Jump to content

sgl_imaging_challenge_2021_annual.thumb.jpg.3fc34f695a81b16210333189a3162ac7.jpg

Recommended Posts

I took 

60s x 90 Lum
120s x 20 RG&B
50 Flats & 50 Darks

I have stacked the L R G and B data in deepsky stacker along with the darks and flats. But I don't seem to be getting much from the data via photoshop.

I am wondering if the data was any good? Bortle 5 sky, good seeing and guiding was excellent last night.

 

Files are located here https://www.dropbox.com/sh/rzkkbbbokj5fqei/AAAR-Jfsyvd3_6gDr3qGCyhwa?dl=0        if you fancy a play and can get anything with it.

 

Kindest regards in advance David

 

 

Edited by Prolifics
  • Like 1
Link to post
Share on other sites
  • Replies 26
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

I did a quick process in Photoshop, there are a couple of slight darkened areas from the use of gradient exterminator which I would need to be more careful about if doing it more accurately, but this

I've got a couple of pointers, hope you don't mind me having a go a this data. First - focus is unfortunately a bit off in luminance (have not yet checked other filters). It's a pity as image cou

Thanks for sharing your data. It looks very good to me.   Here is a quick integration in APP and then tweaked in PS.  

Posted Images

Hi David,

I just had a quick look at the lum with my ImagesPlus processing software, just applied an ArcSinH stretch without calibrating it and you've definitely got the galaxy and a few others in there :thumbright:

1238875930_M101_SGL_Lum32Orig_PS.thumb.jpg.b0b80aeffe217894fb013d9ba5ef5954.jpg

Edited by geoflewis
  • Like 1
Link to post
Share on other sites

Hi Geoff wow you don't messaround :)

Not too hot with Photshop I coverted the files to 16 bit and then applied deep space noise reduction.

Adjusted levels and curves bit by bit and then added a new layer and copied the RGB over and then added the LUm channel next to the background and adjusted to luminosity.

 

Thats about as far as I got.

 

Unfortunately I had some sort of image that I wasn't very happy with so quit photoshop.

 

I really need to go on a course or something for post processing.

 

Regards David

 

  • Like 1
Link to post
Share on other sites
15 minutes ago, Prolifics said:

Not too hot with Photshop

Hi David,

Me neither, I only use PS for final tweaks to my images, so you probably need someone like @ollypenrice @carastro or other expert PS users to advise you. I just wanted to let you know that you have good data in there, so should be able to get a decent final LRGB image I think.

Good luck,

Geof

  • Like 1
Link to post
Share on other sites

Thanks again Geoff for the heads up. there is no way I can afford Pixinsight at the moment and it's probably harder to use than PS :)

I will post a final image if I get one in here.

 

Thanks again David

 

 

 

  • Like 1
Link to post
Share on other sites

I did a quick process in Photoshop, there are a couple of slight darkened areas from the use of gradient exterminator which I would need to be more careful about if doing it more accurately, but this is what I managed to get:

Carole 

PS: I have some tutorials on You Tube on Photoshop processing, there is a link to them on my website.

RGB.png

  • Like 3
Link to post
Share on other sites
27 minutes ago, carastro said:

I did a quick process in Photoshop, there are a couple of slight darkened areas from the use of gradient exterminator which I would need to be more careful about if doing it more accurately, but this is what I managed to get:

Carole 

PS: I have some tutorials on You Tube on Photoshop processing, there is a link to them on my website.

Nice job Carole, I knew that you'd be able to help David with PS much better than me 😉

  • Like 1
  • Haha 1
Link to post
Share on other sites

I've got a couple of pointers, hope you don't mind me having a go a this data.

First - focus is unfortunately a bit off in luminance (have not yet checked other filters). It's a pity as image could have been sharper. If we don't display image at full resolution - we can hide this defocus so it won't be terrible.

Here is what I mean:

Screenshot_1.jpg.35194e66100e0ac87b49d19062a9461f.jpg

See stars being little circles instead of pin point objects? This is due to slight defocus.

Second - you did not take flat darks and your calibration is not ok. This can be dealt in several ways - one is doing synthetic flat and I'm going to do that for this quick processing. Other is to take flat darks - which are darks with exact same settings as flats and use those to calibrate your subs with.

If you don't use flat darks - your flats will under correct and it shows in your sub - there is still some vignetting left as this 10x10 bin and stretch shows:

Screenshot_2.jpg.02a36ff78c03b896ec2326e9573f6bcf.jpg

Now for processing - I'll bin data because your stars are not pin points and there is not much point in going for full resolution. This will boost SNR as well so image won't be as noisy.

Here is what I was able to pull out of luminance:

lum.png.05ed9b986952114479407c51d9c13b2e.png

Will try to add color tomorrow

 

  • Like 3
Link to post
Share on other sites

Hi Red Dwarf

 

Thank you for all the information. I have taken in everything you have said and that all makes perfects sense. I guess that means all my RGB filters must be Par focal and my LUM not matching with them?
Next time I will refocus for each filter that I use.

I will try next outing to re-focus and use the magnifier in apt on the stars to make sure there is no circles and make sure they are solid and round not fuzzy.

I am a bit confused with flat darks are these bias files? I will do a google search and research the flat/darks.

