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

Fake Comparisons

  • Please log in to reply
11 replies to this topic

#1 Tropobob

Tropobob

    Vostok 1

  • -----
  • topic starter
  • Posts: 160
  • Joined: 22 Aug 2014
  • Loc: Cairns Australia

Posted 23 September 2018 - 08:41 PM

How many times do we do this?  We compare apples with oranges etc. I know I am also guilty of it.

 

Remember days gone by when achromats and reflectors were compared? The understated comparison was between long F-Ratio scopes and faster reflectors. There is still a longing for slow refractors and plenty has been written in these forums about their virtues.

 

In a perfect world, any comparison would have terms of reference. I recently made the bold statement that I had found that a quality refractor has similar resolving power to mass- produced Dobs of twice the size. Some very experienced observers took issue with this and I was reminded about cool-down times and collimation. However, my reality is often like guerrilla warfare: I pull the scope out, often have a quick hit/peep at the sky and half the time, the session is over within 20 minutes, sometimes within 5mins.  So, I am a grab-and- go observer. In this frame of reference, and in my observing environment, my statement is true. However, in a better environment where time or precautions are taken to cool equipment properly, etc, my statement may well be incorrect. For a newbie with my behaviors, Newtonians & SCTs should come with a big warning on the side that: "This scope needs be allowed to cool down for 2 hours to enable optimum viewing".  Hmm ... just imagine what that would do to sales.

 

However, my frames of reference may again be wrong. Refractors are becoming larger and lens more massive. This may make having a quick peep a disappointing experience, as larger refractors themselves need to have time to cool down. I wonder if the Tak 100s may be showing the future with their undersized tubes (95mm tube, 100mm lens).  This seems like a sensible way of reducing cool-down times.

 

At times, I feel sorry for manufacturers of high-end equipment that are subjected to bad comparisons. In the pre-internet era, I read a review about a quality refractor, where the reviewer mentioned false color was seen on the Moon's limb when using a 14mm Radian.  I was grateful that they mentioned the EP, because I knew that I saw the same affect using my 14mm Radian with a 6" perfectly-color corrected Newtonian. However, few others would have know that it was the EP rather than the refractor showing the false color. It really must be heartbreaking to develop a great refractor only to have it unfairly disparaged.

 

I guess what I am saying is that so so many things are subjective and distorted by false comparisons and information. What people often say is true for them, their patterns of behavior and their conditions. However, there are also unknown factors, or things taken for granted that are often not considered in a wider context.  If valuing the opinions of others regarding astro-equipment, value most the opinions of people with more experience who have similar observing habits and conditions.

 

I intended to give  this post the title of false comparisons, but we seem to be in an era where Fake is the word of the moment.


Edited by Tropobob, 24 September 2018 - 12:58 AM.

  • Paul Hyndman, Astrojensen, contrailmaker and 7 others like this

#2 jupiter122

jupiter122

    Vostok 1

  • *****
  • Posts: 134
  • Joined: 21 Apr 2013
  • Loc: Sudbury, MA

Posted 23 September 2018 - 08:51 PM

Perhaps “fake” is the fake word of the moment, itself intended to deceive.
  • Paul Hyndman, terraclarke and outofsight like this

#3 The Ardent

The Ardent

    Skylab

  • *****
  • Moderators
  • Posts: 4101
  • Joined: 24 Oct 2008
  • Loc: Virginia

Posted 23 September 2018 - 09:04 PM

There is a lot of talk, but how many actually back it up? 

Attached Thumbnails

  • image.jpeg

  • Scott in NC, Astrojensen, Ed D and 3 others like this

#4 Scott in NC

Scott in NC

    Refractor Fanatic

  • *****
  • Administrators
  • Posts: 30694
  • Joined: 05 Mar 2005
  • Loc: NC

Posted 23 September 2018 - 09:26 PM

"This scope needs be allowed to cool down for 2 hours to enable opium viewing".  Hmm ... just imagine what that would do to sales.

Eh, you might want to edit this part, just so no one gets the wrong idea! lol.gif

 

Let me know if you don't see this until after the time allowed to edit has been exceeded, and I'll be happy to fix it for you.


