Buying just 1 filter (for now)

[_Jimmy (Loren James)]

Hi all,

Just getting my stuff organised for imaging DSOs and obviously want to be able to extend my shooting season each month. I figure starting out I can put some money down for a filter to help with this. After many many hours of research into LPS and UHC filters I think I will avoid them in the first instance.

My plan is this -

spend a little bit more money on a good quailty v. Narrowband Ha filter rather than trying to squeeze two out for now or spending money on a middle road solution such as lps or uhc.

On dark (new moon/moon set in evening) nights I can go out to a dark sky area for straight up rgb imaging (non modded canon 70d), and can image the Ha on other nights closer to home.

Going with the Ha to complement my camera as obviously is doesn't pass as much red due to IR cut, so even though the Ha will not be as good as it would with a modded camera I can still get something to boost my reds in the rgb images.

Does this sound like a reasonable start up idea?

[luka]

You should note that with Ha your DSLR will only see 1/4 of the total intensity (or a decreased resolution) due to the Bayer filter.

Bayer filter is a 4-channel filter (red/green/green/blue) and all DSLRs have it. The DSLR sensors are mono but the colour can get reconstructed after light goes through the Bayer filter. With Ha you won't see anything in the green (two) and blue (one) channels.

[_Jimmy (Loren James)]

Originally Posted by luka

You should note that with Ha your DSLR will only see 1/4 of the total intensity (or a decreased resolution) due to the Bayer filter.

Bayer filter is a 4-channel filter (red/green/green/blue) and all DSLRs have it. The DSLR sensors are mono but the colour can get reconstructed after light goes through the Bayer filter. With Ha you won't see anything in the green (two) and blue (one) channels.

Yeah OK, understand that. Not much i can do about that for now, running up against finite funds and need to try and make the most out of the rest for a bit till I can save a bit more (coming into middle year bill season too).

[billdan (Bill)]

I am looking to purchase this narrowband filter as it covers Ha, Hb and OIII. This way I get Hydrogen Ha in Red, Hydrogen Hb in Blue and OIII in green.

See attached freq response curve.

I am thinking of using it as a luminance channel to complement my QHY-12 OSC.

Ebay link here,
http://www.ebay.ca/itm/Filter-Astron...item485b3f7fbf

Cheers
Bill

[gaa_ian (Ian)]

Hi Guys
Another option to consider is the Kson UHC & OIII filters I have in stock

[rustigsmed (Russell)]

hi Jimmy,

I did a similar thing to what you are planning. I had a dslr (although it was spectrum modded). I ended up purchasing the following:

CCD CLS (light pollution)
Ha
Oiii
S2

and then RGB after I got my mono camera. the process was staggered, I didn't want to end up with a mono camera and not have any filters.

I would recommend the same order. light pollution filter made a huge difference for my images it is nearly like a nb filter for broadband.

A debayered Ha image will be ~ 1/4 the size of the regular image and while it will give a bit of a boost I'm not sure it will benefit a substantial amount with your current camera unmodified.

Also consider that your sub exposure time will go up dramatically for narrowband even more so for an unmodified camera. perhaps keep an eye out for second hand filters as well in the classifieds.

good luck

cheers

[luka]

Russell, was your DSLR cooled? If not how long exposures did you do with it? Camera noise will become significant for exposures longer than few minutes.

[rustigsmed (Russell)]

Originally Posted by luka

Russell, was your DSLR cooled? If not how long exposures did you do with it? Camera noise will become significant for exposures longer than few minutes.

the camera was uncooled, I have a fast imaging system 12" f4 newt, before the light pollution filter I was getting 70 second exposures. with the light pollution 3 mins was pretty much the sweet spot.

for narrow band it depended on the object, faint objects were overwhelmed with noise especially if it was warmer weather.

