The Iris revisited

On a wet and windy bank holiday Monday I finally got back to this subject for another attempt at processing. Having dedicated about 23 hours acquiring the images and spending countless more hours processing the data I still felt that there was more in this image than I’d managed to extract.

I’ve learnt a lot about the Pixinsight tools I regularly use on other projects and added a few more to the toolbox. Overall, I’m very happy with this result.

Iris

NGC 2403

Looking back through my image archive I found a couple of hours worth of images of NGC2403 in Camelopardalis that I took in 2014. Over a couple of clear nights during the past week I added another 8 hours to this and an initial process is quite promising.

NGC2403

Kemble’s Cascade

Located in Camelopardalis, Kemble’s Cascade is a remarkably straight line of colourful 6th to 10th magnitude stars. Named in honour of Friar Lucian Kemble who discovered it while sweeping the skies with a pair of binoculars. It’s a nice fit for the field of view with my FSQ-85 and QHY9 camera.

A near full moon interfered with fainter targets and caused some issues with this one with artefacts due to internal reflections in the camera. Thirty 2 minute exposures, stacked and processed in Pixinsight.

Kemble's Cascade

Aurora

At last, I’ve seen the Northern Lights. A short break in Tromsø and despite a slightly iffy weather forecast the first night we took a tour out off the city. Weather was forecast to be best over Kvaløya so that was the direction we headed and the clouds started to thin after we’d travelled a few miles. This was probably the brightest but I’ve still got some more pictures to process.

_MG_2873

Image annotation

One of the tasks that you might want to do with an image is to identify and annotate the objects within it. With it’s ImageSolver and AnnotateImage scripts PixInsight makes this really easy. The AnnotateImage script comes with several pre-canned catalogs such as Named Stars, Messier, NGC and PGC catalogs but also gives you the ability to specify your own. What I’m going to describe here is how to generate and use your own catalog from a VizieR source.

As I’m interested in Dark Nebulae, for this example I’m going to use the Lynds Dark Nebulae catalog and the first step will be to download it from VizieR. First we have to identify the catalog so we visit the search site http://cdsarc.u-strasbg.fr/viz-bin/Cat

Entering the authors name (Lynds, in this example) returns a list of all matching catalogs. We need the second item in the list which has a catalog ID of VII/7A/ldn. Clicking on the title, Lynds’ Catalogue of Dark Nebulae (LDN) (Lynds 1962), takes us to the catalog selection page http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=VII%2F7A.

We could also search on any other identifying information or, if you’re unsure you can browse the entire collection.

We’re going to use a simple constraint query to return all catalog entries but with just the selection of fields that we require. There’s a lot of flexibility here and you can filter records based upon various criteria such as object size or magnitude to limit the search but we’re going to keep it simple here. The fields we require are LDN and Area so ensure that these columns are ticked and clear all the others. We don’t select the columns for RA and DEC as these are of the wrong epoch and also incorrectly formatted and there’s an easier way to obtain the correct information. On the left of the screen is a Preferences panel with more options; select Compute and tick the J2000 box. This will return correctly formatted, J2000 coordinates which will save us some work later.

Also select ‘ascii text/plain’ from the drop down list and select Decimal for ‘Position in’. Choose a value for Max that matches what you expect in terms of the number of catalog entries. Finally, we’re ready to Submit the query and the results will be returned on the next page.

Make a note of the column headers and then copy and paste all of the catalog entries into a text file on your computer. Next, fire up your favourite spreadsheet program and import the text file such that the data is divided into discreet columns and correctly aligned. I’m not going to describe exactly how to manipulate the data in your spreadsheet; just the general objectives so that the data is correctly formatted.

The AnnotateImage script can work with the following columns:

  • NAME – An object label (optional)
  • RA – Object coordinates in degrees (not hours) format (required)
  • DEC – Object coordinates in degrees format (required)
  • DIAMETER – Object size, in arc minutes. If this is not specified, a point source is assumed (optional)
  • MAGNITUDE – Object brightness (optional)

Put these column names, as required, into the first line of the spreadsheet.

Next, perform any required data manipulation on the object information. In this example, I amended the Name column to include the LDN prefix on each entry and also recalculated the Area values as diameters. Once this is done, save the spreadsheet as a tab delimited text file. The result looks something like this:

Spreadsheet

Now we’re ready for PixInsight. Load your linear image and run the ImageSolver script, entering values and parameters as required in order to plate solve the image. Documentation is available either online or in the program for this and once it’s completed successfully you can progress with any image processing that’s required to form your final image. Note that, once solved, you cannot resize or resample the image so carry out these tasks first.

Run the AnnotateImage script, select any of the predefined catalogs required, click the + button and add a custom catalog, supplying the path to the previously saved text file in the dialog box. You should now have a new image with all the objects identified and marked.

LDN1477_DBE_Annotated

Barnard 150

This has been another of those longer projects gathering 10 minute frames over  3 nights in September for a total just short of 15 hours. Processing has been done entirely in Pixinsight.

B150 is located in Cepheus and isn’t often seen in images. Here’s my attempt to redress the balance.

B150-2_web

Lunar Eclipse

It’s been a while since I photographed a lunar eclipse; the last one was in December 2010 and the pictures are here: Lunar Eclipse. That one reached totality at dawn but this one was in the early hours of the morning against a dark sky. I took pictures from 3am until 3:20 and this is the last of the sequence. The moon is only just into the Earth’s shadow and consequently, there’s still a brighter area on the disk.

Lunar EclipsePicture was taken with a Canon 100D and 75-300mm zoom. Exposure time was 3 seconds.

The Iris nebula

This is a wider field of view around the Iris nebula in Cepheus (vdB139) and shows the extensive dust clouds that surround the reflection nebula itself. This is another of those objects that I’m in a constant state of gathering more frames for; so far this is up to 8 hours in 15 minute subframes.

vdB139