NGC 2264

[Gerry Casa Christiana]

Hello all

I just had a go at the cone nebula NGC 2264 on my unmodified Canon 550d and a Skywatcher 150pds

I managed 31 subs and 20 darks. No flats! To come God willing. Anyone know what is sufficient for darks? I tend to stop at 20 but do not do bias as I hear from Craig Stark that it's not necessary if you do darks. 

Anyway here is my attempt. 

 

http://www.astrobin.com/full/287624/0/

 

Look forward to comments and any advice. 

 

Thanks

 

Gerry

[wimvb]

Nice image, pretty good for an unmodified camera. What exposure time did you use? I think that for Ha with an unmodified camera, you will need multiple minutes sub frame exposures.

You should also consider taking flat frames, to get rid of the vignetting.

As for darks, you will have to experiment. Some people swear by them, others swear at them. Generally, they can be trickier for dslr imaging, where you have less control over temperature. Using aggressive hot pixel removal routines during stacking, can sometimes give better results than darks. I found that for short exposures, I can get by without darks. But for long exposures (10 min +), I get better results with darks.

[newbie alert]

Looks like m45 to me..nice thou

[swag72]

Flats will really help sot out the gradient you have there - Try them and as long as they are done correctly you'll be impressed at the the difference

[Gerry Casa Christiana]

I'm doing flats as we speak. 

Im just using apt on the default flat setting. I hope that's right. I've looked at nebulosity and it says around 11,000 pixels mean out of 22,000 max I hope that means 50%. 

If anyone can tell me what ADU in pixels is using the above program I'd be grateful! 

[Gerry Casa Christiana]

1 hour ago, wimvb said:

Nice image, pretty good for an unmodified camera. What exposure time did you use? I think that for Ha with an unmodified camera, you will need multiple minutes sub frame exposures.

You should also consider taking flat frames, to get rid of the vignetting.

As for darks, you will have to experiment. Some people swear by them, others swear at them. Generally, they can be trickier for dslr imaging, where you have less control over temperature. Using aggressive hot pixel removal routines during stacking, can sometimes give better results than darks. I found that for short exposures, I can get by without darks. But for long exposures (10 min +), I get better results with darks.

You say that with shorter exposures not to use darks. It's strange you say that because mine are 2 minutes because I don't autoguide yet but I have noticed if I use just light frames I get a much clearer picture but with hot pixels. 

Can I ask then what you would use with 31 subs of 120 seconds with 20 darks (I can leave them out) and now with 28 flats just taken 

Just so you know I use DSS. Thanks for any suggestions. I'm just running DSS now with darks and flats on standard. 

Thanks for any help. 

[wimvb]

The most important is to find out what works for you. When doing 2-3 minutes exposures, darks didn't help improving the stacked image. I could get equally good results by using cosmetic correction (PixInsight, but also available in dss) and aggressive pixel rejection during stacking. I also used dithering to spread hot pixels. Now that I use guiding, I have longer exposure times (10 minutes or more), and can't do dithering. Darks now help to get better results. What works for me, may not work for you. Therefore: experiment.

I also use PixInsight and not dss. The result can very well depend on the software. There are enough cloudy nights to experiment. I would stack the subs with darks, and less aggressive pixel rejection. I would also stack without darks, but with a stronger pixel rejection. Then I would compare the final results. If darks don't produce a better image, you'll have to ask yourself if they are worth the extra time.

1 hour ago, newbie alert said:

Looks like m45 to me..nice thou

Nope, the cone is barely visible below the lower bright star. The area is usually much stronger red, but here an unmodded camera is used. Longer sub exposures will help bring out the red.

[Gerry Casa Christiana]

Ok this picture. Is a HUGE difference with flats. This picture is ISO 3200 x 31 x 20 darks x 28 flats. The great thing is I hardly touched it in processing. 

Please let me know your thoughts but the vignetting is gone! 

http://www.astrobin.com/full/287624/B/?nc=user

I will shortly upload another with only flats and no darks. 

Thoughts please. 

