article&id=81&Itemid=120 Baz.

secondary size question

sam85 — Tue, 12 May 2009 03:36:49 GMT

hello guys! i have a quick questions. i have a 10 inch (254mm) skywatcher collapsible telescope. the f/ratio is 4.7 (its fast) and the secondary mirror it came with is 58mm(minor axis). focal length is 1200 mm . i put smudges on the secondary with my fingers accidentally and seems like i scratched the mirror when trying to wipe it off, i would like to get a new secondary mirror, what would you guys suggest in size for the best optimal performance with this size of a telescope. what are my minimum to maximum sizes?

p.s. if you think 58mm is best, i cant seem to find that size because it is unusal and this scope is pretty fast i guess . thank you guys

Laser Collimator?

P08C — Mon, 18 May 2009 18:22:44 GMT

Has anyone successfully built their own laser collimator? If so how did you do it? Are there any good instructions for doing this on the net? I'm going to do some googleing but any input you might have is welcome!

Telescope design guide online... Please check my work out.

pete3000 — Thu, 06 Aug 2009 19:03:29 GMT

All, put my massive telescope design guide online and would like for you to look it over to see if I am on the right path. I plan on publishing it in the future but wanted to offer you all the ability to critique it. it has home made designs for a laser collimator, barn door camera mount, a small digital camera adapter etc..

the site is at www.howtelescopeswork.com and its free!!!

thanks!

Pete

Would this work as a primary mirror?

ctallman — Fri, 31 Jul 2009 07:19:27 GMT

Ok, don't laugh too hard. I took an optics class in college, so I don't think I'm way off base in asking this; I'm planning out a newtonian design, and I was thinking about the primary mirror I want to use. I got to thinking about concave mirrors and how they take objects "at infinity" and create a real image at a certain focal distance. I remembered those magnifying cosmetic mirrors and realized they work in a similar fashion. I'm not entirely sure what the curvature profile is on those things, but if they're close to parabolic, I don't see why they couldn't be used as a cheap primary mirror. In case there's any confusion on what I'm talking about, here's a link to an example mirror: http://www.folica.com/ESCA_7_1_2__1X__t3391_1.html

So, in short, does anyone know if these mirrors exhibit parabolic or spherical (or close) shape? The small pricetags for these mirrors make me want to try it (as least I will have something to laugh at). If they can properly focus, I'm sure I can take the necessary measurements and position it and the eyepiece. Any opinions/facts/feedback on this very odd subject would be greatly appreciated.

-Chris

Crayford Focuser Project

hpmachining — Thu, 02 Jul 2009 23:10:11 GMT

Hello. I was given a used Meade 114EQ-DH recently and am interested doing some do-it-yourself improvements. The first project I want to make is a Crayford style focuser. Any links, information or tips will be greatly appreciated.

I am planning on using aluminum for the body and drawtube. Is this a good choice for these items? If not, what would you recommend?

For the focusing shaft I am planning on steel, but I was wondering if it should be something with some sort of softer coating on it. What do you think, will the steel against aluminum be able to be adjusted to give a smooth feel and not wear out the aluminum drawtube? While I am on the subject of the focusing shaft, will .125" diameter be a good size? If my calculations are correct it would give me .393" of travel per revolution of the knob. Does this sound appropriate for the travel per revolution? I am also a little concerned about the strength of the shaft being that small. Any thoughts on this will be appreciated.

Like I said before, any information you can pass along will be appreciated. Any pitfalls I should be aware of, etc. Thank you.

Our forum policies, including no advertising (updated July 8, 2009)

Karri Ferron — Wed, 08 Jul 2009 20:01:34 GMT

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Mirror Replacement Focal Length Question

hpmachining — Mon, 06 Jul 2009 19:23:19 GMT

Hello,

Can you replace mirrors in a 114mm aperature, 910mm focal length reflector telescope with the same size mirrors that are stated to be 900mm focal length? Thanks.

Aperture masks

savyone — Fri, 03 Jul 2009 23:42:57 GMT

Can someone give me a run down on the different types of aperture masks and they're use? I've heard about them being used to focus during astrophotgraphy, but can they be used in splitting double stars? Do they help in planetary observations????

Randy

Bad weather project

zachsdad — Mon, 08 Jun 2009 19:12:17 GMT

In my real life -- the stuff I do to finance my astronomy compulsion -- part of my job is to analize people's work areas and figure out ways to present tools and materials in the most ergonomic and efficeint way possible. This weekend I applied some of those same concepts to observing.

My 10" Orion XT dob has a small eyepiece rack on the side of the rocker box which allows me to have up to 4 eyepieces handy at all times. My Obsession dob, due to its much lower profile rocker box, has no such rack. This means that I need to travel back and forth from my eyepiece case to the scope, or carry extra eyepieces in the pockets of my coat (if I'm wearing a coat). Not an efficient operation. So on Sunday I designed and built a free standing eyepiece rack which I can position close at hand. The rack holds 5 - 2' EPs and has a tray for my filter case and other handy accessories, like my barlow lens. The eyepieces are at a height where they will be easy to grab if I'm standing, or seated, and the base of the rack is weighted with 2 - 5# weight plates to keep the whole thing stable even when I have all of the eyepiece holes filled with large EPs. I plan to add some sort of hinged dew cover above the eyepieces before I finish the whole thing.

