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Average cost per inch of Aperture

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#1 JKruger13

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Posted 10 August 2020 - 04:11 PM

I made a graph showing how much money you would spend per inch of Aperture for each size of dob.

https://imgur.com/a/R3V3U4M

 

Details:

I didn't include Go-to telescopes because it's optional, it adds more cost and it introduces another variable.

There isn't much 14" dobs at all so it wasn't included. 18" feels like an odd number too.

I started adding custom made dobs at 18" and above. This is where I had trouble deciding when to include them because I believe while you can buy a custom 10" or 12" dob for 3-4k, most people still buy manufactured telescopes and custom dobs are a lot more expensive 16" and under. At 18/20" this is the largest size you can buy before having to go custom-built and they don't really have that much of a cost advantage anymore. I know people start to buy custom dobs around 12-15" so it's not going to be perfect.

This is the list of telescopes I used to calculate the average cost.

Some custom-built telescopes have two different price options to pick so I picked the lower one (ex. f3.3 or f3.6).

I might not include every single model of dob for each size or every single company you can buy a custom dob from. Only enough to get a ballpark estimate of cost.

 

Tell me what you think.


Edited by JKruger13, 10 August 2020 - 04:11 PM.


#2 Eddgie

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Posted 10 August 2020 - 04:25 PM

I think it must be to hot for you to be doing things outside.  LOL.

 

Actually, it is pretty interesting but only for one reason.  Where you see the big jump in price is right at the borderline where you cross from mass market Dobsonian scopes to cottage industry scopes.  The cottage industry tends to be more high end makers, and these makers are making in enviroments where their costs of doing business are far higher and they lack the volume of business one would need to amortize their fixed costs over a large number of units.

 

I mean if the guy is paying $15000 a year for the healthcare he has to pay for his family and he builds only 10 telescopes a year, $1500 of his gross on every scope goes to paying his health care insurance.  Meanwhile, the mass produced instruments are built by low wage earners in systems with socialized health care, so their costs are much less (and this is not meant to be political, this is simply meant to say that being a small businessperson in the US is very expensive and if you don't sell a lot of something, you have to change a lot for each one). 

 

So, that is what I see. When you get out of the mass market, you are mostly buying domestically produced instruments that are built in economies where costs are high, and volumes are insufficient to amortize that cost.  I mean even if the price were linear, after a certain size, you start to shrink your market potential because not everyone thinks they can manage a very large telescope.


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#3 JKruger13

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Posted 10 August 2020 - 04:50 PM

I got bored today and a lot places are closed because of covid :shrug:



#4 eyeoftexas

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Posted 10 August 2020 - 04:51 PM

I agree with Eddgie's summary of the costs.  There are, however, now mass market products up to 20" or so (e.g., Explore Scientific).  In terms of the specialized market, there are many European products that could be added (Skyvision, Taurus, Reginato, Lukehurst), but as I've found the prices are reasonably comparable to US makers (excluding the cost of shipping).

 

I would say that the costs for the larger sizes is skewed by mixing in products that are geared to being transportable (Hubble, Obsession UC), which are also less expensive than comparable size.  On the other side, you could include Spica Eyes.  I know they are GoTo, but that is the cost of them without that being an option.  I may have missed them on your list, but you could add Waite Research, as those are non GoTo.

 

I also note that you included SDM, and I assume you converted the cost to US dollars.  



#5 Jon Isaacs

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Posted 10 August 2020 - 05:01 PM

Actually, it is pretty interesting but only for one reason.  Where you see the big jump in price is right at the borderline where you cross from mass market Dobsonian scopes to cottage industry scopes.  The cottage industry tends to be more high end makers, and these makers are making in enviroments where their costs of doing business are far higher and they lack the volume of business one would need to amortize their fixed costs over a large number of units.

 

 

There's the cost living but there is also the quality of the scope. A premium scope will come with better components and optics. 

 

I didn't see the Teeter STS series in the list but it would have showed what a top notch 8 inch might cost. With Zambuto optics, the 8 inch is about $3600, the 11 inch about $4600.

