Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2703
|
|
That my friend, is the right attitude. Every telescope has its strengths and weaknesses. People should spend more time using their scopes than nit-picking them.
Even Achromats can come surprisingly close to APOs in their ability to display find detail. Once color correction gets to the level of modern ED scopes, there is very little imporvement in visual performance even if you can attain PERFECT color correction, and imagers can take out violet fringing with software. So to me, it all becomes rather acedemic.
I had an 80ED Celestron and is was an INCREDIBLY good performer. Oh, sure, I could see a tiny violet fringe on Sirius, but for 99.9% of the objects I viewed, the level of color correction was esentially perfect.
Oh.. I didn't view any of them out of focus.. Maybe that helped...
Enjoy your 80ED. There are lots of people out there that spend a lot more money on their 80mm APOs that won't see anything that you can't see....
Regards.
--------------------
Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
|
half meter
Postmaster
Reged: 05/05/04
Posts: 12829
Loc: Great Lakes
|
|
Volker and Wolfgang, thanks for the detailed responses.
So it seems that no weighting occurs as the calculation is a simple arithmetic mean of green-red and green-blue. But since the blue and red lines chosen are not at the extreme ends of the visual spectrum, the final average will have value for both visual observing and imaging.
--------------------
Gary
Collins I3 (Thin Film) Image Intensifying Eyepiece
Coronado Maxscope Double Stacked 90mm <0.5A w/BF30
6" f/8 TMB/A&M Carbon Fiber APO; f/5 with 4" Borg ED Field Flattener/Reducer
8" Starmaster Versa V8/Zambuto Mirror/ServoCat Jr dob
30" Obsession/OMI Mirror/ServoCat/Argo Navis dob
|
amirab
super member
Reged: 03/03/04
Posts: 195
Loc: Israel
|
|
"This brings up another question: Should I tell my wife before I buy, or should I buy first and take the beating afterwards?"
Now, this is a tough question . Like everything else in our hobby it depends on the domestic "atmosphere" conditions ......
--------------------
Amir
AT-111 APO TRIPLET
TV Genesis- SDF
MEADE LX90 8' UHTC
MEADE STARFINDER 12.5' DOB.
APOGEE SA-88-RA BINO.
OBERWERK ULTRA 15X70
|
Tom Trusock
Reged: 02/26/02
Posts: 29971
|
|
Quote:
Today would you consider a scope with a single-speed R&P to be a premium scope?
You mean like Tak or Tele Vue?
Uh - yeah.
To me, PREMIUM scopes are largely about the QC.
YMMV (but FWIW, that's what true premium scopes are trying to avoid...)
--------------------
Hyperbole - undoubtedly the best thing ever.
|
Mark Costello
Pooh-Bah
Reged: 03/08/05
Posts: 1311
Loc: Matthews, NC, USA
|
|
Quote:
That my friend, is the right attitude. Every telescope has its strengths and weaknesses. People should spend more time using their scopes than nit-picking them.
Even Achromats can come surprisingly close to APOs in their ability to display find detail. Once color correction gets to the level of modern ED scopes, there is very little imporvement in visual performance even if you can attain PERFECT color correction, and imagers can take out violet fringing with software. So to me, it all becomes rather acedemic.
I had an 80ED Celestron and is was an INCREDIBLY good performer. Oh, sure, I could see a tiny violet fringe on Sirius, but for 99.9% of the objects I viewed, the level of color correction was esentially perfect.
Oh.. I didn't view any of them out of focus.. Maybe that helped...
Enjoy your 80ED. There are lots of people out there that spend a lot more money on their 80mm APOs that won't see anything that you can't see....
Regards.
I've never had the pleasure of looking through an apo, so I can't make comparisons with my 4" F6.5 achro. I can say that I'm VERY happy with its performance on just about everything I've observed with it. I've made sketches of lunar features, Mars, Jupiter, Saturn, and a few DSOs (M11, M13, and M5) at 220X. On the planets and in particular Jupiter and Saturn, I see a bit of deep purple haze and the images are a bit yellow compared to photos I've seen from apos or reflectors, but the refractor still shows me all sorts of swirls on Jupiter and banding and ring divisions in Saturn. A couple of years ago, it showed me Jupiter's Great Red Spot and shiner around it.
I'm in NO hurry to replace it with any kind of ED refractor or apo. I'm more interested at this time in getting a larger reflector (most likely a Cassegrain type) to go along with it ... that is, when I have the big pot of discretionary spending money for it.
Best regards,
--------------------
Mark Costello
Matthews, NC
Wife, son, three daughters, two dogs, ... and
Souped up & Tuned Burgess 102mm refractor on a CG5 & Celestron 7X35's
|
Eric F
member
Reged: 11/02/06
Posts: 31
|
|
Quote:
This brings up another question: Should I tell my wife before I buy, or should I buy first and take the beating afterwards?
