0.00
...
·
 |
|---|
Hello . I have a problem with collimation or maybe backfocus but i dont think that is the problem . I forgot to keep an image of my defocused star but i Found something on Google to explain my problem . I use a quattro 200p . I did my collimation with the ocal collimator . When the Night came , i checked my collimation on a Bright star and the star was a beautifull Donut but on the left and right it was like on the image ....but worst ! Overall , the result Turned out ok but i want to correct this problem . For backfocus : 2600mm screw to the Filter wheel with 22.5mm spacer for 55mm total .  |
9.31
...
·
·
1
like
|
|---|
How do the actual stars look?
|
9.89
...
·
|
|---|
It's collimation. Period.
|
8.11
...
·
|
|---|
andrea tasselli: +1 |
0.90
...
·
|
|---|
Tony Gondola:andrea tasselli: +1 plus round about 0.6mm more Spacer. With your filter you have 1/3 of the thickness of the filter more (if your filter is 2mm thick. Yout backfocus is now 55.6mm or a little bit more. |
8.34
...
·
|
|---|
You probably did these two initial setup items before collimating - but I had to ask...... 1) entering the unit specific number from the spreadsheet. 2) measuring and entering and activating the initial (x, y) offsets in the software using the periphery/aperture of the focuser tube. You may have seen this thread but the best discussion of OCAL use is not in the OCAL threads but this one for the Tak Epsilon. Most of it should apply. OCAL Epsilon |
|
0.00
...
·
|
|---|
Thanks Everyone . I did enter the serial number in the focus tab for the ocal collimator . Im really off with my collimation . Maybe i did something wrong with the ocal . I Will check again ! Im using the starizona coma reducer . So at F3 , maybe it's harder |
5.02
...
·
·
1
like
|
|---|
If your German is not too rusty - this video by @Daniel Nimmervoll is great. https://youtu.be/KKGFGQ4rplk?feature=share I can also recommend shCol - a better software for collimating with the Ocal. https://sh-astro.de/software/ I believe that it’s developed @Stefan Hohenegger and it’s awesome 👌 |
1.51
...
·
|
|---|
Need more details, but if your slightly defocused centered star looked good, then collimation is likely at least close. If your left and right stars all look way off, then backfocus may be the culprit. Agreed, what did an in-focus image look like? That will tell us a lot! Your back-focus numbers don't seem right, with a 2600 mm screw to the wheel (and I assume that includes the wheel itself). Is that supposed to be 26mm? What camera are you using and what is the chip to front the camera body distance? Assuming the 2600 is supposed to be 26, you're chip to camera front distance would have to be 6.5mm to equal 55mm (26+22.5+6.5). That seems too short. At f3, yes collimation and backfocus will be critical. Please fill in the missing details and give us an in-focus image and we can help more. I have the quattro 250 f4 and the Nexus corrector/reducer on the way, so I'm interested in the outcome here. |
|
0.00
...
·
|
|---|
I think my backfocus is ok . Im using exactly what they Say on the zwo website  |
|
1.51
...
·
|
|---|
Sounds good. It’s just that your original post was confusing. That’ll be what I’m using as well (except I have an OAG instead of a spacer). Do you have an in focus image with it? |
|
9.31
...
·
·
1
like
|
|---|
The appearance of the defocused star's central obstruction on the edge of your image / off axis cannot be used to determine collimation. My epsilon's defocused stars on the edge look like crescent moons when collimated.
|
|
0.00
...
·
|
|---|
Thanks Ashraf  So i did checked my collimation on capella and it was a perfect Donut when outfocus. Like i Said , the outside stars were not good . When focused, it was elongated. So maybe it's tilt ? I just changed today the compression ring . The original one was very bad . I got the Baader clicklock clamp . But i tought it was suppose to be perfect Donuts all over the image for good collimation. Here is 3h in HA . You can see that the big stars are not perfect . Thanks to Russell croman and blurx . I dont have an image of my outfocus stars  |
|
9.89
...
·
·
1
like
|
|---|
That example is worthless. You need to provide an unprocessed auto stretched image, possibly without a NB filter in place to get started. The real deal is judging the Airy disk shape with a high-powered EP which I doubt many do. The only way to judge collimation is at the image center, way off center means nothing in that regard. Tilt, however, requires a full view of the field, in focus.
|
|
1.51
...
·
|
|---|
Need an unprocessed (except for stretching) full resolution image If a slightly defocused star in the center looks good, then collimation is likely OK If collimation is good and the in-focus stars are symmetrically enlongated in the corners, then it's likely spacing If collimation is good and the the in-focus stars are enlongated in one corner/side more than another, then it's likely tilt |
|
0.00
...
·
|
|---|
Here is a 2 min sub . It's not High quality because i cant attach big file here . I did 3 crop of the same sub . top left , center and bottom left    |
|
9.89
...
·
·
1
like
|
|---|
Collimation and then tilt
|
|
1.51
...
·
|
|---|
Top left and bottom left show similar elongation and the center one looks pretty good. Not sure if there's horizontal tilt since we don't have the right side. But if the right corners look similar to the left then likely a small backfocus delta or just the optical limitations of a mass produced scope with a pretty extreme focal ratio. ASTAP aberration inspector would tell you much more than a quick visual look. I've not used it before, but would be a place to start if you want to go there |