 

https://www.teeterstelescopes.com/sts

 

You do get what you pay for.

 

Jon


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#6 JKruger13

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Posted 10 August 2020 - 05:16 PM

I agree with Eddgie's summary of the costs.  There are, however, now mass market products up to 20" or so (e.g., Explore Scientific).  In terms of the specialized market, there are many European products that could be added (Skyvision, Taurus, Reginato, Lukehurst), but as I've found the prices are reasonably comparable to US makers (excluding the cost of shipping).

 

I would say that the costs for the larger sizes is skewed by mixing in products that are geared to being transportable (Hubble, Obsession UC), which are also less expensive than comparable size.  On the other side, you could include Spica Eyes.  I know they are GoTo, but that is the cost of them without that being an option.  I may have missed them on your list, but you could add Waite Research, as those are non GoTo.

 

I also note that you included SDM, and I assume you converted the cost to US dollars.  

I was going to say something about ES but I didn't. It's dob price still jumped considerably from 16" to 20"

 

I didn't include every single dob that is out there. I aimed for the average price for each size so yes you can spend less on a transportable or more on something else. Again, not perfect. Go-to is another variable I didn't wanted to deal with.



#7 Allan Wade

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Posted 10 August 2020 - 05:26 PM

Interesting idea. The problem with comparing commercial dobs to premium and custom made ones is it so far beyond comparing apples with oranges. They need splitting into different graphs.

 

I paid over 1000% more for my 16”, and your cost at 32” will get you a decent set of optics, but nothing left over to put them in.


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#8 havasman

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Posted 10 August 2020 - 05:57 PM

While it was surely a good exercise for filling some down time I hope it does not mislead an inexperienced buyer to have false expectations. Omission of premium smaller aperture Dobs is a valid choice if that's what you want to graph but the top value on your graph does not cover the cost per aperture-inch of even a small loaded premium Dob. Omitting tracking is, IMO, an invalid choice in a premium instrument > 12 or 14" aperture. And since Zambuto makes a 14.5" mirror then custom makers WILL offer that structure so it might merit inclusion.

 

Perhaps the graph would be more useful with more than one set of presumptions graphed by more than one set of lines. When you include premium Dobs with a full set of premium options you're going to need a much taller set of cost per inch values. After all, there WILL be more unfilled time in our futures...


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#9 JoshUrban

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Posted 10 August 2020 - 06:03 PM

Hey, this graph looks like a good paper to have around when people ask "why did you buy a 22"?!"  "it's a good VALUE, man!"  (I always like to have justification for my quirks, don't you?)



#10 stargazer193857

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Posted 10 August 2020 - 06:17 PM

When I looked at premium mirrors, I saw the price goes up a bit lower than the square of aperture, until 20" is the turning point.

That is, an 8" costs a bit more than 1/4 as much as a 16" mirror. That is for the full optical set including secondary.

Structures climb slower than linearly, since all have focusers and cables and such.

Starting with 22", the price no longer climbs much. I think that is where many mirror makes can no longer make them diffraction limited and so don't charge proportionally as much.

Mass market mirrors cost less, so should be on a different graph.



So even with all the obsessions and NMT out there, 18" is still rate? Probably because there are no mass produced versions.

#11 JKruger13

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Posted 10 August 2020 - 06:51 PM

While it was surely a good exercise for filling some down time I hope it does not mislead an inexperienced buyer to have false expectations. Omission of premium smaller aperture Dobs is a valid choice if that's what you want to graph but the top value on your graph does not cover the cost per aperture-inch of even a small loaded premium Dob. Omitting tracking is, IMO, an invalid choice in a premium instrument > 12 or 14" aperture. And since Zambuto makes a 14.5" mirror then custom makers WILL offer that structure so it might merit inclusion.

 

Perhaps the graph would be more useful with more than one set of presumptions graphed by more than one set of lines. When you include premium Dobs with a full set of premium options you're going to need a much taller set of cost per inch values. After all, there WILL be more unfilled time in our futures...

