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

Premium dobs Vs mass produced dobs

  • Please log in to reply
55 replies to this topic

#1 Voyager 3

Voyager 3

    Viking 1

  • -----
  • topic starter
  • Posts: 592
  • Joined: 20 Jul 2020
  • Loc: Near Bangalore, India

Posted 08 September 2020 - 07:25 AM

Hi all
I was wondering would a 12.5 teeter match a 20" skywatcher Stargate dob ? The weight is not a matter in this comparison but optical quality and resolution is . Yes some want portability+premium quality but how would that compare to a larger dob of the SAME PRICE RANGE ? If conditions permit the star gate would probably win but ... If portability, the smoothness and overall build isn't a major factor , will anybody go for a ultra premium 12.5" against a 20" ?

#2 Allan Wade

Allan Wade

    Aurora

  • *****
  • Posts: 4,780
  • Joined: 27 Jan 2013
  • Loc: Newcastle, Australia

Posted 08 September 2020 - 07:56 AM

There’s lots of different ways to look at a comparison like this.

 

The Teeter has a much higher build quality. Premium scopes tend to make observing seamless, so you can concentrate on the observing, and not operating the telescope. You can’t underestimate how much more you see when your sole focus is the target, and the scope disappears from your attention.

 

The Teeter can be optioned to a superior set of optics. 12.5” is plenty of aperture for good planetary observing. It’s possible it could provide similar or even better planetary observing as the SkyWatcher, but that will depend on the mass produced lottery as to how good the 20” optics are.

 

For deep sky the aperture gap is substantially in favour of the SkyWatcher, and even the most premium of 12.5” optics won’t match what you will see in a standard 20”.

 

Personally I could never own a mass produced dob again because there are too many cost driven compromises. A 12.5” Teeter could be a lifetime scope. A 20” UL SkyWatcher not so much.


  • Bill Jensen, spencerj, Jeff Bennett and 10 others like this

#3 ShaulaB

ShaulaB

    Vanguard

  • *****
  • Posts: 2,486
  • Joined: 11 Oct 2012
  • Loc: Missouri

Posted 08 September 2020 - 08:14 AM

It is a law of physics--larger aperture yields smaller angular resolution.

https://www.astronom...ms/dawes-limit/

 

Do the math.

https://astronomy.to...pe_capabilities


  • George N and Starsareus like this

#4 KBHornblower

KBHornblower

    Messenger

  • -----
  • Posts: 445
  • Joined: 01 Jul 2020
  • Loc: Falls Church, VA (Washington DC suburb)

Posted 08 September 2020 - 09:08 AM

It is a law of physics--larger aperture yields smaller angular resolution.

https://www.astronom...ms/dawes-limit/

 

Do the math.

https://astronomy.to...pe_capabilities

Provided it is accurately figured.  That could be a roll of the dice with a low-budget mirror.


  • TiSaph likes this

#5 TOMDEY

TOMDEY

    Cosmos

  • *****
  • Posts: 8,047
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 08 September 2020 - 09:11 AM

20" is way bigger than 12.5".

 

Interesting that you put it that way because it does indeed describe both history and reality!

 

For Deep Sky (nebulae, galaxies) Aperture Rules. Explains why Lord Rosse's junkyish 72-inch Speculum Behemoth, John Dobson's junkyish two-foot Porthole Light Buckets, and Jim Jacobson's junkyish Coulter Sonotube Dobs blew the socks off their contemporary competitors. Then we amateurs got snooty, demanding both aperture and wavefront quality.

 

If you can comfortably afford both light grasp and quality, that is of course the best of both worlds. I enjoyed my cheap Coulter 29-inch for decades and it was worth it. Now I'm enjoying my Premium New Moon 36-inch, at 20 times the (era-adjusted) $$$, and it's well worth it!    Tom


  • turtle86 and rowdy388 like this

#6 TOMDEY

TOMDEY

    Cosmos

  • *****
  • Posts: 8,047
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 08 September 2020 - 09:26 AM

Here's pictures of those two mirrors... The Coulter 29-inch, which I had to pull with tunable springs from the back, to tune out the astigmatism. And the Premium Fullum 36-inch Technofusion... which is perfect just the way it is. Both good for the prices; you get what you pay for.    Tom

Attached Thumbnails

  • 72 29-inch telescope force actuators tweaker clock astig 60.jpg
  • 73 Toms 36-inch is operational.jpg

  • George N, Starsareus, City Kid and 4 others like this

#7 Markovich

Markovich

    Viking 1

  • *****
  • Posts: 894
  • Joined: 22 May 2007
  • Loc: Grove City, Ohio

Posted 08 September 2020 - 10:54 AM

There have been several very recent threads similar to this- Would encourage you to read through those first.



