Quote:

---

These are my attemps using Pixinsight. Hope you like them. It was very nice to process this galaxies, because they don't rise over the horizon here and i have never seen them.

The M101 image was harder to process than the M51 one, was it near the horizon or affected by severe light pollution?

---

Post Extras:

Quote:

---

Great processing SGT500.

What did you use to smooth the sky background so much? I tried GradientXterminator and Noise Ninja but couldn't get the strange large-scale halos or rings out of it. IMO those was a worse problem than the horizontal banding, caused by vignetting?

Tom, maybe you should try dithering between sub-exposures to get rid of the banding?

---

Yes very nice work on that SGT500! I saw that and thought "that can't be mine!" Heh!

I have been using this method to try and smooth out my backgrounds - http://www.astrophotoinsight.com/node/528
Seems to work well, but have to be careful not to go too far or the sky looks kind of fake.

I haven't tried dithering, dumb question, but does that happen when imaging or later when processing?

Thank again for trying my data guys, it's always fun to see what others can do with things.

Tom

Post Extras:

Quote:

---

This is my version of M63. I tried to recover the color of the stars and to remove the gradient of the image, using Pixinsight and a lot of luminance masks =). I hope you like it. It's very nice to play with this great data under my currently-clouded skies.

---

Here is more to try during your cloudy skies.
This one is the raw stacked image of NGC4565. It's 11 images at 5 minute each, ISO 800 f/6.3 with the Canon 350d (pretty much the same thing that I always do!)
At least with getting other opinions on my data, I know that I do have some good images, just need to learn a lot about what to do after gathering the photons. Any hints (even small!) are appreciated.


UPDATE: I forgot the link to the raw data on this one I just noticed. Have at it for another challenge, practice, and hopefully advice for me. Again this is reduced to 1500 x 999.

http://www.eastsideastro.org/temp/rawImages/ngx4565x11-smaller.tif


Here is what I did on this one.


Edited by Tom Gwilym (05/24/09 11:45 PM)

Post Extras:

Quote:

---

I haven't tried dithering, dumb question, but does that happen when imaging or later when processing?

---

Hey again Tom. Dithering is done during imaging, but it's not very hard and can greatly reduce banding. Basically, you just shift the telescope (and guidestar if using an autoguider) a little bit in the frame so that the image falls on different pixels of the camera. Then when you stack the frames, the pattern noise tends to get averaged out. I actually did it by accident when shooting Markarian's Chain, because my mount drifted a few arc minutes over the exposure session (due to mediocre polar alignment), but this actually helped me out! You can see the difference in the vertical banding from the my other image of Bodes' Nebula. Otherwise the two are very similar in processing and crop size (although Markarians' Chain had much more integration time):







--------------------
Sky-Watcher Equinox 80ED
EQ6 Pro with EQMOD
Canon 450D
Sky-Watcher 10" f/4.7 Dob

Post Extras:

Quote:

---

Hey again Tom. Dithering is done during imaging, but it's not very hard and can greatly reduce banding. Basically, you just shift the telescope (and guidestar if using an autoguider) a little bit in the frame so that the image falls on different pixels of the camera. Then when you stack the frames, the pattern noise tends to get averaged out. I actually did it by accident when shooting Markarian's Chain, because my mount drifted a few arc minutes over the exposure session (due to mediocre polar alignment), but this actually helped me out! You can see the difference in the vertical banding from the my other image of Bodes' Nebula. Otherwise the two are very similar in processing and crop size (although Markarians' Chain had much more integration time):

---

That makes sense. Probably good for the hot pixels too.
I used to have "auto-dithering" before I did some more adjustment on my drift alignment and got my mount working better. But of course the thing would shift in the middle of a 5 minute exposure. Ha!

Post Extras:

Quote:

---

Great Job Tom!
That looks much better. I dont see any banding noise. That looks lke a really nice ring.

And i gave your Ngc 4565 Data a go. heres the result

---

Wow, very nice work again on my 4565 image. You were even able to pull out some sharper detail on the dust lanes. I guess you do something a little different on the background since the other little galaxy on the lower right has almost disappeared? Of course 4565 is the main focus of this image. Then again this was just practice data for you!

Yes, I did try the dithering trick on the ring. Every few frames I would scoot the scope over, then lock back on to a guide star and expose again. That really did help my noise level. I'll add that to my imaging procedures now and see how that works out.
I really like how you can bring out the details in the object and not noise up the boundary between the sky and the object, that's something I need to work on.
Will you publish your tricks when you get the procedures all down?

Thanks!

Tom

Post Extras:

Quote:

---

Hey Tom I took a shot at your 101, my first reccomendation would be to shoot around 30 flats and double check to see that your calibration settings are correct the dust mote in the upper left should have been removed, also I battled a lot of vignetting but here is what I came up with....overall nice data in the galaxy, I would go back through and check the calibration settings and see if you can get the flats working
this is simple curves stretching and levels adjustments with lots of GradientXterminator, some noise ninja both applied to the background only, as well as some layering techniques and saturation masks.

---

Post Extras: