M51 a vague resemblance

Ray,

actually very good .. you can always try to adjust colours using e.g. curves.  My own interpretation of the data is in the attachment.

My personal preference would have been for more subs to increase SNR, and bring out more of the "plume". Unfortunately, the data was a bit too noisy to achieve this ... and the flats are a recurring issue with Pier1. While post-processing skills are very important, I think that the outcome of any process will always be limited by the quality of the input data ...

Cheers

Manuel

Great result Ray!

Your image contains quite a few more details than I was able to visualize within the Pier 1 dataset.

CS Martin

Looks nice in any case Ray :)

Thank you Manuel and Martin for the feedback and especially for posting your own renditions. I think it's so very helpful to see what other people can produce from the same data. Certainly regarding the colour mine does lack somewhat in impact and in attempting to extract as much detail as possible, the noise in the image and particularly the plume, was the price I paid.

I wonder if we can all agree to submit a request for a replacement set of luminance data. Due to some, as yet unknown issue, the tracking was not quite accurate enough to prevent oval shaped stars, hence the RGB image. To prevent any possibility of this reoccurring and until the problem is 'tracked down', please forgive the pun, I suggest that we go for 240s Lum subs to activate guiding. Also, any thoughts on more RGB data to assist with reducing the noise and an improvement to our images. 

Martin I use pixinsight as well as Photoshop when processing so maybe the tools in pixinsight are a bit better in extracting details than the software you use. It's certainly not down to my skills in processing.

Cheers and CS, 

Ray 

Hi Ray,

first, I agree with the additional Lum as you suggest (240s), as well as possibly activating guiding.  In addition, I would also ask for a redo of the Ha data, as these subs were really not good at all, yet Ha would be great to have. 40x300s would be good.

Do you agree with the latter?

Cheers

Manuel

Hi,

I also agree to the request of additional frames. M51 really is one of my favorite objects and it´s really worth it ;-)

Also agree to the longer and thus guided exposure times - maybe also add some more guided RGB-frames as well?

Maybe I am still too unexperienced in narrowband imaging, but would Ha really add meaningfull data here? Since we are talking about galaxies I thought they rather send a continuus spectrum rather than dedicated Ha such as nebulas etc?

CS Martin

@Manuel: excellent image btw!

Hi Martin,

I agree to add some more RGB as well.

Yes, in my experience, it will add something, i.e. it will allow to bring out more of the Ha regions in the galaxy. I have increasingly been using dual band filters (L-Extreme from Optolong) on galaxies such as M81, 82, 31, 33 from my backyard (I only have an AZI2600MC Pro), and could see the value in doing so, despite what is often said about this filter. So, I think it does add value as it would allow allow to emphasize the red Ha regions more specifically than with Red only.

Cheers

Manuel

Hi Manuel and Martin,

It's great having this discussion and I'm certain that as a result we'll all end up with great images. This galaxy has always had an appeal to me as after viewing an especially good rendition of it I was inspired to have a go at astrophotography myself. Mind you taking into consideration what it's cost over the years, I might have been better off choosing a less expensive hobby.

I'm currently having another attempt but in the meantime as the question of capturing Ha has arisen I thought I'd post a stack of what 12 Ha subs produces. This is 1 hour and a lot of noise as one would expect, so as Manuel suggested we'd need a few more hours to highlight those Ha regions more clearly. I'd be happy with that so maybe we could submit the Ha as an additional job in order that we get one of the 2 jobs back a bit sooner than we would by combining.

CS

Ray

Japp, great discussion.

Beside I have no veto against the Ha narrowband exposures at all - I still try to understand its value as for this galaxy-object:

- sure there is (significant) Ha signal in the data. Just as Rays image shows. The question is: is it any different from the continuuous spectrum signal (e.g. broadband red)? So will it ADD any SPECIFIC information the red signal does not contain? To me the red and the Ha channel look pretty much the same, but maybe I'm wrong?

- I also fully understand that the dualband-filter on your excellent ASI2600MC Pro camera improoves your images a lot. While you mentioned the "backyard" setup I wonder if most of the narrowband-filter-benefit isn't just based upon the strong decrease of light-pollution you might experience in your backyard? Then of course your images with filter turn out much more detailed than without it... but light pollution ain't a problem at the Roboscopes location, so that light pollution reduction effect won't help us here.

-----------

Basic bottom down question to me is:

Does M51 contain dedicated / specific Ha signals that we can resolve with the given optic / setup?

OR

Would we benefit more if we'd rather use the Ha exposure time for broadband LRGB by collecting way more photons in total helping us to improove SNR?

Hi Martin, 

I originally was going to suggest the same thing but didn't want in any way to influence opinion. I certainly would much prefer as much additional LRGB data instead and be rewarded with a better result in my opinion. Plenty of other galaxies where Ha makes a big contribution, so perhaps we can all agree to not collect anymore from this galaxy which is comparatively very weak.

CS, 

Ray 

Second and final version, for now. This is a LRGB version.

Less detail, but hopefully less noise and more colour.

This time I tried to see if I could use the luminance stack of 80 subs to reduce overall noise. Removing the oval-shaped stars and replacing them with stars from a luminance extraction of the RGB stack, seemed to work in this instance.

OK, let's go for the extra LRGB.

Cheers

Manuel

I've just submitted the job. 

Lum 60 x 240s. I believe this should be enough based upon my findings using 80 of the 120 x 3 minute subs that were acceptable apart from the star shapes

For the RGB I'd found there were less usable red subs so have asked for more of those.

Red 30 x 240s

Green 20 x 240s

Blue 20 x 240s.

If you want any changes to these numbers please let me know, as it's very easy to cancel and resubmit a job..

Manuel if you want to please submit a job for extra Ha, maybe 40 x 300s. As a separate job these may well get collected first being that Ha is less affected by the moon. :)

Cheers and CS

Ray

Thanks for submitting the job! I will submit the Ha job later today.

CS
Manuel

my version