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TareqPhoto

Filters ..... how important?!!!

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TareqPhoto    67

Hey'all

I would like to know how important or necessary are the filters for DSO imaging? can someone get DSO without filters if possible?

Let's name 2 or 3 objects, say M42, M45 and Veil Nebula, can those objects be done without filters of any kind? 

The question is about a mono cooled [CCD or CMOS] astro camera, not a modded DSLR or OSC.

I saw the stars of those objects by my naked eye without nebula, not even with a scope or binocular, so does that mean it is impossible to get any kind of clusters or nebula if no filters used? and seeing those objects by naked eyes does it mean the light pollution isn't bad that much yet?

I know filters isn't a substitution or replacement for a dark sky, but if there is no dark sky clear, what is the possibilities to get any kind of DSO nebulosity without filters under any percent of light pollution?

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SonnyE    339

I live North of Los Angeles, California. Almost as far as the county line.

My backyard (Garden) has a considerable amount of light pollution from around me. So I nomally use a Baader Moon and Sky Glow Filter in my filter wheel.

When my Atik Infinity OSC camera arrived, I did some imaging with, and without the LP filter. Surprisingly, the LP filter wins for taking much better images in my location.

I chase mostly Nebula, and most of them are red in appearance. A friend suggested I get a HA7nm filter to bring out the reds. So I have that to roll in if I want to.

I'm not sure if I have any unfiltered images but have these to share:

Veil Nebula with the LP and the HA7nm. You Tube link.

Following that is The Filimentary Nebula with the LP filter, converted to Black & White, followed by OIII, and a processing change called Orton Effect (Photoshop).

Aside from the LP filter which I use most of the time, I mostly use my HA7nm filter, because I like using a color camera.

And the Atik Infinity jumped me lightyears ahead of my old camera.

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TareqPhoto    67

I didn't ask about which filters, because simply i know that Ha is the main filter i will use, and i will add LRGB and OIII laterally later, and ending it with SII, but until i can get any filters of those for narrowbanding i would like to know how much i will miss without those filters.

I do have UHC and OIII filters, but they are very cheap and i heard they aren't a real deal here, so i can't depend on them for imaging, and i also have Baader Moon&SkyGlow filter which they call it [Neodymium], but i thought it is more for the moon and some bright planets rather than light pollution for nebulae.

I keep worry too much about light pollution in my area, regardless how many stars or which stars i can see from my yard, i just have no option but to imaging in my yard for whatever i can, the sky in very late time in my area is really shown as black, not grey or glowing from light pollution, but i call it light pollution here because simply i can't see the milky way with my naked eyes at all, not even with my binocular or scope, so i believe i live in severe light pollution to prevent me from seeing the light pollution, but i was shocked to see the Orion region by my naked eyes from my region so clear, and the Pleiades are very very far but barely i can see with my naked eyes if i keep focus, but with bino or scope they are amazing standing out in the view.

I will try with those filters i already have, i am waiting some budget to buy one filter at least, but it may take long time until something arrive to my hand, and every night passing since last month i keep seeing that M45 and M42 passing the sky late night before the twilight for about 1-2 hours earlier, so i wanted to give it a try within 1 hour maximum if i can, and i don't have Ha filter so i don't know how much i can get without it then.

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kens    120

You can get nice monochrome images without a filter. Light pollution limits how good you can get but stacking with as much integration time as you can should give you satisfying images. Your subs will be necessarily short so you will need lots of them.

A single Ha filter will give nice monochrome results with emission nebulae. You can take longer subs but you'll need more integration time.

LRGB filters let you produce color images and the colors can enhance the image. I think it helps add depth to objects like globular clusters.

You won't damage your gear by not using filters on DSOs so just try it.

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ronin    3,612
4 hours ago, TareqPhoto said:

Let's name 2 or 3 objects, say M42, M45 and Veil Nebula, can those objects be done without filters of any kind? 

The question is about a mono cooled [CCD or CMOS] astro camera, not a modded DSLR or OSC.

Since yoiu say "mono" then really you need filters of some variety, I know that there are mono images and the few I have seen are good but without a filter then you cannot allocate a colour. But you do get different images and usually high resolution as all the pixels are used immaterial of the wavelength. So the camera resolution is some 3x greater - not exactly but it is an idea of what goes on.

M42 is good with filters, as again you specify the wavelength that you wish to collect and the nebula has an assortment of emitted wavelengths, the nebula is a bit of a chemical soup. Additionally with a filter you can collect say Ha but then allocate blue to this set of collected images. So you can alter the colour. Equally with M42 people get good images with OSC cameras so filters are not 100% necessary. When Orion rises soon there will be lots of M42 images.

M45 really is a no filter object, it is a white light star cluster and mono or filters will not really do a lot.

Veil will do better with filters. The allow you get jsut a set of images at specific wavelength that are applicable to the Veil. A set of filters will also block other unwanted wavelengths and so highten the contrast, hopefully making the Veil stand out more.

Adding in another there is M31, usually considered a white light object and so no filters, however there is the option of getting Ha images and adding these in and by that method the star forming regions can be highlighted. So an object that is good with no filters and OSC but the additional use of Ha can/will add something to it.

Catch with use of filters is time, you need to get sets of exposures at different wavelengths so if R+G+B it can take 3x longer. You should get a better image, or the potential of a better image, however collection and processing time will get extented.

