Is it time to get a new camera?

[MylesGibson]

So last night I imaged M81 & M82. Clear nights have been few and far between so was looking forward to getting out. Today, I went through the stacking and processing and ended up with this:

This was using an L-Pro filter for the first time. Apparently it didn't work too well against light from the next door neighbor as there is quite a gradient in the background, but that's not the reason for this post. 

I'm really struggling to get any sort of colour out of this. This isn't the first time that colour has been scarce, I also posted a topic about struggling to get colour in an image of M33, which I was sort of able to do eventually. That was taken without the L-Pro filter, so I don't think that is the issue.

 

Is it possible that my camera is a bit past it? Colour never used to be a real big issue, but recently I have been struggling to get much of it. Even in very colourful targets like M42 the colour is there but it's just a bit..... dull. I would post that image to show, but I had a few unrelated errors that night which blew the core completely so I got annoyed and deleted the files lol. Anyway.... I'll attach the .tif if anyone wants to have a look.

This was 38x 300s lights, 50x bias, 50x flats and 25x darks

Camera is a Canon 1000D with 30k shutter count

Scope is Starwave 102 ED-R

 

Autosave.tif

[vlaiv]

There are few issues with the image.

First is - you are pushing your data too much. You should stop as soon as you hit noise. Sometimes things will be faint, and that is OK. Things are faint. If you want to exaggerate brightness - you really need much more exposure length.

Second - color is there, but again, like brightness, there is not much color. If you want to get stronger color - you need to boost saturation. I'm against that, but people seems to both do it and like images like that. For that reason, I boosted saturation here as well.

Third issue is with your scope - it is not very well corrected, and you really need specific filter to deal with this - or processing trick.

Here is my take of your data:

And straight away - you see the issue. Stars have blue halos - no way around it since scope is relatively fast (F/7) ED doublet. You could try using Astronomik L3 filter with this scope to reduce impact or use processing trick.

With Gimp, it is fairly easy to minimize blue halo - you can selectively desaturate blue color and get something like this:

[Ibbo!]

If the data was collected last night there was a bright moon and a lot of light scatter with the thin high cloud in my area.

 

Wait till a better night and try again before coming to a conclusion would be my advice.

[MylesGibson]

50 minutes ago, vlaiv said:

There are few issues with the image.

First is - you are pushing your data too much. You should stop as soon as you hit noise. Sometimes things will be faint, and that is OK. Things are faint. If you want to exaggerate brightness - you really need much more exposure length.

Not too bothered about a bit of noise right now. I was trying to push it to see if there was any colour there. Sorry, should have made that clear that this wasn't a "finished" thing

50 minutes ago, vlaiv said:

Second - color is there, but again, like brightness, there is not much color. If you want to get stronger color - you need to boost saturation. I'm against that, but people seems to both do it and like images like that. For that reason, I boosted saturation here as well.

That is the actual issue here. Not having much colour. I have used this combination of scope and camera for a while. Colour never used to be much of an issue. The last 6 months or so I have noticed colour has been more difficult to extract from the data. 

50 minutes ago, vlaiv said:

Third issue is with your scope - it is not very well corrected, and you really need specific filter to deal with this - or processing trick.

And straight away - you see the issue. Stars have blue halos - no way around it since scope is relatively fast (F/7) ED doublet. You could try using Astronomik L3 filter with this scope to reduce impact or use processing trick.

Yeah, I'm aware the scope is going to produce halos. Again, it's not something I'm bothered about right now, and isn't the focus of the question. I simply cannot afford a better scope right now, and won't  for some time, so it's not really a big issue for me. Besides, the L-Pro filter should have helped a bit with it too, not sure another filter would have helped.

The issue I want to focus on is why I am not seeming to get much colour in the data the last few months.

Edited January 24, 2021 by MylesGibson

[MylesGibson]

39 minutes ago, Ibbo! said:

If the data was collected last night there was a bright moon and a lot of light scatter with the thin high cloud in my area.

 

Wait till a better night and try again before coming to a conclusion would be my advice.

Yeah, I know the moon was bright, that's why I used the L-Pro filter which is supposed to be decent against light pollution. There wasn't any high cloud were I was, the skies were pretty good!

I would have agreed were it not the fact I have struggled to get much colour over the last few months. That's why I am wondering if my camera sensor or something is degrading

[vlaiv]

10 minutes ago, MylesGibson said:

Yeah, I know the moon was bright, that's why I used the L-Pro filter which is supposed to be decent against light pollution. There wasn't any high cloud were I was, the skies were pretty good!

I would have agreed were it not the fact I have struggled to get much colour over the last few months. That's why I am wondering if my camera sensor or something is degrading

No filter is going to help with moonlight if you are trying to image broad band targets like galaxies.

