Lagoon from Glebe, Plus Ha

[Zuts]

Hi Guys

Managed to get out last night for the first time in weeks. Recaptured the Lagoon. No clouds but moon was very full. I tried my new robofocus and was it sweet. Just press the button and auto focus in 35 seconds, I was absolutely amazed.

The second image is 10 minutes of Ha with my new Astronomic 6nm Ha filter. Robofocus worked OK on this as well. Self guiding was easy through the filter, I just increased the time to 10 seconds.

I would like to combine the two data sets but cant, as the image scale is different. Any tips or pointers to free software on how to do this, and a good tutorial on LRGB processing would be nice as well.

RGB

12 by 300 sec subs, darks plus flats, UV/IR block
TV85, TV 0.8 reducer on EQ6, self guided with SBIG 2000 XCM
Levels and Curves PS2, Sum combine in Maxim
Reduced to 1200 pixels, 30 % compression
Ha

2 by 300 sec subs, darks plus flats, Ha 6nm filter
TV85, TV 0.8 reducer on EQ6, self guided with SBIG 2000 XCM
Levels and Curves PS2, Sum combine in Maxim
55 % compression

Thanks for looking

Paul

[Prickly]

Nice shot Paul. You've really sliced through the light pollution with that one. Heaps of detail.

Not sure whether you can somehow use the Ha for luminance in pixinsight LE. You can certainly select the image you want for the luminance channel. How to get all the images lined up would be beyond me - but maybe the images are close enough as they were taken at the same time.

Maybe there's a simpler way out there?

Cheers
David

[Zuts]

Thanks David,

I only managed two Ha shots before the clouds rolled in. I have been doing some reading and have managed to blend in the Ha on the red channel. The problem is with the Ha filter the image scale changes and so the Ha subs have a different scale than the RGB subs. I can do a manual two star align in Maxim DL but also need a way of changing the image scale.

Manual resize and manual align sort of works but is not exact so I get red rings from the not quite aligned Ha in the red channel.

I would of thought by now there would have been some automated software to achieve this, but I am yet to find something.

Cheers
Paul

[iceman]

Hi Paul

Registar will take your images and combine them, regardless of scale/size, rotation etc. A great piece of software.

Bert, Jase and others use it already.

2 very nice images, well done. The stars look a little elongated - tracking slightly off?

[Zuts]

Hi Mike,

Thanks for that, I will give Registrar a go.

Now that I look I can see some elongation, but only in the Ha. Maybe the flattener doesn't work as well with the Ha filter?

Cheers
Paul

[jase]

The RGB image is looking good Paul - interesting composition in both images. I think your Ha image needs much longer subs (and more of them). I'd recommend a minimum of ten minutes per sub. Also I don't think your field flattner is this issue, but guiding. The ten second guiding correction maybe too long for the mount to guide accurate and deliver pin point stars. Instead of increasing the guider exposure time, try binning the guide chip from 1x1 down to 2x2. Don't be concerned about losing resolution on the guide chip due to the 2x2 binning as software algorithms calculate the star centroid with sub pixel accuracy. Binning will boost the guide chip's sensitivity - critical when guiding through a 6nm Ha filter. You may still need to increase the guider exposure time, but start with five second exposures and work from there. Obviously don't bin the main imaging chip, only the guide chip.

Registar is a remarkable piece of code. I only use it for image registration/alignment purposes, though it does have combine functionality. I use a variety of tools in the processing routine, picking the best fit for the task at hand - unfortunately there is no tool that does it all exceptionally well. An example (a poor one, I should add) of Registar's capabilities in handling different image scales is an image I took of the Cats Paw Neb (http://www.cosmicphotos.com/gallery/image.php?fld_image_id=112&fld_album_id=11). The luminance was acquired using a 12.5" RC operating at ~2800mm FL. I used Registar to align RGB data taken with my FSQ operating at 530mm FL to give the nebula some colour. When you start to get into mosaics, Registar is in a field of its own. Highly recommended.

[Zuts]

Hi Jase, I decided to offset the lagoon to make it a bit different. I will definately try a different binning for the guide chip as that should make the tracking more accurate with shorter exposures. EQ 6's are great but they need all the help they can get :), still when I look at the Ha image i see elongated stars pointing in different directions....?

The cats paw looks fantastic, if that was a test of gathering data at diferent FL's and processing then i think it worked well; I will certainly be looking at Registrar in the future.

Thanks for your suggestions
Paul

[jase]

Paul,
I had a closer look at your Ha image. You're right, stars appear to be going in different directions. I took a sample of a few in MaximDL (see below) - they are far from pinpoints of light. I'd still contribute this to erratic guiding/corrections considering the stars in the RGB image look really good. If desired, pls log your guiding corrections in MaximDL for both RGB and Ha acquisition (next time your imaging). Guiding logs can be enabled under the CCD camera control dialog box, Guide tab, options - tracking log <enable>. This may allude to where the potential problem resides.