What filters do I need for OSC camera (e.g. ASI2600MC Pro)?

[aeneas]

Hi,

I recently purchased a (significant) upgrade for our backyard astro evenings - a C11 EDGE HD scope (and a steady CGX-L mount); ZWO ASI2600MC Pro is in my shopping basket. I also have Celestron's 0,7x reducer and UHC/LPR filter already. Starizona's Hyperstar v4 is on its way, but I'm not sure if that will help with the Horse nebula?

I now received a challenge from my wife: with this "fancy" scope, will I be able to capture the horse nebula? 

Considering that I will not have a mono camera, but a colour OSC, what filters would you recommend me to go for so that I may generate decent combination of data/stacks to put together a nice horse nebula image? I live in Bortle 4 area so sky is relatively decent...

[DaveS]

I would be thinking of a dual or tri band filter to start with.

[aeneas]

13 minutes ago, DaveS said:

I would be thinking of a dual or tri band filter to start with.

Any recommendations perhaps?

[DaveS]

I'm a mono imager, but I might be  thinking of the  L-eXtreme

Here

[kirkster501]

I am just using a LDAS 2” LP filter in front of my, same chip camera.

[aeneas]

11 hours ago, DaveS said:

I'm a mono imager, but I might be  thinking of the  L-eXtreme

Here

Thanks! I've read several reviews and watched a few youtubes with L-extreme... looks like the right filter to go with!

Edited October 29, 2020 by aeneas

[PeterCPC]

Good luck finding one of those ☹️. I have had one on order since September.

[Annehouw]

Let me give you a contrarian view and advise you against the L-extreme.

Looking at the fact that you are planning to image with the hyperstar, you will be living in fast focal ratio land. And everything is a little bit different there (and sometimes a lot...battling tilt comes to mid).

In the case of narrowband filters there is the issue of bandpass shift and resulting drop of transmission off center. The L-extreme has narrow bandpasses that wil make it's transmission at f/2 severely impacted. 

This is a subject that comes along every so often. An authorative discussion on this can be found here: https://www.cloudynights.com/topic/734419-radian-triad-triad-ultra-performance-vs-f-ratio/#entry10585863

Long story short: using these very narrow bandpass filters will give you the contrast between nebulae and background, but will reduce the light gathering efficiency of the scope (in the case of scopes faster than f/4 -f/5).

 

Having said that: my advice is to get yourself the somewhat broader version of the L-extreme, the L-enhance. 

[AbsolutelyN]

Just got a OSC camera myself. I'm not currently planning on using any filters.  

[tooth_dr]

12 minutes ago, AbsolutelyN said:

Just got a OSC camera myself. I'm not currently planning on using any filters.  

I agree with this. Can’t you just image the Horsehead with the camera as it is, from your Bortle 4 location?

[tomato]

I have the same sensor to be used on a f/2 system so I have gone with the broader dual band pass filter, a 2” IDAS NBX.
 

I do agree that you should get good results on the Horsehead as is from a Bortle 4 location.

[DaveS]

4 hours ago, Annehouw said:

Let me give you a contrarian view and advise you against the L-extreme.

Looking at the fact that you are planning to image with the hyperstar, you will be living in fast focal ratio land. And everything is a little bit different there (and sometimes a lot...battling tilt comes to mid).

In the case of narrowband filters there is the issue of bandpass shift and resulting drop of transmission off center. The L-extreme has narrow bandpasses that wil make it's transmission at f/2 severely impacted. 

This is a subject that comes along every so often. An authorative discussion on this can be found here: https://www.cloudynights.com/topic/734419-radian-triad-triad-ultra-performance-vs-f-ratio/#entry10585863

Long story short: using these very narrow bandpass filters will give you the contrast between nebulae and background, but will reduce the light gathering efficiency of the scope (in the case of scopes faster than f/4 -f/5).

 

Having said that: my advice is to get yourself the somewhat broader version of the L-extreme, the L-enhance. 

Ah, thanks I'd missed the Hyperstar bit.

In that case the IDAS NBX might be worth a look.

[Phillyo]

IDAS NBX, it's made for fast focal ratio imaging down to F2. I have one for my Samyang 135, though I haven't used it much yet. I did a test with a single 2 min exposure and the Ha was very evident. Waiting for clear skies to try more.

[ollypenrice]

For the Horsehead you don't need any narrowband filter, though Ha will add to the structure seen in the cloud behind the Horse. The HH itself will be unaffected. Be aware that a duo band filter will block the broadband blue so it will spoil the lovely blue reflection nebula lower left of the HH. (That's NGC2023.)

It provides a wonderful colour contrast with the Ha and, if you go for a wider field, with the yellowish colour of the Flame. This region suits any focal length, longer or shorter.

BTW this thread would be better in the Imaging Discussion section.

Olly

[aeneas]

10 hours ago, Annehouw said:

Let me give you a contrarian view and advise you against the L-extreme.