The following photos show the stand as it is right now. I still need to do some sanding and filling before I seal and finish the project.

Cassie checking out the loaded rack. The EPs shown are a 26mm Nagler, a 10mm Ethos, 13mm and 5mm Hyperion, and a 17mm Stratus.

This shot shows the carry handle, and the tray for additional accessories.

Tips and questions on scope building.

Angel Star — Wed, 13 May 2009 22:02:16 GMT

Good evening everyone. I know my profile says I've been a member of this website since just recently, but I have been looking up toward the heavens since I was a young-un in the early eighties. In fact, Haley's Comet was what got me hooked when I was eleven.

I have recently purchased a 6" scope with a 1400mm focal length, and I have been highly satisfied with my purchase. It is my first true telescope (meaning non Walmart scope). It came with a relatively cheap mount, but I just laugh that fact up, because I like scanning for what I am looking for anyway, and checking the charts to see what I find if I find something unexpected.

Anyway, my purchase has brought me to a sudden interest that I'd like to pursue, and that is building my own larger telescope. I have a large farm with eight large pastrures for horses at my disposal, so transport is not an issue, and all of my tools are at the barn anyway.

My interest is in building something ginormous (yes, I made up a word); something in the area of a 12". I do understand quite a bit about telescopes, as I researched for a year before I finally made my purchase. I have a contact who can make a mirror for me at any specifications, and will probably get it for me nearly as cheap as I can get it anywhere else.

I guess my question is if it is really as difficult as it might seem. I can't imagine that, if you know what you are doing, building your own large reflector can be all that difficult. Most of the featured astronomers I read about have all built their own scopes. Does anybody have any tips for me as to potential problems that I might run in to, or your experiences on the matter, and so on. Does anybody have any suggestions on a focal length of the scope, since larger will allow me more magnification (beneficial for galaxies and nebulae), or leaving it small to keep some integrity intact with clusters? Are there special insurance issues that I'd need to be made aware of (since I live in NW Ohio, and see quite a bit of strong winds regularly). What is the costs that I might be dealing with?

And, don't worry, I'm not giving up on my 6".

Take care everyone. Here's to clear skies!

Hubble Optics

Dale002 — Thu, 21 May 2009 21:51:38 GMT

What's the scoop on this guys?

I'm thinking on building a 14" Dob and was looking at their 14" mirrors

Modding a 12" Meade Lightbridge deluxe model.

P08C — Thu, 14 May 2009 18:28:54 GMT

I purchased my 12" deluxe Meade Lightbridge right around the time they were released (and was very frustrated to learn they released a 16" model not too long ago). Anyway, the scope keeps me quite happy as I have been able to observe lots of really cool objects (i.e. Andromeda galaxy, Orion Nebula, Ring Nebula, and lots of open and globular clusters).

At the time I bought the scope I wasn't too interested in doing astrophotography but now i've taken an interest and want to see what I can do with it. The problem is that I only have the one scope and it's not suited to astrophotography which means I will either have to save up for a tracking scope or mod my lightbridge to track objects. Does anyone know of any good resources that can point me in the right direction so I can successfully mod my scope without breaking anything? Or is this a lost cause; should I save up for a scope that is better suited to photography? If so what scopes are best for this? I want something the same size or bigger than my current scope. After having the giant scope (after my first 8" orion reflector) I don't think I could stand doing anything smaller...meade has spoiled me.

Mirror Grinding How Big?

Wavelength — Thu, 30 Apr 2009 18:04:28 GMT

Hi People,

I have a quick question to throw out here.

For anyone who has built a telescope, what do you think is the largest size mirror that you would attempt to hand grind ?

I have done both a 8 and 10 inch. Both turned out not too bad. There was a lot of time an labor put into them, but nothing that was not easily handeled.

I have been kicking around the idea of trying something large, But I don't want to 'bit off more than I can chew'.

So, what is the biggest you would attempt or heard of being done by hand?

A $25 Homebuilt GoTo GEM

Oriontaage — Thu, 01 Jan 2009 19:26:36 GMT

Hi,

I've recently completed a new project: building a GoTo German equatorial mount for my C90 (I've included a photo below). The design requirements were for a fully adjustable GEM for any latitude, portability, easy GoTo modification to work with an Autostar, and low cost. I wanted the project to be as inexpensive as possible and the entire construction (excluding Autostar motors) has only cost $25 in parts plus an old aluminum tripod from a cheap 76 mm Newtonian. Most of the homebuilt GEMs I've seen use pipe fittings, so I decided to avoid this and try something new; I fabricated modified Dobsonian bearings for the right ascension and declination axis. I still need to play a bit with the prototype to shorten the right ascension axis a bit (it protrudes a bit too far out of the right ascension bearing but still works fine); I will probably adjust the bracket angle and placement on the tripod to allow shortening of this axis while keeping the center of mass over the tripod top. (edit note Jan 2nd: I decreased the bracket angle to 20 deg., and this allowed the RA axis to just protrude outside the bearing but keep the center of mass over the tripod center) The prototype GEM works very well. Its very sturdy with an easy and smooth movement.