#8 rowdy388

rowdy388

    Skylab

  • *****
  • Posts: 4,090
  • Joined: 09 Apr 2013
  • Loc: Saratoga County, NY

Posted 08 September 2020 - 11:08 AM

The general rule we hear is to get the largest aperture you can handle and afford.

A premium 12.5" may cost the same as a mass produced 20", but the viewing experience

will not be the same. Which scope is more desirable depends upon what factors are

more important to you. If money is no object, then get both maximum aperture and quality.

If you want the faintest galaxy and budget is important, maximize the aperture. 

 

Just a note that there aren't many mass produced 20" scopes. Most scopes that size are

are premium and getting a used premium scope may well be cheaper than a new mass

produced one of questionable quality. Also, factors such as having your feet on the ground

vs needing a ladder are important.


Edited by rowdy388, 08 September 2020 - 11:13 AM.

  • havasman and moonrakercat like this

#9 KBHornblower

KBHornblower

    Messenger

  • -----
  • Posts: 445
  • Joined: 01 Jul 2020
  • Loc: Falls Church, VA (Washington DC suburb)

Posted 08 September 2020 - 11:11 AM

There have been several very recent threads similar to this- Would encourage you to read through those first.

Could you provide some links?  My feeble brain often has trouble searching this vast Cloudy Nights forum.



#10 Arctic eye

Arctic eye

    Vostok 1

  • *****
  • Posts: 182
  • Joined: 11 Mar 2013
  • Loc: Finland

Posted 08 September 2020 - 12:03 PM

”I was wondering would a 12.5 teeter match a 20" skywatcher Stargate dob ?”

 

Yes it would, at least based on my experience on two of those 20”:s (actually original optics and then a replacement mirror Synta sent me).

 

My SW16” dob was far better than the 20” stargate, hands down. I think an 8” can beat the 20”. Below a comparison between my 16” and the better of those 20” mirrors. Imaged using same imaging train in turns in both scopes, side by side, several videos in turns...

 

The second 20” mirror was so bad that stars looked like gearwheels. 

 

400p_500p_comparison.gif?img=full

 

Platoncomparison.gif?img=full


  • howardcano, Jeff L and Woj2007 like this

#11 junomike

junomike

    ISS

  • *****
  • Moderators
  • Posts: 20,171
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 08 September 2020 - 05:44 PM

The above post is an exception to the rule (IMO).  I find even a mass produced 12" is more pleasing than a 10" Premium for DSO's.

For Planetary/Lunar It's trickier but the premium mirror needs excellent seeing to overcome even the 2" Aperture difference.



#12 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • Posts: 10,095
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 08 September 2020 - 07:56 PM

The most noticeable difference between mass produced and true premium scopes is smooth slewing above 200x, smaller base dimensions, and lighter weight. There should be other improvements, but those are the minimum.
  • George N likes this

#13 vjstangelo

vjstangelo

    Explorer 1

  • *****
  • Posts: 94
  • Joined: 31 Aug 2010

Posted 08 September 2020 - 09:22 PM

I have a friend who owns an Orion 12i dob. The views are quite nice. I know he bought it used on the cheap. Can’t think a premium dob would give better views, IMHO.

#14 Glory Eye

Glory Eye

    Vostok 1

  • -----
  • Posts: 145
  • Joined: 17 Jan 2019
  • Loc: Southern Utah

Posted 08 September 2020 - 09:37 PM

This might be a debatable suggestion, but have you considered a Hubble Optics UL20"? At $4795, it's cheaper than the Stargate and Hubble Optics boasts Strehl 0.95 on their primary mirror which is in the premium realm. In addition, their mirrors look very innovative in their rapid cooling sandwich design. For a review on the Hubble Optics 16" go here:https://youtu.be/4FuGniNZlg4.


  • spaceoddity likes this

#15 hudsonman

hudsonman

    Sputnik

  • -----
  • Posts: 47
  • Joined: 18 Jun 2008

Posted 09 September 2020 - 06:33 AM

I’ve had a 6” Orion dob for 12 years, and I’ve really enjoyed it. Star test looks great on it. However, compared to similar aperture premium scopes the contrast and detail is obviously lower in the Orion on planets. DSO difference much more subtle.

I’m now also looking for a much bigger scope. I’d heard that while premium optics have improved, mass-produced mirrors have gotten worse. Is this fair? Or is it just that mass produced mirrors have got bigger, so more potential for problems?

