Mark; Are you absolutely sure that it was the OTA? I have seen both diagonals and eyepieces cause astigmatism in scopes. I hope that you checked it w/o a...
... The Petzval is now described as an achromat -- did they change the website? I have seen some commerical "Petzval refractors" that consist of 2 regular...
Hello, This email message is a notification to let you know that a file has been uploaded to the Files area of the Refractors group. File :...
Refractors@yahoogroup...
Aug 4, 2005 9:43 pm
14799
In case you all have not seen this elsewhere, I posted an image taken by Stefan Seip of the Trifid nebula. It shows that little spike coming out of the bulging...
I wish the term semi-ED would just dry up and blow away. Bottom line either ED glass is used or it isn't. With out ED glass it ain't an ED anything there is no...
David; Remember that the sales departments of many companies, including those selling optics, have several problems: The sales staff is not technically...
... Congratulations, Ron!!! Beautiful Telescope! Interesting lens cap. Thanks for the pics. All the best, Rich...
rnapo
rnapo@...
Aug 6, 2005 2:54 am
14804
Wake up , Ron, you're just dreaming. tomorrow Al comes and takes back his telescope. Well, congratulations... i think this scope is in good hands with you. 5"...
Congratulations Ron! But isn't that thing supposed to be much longer? ;) BTW. You have just raised the artistic, imaginative and liberal use of smilies to a...
There is now a more formal review of the Tele Vue Focusmate dual-speed focuser adapter on Cloudy Nights ;-). http://www.cloudynights.com/item.php?item_id=1171 ...
... Gibraltar mount. I like the simplicity of use, and want to observe the planets and the moon. Because I observe from a suburban back yard, I think the APO...
Hello there Steve, Glad to see you chime in and your opinions and responses are much valuable! I recalled at RTMC 2004, I went around looking at various 8",...
not a "premium" apo or anything, but a decent respectable long tube achromat, on an alt az mount. The OTA is the best part of course, as many would probably...
... <astronut1001@y...> wrote: For anyone who wants to learn A LOT about refractor designs and performance here is the link to a downloadable book about them....
There are some 8" achromats available on e-bay and this particular manufacturer will make lenses down to f/6 ratio, has anyone had experience with "great eye"...
Unless the focal ratio is F12 or longer you will have serious chromatic aberration. There is no way around this problem with achromats. Of course, it will be a...
Roland; I agree with your assessment as I have a Skywatcher 150mm F5 which shows lots of color fringing at medium to high powers. It was purchased primarily...
Yes, it's true you can kill the secondary spectrum with fringe killer filters, but what you are essentially doing is filtering out useful light. You can do the...
Here's a website I found with Ronchi/Null test photos for refractors. The main site is here: http://homepage3.nifty.com/cz_telesco/ The refractor tests are...
... spectrum and then focusing critically on the detail in that color. All other colors will be missing and will not rob the contrast of that feature in that...
... Although it would seem that using 3 filters would get around the problem of chromatic aberration, there is still going to be a defocus within each...
Ed; I am really surprised by the errors shown by some very well respected manufacturers lenses. Some of the Takahashi scopes appear to show obvious edge...
Keep some perspective on these images. While the Ronchi test shows defects on the order of 1/2 to 1/4 wave depending on the F-ratio, the knife edge images will...
I appreciate your comments, Roland. This sort of information needs to be qualified and any judgements tempered by more experience than I can offer. Ed T....
