In and out of love with a Dob?

[PeterStudz]

15 hours ago, Whistlin Bob said:

Welcome to the world of playing with dobs!

While playing with kit & DIY isn’t for everyone it’s one thing about DOBs that I like. When I first got into this I had assumed that like most stuff these days a telescope would be largely stuck, glued and welded shut. It’s refreshing that these things can be completely taken to bits and put back together with simple tools. Plus the amount that you can DIY. It’s great 😊 

[cajen2]

2 hours ago, PeterStudz said:

But for me it’s not average - it’s perfect, that’s what I want! I also think that there’s some confusion or misunderstanding of “stiction”. 

No confusion from me: "Stiction (noun) - the friction which tends to prevent stationary surfaces from being set in motion".

[PeterStudz]

1 minute ago, cajen2 said:

No confusion from me: "Stiction (noun) - the friction which tends to prevent stationary surfaces from being set in motion".

Yep, that’s it. And it’s possible to get ideal stiction without a break/knob. 

[PeterStudz]

Just now, PeterStudz said:

Yep, that’s it. And it’s possible to get ideal stiction on a Dob without a break/knob. 

 

[cajen2]

Sigh. There are times when I want stiction weak: when slewing through a large number of degrees, for example, and there are times when I want it strong, while keeping the scope on target while changing EPs, for example. One setting doesn't do both. But if you're happy with yours, fine.

[PeterStudz]

What I’m trying to point out is get the right bearing material and you do/can have both.

When I’m slewing through a large number of degrees moving friction becomes less. Then when I stop it stays where it is. When at rest there’s enough friction to keep it there in order to do things like change eyepiece or attach a camera. When I start to move it moves smoothly without jerking and without overshoot. 

I might be mistaken but my understanding is that stiction is the holding force that must be overcome before the bearing can begin to move.

Edited May 26, 2023 by PeterStudz

[PeterStudz]

38 minutes ago, PeterStudz said:

 

 

Edited May 26, 2023 by PeterStudz

[Guest]

3 hours ago, bosun21 said:

It’s the go to motors that account for a good bit of the weight of the base. The boards are thicker to accommodate them. I used to own the 12” go to and the base was a pain to move manually so I sold it.

I actually prefer a heavier scope.  I have to say that using this one manually is as easy as using my 10 inch maybe even easier. 

[bosun21]

12 minutes ago, Mike Q said:

I actually prefer a heavier scope.  I have to say that using this one manually is as easy as using my 10 inch maybe even easier. 

I meant lifting it and moving it.

[Guest]

2 hours ago, bosun21 said:

I meant lifting it and moving it.

Its on a cart.  I hook it to my mower and move it anywhere i want lol.... piece of cake actually.   Yes i know..... thats cheating 

Edited May 26, 2023 by Mike Q

[Louis D]

Why are commercial truss goto scopes so heavy?  Starmaster's old Sky Tracker system only added 11 pounds to the rocker box (including gel cell).

[Guest]

16 minutes ago, Louis D said:

Why are commercial truss goto scopes so heavy?  Starmaster's old Sky Tracker system only added 11 pounds to the rocker box (including gel cell).

I can only speak for my XX16G, but it has quite a bit of steel in it.  The mirror is house in a fairly deep steel housing.  The mirror holder is metal.  The base is inch thick boards.  It is built like a tank. I will attach the vital stats about the weights. 

Edited May 26, 2023 by Mike Q

[Louis D]

That's wild that it needs 20 pounds of counterweights, especially when the lower tube assembly already weighs 50 pounds.  And what's up with the weight of the groundplate assembly?  That's crazy heavy.  And here I thought using oak instead of aluminum was a heavy material choice.  Why use steel?  Because it's cheap and strong?

[bosun21]

If I were to get a larger dobsonian than my 12” I think I would save for an Obsession. Expensive yes but the quality and ease of use is something else altogether.

[John]

My 12 inch F/5.3 dob weighed 26kg / 57 lbs in total. About the same as a chinese 10 inch. My base was 18mm ply rather than MDF and the tube was aluminium. I didn't have GOTO fitted though. 

I had a Meade Lightbridge 12 inch a few years before and that weighed over 80 lbs in total. Again, no GOTO.

 

Edited May 26, 2023 by John

[niallk]

1 hour ago, bosun21 said:

If I were to get a larger dobsonian than my 12” I think I would save for an Obsession. Expensive yes but the quality and ease of use is something else altogether.

