Where should I post photos for constructive critisism?

[tomb18]

Hi I was wondering where I should post my first astrophotos to get some constructive criticism?  I tried in the gallery but no one responded.  Is this the forum?
Or should I go elsewhere?

[Geoff]

Hi
I was, in fact, about to reply to your post on the Milky Way and Andromeda, but it seems to have been deleted.
The Milky way shot does not have a lot wrong with it,  Stars are tight and there is sharp detail.  Red colour in the nebulae (eg Lagoon and Trifid) is missing, but that's an unfortunate problem with an unmodified DSLR.
The Andromeda pic needs a bit more work.
Try HDRMultiscaleTransform to recover the blown-out centre.
The background has gradients.  Did you use DBE?  I found that a quick once over with ABE even with the stretched image helped a lot.
Hot pixels are best treated with CosmeticCorrection.

As for responses, a quick glance through the Gallery shows that the vast majority of images get very few responses---probably because it takes effort to give a considered response as opposed to the usual anodyne "Great pic" etc that one sees on many forums.
Geoff

[tomb18]

Hi  I will repost here...

Thanks a lot for the comments.  If I look at the milky way shot and zoom in alot, I can see that the sky background looks like "blobs".  Is this normal or an artifact of my processing?  Being new to PixInsight I followed the tutorial for M31 on LightVortexAstronomy almost verbatim for both astrophotos.

For M31, I tried many many time with DBE and was not that successful.  The biggest difficulty was the gradient at the left of the galaxy.  So far it seems that DBE is the tool that takes the most practice, and perhaps I am overdoing it with too many points.
As to the hot pixels, I didn't even know what to look for before lol. Now I know how to identify them and then get rid of them.  Its been about 4 days since I started with PixInsight but compared to what I used in the past this is far far better.

Repost
These two photos are my first attempts at astrophotography and PixInsight. The first is a 40 shot integration of  10 second unguided Nikon D3X (24mpx) photos at ISO 1600 and 14mm focal length.  It was taken from the top of a volcano in Hawaii at 10,000 feet so conditions were pretty good lol.
http://va2fsq.com/wp-content/uploads/final-milkyway-1.png
At first I struggled with the Star Alignment.  The individual subs had tons of noise and there was a lot of lens distortion so that the star positions changed dramatically and non-linearly.  Star Alignment with just some tweaking of the noise parameters fixed it!  This photo seems to have different colors to the right like a gradient but I was unable to fix this.

The second photo was based on 5 5minute shots for blue and 10 5 minute shots for R and G.  The polar alignment was not great and I had a bit of tilt in the image.  My biggest issue here is that I seem to have a lot of hot pixels that for some reaon I could not see when looking for them previously.  Any suggestions?
http://va2fsq.com/wp-content/uploads/M31-web.png

I look forward to any suggestions.
Tom

[oldwexi]

Hi Tom!
Can only underscore where Geoff is pointing to.
Cosmetic Correction needs to be done on the raws to remove the hot Pixels.

With DBE set the points FAR away from bright stars and areas! There should be not a single
Point set near or in M31 because this will create a dark halo around the galaxy.

You get dark bloats when you do a very strong noise reduction.
Using TGVDenoise on a Preview should help to get the right bloatfree noise reduction.
However the best noise reduction is "many images plus long exposures".
I personally do not start with less than 20 Images for stacking, usually 40 to 60.
This gets already smooth Images at the beginning.

By the way, M31 and M42 i would call the most difficult objects to processed by beginners because of their
high dynamic range. But they are always choosen because of their brightness ...

Gerald

P.S.: if you could place your calibrated RAWS of M31 on dropbox i could try to provide the right
Cosmeticparameter and better DBE settings to you.

[tomb18]

Hi Thanks for the offer!  I have uploaded three integrated files, for red, green, and blue.  They are big.  Seems I still need to work out my workflow since these are the only ones I kept. 
However, I have figured out how to see and deal with the hot pixels, that should make a difference.
So that's what you call the blobs, dark bloats...