It's easier to ask for forgiveness than permission. 
|
Rohr
member
Reged: 01/13/07
Posts: 13
|
|
Dear Volker,
blue and red are the ends of our visible spectrum, yellow is near green and much clother to green in most of the lenses. The FH lenses there is green and yellow very closed together and blue and red behind them. At apochromatic lenses sometimes blue has the shortest focus and red the last one, but there is no lens with a big distance of green and yellow. Look my algorhytmus here:
http://rohr.aiax.de/@RC-IndexNumber.jpg
If you see the results of the following HCQ, there is no difference of green and yellow.
http://rohr.aiax.de/@RC-IndexNumberHCQ.jpg
By the way, a lot of lenses are sold as high quality "apochromatic"(???) lenses. Therefore I remembered the way Dieter Lichtenknecker calculated the rest cromatic number of his FH lenses.
look also here: http://www.astro-foren.de/showthread.php?t=6084
Historische Entwicklung und Merkmale eines Apochromaten
RC-Wert bei Lichtenknecker; Algorhythmus zur Berechnung, A... , B... , C... , FH150/2300
Farblängsfehler messen mit dem Bath-Interferometer
Index-Vergleichstabelle; P1, P2, P3
Sekundäres Spektrum an Beispielen: Übersicht, Beispiel-Tafeln
Berechnung der Schärfen-Tiefe
Glasweg-Diskussion am Beispiel Zenith-Prisma und Baader Großfeld Bino
Abbildungsfehler - Wikipedia
--------------------
clear sky Wolfgang Rohr
ICQ-Nr.200281996
http://www.astro-foren.de
email: wolfgang.rohr@t-online.de
Edited by Rohr (04/25/08 12:18 PM)
|
Planetarius
member
Reged: 04/17/08
Posts: 23
Loc: Karlsruhe, Germany
|
|
Thanks Wolfgang, this explains it for me. 
For the last sketch in the index alogrhythmus I need to take some quiet minutes to comprehend. The link to the RC-indexnumberHCQ.jpg does not work, but I also believe you without seeing the picture.
Thanks again for shining some light on this topic.
Volker
|
ngc6475
Fearless Spectator
Reged: 03/02/02
Posts: 4999
Loc: 38°21'N 120°55'W
|
|
Indeed, thank you Wolfgang for your time and patience posting link to, and explaining, your reports! It's good to have you here on Cloudy Nights!
And thanks to you, Volker, for raising the question in the first place! 
--------------------
Walter
"There are nights when the wolves are silent and only the moon howls."
-George Carlin
|
HAC
professor emeritus
Reged: 04/07/05
Posts: 534
|
|
Thank you sir for posting here. And thank you so much for having a website that actually does optical testing to determine the various characteristics of an optic. Quite frankly, this type of assessment is long over due and I wish there were more sites one could go to that provided empirical data.
So thank you again,
john
--------------------
Bring Back The AP Waiting List Thread and Let Freedom Ring
|
John Wall III
member
Reged: 03/07/08
Posts: 73
Loc: Angleton, Texas USA
|
|
Mr. Rohr,
Thank You for the excellent reference, and all the hard work. I will study your information as I can.
Volker,
Sorry, yes, I saw the link. I'll have a look for you when the sky clears.
--------------------
Wishing you Clear Skies,
JVWIII
http://www.pbase.com/lightstuff
|
Rohr
member
Reged: 01/13/07
Posts: 13
|
|
Dear John and everybody,
Jim informed me about this thread at Cloudy Nights. So I tried to give you an answer. If there is another one, and if I can give an informative answer, please tell me that.
Use the contact dates below. (Now I hope the link of my last post is working)
--------------------
clear sky Wolfgang Rohr
ICQ-Nr.200281996
http://www.astro-foren.de
email: wolfgang.rohr@t-online.de
Edited by Rohr (04/25/08 12:44 PM)
|
Planetarius
member
Reged: 04/17/08
Posts: 23
Loc: Karlsruhe, Germany
|
|
Also from my side: thanks to everyone for your valuable contribution to this discussion.
John, I am looking forward to your report. If somebody had told me a week ago that I´d be checking the weather forecast for Angleton, Texas these days ...
Amir, does it make sense to check for the Israel weather as well? 
Thanks,
Volker
|
John Wall III
member
Reged: 03/07/08
Posts: 73
Loc: Angleton, Texas USA
|
|
Volker,
After studying Mr. Rohr's work, I see the value of the information contained in the star set I took the same night as the other not long ago. After zooming in a bit as you stated you needed to, I can see my collimation is off a little, and I have a small pinch on one side. I confirmed that the collimation is off a little by checking it with a collimating eyepiece. Question; If you zoom in to the small stars you can see the color difference, is this from the collimation off a little, or the small pinch, or just my bad photography? Other than those small things, to my untrained eye anyway, I think it seems a little better than the TV102 that is displayed at the link you provided in some ways. My Star Set is displayed in full size at this link.
http://www.pbase.com/lightstuff/testing&page=2
--------------------
Wishing you Clear Skies,
JVWIII
http://www.pbase.com/lightstuff
|
scope dog
Pooh-Bah
Reged: 07/26/04
Posts: 1323
Loc: USA
|
|
Hi Wolf,
Thanks, I would like to say thank you for again sharing your knowledge. Also thank you for providing test of telescopes as you test them openly, this is truly refreshing.