It probably would be better if premium and mass marketed dobs were their own separate lines. My aim was based on general price people typically pay for just for the telescope with the average features. Might mean it includes tracking or not. I know it's not needed for smaller dobs but I never tried to omit it above 14". I chose as much as I could find and I tried to fill each size with the average popular dobs so I admit that I don't know much about bigger dobs. I really tried to find as many choices as I could for 18" and up. I based it more on good value than quality so I never meant that 16"+ is overpriced and below that is good so that's the biggest flaw with the graph right now.



#12 JKruger13

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Posted 10 August 2020 - 07:04 PM

I would do an update version but I don't feel like putting in the time nor do I know much about big dobs anyway.

 

So even with all the obsessions and NMT out there, 18" is still rate? Probably because there are no mass produced versions.

I only found the SkyWatcher Stargate and that's it for 18". The rest are premium dobs on the list.



#13 Allan Wade

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Posted 10 August 2020 - 10:39 PM

Starting with 22", the price no longer climbs much. I think that is where many mirror makes can no longer make them diffraction limited and so don't charge proportionally as much.

You’ve got to be joking. lol.gif

 

At 22”, mirror prices are just starting to get warmed up. Things start trending up real fast through the 30” class, and are going vertical on the exponential price curve beyond 40”.

 

No one is spending $30000 or $40000 for a barely diffraction limited primary mirror. Opticians in this category know what they are doing and produce world class optics. 


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#14 m11

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Posted 11 August 2020 - 02:52 AM

You’ve got to be joking. lol.gif

 

At 22”, mirror prices are just starting to get warmed up. Things start trending up real fast through the 30” class, and are going vertical on the exponential price curve beyond 40”.

 

No one is spending $30000 or $40000 for a barely diffraction limited primary mirror. Opticians in this category know what they are doing and produce world class optics. 

I agree with Allan, you can see the mirror prices got up exponentially where at 32inches and above it nearly even doubles in price, especially US dollars conversion hurts.  I understand when mirror are getting to that size and there is more work involved to get to their specifications with the size of the glass with the faster optics.

 

At those prices you want to know you are getting a premium mirror in all respects for that sum of money. Everyone will have different values in terms of what they want to spend or invest in their hobby. smile.gif

 

I would love to get a 40inch mirror in a SDM scope but that ain't happening anytime soon - chief financial officer said no! laugh.gif


Edited by m11, 11 August 2020 - 02:53 AM.


#15 tommm

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Posted 11 August 2020 - 10:56 AM

Seems it needs to be a family of curves with parameters such as f number of the primary, quality of optics, and quality of craftsmanship.


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#16 Voyager 3

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Posted 12 August 2020 - 07:59 AM

K now I can't resist this question grin.gif . How does a premium 12.5" compares to a mass produced 16" .The price seems to be comparable so will the optics and views be comparable? Sry for this dumb qn blush.gif



#17 Bill Weir

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Posted 12 August 2020 - 03:03 PM

Shouldn’t this comparison be about $ per sq inch and not by linear diameter? It’s like trying to decide the best value in pizza size.

 

Bill


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#18 Chesterguy1

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Posted 14 August 2020 - 08:42 PM

There's the cost living but there is also the quality of the scope. A premium scope will come with better components and optics. 

 

I didn't see the Teeter STS series in the list but it would have showed what a top notch 8 inch might cost. With Zambuto optics, the 8 inch is about $3600, the 11 inch about $4600.

 

https://www.teeterstelescopes.com/sts

 

You do get what you pay for.

 

Jon

Unless one is lucky enough to stumble upon a barely used consignment one that Rob had advertised on his website for a 2/3 of the cost of a new one and shipped using his incredible crates. Best telescope money I ever spent.

 

Chesterguy


Edited by Chesterguy1, 14 August 2020 - 08:44 PM.


#19 rexowner

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Posted 15 August 2020 - 12:29 AM

Agree with the comments.  I was looking at a 12" Dob today, and the price falls right in line with 

$500/inch.  I am OK with this because I have had bad experiences with mass-produced mechanics

and optics being sub-par and I am more than happy to pay a craftsperson for their work.


