Iris Nebula 105 minutes LRGB

[tooth_dr]

No chance of a long session due to weather forecast, so did a vertical plan and ran off 300s subs of L , R , B, G.

In the end I had 105 minutes of subs in total - 6 lum, 5 red, 5 green, 5 blue.

I didnt have any flats with the ATIK.  Manually flattening them has resulted in the green channel being brighter in the middle.  I'll get more flats for next time.

 

Here is the effort:

 

[Adreneline]

An amazing result adam for such a limited time. I really like the brown dusty regions and the star colours.

Adrian

[tooth_dr]

7 minutes ago, Adreneline said:

An amazing result adam for such a limited time. I really like the brown dusty regions and the star colours.

Adrian

Thanks Adrian. I’m still struggling to get smaller stars. The ED80 was giving me nicer stars. I don’t know what to try differently, as focal length and guiding accuracy hasn’t changed.  Maybe I’m over exposing at 300s

Edited November 27, 2019 by tooth_dr

[don4l]

1 hour ago, tooth_dr said:

Thanks Adrian. I’m still struggling to get smaller stars. The ED80 was giving me nicer stars. I don’t know what to try differently, as focal length and guiding accuracy hasn’t changed.  Maybe I’m over exposing at 300s

This is just a thought...

I recently changed my camera from one with 9um pixels to 6um.  The problem that I've had with bloated/fuzzy stars disappeared overnight.  I even have the feeling that the new camera is producing sharper stars when binned.  I know that doesn't make sense, but I am going to take some test shots to find out.

If you have another camera with smaller pixels, it might be worth a try???

 

[alan potts]

That is a better result than I got with longer, not a lot longer but longer nonetheless. I only got 6x240sec subs last night at a target before one of my walnut trees got int the way and then cloud had a say in the matter. Set to improve a bit the next few days but turning cold.

Alan 

[tooth_dr]

6 hours ago, don4l said:

This is just a thought...

I recently changed my camera from one with 9um pixels to 6um.  The problem that I've had with bloated/fuzzy stars disappeared overnight.  I even have the feeling that the new camera is producing sharper stars when binned.  I know that doesn't make sense, but I am going to take some test shots to find out.

If you have another camera with smaller pixels, it might be worth a try???

 

I have another ccd but it also has 5.4um pixels.  I have a DSLR with 4.3um pixels but I’m a little reluctant to go back to dslr

[tooth_dr]

1 hour ago, alan potts said:

That is a better result than I got with longer, not a lot longer but longer nonetheless. I only got 6x240sec subs last night at a target before one of my walnut trees got int the way and then cloud had a say in the matter. Set to improve a bit the next few days but turning cold.

Alan 

Thanks Alan. I think the fast scope helps. What scope are you using?

[alacant]

8 hours ago, tooth_dr said:

struggling to get smaller stars

Hi

Lovely image.

I'm guessing that there's a Baader cc before the sensor; astigmatism and fat stars. If it's not a Baader, then the seeing?

Cheers and clear skies.

Edited November 28, 2019 by alacant

[tooth_dr]

25 minutes ago, alacant said:

Hi

Lovely image.

I'm guessing that there's a Baader cc before the sensor; astigmatism and fat stars. If it's not a Baader, then the seeing?

Cheers and clear skies.

I don’t think the seeing was great initially but it did really settle down and I was guiding at 0.6 or less RMS. 
 

The scope has a built in CC, designed for the scope so I don’t think that’s to blame. 
 

Focus was also ok, I think!

Would over exposing give this effect? Is 300s at F2.8 too much even? I should post the raw stacked data to see if it’s a step in my processing. 

[tooth_dr]

Raw stacked fits attached.

 

St-avg-1500.0s-MSC_1_3.0_none-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AAD-RE-noMBB-Blue.fits St-avg-1500.0s-MSC_1_3.0_none-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AAD-RE-noMBB-Green.fits St-avg-1500.0s-MSC_1_3.0_none-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AAD-RE-noMBB-Red.fits St-avg-1800.0s-MSC_1_3.0_none-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AAD-RE-noMBB-Lum.fits

[alan potts]

1 hour ago, tooth_dr said:

Thanks Alan. I think the fast scope helps. What scope are you using?

