M33

[Rodd]

54 minutes ago, wimvb said:

My guess is that it's a fibre of some sort that's stuck on glass close to the sensor. That's why I recommend removing the camera for closer inspection.

I found this one (but haven't confirmed it):

distance = pixelsize x f-ratio x shadow diameter in pixels

where pixelsize is in microns, and shadow diameter is the width of the dust particle (ideally a small round speck), not the lenth.

This would mean that if you have a pixelsize of 5 microns, an f-ratio of 6 and the width of the dust particle's shadow is 100 pixels, the particle is 5*6*100 = 3000 microns (3 mm) from the sensor.

If the cover glass of the camera (5 micrometer pixels, f/6 system) is 10 mm from the sensor, then a dust particle on the glass would show up as a 330 pixels wide blob in the image.

But that's what flats are for--no?  

Rodd

[Rodd]

I shoty a few subs and there was another V shape someplace else!  They are fibers (tiny ones on the filters).

2 hours ago, wimvb said:

My guess is that it's a fibre of some sort that's stuck on glass close to the sensor. That's why I recommend removing the camera for closer inspection.

Wimwas right--a fiber, but on the filter--I cleaned the filter and there were loads of them.  

 

 

7 hours ago, ollypenrice said:

I wonder if something wandered into the light path between the imaging run and the the blue flat?

Olly was right as well--the fiber was there when I shot my subs, but when I shot my flats it had moved--hence the reason the flats were useless to remove it.

Back up and running.  Won't know until I calibrate my subs.  

Note to camera manufacturers....its not enough that the sensor is in a sealed chamber--the filters should be sealed and a vacuum applied when it is closed up and an inert gas inserted.  There was all kind of dust and fibers all throughout the interior of the camera.  Its olny a matter of time till something like this happened

[wimvb]

That's the reason why I leave the cc permanently on my camera. And after each session, I put the camera in a plastic container with silica gel to capture any moisture.

While it would make sense to seal the filter wheel, it would also add two more layers of glass in the optical train. The risk for condensation would increase, so you'd need a dew heater as well. A camera with built in filter wheel is probably the best and most practical solution, if dust is a problem.

[Rodd]

5 hours ago, wimvb said:

That's the reason why I leave the cc permanently on my camera. And after each session, I put the camera in a plastic container with silica gel to capture any moisture.

While it would make sense to seal the filter wheel, it would also add two more layers of glass in the optical train. The risk for condensation would increase, so you'd need a dew heater as well. A camera with built in filter wheel is probably the best and most practical solution, if dust is a problem.

Pardon my ignorance but what is cc?  I never take my camera off my scope.  If I do--then I have to reshoot my flats (I can never reattach it at  precisely the same orientation).  SBIG makes a big deal about the micron precision of the self guiding filter wheel-how it can rotate filters to within a micron of the previous position.  It is supposed to be good for ensuring accurate flats.  Maybe its marketing hype. My filter wheel is sort of attached to the camera--the self guiding filter wheel (SBIG).   There are really no openings or holes.  Why could they not seal the filter wheel (ie make it water proof).  The only glass required would be a very thin, transparent glass.  My flatner has 6 elements, I don't think an inert piece of glass a tenth of a mm thick (or some such thickness--maybe thinner) would change the optical properties of the system (noticeably).  Besides, the glass could be like a shutter that closes when the camera is not in use and opens when it is activated.  I was surprised at how much detritus was inside the filter wheel. 

Rodd

[tooth_dr]

CC = Coma Corrector 

[Rodd]

18 minutes ago, tooth_dr said:

CC = Coma Corrector 

Ahh...thanks.  

Rodd

[wimvb]

35 minutes ago, Rodd said:

Pardon my ignorance but what is cc?  I never take my camera off my scope.  If I do--then I have to reshoot my flats (I can never reattach it at  precisely the same orientation).  SBIG makes a big deal about the micron precision of the self guiding filter wheel-how it can rotate filters to within a micron of the previous position.  It is supposed to be good for ensuring accurate flats.  Maybe its marketing hype. My filter wheel is sort of attached to the camera--the self guiding filter wheel (SBIG).   There are really no openings or holes.  Why could they not seal the filter wheel (ie make it water proof).  The only glass required would be a very thin, transparent glass.  My flatner has 6 elements, I don't think an inert piece of glass a tenth of a mm thick (or some such thickness--maybe thinner) would change the optical properties of the system (noticeably).  Besides, the glass could be like a shutter that closes when the camera is not in use and opens when it is activated.  I was surprised at how much detritus was inside the filter wheel. 

Rodd

Sorry, I couldn't see your signature when I responded to your post. Of course, your camera already has the filterwheel. Then it would make sense to have it sealed all the way, after you've installed the filters.

[Rodd]

Well--the end of a long road.  I reshot the Blue channel last night.  Only got 24 10 min subs instead of 30, and conditions were not as good--but I was able to keep the FWHM <3 at least.  The new flats worked like a charm and the blue channel looked pretty good. Goodbye unseemly artifacts.  In fact, the red, blue and green channels look great--better on their own than the completed image.  I can't seem to get the color of the galaxy right.  For the first time in a long time I have broadband data that is easy to work with and cont compromised by sky conditions (I had a very unusually clear, dark week).  Yet I can't put it all together.

 

[ollypenrice]

Glad that's sorted. Just bad luck.

After a lot of pondering and admiring the M33 images by the great and the good I came to the conclusion that it just may not be a terribly colourful galaxy. Once I stopped milking it for colour I felt I started to get somewhere. I'd be inclined to try easing the saturation a bit, but it's a persnal thing.

Olly

[Rodd]

3 hours ago, ollypenrice said:

Glad that's sorted. Just bad luck.

