Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

13-15mm jump in aperture doubles or triples scope prices?

  • Please log in to reply
12 replies to this topic

#1 RichA

RichA

    Soyuz

  • *****
  • topic starter
  • Posts: 3,596
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 07 May 2021 - 05:13 PM

It's a modest aperture increase, but going from a 102mm ED refractor which can be had from $600 and up increases the prices dramatically, in most cases double.  Obviously, a tripling of the price usually goes along with going from an ED doublet to a triplet lens, but not always.  Even apart from premium brands there seems to be a disproportionate increase in pricing even among doublets going from 100mm to 115mm.  I figure since the hardware can't cost much more, it has to be in the lens.  Some manufacturing rule that sees a huge cost increase between  the two lens sizes.  In my opinion, it's an incentive to go instead to 120-130mm.  The optical "gain" over a 102mm of a 115mm just isn't there. 

 

 



#2 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 24,542
  • Joined: 27 Oct 2014

Posted 07 May 2021 - 05:22 PM

Note that your measure is wrong.  It should be aperture squared.  102 to 115 is really 102 squared to 115 squared, a 28% increase.

 

The hardware does need to improved for the larger size and longer focal length.  Stronger, more precise.

 

One can choose what you want to spend for what.  But the increased price is neither incompetence, a conspiracy, nor disporoprtionate.


  • bobhen, John Huntley, rerun and 1 other like this

#3 GSwaim

GSwaim

    Explorer 1

  • *****
  • Posts: 65
  • Joined: 04 May 2021
  • Loc: Jefferson, Texas

Posted 07 May 2021 - 05:31 PM

Well corrected optics make a huge difference, there's also a huge price increase with those optics.

 

All things being equal regarding optics of a refractor, going from 3" to 4" or 5" to 6" offers marginal improvements visually on planets for example.

 

Those who see improvements in resolution either have exceptional eyesight or the optics differ in their design and are therefore not equal.

Perhaps using a CCD camera might show improvements in resolution visual also.

Still yet one might try averted vision to notice slight improvements too.

 

Noticeable improves can certainly be seen going from 4" to 6/7" or 5" to 7/8" for example with all things being somewhat equal regarding refractors.

 

Contrast and details will be better in a well corrected 4" APO vs 6" Achro. 

 

Just my experience and opinions over the years with a

variety of different refractors with different apertures and lens cells.

 

-G


Edited by GSwaim, 07 May 2021 - 05:32 PM.


#4 photoracer18

photoracer18

    Skylab

  • *****
  • Posts: 4,177
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 07 May 2021 - 05:33 PM

Its the light gathering power of a given scope size. If the scope sizes are close together as in the next step up you won't "see" that much difference. Also larger optics take proportionally more time to perfect than smaller ones. Its a rule in almost everything there is that a 10% increase in performance costs 10x as much money to reach. So if a cheap scope costs $600 then a 10% better one will cost closer to $6000, and so on. But the difference between a good APO and a great one may only be 2x. You can see the difference side by side but maybe not if you see them at a different time and place. So compared to an 80mm scope a 125mm scope will be obvious while comparing an 80 to a 100 will be more  subtle.



#5 junomike

junomike

    ISS

  • *****
  • Moderators
  • Posts: 21,566
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 07 May 2021 - 05:57 PM

The cost of blacks goes up exponentially.  Much like Diamonds.   The cost a a 2 carat rock is far greater than the cost of two 1 carat rocks.



#6 SandyHouTex

SandyHouTex

    Fly Me to the Moon

  • *****
  • Posts: 5,809
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 07 May 2021 - 06:12 PM

The cost of blacks goes up exponentially.  Much like Diamonds.   The cost a a 2 carat rock is far greater than the cost of two 1 carat rocks.

Glass isn’t diamonds.



#7 junomike

junomike

    ISS

  • *****
  • Moderators
  • Posts: 21,566
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 07 May 2021 - 06:18 PM

Glass isn’t diamonds.

No, but a similar principle appliers it seems........i.e. exponential cost.