Ah yes, didn't think that far ahead, mine is only F 7, though I have a reducer for with it being so big I can't get a Ir/UV filter in the light path. That is without getting a in-line sliding filter draw from TS and a .3 spacer at 165e, which I think is a massive amount for what it actually is, sadly FLO don't seem to be able to offer me a solution. I may just try using it without the filter and see what happens.

Alan

[Spitfire]

That's a great image for so little exposure time.

Can't see what your equipment is but I'm guessing it's a Takahashi Epsilon with an Atik 383L+.

Geoff

[tooth_dr]

21 minutes ago, Spitfire said:

That's a great image for so little exposure time.

Can't see what your equipment is but I'm guessing it's a Takahashi Epsilon with an Atik 383L+.

Geoff

Thanks Geoff.  Yes sorry, Tak 180ed and Atik 383L+

[GiorgioF]

wow. Amazing.

What's the Bortle for your sky? 0,5? Because the result left me amazed.

[tooth_dr]

29 minutes ago, GiorgioF said:

wow. Amazing.

What's the Bortle for your sky? 0,5? Because the result left me amazed.

Thanks Giorgio. It’s Bortle 4 and North where I shot this  would be my darkest part of the sky.  

[GiorgioF]

7 hours ago, tooth_dr said:

Thanks Giorgio. It’s Bortle 4 and North where I shot this  would be my darkest part of the sky.  

 

That's a great sky. You're lucky.

[Xiga]

On 27/11/2019 at 23:45, tooth_dr said:

Thanks Adrian. I’m still struggling to get smaller stars. The ED80 was giving me nicer stars. I don’t know what to try differently, as focal length and guiding accuracy hasn’t changed.  Maybe I’m over exposing at 300s

Hi Adam

Without seeing a Raw sub it's hard to say for sure, but based on the number of saturated stars i'm seeing in the stacks, i would say you're definitely over-exposing at 300s. You should take some test subs and aim for an Avg ADU that gets you to somewhere between 5 and 10 x RN^2. Then stick to that for most targets. 

That being said, you can mitigate the big stars somewhat by masking them a bit while stretching. There's only so much you can do of course when they're over-exposed, but i had a go myself anyhow (thanks for sharing!). The key is to use an inverted, blurred mask of the image itself whilst you do an arcsinh stretch. You need to be careful though, as it will give you harsh cores to the stars if yo're not careful. 

In any case, it's crazy how much this data can be stretched, and with so little exposure! You've got a great setup Adam, looking forward to your future images! 🙂

[Xiga]

Ugh, too saturated now that I see it in the cold light of day. 

It was a joy to process though 😃

[alacant]

Hi

There's loadsa detail in the iris too. Not even 2 hours? Amazing...

 

 

 

[tooth_dr]

10 hours ago, Xiga said:

Hi Adam

Without seeing a Raw sub it's hard to say for sure, but based on the number of saturated stars i'm seeing in the stacks, i would say you're definitely over-exposing at 300s. You should take some test subs and aim for an Avg ADU that gets you to somewhere between 5 and 10 x RN^2. Then stick to that for most targets. 

That being said, you can mitigate the big stars somewhat by masking them a bit while stretching. There's only so much you can do of course when they're over-exposed, but i had a go myself anyhow (thanks for sharing!). The key is to use an inverted, blurred mask of the image itself whilst you do an arcsinh stretch. You need to be careful though, as it will give you harsh cores to the stars if yo're not careful. 

In any case, it's crazy how much this data can be stretched, and with so little exposure! You've got a great setup Adam, looking forward to your future images! 🙂

 

Thanks Ciaran for taking a look at this.  You have a great deal of processing skills, and achieved a better result in no doubt just a few minutes.  I'll look into that inverted blurred mask.  Currently I'm doing a DDP stretch in APP, and before I even import it into PS, the stars are probably already larger than necessary. 

[tooth_dr]

2 hours ago, alacant said:

Hi

There's loadsa detail in the iris too. Not even 2 hours? Amazing...