I'm fairly sure that your sensor is not degrading - you can easily check that with any lens you might have for it - just take daytime photo and check the colors.

Using LPS filter is sure way to disturb color balance and color accuracy and special care must be taken in processing of the data to ensure you get accurate colors back. It is very complex topic and I'm not sure you would like to get into all of that - as there is no simple way to go about it, it is indeed quite involved.

In order to understand a bit more, you can do a little test - it is fairly simple test that you can do if you really want to understand color in astrophotography.

Take your scope and camera and during daytime - point it to something colorful near by (but distant enough so you can reach focus without too much issues) - maybe billboard with colorful commercial or similar. Then take regular photo of that object. Now repeat process, but this time - act as you would with astro imaging:

- use L-Pro filter

- shoot in raw mode without any color balance

- use very short exposures so that image is essentially very dark and histogram is all to the left - shoot 20 or so of them - you'll be stacking those later

- take bias (it will act as darks since exposure is likely to be very short) and flats also

Now, do your regular astro photography workflow - calibrate data, stack it (in software - tell it not to align on stars - as there are no stars, just stack images as they are) and then try to process the image so you'll end up with same colors as on single image you took first.

This will show you what sort of color we are capturing in astrophotography and how it relates to actual color - that both can be captured with camera and that we see with our own eyes.

[MylesGibson]

@vlaiv thanks for the tips on tests to do. I'll have a go at that next time I get everything set up!

Didnt realise the filter would have no effect on moonlight. I did make sure I went for a target that was as far as possible from the moon, but unfortunately was near a neighbor's house which had lights on for the first hour of the imaging run. I did choose this filter as from looking around online it seemed to have the best retention of natural colours over other filters to combat LP.

The reason i thought it was the camera is it used to pick colour up fine, such as in images i took of M97 & M108. Maybe I could have another go at that target again and compare?

[wimvb]

I douwnloaded your image and had a go at it with PixInsight, with the only objective to see how much colour there was. I removed the gradient, but didn't fix the artefact above and to the left of M82. I then extracted the lightness information and processed colour and lightness separately. I left the noise in the image, but reduced the colour mottle in the background a little.

The noise is strongest in the red channel. This channel is also the weakest and the read pattern of the camera shows through. A modern dedicated astro camera has much lower read noise, so you would avoid this issue.

In my opinion it is the noise due to light pollution that is the main cause of the absence of colour. Remember that if you remove the light pollution in processing, you remove the signal part, but not the associated noise. The best way to reduce noise is to collect more data. A rule of thumb is that if you lose a magnitude in sky darkness, you need to increase the integration time by a factor of 2.5. This image needs more data if you want to pull out the noise.

If you decide to invest in a new camera, you should definitely look into a cooled mono-camera, rather than osc. Mono with RGB filters is less sensitive to ordinary light pollution because there is a gap in the transmission between R and G, and this is where man made light pollution generally is strongest. With a mono camera, it will also be easier to do NB imaging. 

Btw, you have walking noise in your image. Dithering 15 pixels between exposures should help.

Edited January 24, 2021 by wimvb

[MylesGibson]

Thanks @wimvb. Maybe I'll have to wait until the lights are off from the neighbor's and moon has gone away and have another go. Cant get out to any dark sky sites right now as I dont think its allowed with current restrictions. 

I did get around hrs worth of images, so thought that would be enough..... as for walking noise, is that where the image moves over time? I think that was due to ground conditions. The ground was still soft from earlier rain when I set up so I think one of the tripod legs started to sink before getting frozen in place! That's why I had to get rid of all my 600s images. 

I'd love to invest in a mono cam with filters but the wife is pregnant so all money is currently going in that direction rather than at hobbies, so just trying to get the most out of my current equipment!

[wimvb]

1 hour ago, MylesGibson said:

the wife is pregnant

All the best wishes to you and your wife.

1 hour ago, MylesGibson said:

as for walking noise, is that where the image moves over time?

In your image it looked as if the walking noise describes a circular pattern. Polar missalignment can do this. Dithering will break up the walking noise pattern. It will also reduce colour mottle that is common in dslrs. But you need to dither at least 12 pixels (according to guru Tony Hallas).

 

[MylesGibson]

4 hours ago, wimvb said:

In your image it looked as if the walking noise describes a circular pattern. Polar missalignment can do this. Dithering will break up the walking noise pattern. It will also reduce colour mottle that is common in dslrs. But you need to dither at least 12 pixels (according to guru Tony Hallas).

 

Poor polar alignment makes sense. After the tripod sunk, that would have put it out quite a bit. I'll need to look into setting up dithering in APT. Thanks for the advice!