M42 Orion Nebula

[lalou]

Sharing my shot of M42 Orion Nebula. This was taken in a dark site here in Philippines. Hope I can get your comments and suggestions so that I can improve on my shots. 

Also will a UHC filter improve my shot? I recently bought the Baader UHC filter.

 

Celestron C6N reflector

Celestron OmniXLT CG-4

Nikon D90

40x2mins lights (from what I can remember lol)

 

Thanks! 

[alacant]

Hi. Very nice shot. The only thing I'd change is that when you adjust levels, don't set the bg too dark. This snap at at this fov should be awash with nebulosity. You can see the effect here. HTH.

**Sorry. I was gonna do a before and after but of course the jpg doesn't have the data. Anyway, you can see that the curve is cut off toward the dark part of the histogram...

[carastro]

Any chance of the stacked file?  Also (having seen your M45 thread) did you take flats?

Carole 

[lalou]

@alacant

Ohhhh ok this is noted. Thanks! Btw I have also attached the RAW file here just in case you wanna try something out.  

@carastro

Hi! I have attached the stacked file here. I usually only take lights and darks. Will try to squeeze in some flats next time. Thanks! 

TRIAL1M42.TIF

[carastro]

Somehow the Raw file has come out B&W.

Agree with Alacant that you have "clipped" the data i.e. cut off the black end, so you lose nebulosity doing that.  The sky is not pure black.  

You don't need a filter in a dark location.

I have got as much out of the data as I can (without flats). As you can see you clipped off much of the Nebulosity. 

You obviously have the skills to do this, you just need a few tips to make things work better. 

One other tip, when you are doing the Orion nebula, the core is very bright, so you need to take a set of 30secs shots as well and combine the two images using a rather complex method as shown here:  I managed to control it by using selective layering, but if you start taking longer exposures you'll need this method below.

http://www.astropix.com/html/j_digit/comp2.html

Carole 

 

[alacant]

20 minutes ago, lalou said:

in case you wanna try something out.

A (very quick and dirty) stretch and layer in GIMP, just to see what's there. Again, flats would improve this. HTH.

[alacant]

9 minutes ago, carastro said:

the Raw file has come out B&W

Hi. In GIMP it's called compose and decompose. In ps I think it's this. HTH.

[lalou]

6 hours ago, carastro said:

You don't need a filter in a dark location.

To clarify, when should I ideally use my UHC filter? From what I have read online, this can be used to enhance images of some DSOs. Thanks for your comments btw  

 

[lalou]

6 hours ago, alacant said:

A (very quick and dirty) stretch and layer in GIMP, just to see what's there. Again, flats would improve this. HTH.

Woah nice! So flats are really important. Will really include them on my next imaging session. Thanks! 

[carastro]

I am not familiar with the UHC filter but I think it is used for visual rather than imaging.  Some-one correct me if I am wrong.

Carole 

[lalou]

Just now, carastro said:

I am not familiar with the UHC filter but I think it is used for visual rather than imaging.

Oh ok. This is noted. Will check the forums as well if others have used it for imaging. 

Thanks for the help! 

[alacant]

17 minutes ago, lalou said:

when should I ideally use my UHC filter?

I think that only you can decide which colour balance is acceptable. Unless you can do some with and without shots, that's gonna be hard if not impossible to judge. I think the UHC cuts more of the spectrum than e.g. my CLS. The latter works well when I'm low down near the horizon: there are some sodium vapor lamps in certain directions and it blocks their effect totally, whilst imparting an almost impossible to correct colour to the shots. Of course, the next question is, 'What's the correct colour?'. HTH.

[bobro]

1 hour ago, carastro said:

I am not familiar with the UHC filter but I think it is used for visual rather than imaging.  Some-one correct me if I am wrong.

Here is the Crescent Nebula I recently imaged, using a UHC filter to bring out the detail by cutting out unwanted light. The image below shows with and without the filter. 10 minute subs.

[lalou]

On 9/4/2017 at 02:03, bobro said:

Here is the Crescent Nebula I recently imaged, using a UHC filter to bring out the detail by cutting out unwanted light. The image below shows with and without the filter. 10 minute subs.

This is amazing! Would you happen to know which targets are better with a UHC and which targets are better without a UHC?

[wimvb]

There is a difference between light pollution filters and uhc filters. Light pollution filters are designed to block the source of man made lights. Mainly sodium and mercury lights. Other light is let through, to get as much colour as possible in stars and galaxies.

Uhc filters are designed to enhance contrast in emission nebulae. They have a pass band at the wavelengths for Ha, Oiii, Sii, and Hb, but block almost everything else. A galaxy imaged with a lp filter will show much more colour than imaged with a uhc filter. Otoh, if you have a modded camera, imaging an Ha target like the crescent with an uhc filter will give more contrast and better results. You don't need a light pollution filter, if there is no light pollution. And you shouldn't use an uhc filter if your target has a large colour range. Also, using an uhc filter with an unmodded camera will generally result in blue images which are extremely anemic in red (Ha).

The Orion nebula is tricky, because it has a huge dynamic range with a mix of stars, reflection nebulae, and emission nebulae.

[tooth_dr]

@wimvb great info, didn't know the differences. Well explained!

[gorann]

I also had a go at it in Photoshop (attached). Fore some reason the colour information in the data was quite weak and it suffer from quite a bit of noise - much more than I am used to from my DSLR. I expect that it has to do with temperature. You are in the Philippines and I am in Sweden and usually do most AP from October to April when night temp is often between +5 and -10 °C here. That helps a lot with suppressing noise in the electronics. Not sure what you could do about it right now. Some people do elaborate modifications to their DSLRs to chill them down, but nowadays I think the best route in the long run would probably to save up for a chilled dedicated astro-camera where prices have gone done a lot recently like some of new ones in the ZWO or QHY lines. If you do not want the job of using colour filters you could go for a chilled colour camera.

[lalou]

19 hours ago, wimvb said:

There is a difference between light pollution filters and uhc filters. Light pollution filters are designed to block the source of man made lights. Mainly sodium and mercury lights. Other light is let through, to get as much colour as possible in stars and galaxies.

Uhc filters are designed to enhance contrast in emission nebulae. They have a pass band at the wavelengths for Ha, Oiii, Sii, and Hb, but block almost everything else. A galaxy imaged with a lp filter will show much more colour than imaged with a uhc filter. Otoh, if you have a modded camera, imaging an Ha target like the crescent with an uhc filter will give more contrast and better results. You don't need a light pollution filter, if there is no light pollution. And you shouldn't use an uhc filter if your target has a large colour range. Also, using an uhc filter with an unmodded camera will generally result in blue images which are extremely anemic in red (Ha).

The Orion nebula is tricky, because it has a huge dynamic range with a mix of stars, reflection nebulae, and emission nebulae.

Wow this is great! Thanks for the info! 

[lalou]

16 hours ago, gorann said:

I also had a go at it in Photoshop (attached). Fore some reason the colour information in the data was quite weak and it suffer from quite a bit of noise - much more than I am used to from my DSLR. I expect that it has to do with temperature. You are in the Philippines and I am in Sweden and usually do most AP from October to April when night temp is often between +5 and -10 °C here. That helps a lot with suppressing noise in the electronics. Not sure what you could do about it right now. Some people do elaborate modifications to their DSLRs to chill them down, but nowadays I think the best route in the long run would probably to save up for a chilled dedicated astro-camera where prices have gone done a lot recently like some of new ones in the ZWO or QHY lines. If you do not want the job of using colour filters you could go for a chilled colour camera.

Ohhhh will try to research more on how I can cooldown my DSLR. Will take this into consideration. Thanks!