--------------------
Jim
Santel MK91
Astreya-SAPO
|
Planetarius
member
Reged: 04/17/08
Posts: 23
Loc: Karlsruhe, Germany
|
|
John,
are the sets the same picture, just zoomed in electronically after you took them? If by the small stars you mean set1, 2, 5 and 6, I t h i n k I can see red in the upper left and blue in the lower right of the circumference. And it looks to be the same intra- and extrafocal. Therefore I don´t think it comes from the color focus differences but from some other effect, but no idea which (I am not an experienced startest analyser). BUT: having the set 4 and 8 available, I would completely disregard the small ones, because on 4 and 8 there is much more to see. At a first glance, I would call them free of color fringes, rather like TMB 115 than TV 102. Intensively searching for color, I think there is a very very very slight red again on upper left and the same intensity blue on the lower right. But to sort this result into the correct drawer, it´s important to know which magnification we are looking at here. Also, I do not know to which extent electronic zooming afterwards yields the same pictures like choosing a high mag. during the test (which can be achieved visually by different eyepiece usage, but for taking pictures you probably only can use barlows to vary mag, right?). And again, it´s the same intra- and extrafocal. My guess would be it comes from the collimation being off.
Regarding the shape: In my view, this is very close to a perfect circle. However, you are right, there is a deviation at the bottom part of it. After viewing 4 and 8 for easy 15 min in the meantime, I come to the conclusion: in #4 (intrafocal) it´s an inward dent at 4 o´clock. A minute ago, I thought it´s an outward dent from 6 to 8 o´clock. Extrafocal (#8), it looks like an inward dent at 7 o´clock, maybe a bit outward at 6 o´clock.
Wolfgang, I know you consider startest images as a rough guide only, but this is all we have for the moment. Do you think it is possible to draw a conclusion out of John´s pictures regarding what is "wrong" (if at all this is worth being called wrong)?
Volker
|
HAC
professor emeritus
Reged: 04/07/05
Posts: 534
|
|
Given the fact that it is absent in some images, I would say it is tube currents.
--------------------
Bring Back The AP Waiting List Thread and Let Freedom Ring
|
John Wall III
member
Reged: 03/07/08
Posts: 73
Loc: Angleton, Texas USA
|
|
Volker,
I agree, the most racked out, or in, are the important pictures. The first two on each side of focus were suffering from atmospheric effect so I deleted them. I also thought the 4 remaining pictures closer to the TMB. The only issue I guess is the dent, if it's an issue at all. Collimation is very simple job on this scope, and it's only off just a touch anyway.
--------------------
Wishing you Clear Skies,
JVWIII
http://www.pbase.com/lightstuff
|
John Wall III
member
Reged: 03/07/08
Posts: 73
Loc: Angleton, Texas USA
|
|
Here are some photo's showing the collimation screws, the dot in the middle of the lighted circle showing alignment after adjustment, and the driver set used for this adjustment. There is a haze outside, and the atmosphere is unsteady because a front just came through so no star test. I found the lens screwed down flat. The three long adjusting screws were all loose and all the way out.
http://www.pbase.com/lightstuff/testing&page=2
--------------------
Wishing you Clear Skies,
JVWIII
http://www.pbase.com/lightstuff
|
John Wall III
member
Reged: 03/07/08
Posts: 73
Loc: Angleton, Texas USA
|
|
Quote:
John,
are the sets the same picture, just zoomed in electronically after you took them?
Volker,
The last photo's were the second set I took that first night, I hand picked the first two that I presented out of both sets to give a good impression. So two of them possibly could have been the same, but I didn't zoom in electronically to present them. What I meant by zooming in was in Windows using the scroll feature. It really gives a good view.
Seeing was good last night so I pulled my newly collimated AT111 out for a test. I tried to be a little more scientific about it this time in that I used the computer to capture and file the star images. Just by comparing the Canon XTi Camera with an eye piece, I figure it to be about the same as a 20mm EP. So I figure the lo power pictures to be about 80X. For the last 4 hi power pix, I used a projection camera adapter with a 12.5mm ortho EP on my Canon XTi Camera. It's a very hi magnification, but I'm not sure how to figure the exact amount because it is a variable adapter. Does anyone have any Idea what it would be with it set at about 1/3? I was able to crank in there pretty good this time, what do you think?
http://www.pbase.com/lightstuff/testing&page=3
--------------------
Wishing you Clear Skies,
JVWIII
http://www.pbase.com/lightstuff
|
|
10 registered and 13 anonymous users are browsing this forum.
Moderator: desertstars, Remy Bosio, Jason B, LLEEGE
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 3273
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
[Re: 
Edit
Reply
Quote
