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

Meade 2045...A good one?

  • Please log in to reply
112 replies to this topic

#51 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 15428
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 28 October 2018 - 02:02 PM

Every scope has some level of optical defects but the question is how will they affect the views. I may just go back to the Chas optical testing technique, the 3mm Delite! It's all about the views not the test.

A 3mm Delite can be a delite to use.  You have owned enough scopes to know what snaps and pops and what don't. I think that is half the fun in buying scopes is not knowing how or bad the optics are going to be. We all know AP TEC, Zambuto and a few others are gonna be good 99% of the time.  It is the SCT that you never know what the heck you are going to get.


  • rolo and Bonco2 like this

#52 rolo

rolo

    Cosmos

  • *****
  • topic starter
  • Posts: 7667
  • Joined: 14 Jan 2007
  • Loc: GA

Posted 28 October 2018 - 02:07 PM

Take this one for example. A few obvious optical issues like spherical aberration, zone, turned edge, too many line on the Ronchi test. Its got to be a bad one right?  Well, it was rated as very good at 1/5 wave and .95 Strehl. Does it have to be perfect to be good? Absolutely not.

 

Attached Thumbnails

  • Forren.jpg
  • ttt.jpg

Edited by rolo, 28 October 2018 - 02:16 PM.

  • Steve Allison likes this

#53 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 28 October 2018 - 02:18 PM

Wow Rolo, sounds like you have ben beaten down. Not like you man.  Edit, that last post is more like the Rolo I know.


Edited by starman876, 28 October 2018 - 02:21 PM.

  • rolo and Steve Allison like this

#54 rolo

rolo

    Cosmos

  • *****
  • topic starter
  • Posts: 7667
  • Joined: 14 Jan 2007
  • Loc: GA

Posted 28 October 2018 - 02:48 PM

Wow Rolo, sounds like you have ben beaten down. Not like you man.  Edit, that last post is more like the Rolo I know.

I've seen many star test and DPAC images posted here and in other forums  and in an instant the criticism begins. No one points out the good in the tests just the defects leading one to believe that if its not perfect its a bad optic. These optical tests are very sensitive and informative but not much is said about how it will affect the views. So what if the lines bow a little or there's a turned edge in the outer region or the star test isn't perfect. The scope could still be an excellent performer. I asked in my Topic is this a good 2045? Based on my tests I would say so but we'll see how first light does.

 

Even the horrible DX8 produced a usable image and The DPAC on that thing was horrible!

Attached Thumbnails

  • Dynamax tetst.jpg

  • memento, kansas skies, Bonco2 and 2 others like this

#55 Bomber Bob

Bomber Bob

    Voyager 1

  • *****
  • Posts: 13971
  • Joined: 09 Jul 2013
  • Loc: The Deep South, USA

Posted 28 October 2018 - 03:18 PM

These optical tests are very sensitive and informative but not much is said about how it will affect the views.

 

I think that's because there are so many factors that it's almost impossible to predict.  In my limited experience with DPAC, the results have to be way below average to see it -- usually in high power planetary.

 

Even the horrible DX8 produced a usable image and The DPAC on that thing was horrible!

 

Even with its non-circular / rough-edged corrector, my DX8 did OK on the planets up to about 180x, and was a very fine low power DSO scope, but it wasn't worth setting up & using when my 4" refractors easily out-performed it.


  • memento and Bonco2 like this

#56 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1566
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 28 October 2018 - 04:45 PM

When you have a easy to compromise optical system, like with multiple elements/surfaces/corrections/astigmatism/obstructions/trapped airflow/axial alignment/non co-planer, you have too many "degrees of freedom" where things can "go wrong".

 

The simplest in this case is a newtonian, two surfaces with one correction and one obstruction. Fewest number of things to go wrong.

 

DPAC on a newt, where you can "change out" the mirrors allows you the most conclusive answers to optical quality. And they can be confirmed with star test and (with a properly baffled and collimated OTA) a planetary view of low contrast (like Jupiter, which isn't well positioned at the moment). That's the ideal, and you can get concrete, reproducible results for these cases.

 

Next best is a two element refractor. After that it rapidly becomes "Guess My Aberration" (like What's My Line).

 

Mass production amplifies this. High quality telescopes are assembled with QC/QA at each step for this reason, to reduce the degrees of freedom of flaw before than can "grow". Lesser ones check at the end, before shipment. The story of what you are looking at with DPAC/star test starts at this point.

 

CAT's have been the worst case of this for me. The only way I know to "improve" on it is to have an outstanding example (the thing we are all looking for) at the beginning of the process, for then one can compare components/spacing/arrangement independently to objectively determine the flaw in another, and then to conclude it's aggregate effect as a complete optic assembly. Because of the reference set.

 

Of course this is impossible. But by just speaking this, it is possible to wrestle with the  difficult, instead of being held hostage by it.


Edited by wfj, 28 October 2018 - 04:47 PM.


#57 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 15428
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 28 October 2018 - 04:59 PM

DPAC is a waste in my book.


  • Gil V likes this

#58 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 28 October 2018 - 06:24 PM

I've seen many star test and DPAC images posted here and in other forums  and in an instant the criticism begins. No one points out the good in the tests just the defects leading one to believe that if its not perfect its a bad optic. These optical tests are very sensitive and informative but not much is said about how it will affect the views. So what if the lines bow a little or there's a turned edge in the outer region or the star test isn't perfect. The scope could still be an excellent performer. I asked in my Topic is this a good 2045? Based on my tests I would say so but we'll see how first light does.

 

Even the horrible DX8 produced a usable image and The DPAC on that thing was horrible!

Once you start doing DPAC it is like a drug.  You got to test everything you have. Some do not understand this and to some it seems too complicated to try and understand.  I would say it is so simple that even a caveman can do it. 


  • wfj, Geo31 and Bomber Bob like this

#59 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1566
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 28 October 2018 - 07:24 PM

... it is so simple that even a caveman can do it. 

And even a caveman can tell good from bad. But it takes more than a caveman to figure out how its bad, and a genius to isolate the specific change(s) and make them.


  • rolo, starman876 and Bomber Bob like this

#60 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 28 October 2018 - 07:31 PM

And even a caveman can tell good from bad. But it takes more than a caveman to figure out how its bad, and a genius to isolate the specific change(s) and make them.

anything seems difficult to understand at first, but with enough practice most things become routine.   Most people are scared of things they do not understand and will shy away from them.


  • rolo, wfj and Geo31 like this

#61 rolo

rolo

    Cosmos

  • *****
  • topic starter
  • Posts: 7667
  • Joined: 14 Jan 2007
  • Loc: GA

Posted 28 October 2018 - 08:13 PM

Once you start doing DPAC it is like a drug.  You got to test everything you have. Some do not understand this and to some it seems too complicated to try and understand.  I would say it is so simple that even a caveman can do it. 

You're not kidding! I'm thinking about DPAC'ing my finder-scopes!


  • tim53, starman876, eros312 and 2 others like this

#62 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 28 October 2018 - 08:17 PM

You're not kidding! I'm thinking about DPAC'ing my finder-scopes!

I know, every piece of glass I have I want to test. It is a lot of fun.  



#63 Bomber Bob

Bomber Bob

    Voyager 1

  • *****
  • Posts: 13971
  • Joined: 09 Jul 2013
  • Loc: The Deep South, USA

Posted 28 October 2018 - 08:19 PM

By the time I built my DPAC rig, I'd already gotten rid of the "stinkers" that failed my star & sky tests.

 

So, I looked for deviations / differences between known near-perfect and subsequent lenses.

 

Like Johann, once I got the rig built, I wanted to test EVERY lens.  Some, like the Swift 838, Royal, & Vixen lenses I've tested multiple times -- to see if I got the same results.  I did.


  • rolo and wfj like this

#64 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 28 October 2018 - 08:43 PM

By the time I built my DPAC rig, I'd already gotten rid of the "stinkers" that failed my star & sky tests.

 

So, I looked for deviations / differences between known near-perfect and subsequent lenses.

