Hi Mike, Lots of interesting questions.... ... I agree 0.95 may be a little high for the astigmatism, but I have not used his scope so I do not know of course....
Hello Mardi, Some nice results with interesting questions! I will try to answer below. ... at ... achromat. ... skewed ... to ... About the image size....
I do not know if it's small enough to effect the accuracy of the test. The software author recommends 100 to 150 pixel image with with 9um pixels (the google...
Based on the JPG images posted of the original intra & extra focal images - I believe that a Strehl of .95 is likely a little to high. Keep in mind that this...
Hello, I have a question re; the size of images used with this program. I stacked two green waveband images from an avi taken with a Neximage at prime focus,...
You may want to try looking at the "cookbook" that John so helpfully put together. It's in the "Files" section of this group and shows exactly the steps...
It is better to not use the Barlow if possible. You need to take images a few mm inside and outside best focus, using same distance on each side of focus. If...
hi to all,i want test my optics whit webcam,i do insert a barlow and defocus a star in intra and extra focal,or i don't insert a barlow and defocus a star?...
You raise some very good points about the "polychromatic" test, which definitely should be put in quotation marks. I think the best that can be said is that...
Using ray-tracing in ZEMAX, I get something like 1/16 wave RMS error (550nm green light) for a spherical mirror with these specs -- pretty good agreement with ...
Hi Philip, It is encouraging that the webcam is in the same range as the CCD camera! This "polychromatic" value is, I think, different from what a lens...
Zoiks! I just processed a NexImage webcam run on the TEC APO180FL using polychromatic data. I took the image with the NexImage attached to an AP MaxBright...
I did another Roddier test, this time of my son's Orion XT4.5 Dob. This is a 114mm f/7.9 dob with a spherical primary mirror. Star testing visually I rated it...
Hi Philip, If you want to post the 10 sec images in the files area, I can try to work on them when I have a minute. There are sometimes tricks to getting the...
I tried a 10 sec run, but the Roddier software will not properly load them no matter how one plays with it. I plan on doing a web cam/CCD test side by side...
Yes, it appears to be a superb lens! One point I noticed -- the brightness range between the bright and dark Fresnel rings is rather small -- maybe only a few...
I posted a short note this morning about a test of my TEC APO180FL. Still hasn't made it to the group as of this afternoon, but I did post the test files in...
I've placed the images of a Roddier test I did of my TEC APO180FL, a 180mm f/7 triplet fluorite refractor by TEC in the folders area of this group. I used a...
... Yes, travel in the focus tube -- inside and outside best focus. I think in terms of making the star image a certain number of pixels in diameter. I would...
Hi, OK - I will give it a try if it ever clears up and isn't too cold here in the Chicago area. When you say 4-5mm defocus, do you mean the travel in the...
You should be fine shooting straight to the detector with 555mm focal length. I've done 600mm scopes straight to the ToUcam with 5.6 micron pixels. Try to...
Thanks for replying. I have a WO 80mm APO doublet, the FPL-53 one, and I have never been able to figure out how to get a decent star test with diffraction ...
I've not yet tried it these cameras. I can see a couple potential issues which should be adjustable or fixable. The first is that you want an image which has...
Hi, Can the tests be done using a digital camera? I have a Canon 20D, which is a DSLR and I have a Canon A540, which is a point and shoot, but can record a...
Unfortunately my old computer with a parallel port died so unless I can get a new hard drive in the damn thing I can't use the SBIG ST-5C! I'll try the tests...
Interesting points. Couple quick comments.... ... it ... I think it is generally reliable, though there are certainly ways it can go wrong. Hopefully we can...
A while ago (~year or more) I did some Roddier testing on my son's Orion XT4.5 dob. I had to go through a bunch of contortions to get it to work, and I have...
Several people have asked me about using the Roddier test for telescope optics. I wrote a short cookbook on it to help answer some of the questions. It can...
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