Looking at the fact that you are planning to image with the hyperstar, you will be living in fast focal ratio land. And everything is a little bit different there (and sometimes a lot...battling tilt comes to mid).

In the case of narrowband filters there is the issue of bandpass shift and resulting drop of transmission off center. The L-extreme has narrow bandpasses that wil make it's transmission at f/2 severely impacted. 

...

Thanks @Annehouw for pointing this out! This was a very informative read and I looked deeper... some quite disappointing reviews with RASA or Hyperstar combo indeed.

 

3 hours ago, Phillyo said:

IDAS NBX, it's made for fast focal ratio imaging down to F2. I have one for my Samyang 135, though I haven't used it much yet. I did a test with a single 2 min exposure and the Ha was very evident. Waiting for clear skies to try more.

This seems to be the way to go! Thanks @Phillyo & @DaveS! Specs look good... seems this one was developed particularly with fast scopes in mind and some initial reviews show it seems to work well with hyperstar. Thank you!!!

 

2 hours ago, ollypenrice said:

For the Horsehead you don't need any narrowband filter, though Ha will add to the structure seen in the cloud behind the Horse. The HH itself will be unaffected. Be aware that a duo band filter will block the broadband blue so it will spoil the lovely blue reflection nebula lower left of the HH. (That's NGC2023.)

...

That's a good point. I still have to learn all the processing stuff, but I've done quite a bit before in regular nature photography with RAW processing in photoshop. So I look forward to learning this. I was thinking: if I have the narrow band filter like IDAS NBX I can take some data without any filter, some data with regular UHC and some data with NBX. Then I could stack the three in layers and play with how they interact into a final image.... Would this make sense?

[ollypenrice]

Just now, aeneas said:

Thanks @Annehouw for pointing this out! This was a very informative read and I looked deeper... some quite disappointing reviews with RASA or Hyperstar combo indeed.

 

This seems to be the way to go! Thanks @Phillyo & @DaveS! Specs look good... seems this one was developed particularly with fast scopes in mind and some initial reviews show it seems to work well with hyperstar. Thank you!!!

 

That's a good point. I still have to learn all the processing stuff, but I've done quite a bit before in regular nature photography with RAW processing in photoshop. So I look forward to learning this. I was thinking: if I have the narrow band filter like IDAS NBX I can take some data without any filter, some data with regular UHC and some data with NBX. Then I could stack the three in layers and play with how they interact into a final image.... Would this make sense?

Yes, that's more or less what a lot of us do. In my case I add Ha to the red channel and OIII to the green and blue channels using blend mode Lighten. That way the narrowband data only ever adds and never subtracts.

Olly

[aeneas]

2 minutes ago, ollypenrice said:

Yes, that's more or less what a lot of us do. In my case I add Ha to the red channel and OIII to the green and blue channels using blend mode Lighten. That way the narrowband data only ever adds and never subtracts.

Olly

Great, thanks! ...this may be the wrong place to ask (and I'm sure a lot is written on it - I still need to read up on a lot), but if you don't mind a question: some nebulas that really impress with their colour spectrum are produced in the "Hubble palette"; would one ever be able to recreate a Hubble palette with OSC and some filters and good processing skill, or is this something one needs to go to monochrome with dedicated filters in order to get there? ...sorry if the wrong place to ask.

[ollypenrice]

13 minutes ago, aeneas said:

Great, thanks! ...this may be the wrong place to ask (and I'm sure a lot is written on it - I still need to read up on a lot), but if you don't mind a question: some nebulas that really impress with their colour spectrum are produced in the "Hubble palette"; would one ever be able to recreate a Hubble palette with OSC and some filters and good processing skill, or is this something one needs to go to monochrome with dedicated filters in order to get there? ...sorry if the wrong place to ask.

You'd be hobbling yourself trying to do Hubble Palette false colour with OSC.  The Ha would be captured using a quarter of the pixels, the OIII with half and the SII with a quarter. Given that mono imagers usually find the SII signal very feeble anyway, dividing it by four wouldn't be a good idea.

An OSC camera is best used as an OSC camera - that is a broadband natural colour camera. You can enhance Ha and OIII signal quite succesfully using filters but, at some point, you have to say, 'Why did I choose an OSC?'

Olly

[AKB]

I have taken a few images with a C.25 Hyperstar and an ASI294 OSC with no filters.

The Horsehead image is 20 x 1 minute exposures.

Album here: 

Tony

 

[dhmiller]

On 29/10/2020 at 15:49, ollypenrice said:

You'd be hobbling yourself trying to do Hubble Palette false colour with OSC.  The Ha would be captured using a quarter of the pixels, the OIII with half and the SII with a quarter. Given that mono imagers usually find the SII signal very feeble anyway, dividing it by four wouldn't be a good idea.

An OSC camera is best used as an OSC camera - that is a broadband natural colour camera. You can enhance Ha and OIII signal quite succesfully using filters but, at some point, you have to say, 'Why did I choose an OSC?'

Olly

"An OSC camera is best used as an OSC camera - that is a broadband natural colour camera." Obvious, but interesting. In your opinion, what are some of the best broadband targets (OSC being deliver next week...). Thanks.

[ollypenrice]

11 hours ago, dhmiller said:

"An OSC camera is best used as an OSC camera - that is a broadband natural colour camera." Obvious, but interesting. In your opinion, what are some of the best broadband targets (OSC being deliver next week...). Thanks.

Almost everything will show to some extent in an OSC camera. The exceptions are the very faint narrowband nebulae. For instance the Squid (Outters4) was entirely invisible in the OSC data which made up Yves Van den Broek's capture of a great swathe of sky in Cepheus. This is a close crop of the Flying Bat from that enormous image. The green Squid Nebula didn't show at all so I added it from my own OIII-mono capture. Also, lower left, you'll see a small blue reflection nebula. While this did show in the OSC data it was very faint and not very blue. Again I enhanced it in processing from my LRGB image from the same region. I get the impression that the present CMOS OSC cameras are very sensitive in the reds, hence their excellent performance on Ha regions, but are less sensitive in blue. (Yves' OSC data went deeper into the Ha than my Ha/mono CCD, which came as a surprise.) If the OSC cameras are tailing off in sensitivity towards the blue (just my impression and not set in stone) then they may not be too hot at finding the OIII which lies on the green-blue border and tends to be faint.

It's important to remember that filters don't add light, they only block it. A NB filter only works because it allows us to go deeper in a selective wavelength by exposing for longer and stretching harder.  You won't get more NB signal with the filter than without it. In fact you'll get fractionally less. But you'll be able to islolate it for selective processing.

The obvious broadband targets would be galaxies, clusters and dusty objects. Some people add Ha to galaxies find the star forming regions and emphasize them but this isn't compulsory. (I used to find my OSC CCD rather disappointing on galaxies because it just seemed slow but I think OSC has been transformed by CMOS cameras.) However, I'm sure your camera will sing on the wintery Ha targets as well - Horse, Rosette, Cone etc etc.

Olly

 

Edited November 13, 2020 by ollypenrice
clarification

[gorann]

2 hours ago, ollypenrice said:

Almost everything will show to some extent in an OSC camera. The exceptions are the very faint narrowband nebulae. For instance the Squid (Outters4) was entirely invisible in the OSC data which made up Yves Van den Broek's capture of a great swathe of sky in Cepheus. This is a close crop of the Flying Bat from that enormous image. The green Squid Nebula didn't show at all so I added it from my own OIII-mono capture. Also, lower left, you'll see a small blue reflection nebula. While this did show in the OSC data it was very faint and not very blue. Again I enhanced it in processing from my LRGB image from the same region. I get the impression that the present CMOS OSC cameras are very sensitive in the reds, hence their excellent performance on Ha regions, but are less sensitive in blue. (Yves' OSC data went deeper into the Ha than my Ha/mono CCD, which came as a surprise.) If the OSC cameras are tailing off in sensitivity towards the blue (just my impression and not set in stone) then they may not be too hot at finding the OIII which lies on the green-blue border and tends to be faint.

It's important to remember that filters don't add light, they only block it. A NB filter only works because it allows us to go deeper in a selective wavelength by exposing for longer and stretching harder.  You won't get more NB signal with the filter than without it. In fact you'll get fractionally less. But you'll be able to islolate it for selective processing.

The obvious broadband targets would be galaxies, clusters and dusty objects. Some people add Ha to galaxies find the star forming regions and emphasize them but this isn't compulsory. (I used to find my OSC CCD rather disappointing on galaxies because it just seemed slow but I think OSC has been transformed by CMOS cameras.) However, I'm sure your camera will sing on the wintery Ha targets as well - Horse, Rosette, Cone etc etc.

Olly

 

If you go to https://www.facebook.com/optolongusa/ you will find this post of the Squid taken with a OSC CMOS camera and a dual band filter. Quite amazing:

 

Edited November 13, 2020 by gorann

[ollypenrice]

1 hour ago, gorann said:

If you go to https://www.facebook.com/optolongusa/ you will find this post of the Squid taken with a OSC CMOS camera and a dual band filter. Quite amazing:

 

 

 

That is impressive. Perhaps I'm being unduly doubtful about NB with modern OSC. In a target with reflection nebulosity as well I think you'd want to shoot some unfiltered data for the blues but that's  a potent image.

Olly

[AKB]

7 minutes ago, ollypenrice said:

That is impressive.

258 x 300s sounds like a long time (21.5 hours), at least, to me.  How long was your exposure, Olly?

Tony

[ollypenrice]

9 minutes ago, AKB said:

258 x 300s sounds like a long time (21.5 hours), at least, to me.  How long was your exposure, Olly?

Tony

The image I posted mostly isn't mine, I just processed it. I had 12 hours of OIII to add to Yves' 90 minutes of OSC. The image in Wim's link is clearly better. To be fair, a Squid as good as that in 21.5 hours is pretty good going. It's a terribly faint object which is why it escaped detection until a few years ago.

Olly