7.19
...
·
 |
|---|
Mike H - Sky View Observatory: If you did flats and darks, they are not done correctly. The gradients are really bad, you have decent information if calibrated right. |
|
7.19
...
·
|
|---|
STF stretch after background extraction and gradient correction in PI.  |
1.20
...
·
|
|---|
I would say this also looks like you have some sag in your imaging train, as the vignetting is not circular.
|
9.89
...
·
|
|---|
They look not properly calibrated at all. Maybe this the main sticking point, the use of WBPP?
|
8.11
...
·
|
|---|
I agree, it doesn't look like flat frames have been properly done or applied. It processes out but might point to a deeper issue.
|
|
7.19
...
·
·
1
like
|
|---|
andrea tasselli: Mikes dark frames were calibrated, there is zero amp glow and I own the 294mc and the glow is terrible unless calibrated and it disappears. His flats were not. I think his light frame info is very nice.. Not very noisy, stars are good, the HA stack had really nice color, just not Flat calibrated at all, worse than the RGB stack. No amp glow in the HA frame either. If Mike shoots some good Flats and Dark flats to go with the Dark frames which are working, he will have a very nice image. Combine the nice corrected HA with the RGB and Mike will have a winner, IMO. The 294mc is kind of difficult compared to other cameras I own. The gradients and Amp glow is terrible but with proper calibration, it all disappears. |
8.91
...
·
|
|---|
OK guys. There were 254 light subs. I let NINA determine the flats. But, how many flats and darks would you recommend on this number lights? Also, my understanding is that I didn't need dark flats. But you say I do? I will certainly include them if it will help. Remember I'm using a 1981 Celestron Orange Tube 8 and a stock Celestron 6.3 reducer. So my image may need to be cropped quite a bit to get rid of some of the vignetting. Am I right? Mike |
|
7.19
...
·
·
1
like
|
|---|
Mike H - Sky View Observatory: Flats can be tricky also with the 294mc. I use a refractor but not sure it makes a difference. I use the white cloth after dawn method, shoot 25 or so, the 294 flat images on the screen looks like the gradients on the non corrected image, not like a simple vignette. I shoot 25 dark flats with the cap on right after at the same time of the Flats. This works well me, I would re-shoot the flats and use dark flats, can't hurt and your light frames have nice data. |
|
8.91
...
·
|
|---|
I’ve been taking the flats with the long dewshield on. I wonder if that could be it? Panel too far away? I have a flats panel. Can’t remember the company off hand but it’s a nice one. I’ll try shooting new ones without the dewshield and see how they look. Mike |
|
8.11
...
·
·
1
like
|
|---|
This might be a good reason to do sky flats because doing them with a panel and dew shield off doesn't replicate how you were imaging. I think using a flat panel with the dew shield on should be better but I think sky flats would be better still.
|
|
1.20
...
·
·
2
likes
|
|---|
Dark flats should be used in lieu of bias frames. I would try that first before reshooting the flats. They just need to be the same exposure, gain and sensor temp.
|
|
9.89
...
·
·
1
like
|
|---|
I’ve been taking the flats with the long dewshield on. I wonder if that could be it? Panel too far away? I have a flats panel. Can’t remember the company off hand but it’s a nice one. I’ll try shooting new ones without the dewshield and see how they look. *Always take flats with whatever you have when imaging and I doubt very much that this is the issue here. More like you didn't include flat-darks and or something got mixed up in WBPP. Best still is to avoid WBPP for once and use ImageCalibration instead and proceed manually till the stacking up point. |
|
8.91
...
·
|
|---|
I always take my flats after each session using the exact setup, filter etc. I have been letting NINA determine the brightness and length of the exposure. I have never taken dark flats, which I assume are the same exposure length as the regular flats. I have read in a number of places that dark flats were not necessary with the 294. However, I will try using them. I'm not sure I follow not using WBPP though. In comparison with other methods, I've always been the happiest with the results from WBPP. I thought it was the most popular method of stacking  However Andrea, I respect your opinion. Can you be more specific about using Image Calibration instead? I'd need to read up on how to accomplish that. Also, I will re-shoot my flats and shoot dark flats. I agree this seems to me to be the culprit as I see the vignetting that still exists after the stack. Maybe I'm not using enough flats. Suggestions as to the number needed? Just found an article that said dark flats are essential for any 294 camera… oops Mike |
|
8.11
...