  • Element79 and Codbear like this

#5 gdd

gdd

    Mercury-Atlas

  • -----
  • Posts: 2512
  • Joined: 23 Nov 2005
  • Loc: Lynnwood, WA (N/O Seattle)

Posted 23 September 2018 - 10:24 PM

Comparing an expensive APO to a huge reflector may be unfair to the APO because it is an apples to oranges comparison. On the other hand, comparing and expensive APO to a reflector of slightly larger aperture is unfair to the reflector because the APO is made of only the best components and no one wants to spend a fortune on a small reflector. An apples to apples comparison can also be a dollars to cents comparison and but a purchaser wants a dollars to dollars comparison because there is a budget to consider. 

 

Conclusion: It is fair to compare $10 of apples to $10 of oranges if all you have is $10.

 

 

Gale


  • ShaulaB, kkt, cookjaiii and 1 other like this

#6 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 73162
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 23 September 2018 - 11:43 PM

In a perfect world, any comparison would have terms of reference. I recently made the bold statement that I had found that a quality refractor has similar resolving power to mass- produced Dobs of twice the size. Some very experienced observers took issue with this and I was reminded about cool-down times and collimation. However, my reality is often like guerrilla warfare: I pull the scope out, often have a quick hit/peep at the sky and half the time, the session is over within 20 minutes, sometimes within 5mins.  So, I am a grab-and- go observer. In this frame of reference, and in my observing environment, my statement is true.

 

 

The important thing is explain what you did and what you found.  If you wrote,

 

"I took my 4 inch apo and my 10 inch F/5 Dob outside, it was 72 degrees inside, 50 outside. The seeing was stable, I immediately began observing Antares, I was able to barely make the split in the 4 inch apo, I could not make the split in the 10 inch Dob, the primary star was very unstable and overly large."

 

Then I don't think anyone would have a problem. But simply stating that quality refractor has twice the resolving power as a mass produced Dob twice it's size without explaining the conditions provides no real information.  Someone like myself who regularly splits double stars with my mass produced 10 inch that are beyond the reach of 5 inch and even larger refractors would be sure to object to your unqualified blanket statement.

 

Jon


  • Astrojensen, HubSky, terraclarke and 1 other like this

#7 Kunama

Kunama

    Skylab

  • *****
  • Posts: 4022
  • Joined: 22 Oct 2012
  • Loc: Canberra, Australia

Posted 23 September 2018 - 11:48 PM

Eh, you might want to edit this part, just so no one gets the wrong idea! lol.gif

 

Let me know if you don't see this until after the time allowed to edit has been exceeded, and I'll be happy to fix it for you.

Bob lives in Cairns, Australia, my years investigating major drug importations tells me he may well have meant opium.... drool5.gif


Edited by Kunama, 23 September 2018 - 11:49 PM.

  • Element79 likes this

#8 Tropobob

Tropobob

    Vostok 1

  • -----
  • topic starter
  • Posts: 160
  • Joined: 22 Aug 2014
  • Loc: Cairns Australia

Posted 24 September 2018 - 01:06 AM

Bob lives in Cairns, Australia, my years investigating major drug importations tells me he may well have meant opium.... drool5.gif

Sorry guys, my unfortunate spelling ability has again risen to the surface.There is not much opium in Cairns, if any. I should know, I spent the last 12 years of my working life in an agency, which assisted homeless kids, who mainly also had drug & alcohol addictions.  



#9 MarkGregory

MarkGregory

    Viking 1

  • -----
  • Posts: 742
  • Joined: 14 Jun 2012
  • Loc: Advance, North Carolina

Posted 24 September 2018 - 02:10 AM

Interesting comments and observations. I do agree it is very difficult to do scope comparisons. Way too many variables to must be accounted for. I also think that if I was a telescope or ocular manufacturer I would cringe every time I saw a topic heading in which my telescope or eyepiece was going to be compared to some other brand. 



