rojach78

5 hours ago, alacant said:

Hi

The flat frames aren't correcting the field and this is making it more difficult than necessary to process. Perhaps start by cleaning the optical train. I'd pay particular attention to the sensor.

If the uneven field isn't due to light pollution, then I'd say get the flat frames correct and you're good to go. A flat led panel may help you with the lighting for the flat frames. 

There may also be a rogue frame which is misaligned. 

Cheers

Thanks!, love the image. I use Sharpcap and a T shirt for flats with an ipad for the white screen, maybe i need to change this? i'll look into better ways to do my flats

2 hours ago, Snoani said:

It can depend on many factors but what the skies around your location are like is going to be a factor.

Markarian's Chain is very much due south in the early night sky at the moment I would hazard a guess that you have some light pollution in your southern skies.  I may be way off but the fact that you have gradients all around the image may be that your mount flipped as it passed the meridian, meaning that you were initially collecting light pollution on one side of the camera and then the other after the flip.  From my location I have a similar problem to my north.  

There are plugins that you can buy of PS to remove gradients and there is a lot of information out there about people's preferences.  I believe that you can request trial periods for Gradient Xterminator and AstroFlat Pro.  

You can remove gradients in PS manually, which I have done with varying degrees of success.  There is a guide here https://astrobackyard.com/remove-gradients-photoshop/.

 

I also thought it was light pollution but as I started imaging after the flip I couldn't work out why it was all around the image, I will trial one of the gradient removers for ps, looks like the way to go. Thanks. 

19 minutes ago, Snoani said:

To be honest it doesn't look too bad.  

Using your TIF I have given it a very quick stretch and removed the green caused by the colour camera. 

There are some gradients which I have quickly removed using AstroFlat Pro but these don't look terrible.  Probably light pollution in your area.  

Otherwise the data looks ok to me.  

I just don't understand why it hasn't been this bad before? very impressed with your processing though, is there some software i can use in PS to remove the gradient to that level?

3 minutes ago, rickwayne said:

First guess, not having seen the image yet: Did you use flats?

Yes, i even re-did them but it may be that i'm doing them wrong?

5 minutes ago, Cornelius Varley said:

@rojach78 Please upload the image as either a jpg or png file so that it can be displayed in the browser.

Hi, I just did a quick stretch to show the issue

4 minutes ago, Astro Noodles said:

Hi 

What kit were you using? Also, what time were these subs take?

What do you think is wrong with the image?

I was using Skywatcher evostar 80ED, an ASI553MC Pro for imaging and a HEQ5 Mount. The subs were taken from 11pm to 3am this morning. After stretching the image i see blue stars all around the the outside of the image and i can't balance the colour with the centre of the image

Hi all,

I have been imaging recently without issue but i'm very new to this, i went for the Markarians chain last night but it seems to have issues all around the image?, I'm not sure whether it's light pollution or poor Darks/Flats. 

I used a UV/IR Filter. Any help would be great just so i can find out what it is to make sure it doesn't happen again as this was a total of 4 hours imaging! Thanks.

1.TIF

On 21/04/2021 at 16:12, vlaiv said:

Here is step by step guide and result:

1. As a first step, I opened TIF in Gimp and separated channels into mono images with Colors / Components / Decompose (use RGB model and turn off decompose to layers)
2. I then export these as fits since I like working with fits files
3. I fire up ImageJ (or rather Fiji - which is distribution of ImageJ with preloaded plugins) and load fits files
4. First step here is to crop edges off and remove stacking artifacts (Images to stack, rectangle select, right click and make a copy - whole stack. Close old one)
5. Next step is to bin x2 as image is from OSC sensor and it has been interpolated to this resolution anyway. I like working with smaller but sharper stars. (image / transform / bin - X and Y set to 2 and method average)
6. Next step is to remove background. I use my own plugin for this that removes gradients as well, but you can just make rectangular selection on piece of background and run stats on it. Then use Process/Math/Subract and subtract median value of background. Do this for each image (each channel)

Here are two rounds of my plugin on Red channel - left is gradient and right is what plugin considers background / foreground:

7. Fire up stellarium and find a star that has B-V index of 0.32 (or 0.35) to be your reference star. These stars are roughly white in color and will help us to do simple RGB weighing

8. Select said star using elipse tool in ImageJ and do Image / Stacks / Measure stack

9. Now we have relative weights for our channels - or rather inverse of those. You need to divide each channel with corresponding mean value (use Process / Math / Divide on each sub - remember to remove selection first),
10. If we now again measure that star - we should get roughly the same values. Don't worry if you don't get exactly 1:1:1 as we have different selection and noise is going to skew values somewhat