 

Hi thanks for having a go at the data.  Using 180mm at F2.8 really helps to gather the data fast.  I really hope to do mosaics with this scope, just need to get onto SGPro, as currently not finging it that intuitive.  Lots of windows, and not knowing whether these can be closed or have to be left open.

[Xiga]

24 minutes ago, tooth_dr said:

Thanks Ciaran for taking a look at this.  You have a great deal of processing skills, and achieved a better result in no doubt just a few minutes.  I'll look into that inverted blurred mask.  Currently I'm doing a DDP stretch in APP, and before I even import it into PS, the stars are probably already larger than necessary. 

I find that DDP really only works best with NB data. Unfortunately, when it comes to Broadband data, you really have to go Full Manual and take control of the stretch yourself, otherwise the stars will bloat (even when properly exposed). I’m not really familiar with LRGB workflows tbh, but I think what I did was first stretch the Lum, but masking it along the way to keep the stars from bloating. Then I used Mark Shelly’s excellent colour-preserving arcsinh stretch on the RGB stack (which I combined manually in PS). Once I got both histograms roughly equal, I layered the Lum on as a Luminosity layer and then just proceeded with the usual saturation, contrast enhancement, NR etc.

The method for protecting the stars is far from perfect though. It can be really hard to prevent them developing a hard edge on the inner-core, and sometimes a little cosmetic correction can be needed on the biggest stars. I’ll try and post a more detailed description later tonight with a few pics for you.

[Xiga]

Forgot to say, the very first thing I did on the unstretched linear RGB file, was to run it through Siril's Photometric Color Calibration routine. I much prefer it to APP's version (which is still a bit too unclear I find). Thankfully, Siril is free and the routine is really simple and quick to do. I'll try and describe that part later tonight too.

[Xiga]

Ok here's how to calibrate star colours in SiriL. 

1. Start by changing the working directory. There's a 'Change dir...' button at the bottom of the main window.

2. Open your linear, unstretched RGB file (File->Open). It doesn't have to be a .ft file, it can be a .tif file that you manually created in PS by combining the R,G, and B channels, but it must not be stretched in any way. 

3. Run 'Image Processing->Color Calibration->Photometric Color Calibration'. 

4. Search for your target, in this case i just typed 'Iris Nebula' and it found it in the Simbad database. Select it to populate the RA and Dec co-ordinates. Enter the FL and PIxel size and hit OK. Note, if it fails, then Untick the 'Auto' checkbox and increase the Limiting Magnitude. I've never had it fail with 17 so far. 

That's pretty much it! You will know that it's worked by the info shown in the Control Panel (see below).

The only thing left to do is then Right-Click anywhere in the 'RGB image' window and choose to save the image as either a fits or tiff file (note, it can only do 16bit, but that shouldn't be a problem if you intend to move into PS from here on anyway).

[tooth_dr]

26 minutes ago, Xiga said:

Ok here's how to calibrate star colours in SiriL. 

1. Start by changing the working directory. There's a 'Change dir...' button at the bottom of the main window.

2. Open your linear, unstretched RGB file (File->Open). It doesn't have to be a .ft file, it can be a .tif file that you manually created in PS by combining the R,G, and B channels, but it must not be stretched in any way. 

3. Run 'Image Processing->Color Calibration->Photometric Color Calibration'. 

4. Search for your target, in this case i just typed 'Iris Nebula' and it found it in the Simbad database. Select it to populate the RA and Dec co-ordinates. Enter the FL and PIxel size and hit OK. Note, if it fails, then Untick the 'Auto' checkbox and increase the Limiting Magnitude. I've never had it fail with 17 so far. 

That's pretty much it! You will know that it's worked by the info shown in the Control Panel (see below).

The only thing left to do is then Right-Click anywhere in the 'RGB image' window and choose to save the image as either a fits or tiff file (note, it can only do 16bit, but that shouldn't be a problem if you intend to move into PS from here on anyway).

You breadth of knowledge never fails to impress me Ciarán.

Regarding exposure. Those 300s subs are giving a minimum ADU of 2500!!  A tad high.  I did 120s tonight and it was at 1300. I still think that’s high.