2.71
#... |
|---|
|
Hello everyone, I have been taking pictures with an Orion ED80 with advanced VX mount and DSLR camera. I’m still learning but I’m getting some decent results with Nebulas. I can practice more on it and I see that I improve. However for Galaxies, it’s another story. I photographed M51. took around 3 hours of exposures 5 mins each, 1 hour Darks, then flats and Bias. My image of the galaxy isn’t really that good. Not sure what to improve or whether the telescope is just not great at this. I processed the picture using DSS, pix insight and photoshop. Will adding more exposures work (7-9 hours) should I take longer exposures, I’m just getting started with autoguiding. The 5 mins exposure were unguided. Any tips or critique is appreciated. feel free to also look at my other pictures and provide feedback thanks  |
0.00
#... |
|---|
|
Hi Mustafa, I've got the same DSLR as you for a long time, and used it both in modded and un-modded configuration. It's a good camera and fits perfectly a 80mm refractor like your Orion 80ED, and can deliver decent images of cluster, nebula and galaxy. Taking 300s subs is also a good point, so long there is no big issue with unguided tracking. Heat noise during warm season could make processing harder. Now, my question is about how do you manage your stacked image under DSS. Before switching to Pix for a full preprocessing stage (calibrate, align and stack), I was using DSS to get a quick result and saved it "unmodified" in FITS format, means without any adjustments made directly in DSS : no histogram, nor exposure, gamma and whatever have been modified. The image in DSS looks sometime totally dark...but hopefully it doesn't affect the next stage of processing  I've processed the "raw" FITS later in Pix. How do you manage stacking and export in DSS? All background in your images are very dark, and contrast looks to strong as well, to my humble opinion. If you need more support, feel free to send me your FITS image to discuss more about stacking and processing ;) There is also a BatchPreProcessing tool in Pix, so you could compare your stacked image with the one from DSS. Make sure to check Pure Raw in Pix File Format > RAW to let Pix interprets your CR2 files correctly.Hope it will help a little. Cheers, Christophe |
3.97
#... |
|---|
|
I am still very much learning too and certainly no galaxy processing expert, but I agree that the background looks quite dark. Is there any chance the file(s) are getting reduced to 8-bit somewhere during the process? I would suggest looking over one or two of your good light frames - look at the raw histogram and test stretching them in PixInsight or UFRaw to make sure your raw data looks reasonable. Integration and calibration of additional frames will certainly enhance detail, but not fix any underlying data or process issues, so I would suggest keep working with what you have now. I am also happy to offer to look at one of your light frames and/or integrated FITS if you think you need more help. |
1.20
#... |
|---|
| What ISO were you imaging at? I have the same ED80 scope and shot M51 with a Rebel T6i, see here M51, and then again with an ASI1600MM, see here M51, so the scope is capable of being used for some decent images of the galaxy. I personally don't like DSS for stacking and get better results doing calibration and stacking in Pixinsight. While processing, make sure you do all of your steps in small increments and don't take the background down so much. |
|
2.71
#... |
|---|
Thomas: Thank you Thomas - Your pictures are amazing!!!! I shot at 1600 ISO. I noticed your image is shot at 3200 ISO, I was worried to go up that much given the light pollution. Actually what got me thinking now is whether I should get the ASI1600MM and the ASTRODON filter set. Its probably as expensive as a new telescope but seems worth it |
1.51
#... |
|---|
|
I'd like to second what Thomas said. When processing and stretching do... not... make... zeros! Leave a little space on the left side of the histogram until you get the exposure and contrast of your image correct. Then you can start carefully clipping the background. WRT cameras. I have an uncooled ASI 1600MC and a Canon T6 and I cannot believe how much banding and color noise my Canon has compared to the ASI 1600MC. |
6.89
#... |
|---|
|
Hi Moustafa, I agree the image feels like it became 8 bit at some stage of preprocessing. The background is pitch black, the stars are white, the galaxy is too green and relatively monochromatic... The dynamic range is too low in other words. Your equipment can definitely do better so I suspect some mistake in postprocessing. Would it be possible to share a raw sub with us? Cheers, Dimitris |
|
2.71
#... |
|---|
|
Thank you all for your awesome suggestions. I would love to see what can be done with the raw .tiff image. I uploaded it here: Raw image M51 I tried some of the suggestions. I still cant get the cool colors of the galaxy out. I really have no idea what goes wrong. In photoshop I have to convert the 32 bits to 16 bits to do threshold processing, etc.. Then somewhere along the process I notice that it switches the mode to 8 bits. |
0.00
#... |
|---|
|
here is my fast try in pixinisght , i crop the edges ( here direct link with best resolution ) https://ibb.co/1R53g7H  maybe 5 min exp is too much if you are not guiding your scope , and some lights are not puntual , try with 30 , 60 or seconds with high iso if you are not guiding here is my try of m51 with my 80 ed , with asi178 camera 40 x 180 seconds with gain nearly 0 https://www.astrobin.com/f06oxc/B/?nc=user |
|
6.89
#... |
|---|
|
Hi Mustafa, Thank you for sharing the tif. In summary, I think DSS has killed half of the reds .Checkout the histogram and the statistics:  Clearly, red has been seriously clipped, unlike the other two channels. By the look of it, the entire left side of the red histogram has been clipped. This is very big information loss and cannot really be repaired, also you are bound to have problems since you are essentially trying to process a GB image as RGB (ok technically it is 0.5R-GB but you get the idea) . It is probably not helping that all standard workflows published in tutorials generally assume no channel has been clipped.I suspect the reason for the information loss is DSS's background calibration: if you have too much light pollution, this affects Red which has huge values. DSS will try to bring the background (i.e. most of the pixels) as close to 0 as possible, so it subtracts (or divides by?) a very large number. Think about it: if your signal is 2-3 and light pollution is 50000, it is very easy for a naive algorithm to decide that "background" is 50002 and thus turn all the 2's in your data to 0's. You probably want to fiddle with the Per Channel Background Calibration checkbox (if it was on try off and vice versa), or better use PixiInsight for the integration. Now, with the reservation that the Red channels is missing a lot of data, I was still able to pull out what I think is some extra detail from your file. The result is not very pretty but I only spent 15 minutes on it, it's what I usually do to see "what's there".  The processing workflow was very basic and quick. On PixInsight: - Crop - AutomaticBackgroundExtraction - PhotometricColorCalibration (it was quite tricky getting the settings for Background Neutralization right which was were I started to suspect something was wrong with the data) -MaskeStretch + a little exponentialtransform to lighten the result, this is actually a very quick and dirty way to stretch without burning the stars Then I brought it to Darktable for some very basic denoising, temperature adjustment (would not have been necessary if it wasn't missing so much red) and highlighting of the spiral arms with Equalizer (corse preset - Softlight blending) which I have found to be very similar to PixInsight's MultiscaleHDRTransform. In conclusion, I think you can pull a truly amazing result if you ensure red is not clipped so early in your workflow. Tell DSS to leave background alone (or better: use PixInsight for the integration, or Siril which is free software, both will do a great job) and be amazed. Cheers. Dimitris PS as a secondary remark, I did observe a checkerboard pattern in your background. It is not so significant but if you want to be able to stretch your image as much as possible, I think you should use Bias frames (or if you are using them already, try using more of them). Luckily they are the easiest type of calibration frame to obtain. |
1.43
#... |
|---|
|
Hi, Here is an image taken with equipment similar to yours: https://astrob.in/346655/0/ Regards Ulf |