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#20 John SC

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Posted 18 August 2020 - 11:51 PM

I just picked up my 12.5" Dob today. Just about $430 per inch, has Ostahowski Optics mirror that tested out as the best I have ever heard of (1/53 wave RMS...)  Very happy to pay that for this scope.  But it does not fit the chart.


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#21 stubeeef

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Posted 19 August 2020 - 09:54 AM

Agree to separate premium and mass marketed. 

Thing is most mass marketed include optics and most premium don't.

I'd probably remove Webster and add Star Structure to your list.

Bill is spot on with square inches vs diameter IMHO.

 

Nice info though-thanks for sharing.


Edited by stubeeef, 19 August 2020 - 09:56 AM.


#22 mwedel

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Posted 20 August 2020 - 10:10 PM

Interesting. I did a similar analysis a few years ago, strictly for Dobs 16" and under, and based on cost per square inch. Results here:

https://10minuteastr...aperture-costs/

 

At that time, and probably still, the 8" and 10" Dobs offered the most light grasp per dollar, with prices rising slightly on either side. 

 

I think this discussion is very similar to the one going on in Refractors about why there isn't an 80mm triplet for $200, with good glass and bargain-basement everything else (that thread is here). The answer in both cases seems to be that really good glass (either exotic stuff for refractors, or Zambuto-level figuring for reflectors) ain't cheap, and having paid for the good glass, it's silly to skimp on everything else.

 

It would be interesting to do a similar analysis for refractors, and see where the breaks in the line fall. I'm guessing past 130mm is where the prices really start to climb for both achros and apos.



#23 Sky_LO

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Posted 22 August 2020 - 08:48 PM

I agree with John SC - custom doesn't fit the chart.  

 

What would you pay for.......

A scope that has: 

 

A 13 inch mirror that weighs only 8 pounds ?

Folds up into a 20 x 20 cube.

Total Weight of 31 pounds

Where the optics are F3 and finished to near zero error tolerance? 

Provides  wide FOV - with Zenith accessible while seated.  

 

The custom work can be well well worth the premium price.     

I love my custom Zip Dob.

It is totally apples and oranges to try to compare. 

 

-Lauren  

 

.    


Edited by Sky_LO, 22 August 2020 - 08:49 PM.

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#24 Peter Natscher

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Posted 01 September 2020 - 01:22 PM

Paying average cost for a mirror gets you average mirror specs.  You can get professional observatory mirror quality if you pay 10X more. From the well-known opticians we all know, smaller mirrors get better RMS and wave-front compared to larger ones.  For this price, that's what you get for the optician's time and substrate quality.  It's a business.  Getting better than average mirror smoothness producing better contrast is another quality that varies with optician.  I'd say most mid-sized Dob mirrors with 'premium' optics are produced with a 1/6 wave surface, which is good enough for amateurs. Opticians know this. This will perform to 50X per inch aperture.  In using the usual 100X-450X magnifications on Dobs, 1/6 wave with good figure and surface smoothness, most Dob owners are well satisfied.

 

I made a graph showing how much money you would spend per inch of Aperture for each size of dob.

https://imgur.com/a/R3V3U4M

 

Details:

I didn't include Go-to telescopes because it's optional, it adds more cost and it introduces another variable.

There isn't much 14" dobs at all so it wasn't included. 18" feels like an odd number too.

I started adding custom made dobs at 18" and above. This is where I had trouble deciding when to include them because I believe while you can buy a custom 10" or 12" dob for 3-4k, most people still buy manufactured telescopes and custom dobs are a lot more expensive 16" and under. At 18/20" this is the largest size you can buy before having to go custom-built and they don't really have that much of a cost advantage anymore. I know people start to buy custom dobs around 12-15" so it's not going to be perfect.

This is the list of telescopes I used to calculate the average cost.

Some custom-built telescopes have two different price options to pick so I picked the lower one (ex. f3.3 or f3.6).

I might not include every single model of dob for each size or every single company you can buy a custom dob from. Only enough to get a ballpark estimate of cost.

 

Tell me what you think.

 


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