I designed this mount to work with my 497 Autostar. I have two spare Autostar gear sets that will be attached to the GEM axis. The metal axis are already plugged and tapped to fit a threaded rod. All thats left to complete the GoTo modification is to bolt on the Autostar worm wheels and worm mounts, and then order a spare set of 492 Autostar motors.

As with all of my projects, I post lots construction details on my website. I will start working on a web page for this project and update this post when its on line. Below is a photo of the prototype (prior to GoTo modification and final painting). This was a very inexpensive project that was both easy and fun.

Jan. 4 Edit Note: I have a first draft webpage on-line with all GEM construction details at:

http://www.astronomyasylum.com/gem.html

I have also added a webpage about basic celestial motion, field rotation, and equatorial mounts in general to support my GEM construction page. This webpage can be found at the following address:

http://www.astronomyasylum.com/equatorial.html

Bill

Zhumell secondary reassembly order.

G.Lyell — Thu, 09 Apr 2009 16:02:58 GMT

Reinstalling a secondary in a Zhumell 10" DOB. I forgot the order because it was over a month ago when I removed it.

I think I got it right, but if anyone knows please verify me.

Bolt through the center of the spider.

Spring over the bolt

Round metal protection washer on top of spring

Screw secondary holder on bolt

So it would be this.

bolt, spring, washer and secondary holder

Thanks everyone

Is longer better?

jared64 — Thu, 16 Apr 2009 06:56:31 GMT

I was thinking of building a scope and was wondering if longer is better. I know that the focal length depends on the curve of the mirror, but will a 4" mirror with a 450mm focal length provide better images than a 4" mirror with a 350mm focal length? *random numbers*

Also after looking around...is it cheaper to build your own scope or simply self-satisfying?

connecting scopes

jared64 — Thu, 16 Apr 2009 07:06:46 GMT

I was thinking the other day, is it possible to use several small "junk" scopes in an array? Any ideas on how to do so? I'm not talking about making them binoculars but connecting 2 or several together to the same eyepiece. I know they do something similar (though likely vastly more complicated) with the big observatories.

focussing issues 12" f6

meade man — Wed, 01 Apr 2009 12:14:48 GMT

Not sure i should have posted this here, but i guessed its a great place to get info on these kind of problems

As some might be aware I recently had Orion build me a custom SPX 300 F6 Newtonian. This telescope came with a 2" adapter (for 2" eyepieces) and also to allow focusing travel differences for visual or imaging applications. John fron Orion optics told me that I should remove the 2" adapter for imaging applications. However so far I have found this often is not the case.

On my old 10" Europa F6.3 without any adapter I used to be able to use a 5x Antares barlow, I used to have to pull the barlow out of it's housing about 5mm to get focus ( slightly short focusing travel ).

On the SPX 300 without adapter ( as John advised ) I could not reach focus at all by quite a large margin. So I then put the 2" adapter on and still found this barlow would not focus. But by pulling it out from it's housing about 1" focusing was achieved, the only problem is with the extension already mentioned I don't think I was at 5x anymore more like 6 or 7. What could this problem indicate ?

A televue 3x which has a long barrel I could reach focus with. But if I remember correctly I think the draw tube went inside the image, so I then used a small extension and the draw tube was just ouside of it's housing. ( I will need to write these things down as my memory might be wrong on this one ) but I'm sure there was some kind of focusing issue.

A Celestron 2x that I used to use with a 3" tube extender on my old Europa with no problem, also caused problems. Without the 2" adapter ( supplied by Orion ) to reach focus with the 3" tube extender ( for more power ) went right inside the focusing housing and hence the image causing a large bite out of the image. I had none of thse problems with my old Europa 10" F6.3 what could these problems be indcating, any help much appreciated. I do have 2 holes on the primary cell so i could possibly pull the cell back about an inch or slightly less. if this is the reason. But i havent a clue. The exact focal length for a 12 f6 optic measured between primary and flat is what i wonder ? i hated maths if anyone knows the figure no calculations please lol Neil

secondary mirror measurement question

G.Lyell — Tue, 31 Mar 2009 04:05:08 GMT

Hello everyone.

I was wanting to know, how are the secondary mirrors sized and measured? What I mean is, when you see a secondary that says 3.5" that 3 and a half inches.

What I want to know is, the secondary is shaped like an egg. Do they measure left to right, or from top to bottom. left to right would refer to it mounted in the tube and looking down on it from the focuser tube.