Anyone actually measured Strehl of some Synta scopes?

Edited by hudsonman, 09 September 2020 - 06:34 AM.

  • dledenican likes this

#16 Voyager 3

Voyager 3

    Viking 1

  • -----
  • topic starter
  • Posts: 592
  • Joined: 20 Jul 2020
  • Loc: Near Bangalore, India

Posted 09 September 2020 - 07:08 AM

This might be a debatable suggestion, but have you considered a Hubble Optics UL20"? At $4795, it's cheaper than the Stargate and Hubble Optics boasts Strehl 0.95 on their primary mirror which is in the premium realm. In addition, their mirrors look very innovative in their rapid cooling sandwich design. For a review on the Hubble Optics 16" go here:https://youtu.be/4FuGniNZlg4.

Whow whow whow actually eh... I don't have a mood/(budget technically) to upgrade to 4-digit scopes now lol. Actually this is for just a general knowledge of how the premium mirrors compare with mass produced ones !!

#17 Keith Rivich

Keith Rivich

    Vanguard

  • *****
  • Posts: 2,454
  • Joined: 17 Jun 2011
  • Loc: Cypress, Tx

Posted 09 September 2020 - 09:11 AM

Just a thought...

 

We see a lot of "premium vs mass" topics on these pages. 

 

After many years of using both the difference is nil if one doesn't get the scopes out to dark skies and really push them to their limits. Everything else is just idle chatter. 


  • Bill Weir, Markovich, Mike Wiles and 5 others like this

#18 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 88,212
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 09 September 2020 - 10:10 AM

”I was wondering would a 12.5 teeter match a 20" skywatcher Stargate dob ?”

 

Yes it would, at least based on my experience on two of those 20”:s (actually original optics and then a replacement mirror Synta sent me).

 

My SW16” dob was far better than the 20” stargate, hands down. I think an 8” can beat the 20”. Below a comparison between my 16” and the better of those 20” mirrors. Imaged using same imaging train in turns in both scopes, side by side, several videos in turns...

 

The second 20” mirror was so bad that stars looked like gearwheels.

 

 

The moon is not an object I would use as an example of the difference between a 12 inch and a 20 inch.

 

Jon


  • peleuba, Markovich, Keith Rivich and 3 others like this

#19 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • Posts: 10,095
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 09 September 2020 - 10:22 AM

Just a thought...

We see a lot of "premium vs mass" topics on these pages.

After many years of using both the difference is nil if one doesn't get the scopes out to dark skies and really push them to their limits. Everything else is just idle chatter.

Mass produced have the best chance of competing on galaxies, no? Seems the dark sky site would level the field. At home, the premium should outperform on planets, at least till the atmosphere limits the view. Even then, the smoother mechanics and lighter weight are noticed.

Although, mirror smoothness would be noticed more at a dark sky site, but maybe also around a planet.

Edited by stargazer193857, 09 September 2020 - 10:23 AM.

  • TiSaph likes this

#20 Keith Rivich

Keith Rivich

    Vanguard

  • *****
  • Posts: 2,454
  • Joined: 17 Jun 2011
  • Loc: Cypress, Tx

Posted 09 September 2020 - 10:50 AM

Mass produced have the best chance of competing on galaxies, no? Seems the dark sky site would level the field. At home, the premium should outperform on planets, at least till the atmosphere limits the view. Even then, the smoother mechanics and lighter weight are noticed.

Although, mirror smoothness would be noticed more at a dark sky site, but maybe also around a planet.

 

At a dark site, on extended DSO's, aperture wins, period....as long as the mirror is not a total piece of junk. 

 

Planet observing and DSO observing are quite different on needs. Except when seeing is absolutely fantastic at our dark site I find my 8" f/9 mass produced scope out performs my 25" premium on the planets. On DSO's...no contest. I leave the 8" in the closet. 


  • George N, Michal1 and havasman like this

#21 bobhen

bobhen

    Aurora

  • *****
  • Posts: 4,615
  • Joined: 25 Jun 2005

Posted 09 September 2020 - 10:54 AM

It is a law of physics--larger aperture yields smaller angular resolution.

https://www.astronom...ms/dawes-limit/

 

Do the math.

https://astronomy.to...pe_capabilities

One must also consider these “laws of physics”…

 

Seeing will limit a telescope’s resolving potential and in most US locations the seeing will be the determining factor regarding the potential resolving capability of a telescope.