7 min subs on a bright object
https://www.flickr.com/photos/803366...posted-public/

10 min subs for bicolour helix
https://www.flickr.com/photos/803366...posted-public/

30 min helix raw trial sub - not recommended
https://www.flickr.com/photos/803366...posted-public/

here is another effort that I really didn't succeed digging out any faint detail because of the noise
https://www.flickr.com/photos/803366...posted-public/

so pretty much you're ok if its not hot and the object isn't too faint and you don't go over 10 mins as long as you get a fair bit of data. this of course isn't very scientific but just how I saw it. keep in mind the amount of Ha getting through on your chip will be way less so you will have more of a noise problem for me if you were considering Ha.

[_Jimmy (Loren James)]

Originally Posted by rustigsmed

hi Jimmy,

I did a similar thing to what you are planning. I had a dslr (although it was spectrum modded).

Thanks Russ for for that.

Yeah the idea is the expand in stages. I guess I am trying to find out what would be best bang for buck at this stage. I can't mod my camera as it is my only one. I do plan on buying a dedicated camera down the track but $$ So I was thinking if I can colour image without a filter and knowing that I get little red through, boost that a bit with an Ha image (again, knowing this won't be optimal due to the built in IR filter).

But you are thinking a CLS or similar might be the way to go here first? Do you have some CLS only images you could share (your Ha Carina looks awesome!). Given they are normally a bit cheaper, I might be able to squeeze out a CLS and Ha maybe?

I know there will be limitations in my setup, and I think as long as I understand what they are I should still get plenty enjoyment out of a limited set up.

Cheers,
Jimmy

[ZeroID (Brent)]

I would suggest the CLS as the best real filter. My 1200D is unmodded ( I have a full spectrum 450D for clever pix ) and it more comes down to the processing to manage the LP red sky. Actually Photoshop2's auto effects seems to do a dang good starting cleanup for most situations.
The CLS will put a slight blue cast on everything but easy enough to balance the histogram and it means that you start with cleaner data without the overriding LP fog.

[rustigsmed (Russell)]

Originally Posted by _Jimmy

Thanks Russ for for that.

Yeah the idea is the expand in stages. I guess I am trying to find out what would be best bang for buck at this stage. I can't mod my camera as it is my only one. I do plan on buying a dedicated camera down the track but $$ So I was thinking if I can colour image without a filter and knowing that I get little red through, boost that a bit with an Ha image (again, knowing this won't be optimal due to the built in IR filter).

But you are thinking a CLS or similar might be the way to go here first? Do you have some CLS only images you could share (your Ha Carina looks awesome!). Given they are normally a bit cheaper, I might be able to squeeze out a CLS and Ha maybe?

I know there will be limitations in my setup, and I think as long as I understand what they are I should still get plenty enjoyment out of a limited set up.

Cheers,
Jimmy

g'day jimmy,

yep that is the why I did it to stagger out the costs
I am not sure if I have any before and after shots of cls vs no filter but here are a few with the filter shots:

https://www.flickr.com/photos/803366...blic/lightbox/

https://www.flickr.com/photos/803366...blic/lightbox/

also it is possible to modify your dslr to astro and still use for daytime, for example some people just use auto white balance in the camera to offset the extra red, or you can buy an Original White Balance filter.

[_Jimmy (Loren James)]

Originally Posted by ZeroID

I would suggest the CLS as the best real filter. My 1200D is unmodded ( I have a full spectrum 450D for clever pix ) and it more comes down to the processing to manage the LP red sky. Actually Photoshop2's auto effects seems to do a dang good starting cleanup for most situations.
The CLS will put a slight blue cast on everything but easy enough to balance the histogram and it means that you start with cleaner data without the overriding LP fog.

Ah ok. Good to know you seem happy with results on a unmodded camera.

Originally Posted by rustigsmed

yep that is the why I did it to stagger out the costs
I am not sure if I have any before and after shots of cls vs no filter but here are a few with the filter shots:

Thanks for the samples Russ. Interesting how the diffraction spikes band red and blue like that.

Am now leaning more towards the CLS first up. This will allow me to at least get multi-coloured images from brighter areas, and I can go to dark sites on new moon weeks (usually moon is up during day at the moment that week as well) and see what my camera is capable of straight up.