Camera Labs

Hi folks,

My astrophotography goal for the summer is a four panel mosaic of the North America nebula. I've previously taken an ultra-widefield image of the region using my 165mm f/2.8 Pentax medium format lens (this post) but there's much more detail to be had with the 980mm focal length of my TEC 140. The only problem, of course, is that imaging at f/7 needs a lot more patience. Today I thought I'd see if the 16 unguided Hα subs I've captured so far, each of 1,000 seconds exposure time, would be enough to get the depth I wanted and here's the result of part of the image at 50% scale (you can click the image for a 100% crop factor version which also shows fainter stars):

No red, green or blue subs yet but they are planned for the future to add star colour. I'm still trying to refine my processing skills being pretty new to the game so for the first time I tried blending differently processed versions of the nebulosity. I blended a "No Stars" clone of the image with a copy of that "No Stars" image which had been HDRMultiscaleTransform-ed courtesy of PixInsight. The result was coloured (that will need more fine tuning - Hα colour and intensity always seems to be a difficult step to get right!) and then a "Stars Only" clone, which had also passed through PixInsight for a spot of deconvolution, was added back.

As I say, just a test image to find out if about four and a half hours of exposure time gives me the depth I want. The good news is "Yes, it does", the bad news for me is that I'm going to have to retake about half of the subs as the earlier images were taken with the camera rotated about 7°, enough to mess up the joins of the mosaic panels. Oh well, it keeps me out of the pub and reminds me how meticulous attention to detail isn't optional for astrophotography. At least I now know that the telescope, mounting and camera will eventually reward all the time spent over the coming months!

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi folks,

Nominally my Hα captures are complete with 16 x 1,000 second exposures for each of the four panels of the mosaic (total time nearly 18 hours). Until the Moon gets out of the way, even if tonight is clear, I won't have a chance to collect all of the RGB subs I need to replace the stars with coloured versions (frustratingly I might be as little as one hour short of the time needed) so I thought I'd process the Hα to see where I've got to. Not ideal because of issues with star intensity where the nebula is strongest (due to the way I separate out "NoStars" and "JustStars" versions to allow separate processing of the nebulosity in particular) but I thought I'd share. Here's the thumbnail and you can click on it to view the 7720 x 7100 pixel 100% version (6.5 MB):

Bob.

_________________
OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

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Well, it has meant a seven and a half week wait for a suitable opportunity but, I hope, I have finally captured the remaining green and blue subs. Processing might have to be put on hold for a week or two but at least I can now move on to another target!

Bob.

_________________
OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi folks,

Having got back from a couple of weeks away I finished off the star removal of the four pane H-alpha part of the mosaic, a process that took many day's at it my normal automated procedure didn't work well with this image, and made a start on contrast enhancement and it has proved a bit of a mare. In addition to the camera's infra-red RBI illumination issues in the lower left pane which reduced sensitivity of the final image (still trying to work out why and my best guess is I was fighting dew on the camera window and as a result the normally excellent dark frames I created earlier in the year weren't correct) there have also been differences in the background noise which really start to show up when the processing gets on the fruity side!

Some of these issues will get hidden again when I add stars back later on but here's the preliminary "No Stars" version which is clickable to view the full size image. I hesitate to provide it because the pixel peepers will find lots to dislike so if you are a pixel peeper then view it at your own risk. Hopefully it will get better...

One thing I've already learned is huge respect for anyone who produces four frame, or larger, mosaics. The amount of work seems to grow exponentially and while I'll be happy enough to tackle two framers again I think four framers have just moved a long way down my personal priority list!

Bob.

_________________
OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Nice detail in there, even if masked somewhat by the high jpeg compression of the big version. If we ever get clear skies again before Cygnus disappears from field of view, I hope to give my new mount a workout and see if I can get closer to this than I have previously.

Also, I recently did my first mosaic, not deep sky, but of the sun. That took a while! To me the main challenge was to ensure consistency so it'll go back together nicely.

Out of interest, what's on your target list? More data of existing, or what new targets are lined up?

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Hi popo,

There is a lot more work to do on this mosaic and I also want to return to my M31 data with a view to producing a version suitable for a 24" print.

If weather permits I want to tackle the Heart and Soul nebulae - two separate images - but the priority will be the Horsehead and Flame nebulae and the Orion nebula, all with the TEC 140. Old chestnuts, I know, but new to me at that resolution and they all have challenges.

Bob.

_________________
OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

I know the feeling... the mount upgrade I had recently should enable longer focal length usage. No more crop zooming! So everything I've done already... could be redone better. In theory at least... still haven't finished the software configuration!

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Hi folks,

Hmm, colouration! The nebulosity visible in the image below is entirely from H-alpha subs while the stars are from separate RGB exposures with the nebulosity removed.

The colour of the nebulosity has been modified from my usual deep red by using a "No Stars" version of the RGB data. That RGB image was a good deal shallower than the H-alpha data but it seemed to indicate colour shifts away from pure red in the brighter areas. As a result I used an RGB "No Stars" image, with red and a little blue added to the darker areas of the image via a curve to provide colour information that would otherwise have been lacking in the very dark areas of that RGB image, as a "Color" layer in Photoshop to modify my usual H-alpha colouration of the "No Stars" H-alpha data.

The image below is slightly cropped and one quarter scale but hopefully it is good enough for me to be able to request feedback on this method of colouration. Does it work, does it look unnatural or is it a step too far? Thanks for your time.

Bob.

_________________
OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Don't think I understood what you were doing, but based on the output... some areas are going a bit pinkenta, so unless you're going for a job with DRTV that could be checked. Of course, we're likely to go back to the monitor colour calibration questions if you don't see it too... guess I should quickly check with other browsers... and now that I've done that, I can report the FF looks different from IE and Chrome. FF is less saturated, and I prefer that look. The other two look overcooked. For comparison, I've also opened it in PSE, and confirm the FF look resembles the optimise for screen option, and IE/Chrome look unmanaged.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.