 

Consider…

 

“How often do nights of excellent seeing occur? At the William Herschel Telescope site in the Canary Islands, even this superb viewing location  (second best in the northern Hemisphere) has many nights of relatively poor seeing: the distribution is positively skewed, and at this excellent site, a 10 inch telescope will be seeing limited on 9 out of 10 nights.”

 

I presume most don’t live in a location with anything like the seeing at the above.

 

Here is a quote “from the link you posted”…

 

“The ability of a telescope to resolve to Dawes' limit is usually much more affected by seeing conditions,...”

 

One must also consider the optical quality of the primary. For example, a 1-wave optic will show soft images no matter how large it is. Images might be bright but resolution will be impacted.

 

Bob



#22 hudsonman

hudsonman

    Sputnik

  • -----
  • Posts: 47
  • Joined: 18 Jun 2008

Posted 09 September 2020 - 10:55 AM

Just a thought...

 

We see a lot of "premium vs mass" topics on these pages. 

 

After many years of using both the difference is nil if one doesn't get the scopes out to dark skies and really push them to their limits. Everything else is just idle chatter. 

Absolutely true in my experience if you get a good mass produced scope. There are bad ones out there, like Arctic eye's where you can see the difference just looking at the Moon.



#23 bobhen

bobhen

    Aurora

  • *****
  • Posts: 4,615
  • Joined: 25 Jun 2005

Posted 09 September 2020 - 11:15 AM

For deep sky observing (not double star splitting) like hunting down galaxies etc., light gathering is important. Resolving fine lunar and planetary details is more dependent on seeing and optical quality whereas observing faint fuzzies is more dependent on contrast (hence the need for dark skies) and light gathering (hence the need for size). 

 

A large “decent quality optic” in a dark sky will satisfy many. A “same size or maybe “slightly” smaller but higher quality optic will deliver better contrast and therefor better performance for those that don’t want to leave anything on the table.

 

Bob



#24 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • Posts: 10,095
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 09 September 2020 - 12:05 PM

At a dark site, on extended DSO's, aperture wins, period....as long as the mirror is not a total piece of junk.

Planet observing and DSO observing are quite different on needs. Except when seeing is absolutely fantastic at our dark site I find my 8" f/9 mass produced scope out performs my 25" premium on the planets. On DSO's...no contest. I leave the 8" in the closet.


Was that at the same magnification, or same eyepiece with the apparent resolution worse?

Also, are you sure the 25" was cooled fully?

#25 TOMDEY

TOMDEY

    Cosmos

  • *****
  • Posts: 8,047
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 09 September 2020 - 01:19 PM

Looks like we've arrived at the usual place in this ongoing topic. That each scope is different.

 

Here's a quick, easy, and free experiment that you big scope guys can try tonight. Craft a ~spinap~ off-axis stop for your light bucket, whatever its certified wavefront quality. I made mine out of foam board, 6.5-inch on my 17.5-inch Coulter. Aim at e.g. Jupiter, Saturn, opens, globs, nebulae, galaxies. Be aware that is the combination of your scope, atmosphere, eye... that combine to formulate your perception. Here are my observations, on an averagely decent night:

 

> Saturn - spinning the ap while viewing finds the sweet spot on the high-side of the tube. Image luxuriously-resolved, better than any 6.5-inch refractor, because chromatic aberration is identically zero, wavefront is superb, and atmosphere is supporting good resolution. At F/12 200x 1mm pupil, my eye is enjoying 20/10 acuity. Saturn is razor-sharp and holding that breathtaking presentation. Contrast is wonderful and the ball and rings are bright enough, not too bright. Yank off the mask and the planet degrades to OK but not at all impressive. Seeing is meh and the ball and rings look ~too bright~ ... but... but... a bunch of cute little moons pop into view, that I hadn't noticed before!

> Jupiter - ditto.

> Open Clusters - ditto, but generally prefer full aperture.

> Globulars - interesting, prefer full aperture.

> Nebulae - interesting, generally prefer full aperture.

> Galaxies - full aperture blows the socks off any smaller scope.

 

I have the best of both worlds in this one cheap scope, on a night of decent, but not superb seeing, just for building a half-pound foam-board OAS.

 

You can craft other experimental stop boards. Be sure to make them so you can readily pop on and off, and spin them, while looking through the eyepiece. On the very best of nights, you will want to leave the stops off... if your scope is superb, if the sky is superb, if your eyes are superb... noting that each of those three is very rare. For most of us, that last one is most commonly deficient and most commonly ignored.    Tom

 

 

Attached Thumbnails

  • 78 off-axis stop.jpg

  • George N, Pierre Lemay, Glory Eye and 2 others like 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