Hey, folks! I made a sight tube following Phil Harrington's plans, and I'm not sure how short to make it. I have an f/8 SkyQuest XT6, and I can't see the edges...
Length of tube should be (tube ID) x (scope f-ratio); (8 in your case). Regards, Jim Fly CATSEYE Collimation ... From: Kevin Palm To: atm_free@yahoogroups.com ...
... sure how short to make it. I have an f/8 SkyQuest XT6, and I can't see the edges of the secondary when I insert the tube, so I know it's too long. Isn't...
Hello, my name is Leandro and I'm new to this group. I'm brazilian (South America) and often get some ATM things to keep me busy on rainy weekends :-) In...
Hello Leandro, Welcome to the group! I cannot give any input regarding the 16" x 2" thick blank. I have made a 16" x 1" f/5 from plate glass (ship porthole)...
Hello, I know of a young man who made a 6" mirror from 8mm thick ordinary glass. Ali ... From: Polk, Tom To: atm_free@yahoogroups.com Sent: Thursday, October...
Hello, I know of a young man who made a 6" mirror from 8mm thick ordinary glass. Ali ... From: Polk, Tom To: atm_free@yahoogroups.com Sent: Thursday, October...
Hello Tom, hello Ali, thankyou for the input. so I will check for stress before using a polarized glass. The question on thermal seems important. I will think...
I have come across references about glass flowing from time to time. Usually relating to church windows in the UK. Seems they get thicker at the bottom over a...
I've heard that in the southern hemisphere it is the other way around. they get thicker at the top. Jerry ... From: a.johnw I have come across references about...
not true. Original window glass was made by spinning a lump of molten glass on the end of a pole. The resulting disk was thinner at the edge than in the...
Jerry, Don't give credence to the myth of glass flowing re church windows. Restorers say the thick part is sometimes on the top or the sides. The glass was...
when they put the colored glass in those church windows they use to turn them over after 98 years (2x7x7)so the devil could not look in 1 cent peter ... The ...
... On past june I have finished my first homemade optics, a 6" parabolic f/D 4.5 for an RFT I have in mind. I guess the center is a little bit spheric but I...
Yes, there is a kink in the lines at about the 65% zone. At this F ratio a defect that visible in the ronchi lines usually means you're out of the envelope. Do...
thankyou Mel, I will try some eyepieces to see what happens. I've been using your diagonal calculator and seems that if I use my 2" 30mm 80º eyepiece in this...
Hi Tony, I did not have a zonal test still. A friend of mine who is a very experienced ATM will test the mirror for me, calculate PV, RMS, Sthrel, etc. I will...
Hi everyone, the DK. Cass. primary I have has a central hole off center. Can someone educate me where is the optical center is? Should I take the center hub as...
I have a 16 inch F5.5 mirror in progress that is very thin. I started this project when I was not ready and have created an astigmatic mirror. I have since...
... Hi Mick, Had to say for sure about the core. If the mirror is spherical there's no optical center. I'd suggest to shim your hub to fit the mirror and align...
Dave, ... Here's a simulation: http://tech.groups.yahoo.com/group/atm_free/files/Steve%20Koehler/astig_tilt.png The left pane shows a wavefront map. The high...
... started ... Hi Dave, With astigmatism the "Devil's in the details". You may spend even more time trying to polish it out rather than first starting your...
... Dave, I should have realized that if you're polishing, the mirror is close to spherical. Here's an update of the simulation using a sphere. The top row...
... Thanks Steve, That is very helpful. It does answer my question as was the way I interpreted the Ronchi. I should have stated inside COC. What are you...
Dave, ... My own code in R, based a long time ago on some stuff written by Mike Peck. It only has a command-line interface, but that makes it nice for...
... Amen to that. I have done alot of research since the early days and I think I broke just about every rule. ... I definitely agree starting with no astig...
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