  • Heywood likes this

#8 Suavi

Suavi

    Viking 1

  • -----
  • Posts: 609
  • Joined: 05 May 2017
  • Loc: 20.25 deg South of the Equator

Posted 07 May 2021 - 07:18 PM

It's a modest aperture increase, but going from a 102mm ED refractor which can be had from $600 and up increases the prices dramatically, in most cases double.  Obviously, a tripling of the price usually goes along with going from an ED doublet to a triplet lens, but not always.  Even apart from premium brands there seems to be a disproportionate increase in pricing even among doublets going from 100mm to 115mm.  I figure since the hardware can't cost much more, it has to be in the lens.  Some manufacturing rule that sees a huge cost increase between  the two lens sizes.  In my opinion, it's an incentive to go instead to 120-130mm.  The optical "gain" over a 102mm of a 115mm just isn't there. 

Cost of hardware goes up quickly too.

 

For example, 1.5" FTF costs US$249 ($166/inch of drawtube's diameter), while 3.5" FTF costs US$885 ($253/inch of drawtube' diameter).


  • gnowellsct likes this

#9 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,683
  • Joined: 24 Jun 2009

Posted 07 May 2021 - 10:36 PM

Cost of hardware goes up quickly too.

 

For example, 1.5" FTF costs US$249 ($166/inch of drawtube's diameter), while 3.5" FTF costs US$885 ($253/inch of drawtube' diameter).

I was gonna say....



#10 RichA

RichA

    Soyuz

  • *****
  • topic starter
  • Posts: 3,596
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 08 May 2021 - 12:39 AM

Cost of hardware goes up quickly too.

 

For example, 1.5" FTF costs US$249 ($166/inch of drawtube's diameter), while 3.5" FTF costs US$885 ($253/inch of drawtube' diameter).


Interesting way of looking at it. 



#11 RichA

RichA

    Soyuz

  • *****
  • topic starter
  • Posts: 3,596
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 08 May 2021 - 12:41 AM

Note that your measure is wrong.  It should be aperture squared.  102 to 115 is really 102 squared to 115 squared, a 28% increase.Siogh

 

The hardware does need to improved for the larger size and longer focal length.  Stronger, more precise.

 

One can choose what you want to spend for what.  But the increased price is neither incompetence, a conspiracy, nor disporoprtionate.

Sigh.  No one said anything about a "conspiracy."  Or paranoia.
 



#12 therealdmt

therealdmt

    Viking 1

  • *****
  • Posts: 736
  • Joined: 05 Mar 2015
  • Loc: 35° N

Posted 08 May 2021 - 08:06 AM

Now two people have said "conspiracy"!

 

Wait, now three shocked.gif

 

lol.gif

 

 

Fwiw, I’m not thrilled with the price jump myself, in particular regarding 100mm to 120mm


  • Usquebae and Northern Jeff like this

#13 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 18,683
  • Joined: 24 Jun 2009

Posted 08 May 2021 - 09:49 AM

The weight of the glass will increase with the square of the radius. But it will probably increase more than that because as the diameter gets bigger the glass has to be thicker to support itself and also hold its optical figure. That puts additional constraints on the tube design. Even if you keep the focal ratio the same as you increase the aperture, the focal length will continue to elongate the tube.

This means that the moment arm or leverage exerted upon the entire apparatus is increasing as well. If you measure it in inch-lbs you've got both more pounds and more inches. This is going out in the rear direction as well as forward because the tube will be balanced approximately in its center. At the same time you want to keep the light cone from the objective precisely targeting the center of the focuser for optimal photography or eyepieces viewing.

In the old days they basically used industrial pipe to solve these problems.

At the same time a lot of oems want to make the refractor available at a price where it will sell more units. This invites cutting corners in the models which are not in the to-hell-with-price top tier of the market.

In a sense the inexpensive models are underpriced relative to desired performance. That's why so many people who buy these look around for aftermarket focusers. The aftermarket focusers will improve performance but they will be put onto a tube that was not necessarily designed for the additional stress of the fancier focuser.

Over a century ago in professional astronomy the limits of the refractor design in terms of cost and aperture were reached with the 40 inch refractor. Beyond that you got to face the facts, buckle down, and get some kind of alternative design telescope. In amateur astronomy today you face steeply rising curves for refractors after about 5 in.

Edited by gnowellsct, 08 May 2021 - 09:54 AM.

  • jena100 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics