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First light for our new CCD - Horsehead and Flame nebula


Zadoq

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Hi,

Last Sunday was the first light of our new CCD camera and filterwheel.

Attached is a single Ha 600s sub. It was everything we were hoping for considering the amount of time I normally have to spend on post-processing without being able to achieve anything that good.

I would like some advice / thoughts as to what to do next. We've never done narrowband imaging before

I initially thought that we'd capture OIII and SII subs and combine them HST style, although maybe for this one Ha to Red to keep the usual overall red colour.

But then I wondered about using Ha as the luminance layer and capturing RGB.

FYI, we live and image from a moderately light-polluted area, hence the use of narrow-band to cut out the light pollution.

On the subject of light polluted area, what would be the best way to image galaxies? Could Ha/OIII/SII be combined in a single luminance layer to cut out the pollutin and that luminance layer then be used with standard RGB subs?

Thanks

Nico & Carly

Horsehead NGC2023-1_600sec_1x1_HA_-15.0C_frame2.tif

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Not much noise going on there for a single sub, very nice! looks almost like a completed image but its just one sub!

I take it your new camera is the 460EX in you sig? It gives a good field of view for a CCD doesn't it :) 

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I forgot to ask the question I started the post in the first place lol

You'll notice that the star above the Flame nebula is massive. I assume the best way to reduce it is to take shorter Ha subs and blend their stacked version in Photoshop. Is that right?

And presumably if this happens with the other channels (whether narrowband or broadband), shorter subs would have to be taken for the other channels to?

Sorry about what are probably basic questions, but narrowband post-processing is new to us

Thanks

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Not much noise going on there for a single sub, very nice! looks almost like a completed image but its just one sub!

I take it your new camera is the 460EX in you sig? It gives a good field of view for a CCD doesn't it :)

Chris,

Yes, you're right it is the 460 EX.

We were planning on getting this much later but given the amount of time we were spending on post-processing and relatively poor results we were getting because of lack of data, we decided to get an early xmas present and rob our bank (account).

Of course, the xmas present had to be tested to avoid disappointment under the tree ;)

Nico

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Hi,

Last Sunday was the first light of our new CCD camera and filterwheel.

Attached is a single Ha 600s sub. It was everything we were hoping for considering the amount of time I normally have to spend on post-processing without being able to achieve anything that good.

I would like some advice / thoughts as to what to do next. We've never done narrowband imaging before

I initially thought that we'd capture OIII and SII subs and combine them HST style, although maybe for this one Ha to Red to keep the usual overall red colour.

But then I wondered about using Ha as the luminance layer and capturing RGB.

FYI, we live and image from a moderately light-polluted area, hence the use of narrow-band to cut out the light pollution.

On the subject of light polluted area, what would be the best way to image galaxies? Could Ha/OIII/SII be combined in a single luminance layer to cut out the pollutin and that luminance layer then be used with standard RGB subs?

Thanks

Nico & Carly

This is a good start but you need a lot more data. I use the Ha to enhance the RGB or OSC data. Depending on which software you use there are many ways of combining the Ha with RGB. In PS the best way is to split the channels in the layer palette highlight the red channel and then copy and paste the Ha to RED. You need to register the Ha and the RGB prior to this. If the Ha data has a lot of deatil you can try and paste it on top of the Ha/RGB in Lighten mode to enhance the data and adjust the opacity to get a decent mix. I am not very good with PS but if Olly or other good people of the forum are reading they might be able to suggest a better way. NB imaging of a galaxy is pointless as galaxy is a full spectrum emission target. The best way is to image it in either RGB or OSC and then blend in the Ha to bring out the Ha regions. Hope this helps. 

Regards,

A.G

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This is a good start but you need a lot more data. I use the Ha to enhance the RGB or OSC data. Depending on which software you use there are many ways of combining the Ha with RGB. In PS the best way is to split the channels in the layer palette highlight the red channel and then copy and paste the Ha to RED. You need to register the Ha and the RGB prior to this. If the Ha data has a lot of deatil you can try and paste it on top of the Ha/RGB in Lighten mode to enhance the data and adjust the opacity to get a decent mix. I am not very good with PS but if Olly or other good people of the forum are reading they might be able to suggest a better way. NB imaging of a galaxy is pointless as galaxy is a full spectrum emission target. The best way is to image it in either RGB or OSC and then blend in the Ha to bring out the Ha regions. Hope this helps. 

Regards,

A.G

Thanks AG.

We are planning on getting many more subs, but when you say "need a lot more data", did you mean also longer exposures? We've so far taken 600s but were wondering about going to 900s for that target (although that bright star worries me at that exposure)

I assume OSC = One Shot Colour, right?

So, if I understood your processing correctly you use the Ha data as Red channel and if it has a lot of data, you also use it as a luminance layer. Did I get this right.

Thanks for answering the galaxy question. It makes sense now

NIco & Carly

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Thanks AG.

We are planning on getting many more subs, but when you say "need a lot more data", did you mean also longer exposures? We've so far taken 600s but were wondering about going to 900s for that target (although that bright star worries me at that exposure)

I assume OSC = One Shot Colour, right?

