A couple of saturday nights ago it was very clear apart from a little smoke haze from a burn off just south of us so I decided to set up both scopes for a little shootout on the Moon , Mars , Alpha Centarui and M42 .
Both scopes were set up about an hour before full dark with the 102mm f10 ( fl 1000mm ) on my wife's Mizar mount all sitting on a sturdy Celestron 2 inch s/s tripod .
The LP 110 f6 ( fl 660mm ) was on my Vixen SP all sitting on the solid Meade HD field tripod .
So as you can see vibrations were not going to add any aberrations at all as both these setup's are super solid .
Eyepieces used were all TV's , Plossls , Panoptics , Radians and Naglers giving magnifications ranging from 200x - 40x in the 102mm and 200x -37x in the 110mm .
2 inch diagonals used were a nice Bintel 99% dielectric Mirror in the 102mm achro and a WO 2 inch 99% dieletric CF in the 110 APO , so any problems here would be invisable to the eye and this is a totally visual shootout .
Here are a few photos of the scopes settling down before the battle's begun .
As we see , eyepieces , diagonals , mounts and seeing wont add to any problems seen to the eye ,,,, it's going to be all about the optics , cool as .
So lets see if 8mm in diameter , 340mm in fl and the use of good quality ED glass makes any real difference ?? lets go ,,,
More to follow and comments are really welcome , as always .
Brian.
Last edited by brian nordstrom; 01-12-2018 at 06:20 AM.
Ok, I will back the LP110, if you were up late enough for Orion to get high, the LP should have shown the 5th star in the trapezium with ease. The 102 achro may have struggled. Mars is much smaller now but showing some detail - my prediction is that this will be readily apparent in the LP but not so in the 102.
Must have been a fun comparing both scopes Brian. And what an impressive collection of eyepieces!
I think both scopes should be capable of showing both E&F components of the trapezium, as I can resolve them quite easily with my 105mm even on humid nights in NQ.
My instinct is they’re pretty much equal. Despite the LP having better glass capable of better correction in angular terms, a focal ratio of f/6 pretty much negates any advantage it may have had for lateral and longitudinal chromatic aberration.
Despite the availability of modern glass types, many refractor designs exploit this to achieve faster f/ratios or wider fields of view - but not image quality better than the basic ¼ wave criterion.
Provided you can accept a focal ratio of f/15 a humble 4” achromat can deliver superb high resolution images that would slay the fast LP.
So.. a draw is my guess.
If both had the same focal ratio ... now that would be a more interesting comparison.
My instinct is they’re pretty much equal. Despite the LP having better glass capable of better correction in angular terms, a focal ratio of f/6 pretty much negates any advantage it may have had for lateral and longitudinal chromatic aberration.
Despite the availability of modern glass types, many refractor designs exploit this to achieve faster f/ratios or wider fields of view - but not image quality better than the basic ¼ wave criterion.
That's why I could never really understand why some folks would be happy to pay in excess of $10k for a 5" F/6.3 refractor, a decade after they put their name on a waiting list.
Brian, over to you
(Cool photo BTW the first one, and the achro is too short - on paper - to be a serious challenger for a halfway decent ED, so if the Saxon wins, that will say more about the LP than the achromat)
Hi all and thanks for the imput , much appreciated .
So here goes with a few moon shots taken at very similar magnifications with both scopes taken at the eyepiece using my google pixel2 phone .
First 2 are with the 102mm f10 achro using a 25mm TV plossl @ 40x and 12mm Radian @ 83x .
Numbers 3 and 4 were the 110mm f6 APO using an 18mm Radian @ 37x and an 8mm Radian @ 82x .
It was not fully dark uet but at these lower powers the difference is small but at the 83x the APO has less CA , but this is very small as the camera shows more than is seen at the eyepiece .
Some of us gotta start somewhere mate !! What part of ongoing don't you understand ?? .
When was the last time you viewed Sirius at 400x with a 102mm f10 achro >> didn't think so , please keep remarks like this snobbery out until its finished can you ? .
Brian.
Quote:
Originally Posted by Wavytone
40X is meaningless and against blue sky even more so.
I was hoping to see a comparison at more like 150-200X and ideally 300X (Dawes limit is X80 per inch of aperture).
A photo of Sirius or Rigel from each at the sharpest focus in enough detail to show diffraction rings would be ideal.
Brian, you're gonna have to do a lot of explaining, I mean what where you thinking - daytime use, 40x. I'm surprised the space-time continuum is still intact...
Please read and understand below comments ,,, man , this is terrible ! Gotta do something while the scopes acclimatise dont we ?
Brian.
Quote:
Originally Posted by N1
Brian, you're gonna have to do a lot of explaining, I mean what where you thinking - daytime use, 40x. I'm surprised the space-time continuum is still intact...
200x -37x in the 110mm .
.
.
The photos would not download in order so the 2 in the last post were the 102mm and these 2 are the 110mm .