11. Now we have to "equalize" the subs. This is due to Gimp and how it reads subs. We need to make sure that we have the same max and min values on all three color subs for it to match them when it loads them (to apply same 0-1 stretch on them). Undo selection on all three files and measure them. Set the largest of three minima to be minimum on each image - here -0.1096 and set lowest of the three maxima to be maximum on each image - here 57.4

12. Save each fits file

13. Now we open each of them in Gimp back again. Note that Gimp says it will scale fits values - and since we are opening each channel independently - it would apply different scaling had we not made sure each of them has the same min and max value

14. Do channel compose again (opposite of channel decompose we did in first step)
15. Extract luminance information by now decomposing that RGB image in LAB model. Keep L component and discard a and b

16. Stretch and process luminance to your liking. I'll do basic three step stretch:
- step 1: use levels and bring down top slider so that galaxy core starts to show (apply levels)

- step 2: move middle slider so that galaxy is nicely visible (again apply levels)

- step 3: move bottom slider up to the foot of histogram (again apply levels)

17. You can also apply denoising at this stage or whatever you want - but I won't as this is tutorial for color processing.
18. Switch back to original image and apply one round of levels - but making sure you enter value of 2.2 in middle box. This simulates gamma of 2.2 for sRGB color space

19. Copy stretched image and paste it as layer over original. Set layer mode to luminance.

Here is the final result of this operation:

Now, this is approximate method as it uses only single star (and B-V index in Stellarium is not very reliable). For best results - data should be first corrected with derived color matrix and then calibrated against multiple stars of known stellar class - but that is much more complicated procedure.

 

Thanks for this, I am learning a lot Thanks to you, much appreciated!

11 hours ago, alacant said:

Hi

Nice shot.

To my eyes at least, the colour looks ok. But I'm the last person to ask about colour;)

Maybe you could try adding flat frames to the mix and/or try cleaning the imaging train?

Cheers

 

Thanks for this, i think i have corrected the issue thanks to 

10 hours ago, vlaiv said:

I think that flats were taken and applied and did a good job - except for that one dust particle that moved between lights and flats - which is causing that emboss effect.

 

I don't know - that is typical star tools coloring of the image. There are no teal stars out there, nor greenish ones.

11 hours ago, alacant said:

Hi

Nice shot.

To my eyes at least, the colour looks ok. But I'm the last person to ask about colour;)

Maybe you could try adding flat frames to the mix and/or try cleaning the imaging train?

Cheers

 

Thanks for this, i think i have corrected the issue thanks to Vlaiv's "save as" settings. I have applied Flats and Darks but there i a huge dust spot which i am going to clean before i next image!

15 hours ago, Budgie1 said:

I've had a look at all three and the only one I could do anything with is Needle.TIF and that does seem to have colour in it, along with a nice dust mote.  

The Per Channel and reg calibration images are a lot larger (file size) than the other one. When I stack my images as TIF they are mostly 100mb or less, so I don't know why yours are 4x that size.

Rather then giving incorrect or confusing info, I'm going to let Vlaiv advise on this because his knowledge is vastly superior to mine when it comes to these issues.

Once you get the stacking sorted, the data is good and the stars are nice & tight. Below is what I managed to get from Needle.TIF using PixInsight, although a very basic processing of the image.

Thanks for this, i now think i have fixed the issue, i have uploaded a new stack if you want to take a look, if not then thanks for your help, much appreciated!

I have added flats and dark flats but there is a huge dust spot that you are refering too, i will be cleaning before i image again

13 hours ago, vlaiv said:

Something is still not good with stacking.

Two 400mb images have been drizzled for no good reason. You should not turn on drizzling.

Also, when exporting data, don't apply stretch that Deep Sky Stacker makes:

In above image:

- Use 32bit format (that is OK - you did that)

- Prefer Fits file format for linear data (like when posting here on SGL) as fits is standard for astronomical data (it keeps actual values and is easier to diagnose and work with in other software than PhotoShop and Gimp).

- Use compression for TIFF (makes smaller files and nothing is lost - use ZIP) if you want to post TIFF

- Embed but do not apply adjustments

In any case - something is wrong with stacking. What stacking parameters did you use?

Here is histogram of green channel data in Needle.TIF image:

Histogram should not look like that and this implies that something wrong was used for stacking - maybe median stacking instead of sigma clip or similar?

Thanks for this info, using your "Save as" settings has definately re-instated my colours, there does seem to be more green in my images but isn't that normal in these cameras?

NGC4565- 28 x 5 min,101g.TIF

1 hour ago, Budgie1 said:

I've had a look at all three and the only one I could do anything with is Needle.TIF and that does seem to have colour in it, along with a nice dust mote.  

The Per Channel and reg calibration images are a lot larger (file size) than the other one. When I stack my images as TIF they are mostly 100mb or less, so I don't know why yours are 4x that size.