 

Gerry

[swag72]

Much better

[newbie alert]

2 hours ago, wimvb said:

 

Nope, the cone is barely visible below the lower bright star. The area is usually much stronger red, but here an unmodded camera is used. Longer sub exposures will help bring out the red.

Yes..i looked it up but you get what i mean thou..same sort of star formation with blue nebulosity...

Another target for me then..

[Gerry Casa Christiana]

18 hours ago, wimvb said:

The most important is to find out what works for you. When doing 2-3 minutes exposures, darks didn't help improving the stacked image. I could get equally good results by using cosmetic correction (PixInsight, but also available in dss) and aggressive pixel rejection during stacking. I also used dithering to spread hot pixels. Now that I use guiding, I have longer exposure times (10 minutes or more), and can't do dithering. Darks now help to get better results. What works for me, may not work for you. Therefore: experiment.

I also use PixInsight and not dss. The result can very well depend on the software. There are enough cloudy nights to experiment. I would stack the subs with darks, and less aggressive pixel rejection. I would also stack without darks, but with a stronger pixel rejection. Then I would compare the final results. If darks don't produce a better image, you'll have to ask yourself if they are worth the extra time.

Nope, the cone is barely visible below the lower bright star. The area is usually much stronger red, but here an unmodded camera is used. Longer sub exposures will help bring out the red.

Hi there

Just for a point of interest. I tried the same processing with flats and darks on DSS and the flats and darks definitely wins in terms of noise. So you have a pix insight obviously does things slightly different. 

This is what I ended up with. Im pleased with it considering no guiding. No camera mod. 

http://www.astrobin.com/full/287624/C/

Thanks for all the help

Gerry

[alacant]

Hi. I got better results -I've a Canon 700d- not using dark frames. Light, flat and bias frames work well and take the drudgery out of making the darks in the first place; win/win... HTH.

[Gerry Casa Christiana]

1 hour ago, alacant said:

Hi. I got better results -I've a Canon 700d- not using dark frames. Light, flat and bias frames work well and take the drudgery out of making the darks in the first place; win/win... HTH.

Thanks for that. I'll try that on my next session and see how the difference is. Yes it's time consuming doing darks. How many bias and flats are you using to get good results? 

Thanks for the help 

Gerry

[alacant]

1 hour ago, Gerry Casa Christiana said:

bias and flats are you using to get good results? 

Bias 32, flat 16. Bias can be reused, The flat frames must be taken with exactly the same orientation and focus as the light. HTH.

[wimvb]

Much better. The Ha areas are showing in red, as they should. On my mobile device, it looks like you got some green left. Hasta la vista green in photoshop (scnr in PixInsight) will remove this and make the red stronger still.

As for dark frames, it isn't just a question whether or not, you will have to determine if they work for YOU. That's why I recommended testing.

Always take as many calibration frames as possible. I usually take 50 - 60 bias frames (they're easiest), at least 12 flats and more darks than light frames. For darks, I put the camera outside in a dark box with covers, and let it shoot with an intervallometer/timer.

You take bias and dark frames to correct for the camera's electronics (fixed pattern read noise and fix pattern dark current/hot pixels). You want as little random noise as possible, since any random noise in the calibration frames will be added to the light frames.

[Gerry Casa Christiana]

1 hour ago, wimvb said:

Much better. The Ha areas are showing in red, as they should. On my mobile device, it looks like you got some green left. Hasta la vista green in photoshop (scnr in PixInsight) will remove this and make the red stronger still.

As for dark frames, it isn't just a question whether or not, you will have to determine if they work for YOU. That's why I recommended testing.

Always take as many calibration frames as possible. I usually take 50 - 60 bias frames (they're easiest), at least 12 flats and more darks than light frames. For darks, I put the camera outside in a dark box with covers, and let it shoot with an intervallometer/timer.

You take bias and dark frames to correct for the camera's electronics (fixed pattern read noise and fix pattern dark current/hot pixels). You want as little random noise as possible, since any random noise in the calibration frames will be added to the light frames.

Yes I saw the green there but I thought I got most of it. Unfortunately I do not have either of those software programs. I'll try again to remove the green. 

Thanks again!