No more 12.5" being made, unfortunately!

[bosun21]

3 minutes ago, niallk said:

No more 12.5" being made, unfortunately!

I wouldn’t go from my 12” to a 12.5” anyway. I would probably be looking at a 16-18” maximum.

[Guest]

1 hour ago, Louis D said:

That's wild that it needs 20 pounds of counterweights, especially when the lower tube assembly already weighs 50 pounds.  And what's up with the weight of the groundplate assembly?  That's crazy heavy.  And here I thought using oak instead of aluminum was a heavy material choice.  Why use steel?  Because it's cheap and strong?

Strong and cheap is fine with me lol.  FYI twenty pounds isnt enough either, at least not for my scope.  I added another 15 or so which made it much better. 

[Guest]

1 hour ago, bosun21 said:

If I were to get a larger dobsonian than my 12” I think I would save for an Obsession. Expensive yes but the quality and ease of use is something else altogether.

I have used two different Obsession telescopes now.  There is no doubt that they are a fine piece of artwork and i came within a hairs breath of buying a 20 inch F5.  With that said, while the images are better they are certainly not 2x better.  I could have cut a check for a new Obsession but decided that another 6 grand or more on top of what i paid for my 16 just wasnt worth it.  

[bosun21]

2 minutes ago, Mike Q said:

I have used two different Obsession telescopes now.  There is no doubt that they are a fine piece of artwork and i came within a hairs breath of buying a 20 inch F5.  With that said, while the images are better they are certainly not 2x better.  I could have cut a check for a new Obsession but decided that another 6 grand or more on top of what i paid for my 16 just wasnt worth it.  

Well there is that point 😂.

[Guest]

Just now, bosun21 said:

Well there is that point 😂.

My buddy Jason has a XX16G.  He had his set up next to a 18 inch Obsession.  We went back and forth between the two scopes using the same eyepieces and i really couldnt see a significant difference. That is something i have noticed about Orion scopes.  The trend i am seeing is they tend to be a bit brighter then other GSO and Synta scopes.  There is a rumor floating around that Orion specs a slightly better mirror.  I can say based on taking my 10 inch out on outlook programs that it is brighter then other 10 inch scopes with different namws on them. 

[bosun21]

8 hours ago, Mike Q said:

My buddy Jason has a XX16G.  He had his set up next to a 18 inch Obsession.  We went back and forth between the two scopes using the same eyepieces and i really couldnt see a significant difference. That is something i have noticed about Orion scopes.  The trend i am seeing is they tend to be a bit brighter then other GSO and Synta scopes.  There is a rumor floating around that Orion specs a slightly better mirror.  I can say based on taking my 10 inch out on outlook programs that it is brighter then other 10 inch scopes with different namws on them. 

They are the exact same scopes with a different paint job. Rumors tend to be just that. An Obsession with a quality mirror set would beat any production model easily.

[Guest]

4 hours ago, bosun21 said:

They are the exact same scopes with a different paint job. Rumors tend to be just that. An Obsession with a quality mirror set would beat any production model easily.

I will say this again.  I really couldnt see a significant difference.  Certainly not multiple thousands of dollars worth.  

[bosun21]

Just now, Mike Q said:

I will say this again.  I really couldnt see a significant difference.  Certainly not multiple thousands of dollars worth.  

Possibly the case, however the sky conditions play a significant role in this. On very good seeing and transparency the Obsession would pull ahead easily with its quality mirror kit not to mention the additional 2” of aperture.

[Jim L]

The soap trick worked beautifully, Monica is once again in love with Dobs, and I can see a new 10” Dob in our future.

I never did get to star test collimate the primary mirror, but the Barlowed-laser collimation I did on my work bench was good enough that the moon showed astounding detail, and M13 took on a decidedly 3D appearance with dozens of resolved stars in the foreground surrounding and framing the luminescent core.

There were a couple of other large reflectors at the party, including a 14” Meade Schmidt-Cassegrain, but the big Orion out performed them handily, being brighter, having more contrast, and being sharper both on and off center. Honestly, I was surprised by how much better it performed than it’s far more expensive peers, but perhaps their mirrors were dimmed by age, and their collimation wasn’t optimal. I don’t know, but I was very impressed with the Orion 12” Dob.