I am really happy you brought these points up. This will make me move further forward in the right direction. I am quite new to Astro photography this is my 5th image. Althought I have been into astronmy for 4 decades :)

So better focus and dark/flats next on the menu for me :)

You have done a great job on the image can hardly wait for the colour version :)

KIndest regards David

 

Edited by Prolifics
Link to post
Share on other sites

Now that I done a bit of research. When I make my flat plans at the end of the session, I can use them again with the cap on the scope to take the dark/flats in a different directory as they will be named the same. Then just add them to deepsky stacker when stacking?

 

Cheers David

Link to post
Share on other sites
3 hours ago, Prolifics said:

Now that I done a bit of research. When I make my flat plans at the end of the session, I can use them again with the cap on the scope to take the dark/flats in a different directory as they will be named the same. Then just add them to deepsky stacker when stacking?

 

Cheers David

Indeed. Flat darks are just darks for flats - same way you take darks for regular lights - you do the same for flats. Same exposure duration, same settings, everything the same as flats except you put scope cover on to block any light.

Link to post
Share on other sites
48 minutes ago, vlaiv said:

Indeed. Flat darks are just darks for flats - same way you take darks for regular lights - you do the same for flats. Same exposure duration, same settings, everything the same as flats except you put scope cover on to block any light.

Great all understood!

 

I have had a look at all my frames and I do not see any out of focused doughnut stars. Maybe deepskystacker was the culprit? The HFD is between 0.50 and 1.37 for the whole starfield.

 

Here is a sample of a frame.

 

Regards David

2020-03-29.png

Link to post
Share on other sites
1 minute ago, Prolifics said:

I have had a look at all my frames and I do not see any out of focused doughnut stars. Maybe deepskystacker was the culprit? The HFD is between 0.50 and 1.37 for the whole starfield.

Did you look at Lum subs? I've just looked lum stack and not color (yet).

It could be that only few of subs are out of focus - it can happen due to temperature shift during the imaging session - tube gets shorter and there is focus drift. On the other hand, it could be due to Lum filter not being parfocal with other filters if you did not refocus on each filter change.

 

  • Like 1
Link to post
Share on other sites
7 minutes ago, Prolifics said:

Yes looked at 5 frames from each filter and nothing. Maybe your correct in temperature change. I will however in future refocus every filter to stop this issue.

David

Depending on the speed of your scope and tube type you might need to refocus on every 1-2C of temperature change as well.

There is a way to approximately calculate this, but it's a bit involved - you need to figure out material of the tube, length of the tube, critical focus zone depending on the scope speed and such and then see how much temperature change will not move you out of critical focus zone.

If you don't want to do calculation, I would say for regular steel / aluminum tubes rough values would be - scope less than F/5 - refocus every ~1C of change, scope F/5 or slower - 2C.

  • Like 1
Link to post
Share on other sites

my scope is F6.5 or F5.13 with the focal reducer.

I have the Pegusus power box so the dew heaters come on and off automatically when the due point gets near the temperature point. That would make a difference if the tube was getting slightly warmer by .5c would expand the tube?

Maybe having the due heaters on all the time would be better when its cold outside?

Regards David

20200211_110933_HDR.jpg

Edited by Prolifics
  • Like 1
Link to post
Share on other sites
11 minutes ago, Prolifics said:

I have the Pegusus power box so the dew heaters come on and off automatically when the due point gets near the temperature point. That would make a difference if the tube was getting slightly warmer by .5c would expand the tube?

Maybe having the due heaters on all the time would be better when its cold outside?

I have no idea - never considered dew heaters and their impact on tube temperature. Maybe best way would be to examine your subs and also if you can - record temperature (if not use forecast data to get rough idea of how temperature changed in the night). If you see that your subs change FWHM/HFR at some point in the night - compare that to temperature and figure out if you need to refocus and under which conditions.

  • Like 1
Link to post
Share on other sites

Temperature changes in the lens can affect focus too  as I found out when I used a somewhat oversized dew heater on my Esprit100. It was autofocussing every 1 deg C but focus drifted way off between runs because the lens was warming up.  Based on this I keep them on all the time just enough to keep dew away so that the whole system temperature moves together.  I'd suggest you do the same and see if this improves things..  

  • Like 3
Link to post
Share on other sites

At least we know they are not par focal all same manufacturer .

 

Blue was taken last and would have been coldest part of the night probably 3c less than when Lum was taken.

 

Order Lum R G B

 

David

Link to post
Share on other sites
2 minutes ago, Prolifics said:

At least we know they are not par focal all same manufacturer .

 

Blue was taken last and would have been coldest part of the night probably 3c less than when Lum was taken.

 

Order Lum R G B

 

David

I don't think this shows that filters are not parfocal - it certainly points to temperature drop. It is also consistent with 1C temp drop shift in focus from critical zone.

Although R should be less defocused than L if temperature was dropping steadily - there could be couple of things that impacted this - dew heaters and the fact that scope is refractor. I know that it is triplet lens and you should not be able to see significant shift in focal position between colors - maybe there was some impact still.

In any case - refocus on filter change and refocus on temperature change of 1C or higher (usually every hour or so if things are normal - in rapid temperature drop nights it could be down to half an hour).

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.