So, if I understood your processing correctly you use the Ha data as Red channel and if it has a lot of data, you also use it as a luminance layer. Did I get this right.

Thanks for answering the galaxy question. It makes sense now

NIco & Carly

Yes, with an Ha filter the longer the sub usually the better. subs of 900s~1200s are normal if your  guiding keeps up. OSC is one shocolour CCD or DSLR. Yes you add the Ha to the RED channel but adding the Ha as LUM can play havoc with your star colours . As I said I use Pixinsight but I think that the procedure I outlined earlier in PS should work. If you image a galaxy in RGB then leave the LP filter on as LP does interfere with RGB imaging.

A.G

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Yes, with an Ha filter the longer the sub usually the better. subs of 900s~1200s are normal if your  guiding keeps up. OSC is one shocolour CCD or DSLR. Yes you add the Ha to the RED channel but adding the Ha as LUM can play havoc with your star colours . As I said I use Pixinsight but I think that the procedure I outlined earlier in PS should work. If you image a galaxy in RGB then leave the LP filter on as LP does interfere with RGB imaging.

A.G

Thanks for clarifying the exposure time. Didn't realise 1200s was common.

Regarding LP filter and imaging RGB, that's an interesting and very sensible thought...

However, we're wondering how that would look physically?

  • Does it mean there would be a LP filter somewhere in the path before or after the filterwheel and if so would that affect the use of the narrowband filters (I know that the right narrowband wavelength would go through but was wondering about the reduced amount of light due to the extra filter - we have quite a static setup that we try to change as rarely as possible)
  • Or is it possible to overlay LP+R, LP+B, LP+G in the filter wheel (not sure if one could be screwed to the other and how much thickness the combined filters would have)

Thanks

Nico & Carly

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deal with

Thanks for clarifying the exposure time. Didn't realise 1200s was common.

Regarding LP filter and imaging RGB, that's an interesting and very sensible thought...

However, we're wondering how that would look physically?

  • Does it mean there would be a LP filter somewhere in the path before or after the filterwheel and if so would that affect the use of the narrowband filters (I know that the right narrowband wavelength would go through but was wondering about the reduced amount of light due to the extra filter - we have quite a static setup that we try to change as rarely as possible)
  • Or is it possible to overlay LP+R, LP+B, LP+G in the filter wheel (not sure if one could be screwed to the other and how much thickness the combined filters would have)

Thanks

Nico & Carly

Leave the LP filter at the end of the FF/FR and shoot the L through an open hole in the FW and the RGB with the  LP on. Some people keep on saying that with RGB an LP filter is not necessary but I guess they don't have LP to deal with. take individual flats for LP and R,G and B. There may be a slight issue with the spacing of the FF/FR depending on the type of the FF/FR but in general 0.5mm will not make much difference with a short FRAC.

A.G

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very nice start! and only 1 sub, you have a nice blueprint here to build on with many more hours worth of data, look forward to seeing your progress :)

Thanks Marin.

That's the idea: many, many more hours on this project ... as soon as the weather permits :)

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Leave the LP filter at the end of the FF/FR and shoot the L through an open hole in the FW and the RGB with the  LP on. Some people keep on saying that with RGB an LP filter is not necessary but I guess they don't have LP to deal with. take individual flats for LP and R,G and B. There may be a slight issue with the spacing of the FF/FR depending on the type of the FF/FR but in general 0.5mm will not make much difference with a short FRAC.

A.G

A.G

Ok got that. Sounds good

What about narrowband filters? Currently, all our filters are in the filterwheel at the same time. We specifically bought the EFW2 FW because it holds 8 filters at once and we didn't like the idea of regularly swapping filters out.

If the LP filter is fitted where you mentioned at the FF/FR end, would it be silly to shoot narrowband through the filter as well? I know there is no optical benefit to it. The only benefit is that we wouldn't have to dismantle the optical assembly to place or remove the LP filter.

The LP filter we have is an IDAS P2. From Hutech's chart, it looks like the transmission factor is around 95%, so to compensate for the filter being there ,it looks like we should be increasing our narrowband exposure times by just  over 5%

Do you think that would work or is it just silly?

Thanks

Nico

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That luminous horror is, of course, Alnitak, which at least you've manage to show as a double.

Olly has an artical in the latest issue of Astronomy Now about imaging the Flame and Horsehead, where he discusses how to keep Alnitak in check.

Edit

I have tended to keep a 2" LP filter in the opticle train screwed into the front of any FF / FR. In my (Unscientific) tests I've found the Astronomik CLS to be better than the IDAS at contoling my LP which is a mixture of LP and HP sodium. The non-ccd version of the CLS has a better band in the red for picking up [sII]

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That luminous horror is, of course, Alnitak, which at least you've manage to show as a double.

Olly has an artical in the lastest issue of Astronomy Now about imaging the Flame and Horsehead, where he discusses how to keep Alnitak in check.

Thanks for the info Dave. We'll check it out

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