After a lot of pondering and admiring the M33 images by the great and the good I came to the conclusion that it just may not be a terribly colourful galaxy. Once I stopped milking it for colour I felt I started to get somewhere. I'd be inclined to try easing the saturation a bit, but it's a persnal thing.

Olly

Great advice. I agree. I am left with the following.  Seems pale.  Getting there?.  The green cast bothers me--but I can't seem to rectify it  Ha areas seem pink too. 

 

 

[ollypenrice]

That's really good. I don't see a green cast. Indeed it seems a bit magenta on my screen, but perfectly happy. You could try the top slider in reds, selective colour, in Ps and lower the cyans in red.

Olly

[Gina]

I was going to say the dirt must be on the blue filter since it only affected the blue.  Strange that having the filter wheel within the camera body gave problems with dust, fibres or whatever.  I use a separate EFW and adopt as much cleanliness as I can manage and rarely have dust motes.  Maybe the atmosphere here is cleaner than yours.  Once the optical train is assembled it stays together until I need to change it for a different FOV.  I do have a good rocket blower

[geoflewis]

A very interesting thread and a superb final version of M33, your perseverance certainly paid off, well done.

[johnrt]

Very nice Rodd. I feel your still milking the outer arms a little for saturation and there is some colour to be found in the core, whereas yours is white, but you have succesfully moved away from the "processed in pixinsight" look of the early versions.

[StargeezerTim]

Beautiful image. Well worth the hard work and definitely much improved. Given me the motivation to try M33 again.

[Rodd]

 

5 hours ago, ollypenrice said:

That's really good. I don't see a green cast. Indeed it seems a bit magenta on my screen, but perfectly happy. You could try the top slider in reds, selective colour, in Ps and lower the cyans in red.

Olly

Thanks Olly--I just realized I missed a big step--so it looks magenta.  I forgot to remove the red sky signal from the Ha master, so instead of the Ha only going to the Ha regions, it goes everywhere to some degree.  Mostly in the Ha regions, but a bit elsewhere too.  I have never mastered the step of "cleaning the Ha".  Too many things to remember!  One minute I look at it and I see a mess, but if I keep looking, it improves.  Even on one screen it seems to change from hour to hour.

Rodd

[Rodd]

1 hour ago, Gina said:

I was going to say the dirt must be on the blue filter since it only affected the blue.  Strange that having the filter wheel within the camera body gave problems with dust, fibres or whatever.  I use a separate EFW and adopt as much cleanliness as I can manage and rarely have dust motes.  Maybe the atmosphere here is cleaner than yours.  Once the optical train is assembled it stays together until I need to change it for a different FOV.  I do have a good rocket blower

Actually this is the first time I had an issue with a flat not removing something.  The most amazing thing I suppose is that it actually did move between my subs and my flats--taken the same night.  That's never happened before.  And I still don't see how the material enters the camera/filter wheel system--there are no holes and the camera remains threaded to the scope, which is a closed system itself.  I am fearful of using a blower because it might stir up the dust and make things worse.  A rocket sucker might be better.  Not sure they even exist.

Rodd

[Rodd]

1 hour ago, geoflewis said:

A very interesting thread and a superb final version of M33, your perseverance certainly paid off, well done.

Thanks geoflewis. 

Rodd

[Rodd]

19 minutes ago, johnrt said:

Very nice Rodd. I feel your still milking the outer arms a little for saturation and there is some colour to be found in the core, whereas yours is white, but you have succesfully moved away from the "processed in pixinsight" look of the early versions.

Thanks John.  I played with the core for hours--but anything I did was little more than me adding color of my choice--which is not what I want to do.  I used PIs new photometric color calibration tool--Probably should try it the regular way.  Usually, I do not touch saturation in my images--I find that using curves the histogram brings out enough color.  But this image looked so pale I thought I had to.  The reason I brought the blue out in the spiral arms is due to the amazing image of Gnomus I saw somewhere.  Back to the drawing board I guess--but at least I have an image I can stomach until I either find a way through the briar patch, or surrender to the data gods (most likely the latter).

Rodd

[Rodd]

17 minutes ago, StargeezerTim said:

Beautiful image. Well worth the hard work and definitely much improved. Given me the motivation to try M33 again.

Me Too!!!  Not anytime soon.    Thanks for the kind words.  I agree, it is a substantial improvement.  But I feel I am dancing around the nail instead of hitting it on the head.  I have learned that the tiniest adjustments can make big differences, so probably a number of little things.  But at least for once I was able to capture some pretty good broadband data.  Usually my broadband is loaded with gradients and is a mess.  Not so this time.

Rodd

[Rodd]

Well--I had a redo, keeping John's comment of too much saturation in the spiral arms band Olly's Magenta cast in mind (Not sure I was successful in either case)..  I was able to figure out how to add the Ha to the red and lum channels while in linear state and to keep the Ha from being added in places other than the Ha nebula regions.  But--I was not able to really improve much on the image.    Here is the best I could manage.  The first image is my final attempt.  The second image is  the image right after the Lum insertion as the first step in linear state.  It represents the starting point really.   In some ways I think it the best.  That's unfortunate, as 90 of the processing effort came after that step!  Thanks for your help and patienece. 

Rodd

 

 

[tooth_dr]

I think the first one of those looks great with the stronger blues coming through. 

[Rodd]

5 minutes ago, tooth_dr said:

I think the first one of those looks great with the stronger blues coming through. 

Thank you--

Rodd

[Rodd]

Actually--I think This is a good balance.  The core and disk have lost the greenish-muddy cast and the blue stars remain.  Spiral structure can now be followed to the core.

 

[geoflewis]

4 hours ago, tooth_dr said:

I think the first one of those looks great with the stronger blues coming through. 

Ditto, I think the version where Lum had just been added is a bit washed out, so definitely worth the extra (90) processing effort