 

Like Johann, once I got the rig built, I wanted to test EVERY lens.  Some, like the Swift 838, Royal, & Vixen lenses I've tested multiple times -- to see if I got the same results.  I did.

It is great fun.   I want to get some more test gear so I can perform other tests.   


  • Bomber Bob likes this

#65 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1566
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 28 October 2018 - 09:16 PM

The sane bound for me is about 1/8th wave. If that, passes my "good enough" test. Rather observe than test.

 

But yes have a "no stinkers" policy. Try to not even acquire one in the first place.



#66 wfj

wfj

    Surveyor 1

  • *****
  • Posts: 1566
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 28 October 2018 - 09:20 PM

Oh, and there are things that DPAC doesn't help with. Diffraction. CA. HSA. CO. Glare. These still afflict your optics.

 

For me the tough one to wrestle with is HSA on short APO's , fast (f/ < 3) primary mak's, and SCTs.



#67 Geo31

Geo31

    Voyager 1

  • *****
  • Posts: 10127
  • Joined: 28 Jan 2013
  • Loc: Willis, TX

Posted 28 October 2018 - 09:36 PM

Ugh.

 

This is Rolo's thread and I'm trying to respect that (I certainly respect him).  I understand what he is trying to say.  And he has a very valid point that we don't talk about what is GOOD.

 

But....

 

I also understand Dave.  How many times has he said, if you're happy with your scope that's great.  I look at the DPAC testing like some of the technical information on car forums I'm on.  Those who try to post correct and valid information are often vilified.  Honestly, from where I sit, all Dave is doing is making sure those who may read the thread or even search for information are not mislead.  NOTHING wrong with that.  Nothing.  I've personally found all these discussions educational.

 

But, back to Rolo's thread and his point, this is about the 2045 and regardless of testing against an ideal standard, as 2045s go, this seems to be a good one.  That is great.  But, even more importantly, if Rolo is happy with it, that's all that matters, and I think Dave would agree.


Edited by Geo31, 29 October 2018 - 05:14 AM.

  • starman876, memento, Bomber Bob and 1 other like this

#68 shredder1656

shredder1656

    Apollo

  • *****
  • Posts: 1128
  • Joined: 24 Sep 2017
  • Loc: Indiana

Posted 29 October 2018 - 04:58 AM

As a rookie with a grasp of most of these concepts that is almost as powerful as a rusty used mouse trap that is missing the spring, I really have benefitted from much of the stuff posted in the classics forum.  I appreciate it all.  The goal, I think, for all of the stuff posted on this specific forum is intended to benefit noobs like me, or at least to benefit the group as a whole.  Sometimes, though, the criticism is confusing to me.  

 

I think I read it mentioned somewhere else, but someone mentioned that DPAC shows errors, but not always the significance, how the errors can be corrected, or how the error will present itself at the ep.  I might be taking what was said out of context and/or not understanding what was written at all, but it seemed to me when I read it that the point was that DPAC was a reliable tool, but it showed errors...not how GOOD the scope actually is.  It might show how good the scope is NOT, but how GOOD the scope is might not be as conspicuously affected at the ep by the errors that the DPAC shows.  So, an excellent scope might not have an excellent DPAC.  A gold medal sprinter might run a race in a crappy pair of shoes, but will still blow the doors off of nearly every competitor they go up against.  The time vs their personal best is likely affected by the crummy shoes, but you won't have a clue that their shoes slowed them down when your jaw hits the floor as you watch them bust the tape.  

 

My rambling point is this, I guess.  I appreciate the detail and critiquing of someone's DPAC results, when they are specifically requesting it.  When they are not requesting it, for me (and, I realize that it might not be the same for brighter noobs), it gets more confusing.  I like when the post has the DPAC, plus the star test, plus the real-life at the ep pics too.  Like this thread.  

 

Late to the dance, and two left feet anyway, but I like trying to sort out the details for each of the separate types of threads.  Just gets confusing when the two are intertwined.  

 

Anyway, on the intended topic, this 2045 is impressive to me regardless.  I like the Meade blue, and I like the tiny size.  Seems like a good choice for a packable option.  Should fit into carry on, right?  Those pics were awesome.  