#10 Tropobob

Tropobob

    Vostok 1

  • -----
  • topic starter
  • Posts: 160
  • Joined: 22 Aug 2014
  • Loc: Cairns Australia

Posted 24 September 2018 - 02:55 AM

The important thing is explain what you did and what you found.  If you wrote,

 

"I took my 4 inch apo and my 10 inch F/5 Dob outside, it was 72 degrees inside, 50 outside. The seeing was stable, I immediately began observing Antares, I was able to barely make the split in the 4 inch apo, I could not make the split in the 10 inch Dob, the primary star was very unstable and overly large."

 

Then I don't think anyone would have a problem. But simply stating that quality refractor has twice the resolving power as a mass produced Dob twice it's size without explaining the conditions provides no real information.  Someone like myself who regularly splits double stars with my mass produced 10 inch that are beyond the reach of 5 inch and even larger refractors would be sure to object to your unqualified blanket statement.

 

Jon

Hi Jon, yes you were one of the experienced observers that took issue with my statement. However, it was a statement with an example, as I wrote:-

 

"3. From my experience, a mass produced Newtonian only has about half the resolution of a well-made refractor. For instance, I observed Titan's shadow on Saturn with a Vixen 4" refractor. The 8" Dob that I owned at the time also showed it, but the 6" Dob did not. Actually, it was better though the Vixen than the 8" Dob."

 

If it helps, the 8" was a GSO, F6 Dob. The Vixen was a ED 102mm SS, F6.5.  The Vixen showed the shadow as a darker dot on the surface of Saturn. I also used an 6" F8 GSO Dob and could not see Titan's shadow at all. Furthermore, I used the 80mm Orion F7.5 and I could sometimes see the shadow. It came and went almost from moment to moment. From memory, conditions on that night were 'normal' for a good night at my location and the Dobs had cooled-down for approximately an hour before the observation. I used Radian EPs to view Titan's shadow.   

 

But there is a bigger picture here. I am not insisting that I am right, though I had previously thought so. I am now sadder, but wiser on how we all have different experiences and preferences when using our astro-equipment and more importantly; the difficulties and pitfalls that we face in comparing our astro-gear, thus "Fake Comparisons." Not everything is known, or understood, or as generally applicable, as is often implied.  Some like to test their equipment in near perfect conditions to explore their limits. Fair enough for them, but for me, it is of no relevance when people talk about using 100x per inch, because such magnifications are of almost zero value with my seeing conditions; even though I own a Tak.

 

I am mainly a visual observer and work within the limits of my local conditions, equipment and my weary body. Many observations planned and made by me are on file in the observations section of the Ice in Space Website. I know, what works best for me, however, even this may change over time because of changes to my eyesight etc. 

 

Finally, if anybody is interested in the rather unusual method that I use to observe Antares, please look at my post in the Double-Star forum.  

 

Bob.


  • Erik Bakker likes this

#11 sg6

sg6

    Soyuz

  • *****
  • Posts: 3981
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 24 September 2018 - 03:31 AM

I would say we should not be asking or making comparisons. Simply ask about information and experience on each of the items in question.

 

Guess about 18 months back someone asked about a comparison between one of the AP scopes and one of the TEC items - something like that and both costly. One reply was "Do you expect me go out and purchase two $6000-8000 scopes and make a comparison for you?"

 

The reply was very relevant, comparison is the wrong question, simple information is the real question.

 

Another aspect is what do I like about a scope that you either will agree with or disagree with. Some seem "warmer" or "cooler" then others, color transmission through the system. I like cool (bue/green) views, others may prefer the "warmer" tones.

 

But the "standard" A vs B questions should really be dropped.



#12 terraclarke

terraclarke

    Hubble

  • *****
  • Posts: 18114
  • Joined: 29 May 2012
  • Loc: Third from the Sun

Posted 24 September 2018 - 08:38 AM

I think a lot of these comparisons are truly tainted by the ergonomics factor, tho it is seldom mentioned. Me? I’m big on ergonomic and am happy to state so. I enjoy smaller tellescopes more than bigger scopes because they show me more. How do they do that? Simply because I use them more. To me the best telescopes are the ones I use most and I’m done with big telescopes. That goes for long refractors exceeding 3” of aperture, Newtonians exceeding 6” of aperture and F6, and anything over 8” (my C8).


  • Astrojensen, Nippon and nowhere 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