I'm currently building a dobsonian, following Kriege's book, in which he states to use laminate and teflon pads and kydex. How important are these, and what purpose do they serve?

Previous post: https://www.reddit.com/r/atming/s/ybyPHk9w4Z

After thinking about it a lot, I decided to grind the chip off to avoid its possible expansion from heat when it gets aluminized.

This is how it came out: https://imgur.com/a/zjDlYbY (The blank was wet when the pictures were taken. Also, the mirror is UPSIDE DOWN, the chip was on the back)

I'd really like to hear your thoughts, this is honestly the best I could do; as it's my first mirror, I don't know if it's good or if I've done something incredibly wrong. If so, I'll just get a new blank =\

Thanks to anyone who replies

I'm beginning a project to build a 6" f15 refractor and I'm having a problem deciding on a material for the tube. I initially thought about aluminum but the size I need 6 5/8 inner diameter by 96" would be slightly out of the price range I'm wanting to spend on the tube. I'm a carpenter by trade so I have the tools and skills to make a wooden octagonal tube. However, I wonder about longevity and potential warping problems. I would assume that a baffled octagonal plywood structure would be fairly warp resistance but I've never built one. Is PVC tubing something that would be suitable for the task?

I'm trying to make a good telescope that can look at galaxies clearly. I found a parabolic mirror online that is only D114 but has a focal length of F450. Would this be good for viewing galaxies and what not?

I have a parabolic mirror with a 8" diameter and a focal point of 2.563", how do I determine the size of the secondary mirror that I need?

First time making a parabolic mirror, and I found a cheap mirror blank on eBay. But, it says it has a “vintage coring”. Does that affect anything?

So recentley i made a small 20ish mm refractor for the moon and it worked fine, so today i picked up some 75mm magnifying glasses with a 131mm focal length.. And i cant for the life of me figure out how to make a functioning telescope

materials

2.3"ish diameter 12 inch long tube
cups that fit the magnifying glasses
2 75mm Convex lenses
Multitude of small + and - diopter lenses (from salvaged glasses)
a will to live
i can custom make a bigger tube

h e l p

im also trying to figure out wether to use one magnifying glass as the objective lens and a smaller - diopter lens as the eyepiece while using the cup as an adapter to the tube or 2 magnifying glasses in one big tube.. i cant for the life of me figure it out

I’m working on a 6” dob right now, and I’m reusing a mirror that is probably around 40 years old. It’s in pretty good shape, but it could use a re-coating. Do you guys have any recommendations for places I could get this done in the US?

I have been polishing this mirror for quite a while and spent the last 12 or so hours trying to fix the tde. Only problem is that about 6 hours of polishing ago the edge stopped changing and looked the same as it does now. Is this still TDE or just a diffraction ring because visually there was a faint ring on the left, but it is not as bright as the one on the right. Image is outside of ROC, knife is on the left and dont mind the hill in the center.

I just picked up a secondhand Orion SkyQuest 12" Dob, that was in rougher condition than I initially thought, with the base missing various components like a peg, the encoders, and the Intelliscope hand controller, and all but falling apart. Since I bought a truss tube specifically for portability, I'm starting to think I'd like to salvage the mirrors and focuser and build a more portable version of the scope instead.

Specifically, I'd like to build something like this: https://youtu.be/ZcqlvLu_6yo?si=MT_irh5bNtB2o9HW

The biggest problem is I work a lot better with plans, but I can't seem to find any plans for this specific type of design, minus some blogs covering the process but with no specs.

I've got a shop full of tools and can build things effectively, I just need some guidance here. How are these mirror cells put together, how are the radii for the altitude bearings found, how is the distance to the secondary calculated, and later achieved, what materials are used for the trusses? The list is not exhaustive, I'd like to learn all that I need to know about building scopes, but specifically for application to this type of design.

Thanks!

I spent months with my dad perfecting the mirror but the Dobsonion telescope (from that famous Berry book) we built around it didn't work. Weights were wrong, balance off, etc. I have a mirror mount for it. I'm looking for someone who could build a nice scope out of it. It's been 25 years and I've never really been able to use it.

Basically the title. I’ve seen estimates anywhere from $100-$150, and given the rollercoaster of material costs over the last few years, what was true this time last year almost certainly isn’t true now. Does anyone have a decent estimate of what one costs to build today? I’d also assume most cost estimates I’ve seen don’t include eyepieces that are needed to actually make the scope functional.

EDIT: I guess I should mention that I’m in the US.

My current setup is Arduino mega 250 with ramps 1.5 and I want to use 2 ST820 stepper drivers for x and y axis.

1. Can someone tell me whats the stepper driver adjustment formula for the ST820?

2. What changes do i need to make on the config.h on the onstep firmware given im using ST820?

I'm using the mirror cell program Plop and am getting error vlaues of:

P-V Error = 1.28592e-5 RMS Error = 2.25998e-6

What are the units of these errors? My input units are in mm.

I've heard a lot of people talking about how you shouldn't use sandpaper because of how fast it gets rid of material. I was wondering if you could use sandpaper for something like the rough grinding of an f3 or f4 12-16" mirror.

Hi, I'm new to this, and I was wondering if I could 3D print a telescope.

Looking for lens mirrors, I found some relatively cheap lens mirrors*. A D203F1600 is considerable cheaper than a F1000/1200.

Why is that?

Won't the F1600 provide more zoom? Is this a bad thing?

Or is it because the telescope will also grow?

Hi all,

I am trying to make a dob. I think im going to use a 8" f/6 Primary, and either a 46.5 or 50 mm minor axis secondary. My question is about how to select the correct eyepiece for this. I have calculated that I need an eyepiece focal length of 24 mm to create an exit pupil of 4 mm. Does this mean that I can buy any eyepiece height (1.25",2",3") and as long as it is a 24 mm focal length that it will work with my build? How should I go about making a selection for this.

