M82 in colour and b&w

[RobertI]

Two captures from a very quick session last night with the Lodestar Mono. The first uses the recently acquired RGB filters and the second a luminance only filter. 

 

Transparency was poor and in addition to the usual nearby sodium lights, the local rugby club had its stadium lights on.

I'm still learning about filters but I am pretty happy with the colour capture, and I did virtually no adjustment of colour/saturation. However there is a gradient of some sort with the sky looking redder towards the top, perhaps from the sodium lights?

Comparing the rgb and mono captures, it's clear that the mono has captured more of the dimmer information and shows more detail within the structure of the galaxy (note that the mono has slightly more exposures but even so I think the difference is there). I can understand that the mono would pick up the fainter stuff as the rgb filters block some light. Would this also explain the lower detail in the colour and if so would more stacks get the colour to the same level of detail of the mono?

Final question - how do people think that the above rgb result would compare to a Lodestar X2C with the same exposure lengths? Would the enhanced sensitivity of the X2C make up for the reduced resolution?

Any thoughts appreciated.

Rob

[HiloDon]

Very good work, Rob.  There's no question that the mono shows more detail.  Pretty typical with the X2 v X2c.  I dug up a capture of M82 with my LSX2c.  Your RGB color in my opinion is better.  My capture was with my ES152AR with Baader UV/IR cut and Contrast Booster filters I was testing.  Your image also appears to be sharper.  It could be the optics or my focusing.  I do remember that the transparancy that night was not the best, but I wanted to test my new Contrast Booster filter with the achro. I was very happy with the results.  It made a big difference with the achro and virtually eliminated the violet fringing without turning things yellow.  I would highly recommend that filter with achros.

Don

[Chris]

Great shots Rob  Are you going to try combining RGB+L so you get both the colour and detail?

[aparker]

Nice shots Rob.  I do prefer the mono for the crisp detail.  Do you know what's causing the top to bottom gradient?

[RobertI]

Thanks Don, very interesting to see your results with the 152 achro. That X2 certainly captures a lot with very few exposures. As you say, colour seems less vivid.

Chris, thanks, I would like to try LRG&B. I assume I will keep the exposure lengths the same for LRG&B (to match the darks) but just have more stacks of the RGB compared to L to make sure the colour isn't washed out? At this point I have no idea what I am talking about so any pointers appreciated.

Alex, thankyou, I am not sure what the gradient is caused by, it was a bit misty that night so its possible the nearby sodium lights were illuminating the mist, another possibility is the stadium lights illuminating the sky at a higher altitude but this is white llight as opposed to red. Perhaps I shall try the same shot on a different night......

[Chris]

2 hours ago, RobertI said:

Chris, thanks, I would like to try LRG&B. I assume I will keep the exposure lengths the same for LRG&B (to match the darks) but just have more stacks of the RGB compared to L to make sure the colour isn't washed out? At this point I have no idea what I am talking about so any pointers appreciated.

Hi Rob, it's been a couple of years since I've done this myself, so I'm trying to remember what I did when I had my BrightStar Mummut mono CCD. I think I shot luminance binned 1x1 which provided the resolution, then binned 2x2 for the colour so I didn't need as much colour because 2x2 is so sensitive (sub length kept the same though like you say). The colour shouldn't get washed out too much because you have control over the intensity percentage of the luminance layer when you combine it with the RGB. 

Here is my first effort with it a while ago now, showing just L, then LRGB. Just to give you an idea really. I've never guided or use long exposures so feel it almost qualifies for this side of the fence  30x80sec.

  

[RobertI]

7 hours ago, Chris Lock said:

Hi Rob, it's been a couple of years since I've done this myself, so I'm trying to remember what I did when I had my BrightStar Mummut mono CCD. I think I shot luminance binned 1x1 which provided the resolution, then binned 2x2 for the colour so I didn't need as much colour because 2x2 is so sensitive (sub length kept the same though like you say). The colour shouldn't get washed out too much because you have control over the intensity percentage of the luminance layer when you combine it with the RGB. 

Here is my first effort with it a while ago now, showing just L, then LRGB. Just to give you an idea really. I've never guided or use long exposures so feel it almost qualifies for this side of the fence  30x80sec.

  

Thanks Chris, very helpful. I beleive the imminent new version of Starlight Live incorporates binning so I shall give this a go when the release is available.  

[laudropb]

Very nice images. The mono is very sharp and detailed.

[Astrojedi]

Rob,

Very nice images. Are you using the Baader LRGB filters?

Hiten

[RobertI]

Yes Hiten, I have the premium filters rather than the cheaper absorptive filters. The mono M82 shown above is so much better than a previous session I had back in Jan. There could be a number of reasons for this, most probably seeing conditions, but my understanding is that the luminance filter would reduce star size and bring out a bit more detail?

Rob

[Astrojedi]

Rob,

Good choice on the filters. That is the value of better filters. 

Yes the IR cut helps as M82 is strong in NIR which tends to smudge out some finer detail especially when seeing is poor.

Hiten