  • rolo and Bomber Bob like this

#69 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 15428
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 29 October 2018 - 05:21 AM

And even a caveman can tell good from bad. But it takes more than a caveman to figure out how its bad, and a genius to isolate the specific change(s) and make them.

Funny thing is the Cave man posted some bad test that were not even done right.  So it takes more than just slapping up some pics.

 

Just odd the spotter versions have better optics on avg vs the astro versions.  Maybe that was my spotter Rolo bought.


Edited by CHASLX200, 29 October 2018 - 05:24 AM.


#70 rolo

rolo

    Cosmos

  • *****
  • topic starter
  • Posts: 7667
  • Joined: 14 Jan 2007
  • Loc: GA

Posted 29 October 2018 - 07:48 AM

Ugh.

 

This is Rolo's thread and I'm trying to respect that (I certainly respect him).  I understand what he is trying to say.  And he has a very valid point that we don't talk about what is GOOD.

 

But....

 

I also understand Dave.  How many times has he said, if you're happy with your scope that's great.  I look at the DPAC testing like some of the technical information on car forums I'm on.  Those who try to post correct and valid information are often vilified.  Honestly, from where I sit, all Dave is doing is making sure those who may read the thread or even search for information are not mislead.  NOTHING wrong with that.  Nothing.  I've personally found all these discussions educational.

 

But, back to Rolo's thread and his point, this is about the 2045 and regardless of testing against an ideal standard, as 2045s go, this seems to be a good one.  That is great.  But, even more importantly, if Rolo is happy with it, that's all that matters, and I think Dave would agree.

The problem is quite the opposite. Most people are mislead because they think that unless the DPAC lines are perfectly straight then their scope is bad. I see it all the time here and in other forums and it does more harm than good.


  • Bomber Bob likes this

#71 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 29 October 2018 - 08:14 AM

The problem is quite the opposite. Most people are mislead because they think that unless the DPAC lines are perfectly straight then their scope is bad. I see it all the time here and in other forums and it does more harm than good.

I agree with you.  It takes understanding of the test results to be able to state what issues might be with a lens.  Funny thing is that most people think it can only be done in green light.  Shows their ignorance of DPAC testing.   Green, red and blue are all colors the DPAC test can be done in.  Green is most common because that is wavelength of light where most lenses are figured in because that is where our eyes are most sensitive.  



#72 tim53

tim53

    Voyager 1

  • *****
  • Posts: 13608
  • Joined: 17 Dec 2004
  • Loc: Highland Park, CA

Posted 29 October 2018 - 09:57 AM

 

 

Anyway, on the intended topic, this 2045 is impressive to me regardless.  I like the Meade blue, and I like the tiny size.  Seems like a good choice for a packable option.  Should fit into carry on, right?  Those pics were awesome.  

That was my thought.  https://www.cloudyni... carrion tim53

 

I actually did take the scope on a flight where I thought I'd have some evening time to fiddle with the scope.  I ended up buying a portable hand truck at my destination to go with it, because these aren't light.  And my arm got longer carrying it to the gate on the outbound flight.

 

-Tim.



#73 rolo

rolo

    Cosmos

  • *****
  • topic starter
  • Posts: 7667
  • Joined: 14 Jan 2007
  • Loc: GA

Posted 29 October 2018 - 12:11 PM

Tim, can you or anyone tell me if these Japan made 2045's wer made by JSO, Japan Special Optics?



#74 Bomber Bob

Bomber Bob

    Voyager 1

  • *****
  • Posts: 13971
  • Joined: 09 Jul 2013
  • Loc: The Deep South, USA

Posted 29 October 2018 - 01:09 PM

Hino / Mizar made the 2045, and all those blue-tube refractors with the Meade labels -- EXCEPT for the transitional blues with the Towa 339 focusers, adapted from .965" to 1.25" format...


  • tim53 and rolo like this

#75 starman876

starman876

    Hubble

  • *****
  • Posts: 17958
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 29 October 2018 - 03:13 PM

What happened to that 2045 scope that started all this? what is the status?




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