As to the number of subs for stacking...does this apply to long exposures as well?
The reason I ask is that since the above sets of images were taken, I now have a permanent installation that is very well polar aligned and optimized so I have just started getting much better images.  I will be imaging exclusively in narrow band and my first subs (started last week) are 30 minutes long.  So are you saying I should use 20 of these 30 min subs?  I have only 4 at the moment and initial tests show very good images.
As to the DBE, yes I did have a lot of points very near M31, especially on the left of it.  I would be very interested in how an expert deals with it!
Here is the link. https://www.dropbox.com/sh/w5qfvw6mz87c3n0/AADs-9e_yT3TL1DUWAG5I2IYa?dl=0
Thanks for the help.

[oldwexi]

hi Tom!
Got your images. Could it be that you did already an ABE or DBE to these Drizzle Stacks?
The black halo is on all three images, a halo which usually is created when you set the DBE points wrongly,
Could also be that the flat is not perfect and creates a darker circle in the middle of each image.

So it was a little difficult to get rid of this dark halos.
It would be better to attack these issues when thea are created, either during calibration
or at first processing.

Here the link to my version using DBE, first with division and than with subtraction:
http://www.werbeagentur.org/oldwexi/Image64_clone_small.jpg

The DBE processes with settings will follow tomorrow.

Gerald

[tomb18]

Hi,
No there was no DBE on these images but there was an issue with the flats.
However, this is already better than what I had!
The DBE will be interesting.

One question about the flats...I can acquire them from my STL11000 as already calibrated by the software (it acquires the flat then the dark and automatically reduces them itself) or I can get them separately.  Which is better?
Thanks!

[oldwexi]

Concernign Flats,
If you are able to keep the temperature equal with lights, flats, bias and darks i would recommend
to shoot many bias for creating a master bias. Than shooting the flats and calibrating them with the master bias.
Temperature with flats and lights in my experience is a severe issue with the ST11K. If you shoot the flats
during daytime under higher temperature it could be that your cooling will not get as deep
as during the night with the lights - in this case the flats are more or less unusable for good results.
The STK11 is very temperature sensitive.

Gerald

[oldwexi]

Hi Tom!
Find attached as promised the link to the zipped process containers.
Each Container has the DBEs with their parameter.

http://www.werbeagentur.org/oldwexi/tomb18_DBEs.zip


Gerald

[tomb18]

Hi,
Thanks for this!  It is clear that I was putting way too much points.  I do have a couple of questions.
I noticed that you always seem to have one point in the DBE right on the core of the galaxy.  I thought they shouldn't go there?
I also noticed that there is an additional diagonal line in the blue DBE.  What exactly is that?
This is going to take a while to decipher lol.  A lot is new for me here.
As to flats, are you saying that with the STL11000, that even if the temperature is reported as the same within a few 10ths of a degree this could be an issue?
Thanks very much for the help.
Tom

[oldwexi]

Hi Tom!
Sorry, the single point set in DBE in the center is an artefact left from several tries.
Remove it. But it does not affect really.
Also the diagonal line in blue is the same.
Remove it. So the upper right corner will be better.

The horizontal line at the bottom is needed as it corrects the horizontal strip which
is missing red and partly blue.

As to flats.  No, my experience with ST11K flats is:  we had -25 celsius on the chip during the night and could get
only -15 during the day for flats, this created unusable flats.

Gerald

[tomb18]

Ok.  I make sure that the flat temperature is the same as when I take the darks.  Since I only do photos in winter up here, I have no issues at -30C.
I tried again but this time I used my flats.  I now remember why I didn't use them earlier in this thread...they are obviously unusable.  If you think the gradients are bad here, well you should see these!
An7how thanks for your help.  I'll be sure to keep these around for my next try at M31.
Regards, Tom