Rather then giving incorrect or confusing info, I'm going to let Vlaiv advise on this because his knowledge is vastly superior to mine when it comes to these issues.

Once you get the stacking sorted, the data is good and the stars are nice & tight. Below is what I managed to get from Needle.TIF using PixInsight, although a very basic processing of the image.

Thanks! That's a lot better than I have achieved in PS, there just doesn't seem to be enough colour in any of my images? Frustrating!!

Needle.tiff is no calibration, per channel.tiff is as.

Needle.TIF Per channel.TIF rgb calibration.TIF

Hi again, i have tried all of the above but i'm still not getting colour in my images? i have attached a dss stack to show the colour channels, shouldn't they be over to the left?

13 minutes ago, Budgie1 said:

You need to debayer in DSS before heading over the PS.

Open DSS, in the Options menu click on the RAW/FITS DDP Settings and a new window opens.

Click the FITS Files tab and put a tick in the "Monochrome 16bit FITS files are RAW files created by a DSLR or a colour CCD camera". Now you need to make sure the bayer pattern for your camera is correct in the drop-down box. I think RGGB is correct for the ASI533MC, but check to make sure.

You can leave the colour adjustments at 1.0000 and the Bayer Matrix Transformation at Bilinear. Now click the Apply button at the bottom of the window and restack your image and it should be colour.  

Thankyou, you just saved me from eternal frustration!

6 minutes ago, vlaiv said:

You need to debayer your images as part of your workflow.

What software are you using for stacking and what is your workflow?

 

Thanks for your speedy response, i'm very new to this so please bear this in mind with my answers. I use DSS and i just put the stacked image straight into Photoshop, i then convert it to 16bit, level the colours, stretch using curves and levels until i'm happy with the image.

Hi All,

I'm new to Astrophotography, i'm just trying to find my feet. Please could someone explain why my colour images coming out in black and white with very little colour, i have the following setup and use Photoshop to stretch the image. Thanks.

HEQ5 Pro

UV/IR Filter

ASI533MC Pro

Evostar 80ED

20 x 5Min Exposures at gain 101 on attached example

5min.tif

2 hours ago, Richie092 said:

Hi.

Have recently started using the 533mc myself, it is a great camera.

All the research I did for my LP level (Bortle 5/6) led me to try without any filters at all. I was very pleased with the results. I have just purchased an IR/UV blocker but not tried it yet.

This is M42 32 x 3 min subs very basic processing.

I am told the IR/UV will cut the star bloat a little but I'm pretty happy with that kind of result as a beginner. What is your light pollution like locally?

Love the picture, that's exactly the type of image i want to be able to get, i'll invest in the uv/ir blocker, i'm in Bortle 5 so i get a descent view, also our street lights go off at 1am so i'll be doing quite a lot of early morning imaging! I'll be interested to see how you get on with the blocker if you can let me know. Thanks.

59 minutes ago, Knight of Clear Skies said:

Can confirm there are no problems imaging the Moon, it's just the Solar imaging that requires special filters and careful handling.

Thanks for that, would there be any filters that you can recommend for imagery? for planets, DSO's? 

Hi all,

I'm looking for some advice as i have only been observing until now, i'm awaiting a delivery of a HEQ5 Pro to get in to imaging, this will be a while as no-one has any stock, i have a 10" Dobsonian now and i have bought an ASI533MC Pro so my question is if i take short exposures of the Moon to star practicing imaging, will i need to use any special filters as i know the ASI is not a regular camera and i don't want to damage the sensor. Thanks.

21 hours ago, Tiny Clanger said:

This site is a few years old, but has some useful insights http://washedoutastronomy.com/washedoutastronomy.com/content/urban-galaxies/index.html

And I've posted a link to the Loughton list several times in the past, one more can't hurt : think of it as a free printable to keep you busy until you can get a copy of the excellent ' turn left at Orion' . You don't give a location, so I have no idea if the fact it has UK season references is a good thing for you or not .

https://las-astro.org.uk/docs/Loughton_List_v2_0.pdf

I'm in the UK, thanks for this 

Thanks all, great advice and lots of helpful advice. Roll on tonight! 😀

Hi all, i recently purchased my first telescope, I have a 10" Dob, I'm in a bortle 5 area, I want to see Dso's ,I have lined up my finder to my scope, i can easily find m42, however after 10+ hours of viewing, the orion nebula is still the only nebula i can find! I have a 2" ep which I use for finding, I also have a light pollution filter attached, I use stellarium for locating nebulas. Any idea what I could be doing wrong? I have been trying to view the jellyfish nebula as it's easy to find but I only see stars? Any help will be much appreciated. Thanks.