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I am reading the Dobsonian telescope by Kriege and Berry and their material has been very clear until this point, but they kind of lost me in the section explaining how to pick an eyepiece.

Thanks!

I decided to read about figuring from jeff baldwin's website because i didnt understand mel bartels, but i keep getting thrown off because of the numbers, since they look wrong. take his tornado graph of the 12", f8 mirror which says that if r=6, R=2.54×12×8=243.48 then the reading should be r²/R×2=0.0738 but his graph shows it at around 0.09. also at the last graph where he gets the adjusted readings, he is supposed to be subtracting 0.508 from every "actual reading" but he's subtracting 0.516. this and many other mistakes have me in a daze asking if im wrong or is he wrong?

Looking to find homes for some more optics/parts, prices do not include shipping. Selling more or less for what I paid. Have some secondary mirrors too.

* 6" f/5 Vixen primary mirror, plate glass - excellent figure, few spots in coating. $50 SOLD

* 6" f/8 Edmund primary mirror - 1" thick Pyrex. Excellent figure, few spots in coating. $40 SOLD

* 6" f/8 Celestron Starhopper conical primary with cell - Excellent condition, good figure, coating looks great. Cell will not fit tubes smaller than 7.25" ID and cannot be removed from mirror. $90 SOLD

* 10" f/2.8 full thickness spherical Pyrex primary, could be parabolized for a fast Newtonian. $150 SOLD

• 12" x 1" plate glass former tool/blank - $65

• 16.5" x 1" plate glass mirror blank/porthole - $200

• 2.6" Galaxy Optics secondary mirror with enhanced coating - $65

DM or send a chat if interested. I'm happy to ship all internationally (I'm in the US - Arizona specifically), though it may not be cost-effective to do so for many countriesI take PayPal, cashapp, venmo, checks, bitcoin, or potentially other telescope/optical stuff if you wanna trade

These were actually "off-loaded" on me by a world-class optician. He said his basement is full of this 'trash' 🤣

He said he was going to give me a blank for a Newt (super overjoyed by that alone!) but accidentally grabbed one for a Cass instead so Imma make a Gregorian instead AND a Newt! It's going to be a dual system and the optician thinks this is fabulous idea!

He gave me a bunch of literature, told me to grind this to f/5 and call him if I have any questions, we plan on grinding the Gregorian secondary to f/20! He makes f/30 Hydrogen-Alpha solar refractors in his kitchen though so I think I'm with the right teacher 😉

I'll try to update soon but this is one on MANY projects and my day job is just as insane if not even more cool!

I'd like to grind a 6" f/8 mirror and I was wondering if the kit from Firsthand Discovery was worth it. I'm not concerned about the cost, but if the kit overall is high quality. Thanks!

[Link to the kit in question(https://firsthanddiscovery.com/telescope-mirror-kits.html)

I've found plans for building a reflector with the printed parts but have no way of knowing how good a job they do. Please can you recomend known good plans?

None of the printing seemed especially difficult I can manage that well enough but a mirror is very costly.

Years ago I considered hand grinding my own mirror but life moved on and I missed the chance.

So far I've found 3 diy grinding machines none look as if they would be a worthwhile build to make 1 mirror.

Do you know of a mainly 3d printed grinding machine? I would expect to add bearings, linear rods and so on.

Thanks..

I'm building a 114/900mm telescope as a first build, I've got the 2 mirrors (primary and secondary) and 2 eyepieces (20mm and 10mm) and I just want to know, what other parts do I need? And how far apart do the 2 mirrors have to be? 114?

I see complex cells with 3/6/9/18 or more contacts points. but we could imagine a simple flat surface with some hard foam.

Are the mirror cells done this ways only so that the mirror gets air to cool/heat ? Or are there other reasons ?

Prepare yourselves for a series of potentially stupid questions, and thank you all in advance for those indulging me...

To start, I purchased THIS pair of mirrors _ going the Newtonian approach _ as well as THESE lenses (correction, eyepieces*?).

From the (sometimes contradictory) information I've gathered online, I'm still left a bit confused as to the measurements that need to be made and construction of_

I know that the focal point needs to be determined, of course.

The Amazon page does say that it is supposed to be 900mm, though I did the 'light bulb' trick to more accurately measure 885.83mm as the closest point of clarity.

1.) I assume that the 885mm needs to be the total distance added between the 'x' and 'z', correct? HERE

_

2.) First dumb question being _ is this meant to measure up to the inner-most/bottom part of the lens (Blue), or the top (Red)? REFERENCE

_

3.) How do you determine where to measure first, with regard to the positioning of the secondary mirror and the height of the lens?

note: there weren't any local cardboard, cement tubes smaller than 8" in my area, so I have a narrower 4" PVC tube to work with (eliminating some of the light capture aside~)

_

4.) Would it behoove me to put all components on an adjustable mount - primary mirror, secondary, lens, etc.?

If there's anything else I'm missing, not mentioning, or not considering - please let me know.

Again, I appreciate any input!

You may have seen in my previous post (https://www.reddit.com/r/atming/s/7Z1c5wSZUx) that I got a 300mm f/5 badly scratched mirror. I want to regrind this mirror. Not sure if I do the telescope before or after regrind as the mirror is not so bad.

I suppose I must still start with K80. If it's not for the mirror it's to match the tile tool. But because the mirror is already spherical, must each tile be spherical or is it acceptable if only 30% 50% 80% of tiles match the mirror ?

Also, should I keep f/5 (1500mm) or should I aim for 1200mm focal ?

And should I do a full carbon tube like my 155mm or a smaller rocker box and small tubing to hold a secondary ?