Learn optics is almost another prerequisite. I was reading of a filter the other day that was described as "increasing red", no filter invreases any colour or wavelength, they all decrease. A red filter does not increase the red, it removes the green and the blue and so leave only the red, and usually about 95% to 98% of the red so even that is decreased.

If you get filters then you either have to check focus between exposures with each or get a match set. The filter substrate thickness can alter and that alters the focus.

Usually a "white" source (M45) gains little advantage from a filter, others can or may.  M45 is in or passing through an area of gas so adding in that specific wavelength may bring out the gas emission a bit.

Also learn about the camera, they tend to not do R, G, B equally in the OSC variety, the green is "more", supposed to match the human eye response better. The Bayer mask applied is likely to be:

RGRGRGRGRGRGRGRGRG, then on the next row

BGBGBGBGBGBGBGBGBG

Twice as much Green as Red and Blue, on a mono they are all unfiltered and all used, but you cannot without filters get a specific colour.

 

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swag72    5,138
8 minutes ago, ronin said:

.......But you do get different images and usually high resolution as all the pixels are used immaterial of the wavelength. So the camera resolution is some 3x greater - not exactly but it is an idea of what goes on.

So you get a higher resolution image when no filters are used..... I really didn't know that.... so my LP filter that I use as luminance is stopping me from getting a full resolution image... 

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ollypenrice    16,505
1 hour ago, ronin said:

Since yoiu say "mono" then really you need filters of some variety, I know that there are mono images and the few I have seen are good but without a filter then you cannot allocate a colour. But you do get different images and usually high resolution as all the pixels are used immaterial of the wavelength. So the camera resolution is some 3x greater - not exactly but it is an idea of what goes on.

M42 is good with filters, as again you specify the wavelength that you wish to collect and the nebula has an assortment of emitted wavelengths, the nebula is a bit of a chemical soup. Additionally with a filter you can collect say Ha but then allocate blue to this set of collected images. So you can alter the colour. Equally with M42 people get good images with OSC cameras so filters are not 100% necessary. When Orion rises soon there will be lots of M42 images.

M45 really is a no filter object, it is a white light star cluster and mono or filters will not really do a lot.

Veil will do better with filters. The allow you get jsut a set of images at specific wavelength that are applicable to the Veil. A set of filters will also block other unwanted wavelengths and so highten the contrast, hopefully making the Veil stand out more.

Adding in another there is M31, usually considered a white light object and so no filters, however there is the option of getting Ha images and adding these in and by that method the star forming regions can be highlighted. So an object that is good with no filters and OSC but the additional use of Ha can/will add something to it.

Catch with use of filters is time, you need to get sets of exposures at different wavelengths so if R+G+B it can take 3x longer. You should get a better image, or the potential of a better image, however collection and processing time will get extented.

Learn optics is almost another prerequisite. I was reading of a filter the other day that was described as "increasing red", no filter invreases any colour or wavelength, they all decrease. A red filter does not increase the red, it removes the green and the blue and so leave only the red, and usually about 95% to 98% of the red so even that is decreased.

If you get filters then you either have to check focus between exposures with each or get a match set. The filter substrate thickness can alter and that alters the focus.

Usually a "white" source (M45) gains little advantage from a filter, others can or may.  M45 is in or passing through an area of gas so adding in that specific wavelength may bring out the gas emission a bit.

Also learn about the camera, they tend to not do R, G, B equally in the OSC variety, the green is "more", supposed to match the human eye response better. The Bayer mask applied is likely to be:

RGRGRGRGRGRGRGRGRG, then on the next row

BGBGBGBGBGBGBGBGBG

Twice as much Green as Red and Blue, on a mono they are all unfiltered and all used, but you cannot without filters get a specific colour.

 

I'm sorry but, once again, so much of this incorrect. 

R+G+B does not take three times as long as OSC. It is, if anything, a little faster and it becomes a lot faster if you take a luminance layer. There is really no such thing as one shot colour. It is best thought of as 'quarter of a shot blue, quarter of a shot red and half a shot green.'

'M45 really is a no filter object.' This cannot be true:

M45%20COMPOSITE3%20FL-M.jpg

Filters do pass light onto all the pixels except in the case of an 'OSC' chip.

What has not been said about imaging with no filter, and needs to be said, is that electronic chips are sensitive to wavelengths outside the visible spectrum and, very likely, outside the range of the colour correction of your optics.  This means that, with no filter at all, you are very likely to see bloated stars.

We also need to define 'monochrome' because it is often inorrectly used. It means 'one single colour.' It does not mean 'black and white' or 'greyscale.' So a luminance filter, which captures all colours without distinguishing between them and gives a greyscale result, is a polychromatic  filter which gives a monochromatic result. The job of a luminance filter is to block wavelengths which lie outside the visible spectrum, though they are designed to pass rather deeper reds that their non-astronomical counterparts found in daytime cameras so that they will pass H alpha light.

Sara's LP filter used as a luminance filter is enhancing her resolution by preventing unwanted wavelengths from flooding her chip. (As I'm sure she knows...)

Olly

 

 

 

Edited by ollypenrice
Typo
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AKB    305
6 hours ago, TareqPhoto said:

can those objects be done without filters of any kind? 

Here's a link to some processed images from an EAA session I did just a few nights ago.  Very short subs (30-60 secs) with total exposures of 5-10 minutes, or so.  Don't know if you're after higher quality than this?  Images include M13, M51, M101, and the Pelican, all with no filters. You could, of course, take more subs than this.

 

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