·
·
1
like
|
|---|
I generally shoot 40 flats and it always seems to work well. I really don't think the number of flat frames you took or how you took them is the issue. I just think your flats calibration just didn't happen.
|
|
8.91
...
·
|
|---|
I'll go back and recheck that Tony. Mike |
4.51
...
·
|
|---|
Are you quite sure this isn't dew forming on the corrector plate? The amount of brightness in the centre just reminded me of what I was seeing with my own SCT (before I modded it with fans).
|
|
8.91
...
·
|
|---|
No dew Jan. I have an aluminum dewshield and a dew heater band around the tube at the back edge of the corrector plate just behind the edge of the dew heater. So far, despite Florida’s typical high humidity, no dew has formed even facing the zenith something I could never achieve with my C14 😒 Mike |
|
4.51
...
·
·
1
like
|
|---|
Mike H - Sky View Observatory: That's a very different climate than what I'm used to for sure  I had severe issues with my C8EHD which looked very similar to this after calibration with flats. And that was also with the dew shield and the dew heater ring on it to no avail. Many of the lights were fine, but some quite far into the session weren't.Hope you figure it out though! For what it's worth I do my flats with a panel and the dew shield on. Not had any issues with it so far. |
|
9.89
...
·
|
|---|
Mike H - Sky View Observatory: Flat-darks are absolutely necessary with the 294MM/MC and bad calibration will ensure if you do not use them to calibrate your flats. I have two of them since a number of years (it's my main workhorse, so to say) and I can swear to that. As for the alternative way to calibrate your light frames, assuming you have the master dark and the master flat is to fill in the form as shown below:  The use Debayer . Just fill in with the files you produced at the step above. The register the light frames, as in the example below:  Then add them together with:  This is just a basic workflow and I am omitting non-essential steps here. The point is to get a fail-proof results and take if from there (if WBPP doesn't work well for some reasons). |
|
8.91
...
·
|
|---|
Andrea, I re-ran WBPP. Carefully examining every entry and detail. The final image came out without the vignetting. Somehow the flats were not being used and I don't know why. However, I will aquire flat darks from now on. I may try to get some tonight if I can duplicate the flats parameters. Your help as been invaluable. My friends, thank you for all your help. I will consider all of the above pointers from now on  Mike Both files are untouched: M106RGB M106Ha |
|
9.89
...
·
·
1
like
|
|---|
Mike H - Sky View Observatory: *While there is an ocean of difference from before and kudos for that there is a persistent issue with the flat-field creating green banding and an overall green-yellowish cast which couldn't get rid of. I ended up speculating whether there is an IR leak somewhere... Yet, the issue with light leak remains and improvement in that area are key to advancement here.  The purple tone of the sky is entirely mine though. |
|
8.91
...
·
|
|---|
Andrea, I did run Photometric Color Calibration because the stacked image comes out green. The Ha comes out red. My understanding this is typical of a OSC image, right? Is this the green you're talking about on the RGB image? I don't think there could be any IR leakage. The scope is working inside an observatory only pointing to the sky. There are no lights in my backyard or my neighbor's. You can see my image train on my public image page. Every piece is solidly threaded together using a filter wheel. In the post right before yours, I uploaded the files right out of WBPP absolutely untouched. Mike |
|
9.89
...
·
·
1
like
|
|---|
Hi Mike, The IR leak I'm referring to is in the image train, specifically the filter(s). Best advice is to get a proper LP filter, given your LP situation. Beside that, I think you have a light leak in your image train that renders calibrating the images difficult (and by light leak here I mean there is something reflecting light back). Can you post an uncalibrated, raw file and your master flat? |
|
8.91
...
·
|
|---|
I have a Optolong L-Pro. But I thought the UV/IR produced better images. I might try the L-Pro next time. Tonight and tomorrow night will be clear and the moon far enough away so I'll get several more hours of M106 with the UV/IR. I will also get more flats and some dark flats. Mike |
However Andrea, I respect your opinion. Can you be more specific about using Image Calibration instead? I'd need to read up on how to accomplish that. 