Leo triplet through the murk

[IanL]

The results of my first semi-successful imaging run since last December. Managed to get 19 x 600s subs of the Leo Triplet from March 2nd. Transparency was poor but beggars can't be choosers; on the upside as is often the case with murky conditions round here seeing was excellent.

Taken with the 80ED, 0.85x Reducer, Hutech IDAS LPS P2, Canon 500D (unmodified) and guided using the ST80, QHY5 and PHD. Processed entirely with PixInsight.

I am struggling with background noise, especially in the red channel due the Hutech (necessary due to the murky conditions increasing the visible LP, but it really limits the red channel). Not at all satisfied with the background in either version, but I am not sure there is much more I can do with this unless I can get more data. On the plus side, I now know I have cracked my flats thanks to the LED light box, though I do think I will add extra red LEDs as it is biased too much to the blue/green end and may be adding to the red noise issues.

[ultranova]

very nice Photo, I have found with the photos i Take with the canon 1100d I nearly always have to tame the red channel down

a bit Im not sure if its just the canons are fairly red sensitive or it has something to do with the Bayer matrix pattern

this normal adds a slight green cast over the whole of the picture i then use Pi or hasta la vista, green to remove this cast

to get to a more normal background colour.

Paul

[Gina]

Very nice 2nd image

[IanL]

I downloaded Aladin (http://aladin.u-strasbg.fr/aladin.gml) in order to help with some planning for my foray in to rent-a-scope imaging, but as part of the learning process I put my Leo Triplet image in to it to see what I could find:

I found three additional galaxies (labelled); one I knew was a galaxy from the shape, but the other two just looked like stars until I overlaid a catalogue. Also the green arrows show the proper motion of some of the stars. (Not a great image, I'll try to get a better resolution one and upload it later).

Aladin is a pro astronomer tool but available to us mere mortals. It has only taken me a couple of days to get to grips with it; the hardest part is figuring out how to use your own images.

There's an intro to Aladin here:

http://www.farnham-a...campbell-burns/

This guide on using your own images was my starting point:

http://bf-astro.com/aladin.pdf

There are a few wrinkle I worked out for myself though:

- A stated, your image needs to be plate solved and have the solution embedded in the FITS headers (it is also possible to add them to a JPEG as per the process below once the image is in Aladin). If you don't plate solve, then your image can be loaded and viewed, but you can't overlay any other data from catalogues or surveys since Aladin doesn't know where your image is in the sky.

- I tried using PixInsight's plate solving script but for some reason the solution places the image at 90 degrees and offset from the correct position relative to survey images sourced within Aladin. I'll play with it a bit more, might be something stupid I have done.

- You might try the astrometry.net online solver (or local version if you are an AstroTortilla user). Either can produce a WCS solution which you can add to your image via the "astronometriical calibration" dialog in Aladin as per the instructions in the guide above.

- What I did was use the Aladin Star matching process. When you get to the 'astronometrical calibration' step of the guide above, just switch to the "by Matching Stars" tab instead of the "by WCS header" tab. You will need to have located and loaded a survey image in Aladin covering the same part of the sky as your own image. Switch to multi-view (two panels) and have your image showing in one panel and the survey image in the other.

- Now you click on a star in your own image. Hold down the shift key when clicking and this should center the point in the middle of the star by analysing the local area. The x-y coordinates of the point will appear in the left column of the dialog. Now do the same for the corresponding star in the survey image. The RA and Dec should appear in the right column. Repeat this process for at least four stars, or more if you have the time. Try to space them across the image area. (You may get an error dialog if you click too far away from the centre of a star, just try again).

- Once ready, click the 'Create' button and this will add a 'projection' (solution) to your image and you should now find that mousing over your image in the stack (right hand side) puts an outline of its area over the survey image. Check it is the orientation and scale you expect and then you're good to go.

- You can export/save your image with the solution to a new FITS file using the Aladin menus, so next time you load it, it will be correctly set up.

- Now just start searching catalogues for interesting stuff. I just used the Simbad service with a filter for galaxies only. This overlaid ellipses showing all the galaxies in my image, and I scrolled around until I found the three that had actually been captured on my image. Clicking the catalogue marker will bring up some details in the table at the bottom of the page with hyperlinks to even more information (most of which is over my head!)

By default Aladin will show one plane of a colour image (R, G or B ), and you can use the cube slider to switch between them. There are three ways to create colour images:

1. Save your image as a PNG or JPG from your processing software, making sure it is flipped vertically as per the guide above. You can load the image and then use the "astronometrical calibration" dialog to cut and paste the WCS solution from the monochrome FITS image (as per the guide).

2. I extracted my FITS to three separate R, G and B planes in different FITS files. I created an astronometrical calibration for one (using star matching), and then switched to the WCS tab and cut and pasted the equivalent WCS header in to the other two planes. You can then use the Aladin RGB tool to join the three images in to a single colour plane.

3. Apparently Aladin can now deal with RGB FITS files if you put the right keyword in the header (e.g. using PixInsight you can add keywords, and I think you can do it in Aladin too). Try either the CTYPE3 = 'RGB ' keyword, or maybe the COLORMOD = 'ARGB' keyword.

Manual for V6 is here:

http://aladin.u-stra...adinManual6.pdf

FAQ includuing changes up to V7.5 here:

http://aladin.u-stra...a/FAQ.htx#ToC35