Attempt to mosaic

After creating the Heart nebula in a mosaic a month ago, we had some semi-clear nights last week, in which I could try and stitch the Soul nebula to the Heart.

Unfortunbately these nights were also very foggy, sometimes fog banks floated over, with barely star visibility. The good news is that SGP (Sequence Generator Pro) kept up trying, despite star loss in PHD, to continue making lights. While sleeping. So that’s really wonderfull.

The end result, needless to say, did have that much gradient sin the final image that I do not consider it a result. It’s more an exercise. The final mosaic had 10.000×12.000 pixels and took 1,5 Gb TIFF or FITS size. Both AstroPixelProcessor and Photoshop had issues digesting this large file. In fact it’s so large that Astrobin or this website cannot upload it.

10% of a 11.000×12/000 pixel mosaic 6-panel.
A 2-panel (part of ) the Soul nebula. It’s clear by the halo’s around the brighter stars how foggy it exactly was.

This is a two-panel mosaic each panel of about 10 300-seconds 800ISO frames with the 120mm Esprit F5,5 and Nikon D750
. The remaining panels on the left of the “foetus” were fogged out.

Heart in the Sky

The Heart Nebula in Perseus is an interesting region of red hydrogen clouds mixed with dark nebulosity and bright star clusters. This was a test-run: first light with the Sequence generator Pro combined with the Nikon D750 (with autofocus by PegasusAstro, worked wonderfull). Second test (living dangerously!): first attempt to mosaic automatically with SGP.

The D750 would crash SGP when hitting the “link” button: as soon as I touched that button, SGP would collapse and simply vanish in thin air. Solution: install the 2013 C++ redistributables.

The Optolong Pro filter OR the reducer/flattener (or the combination) imho added a lot of vignetting and uneven illumination to the image, which I had a hard time eliminating. So next test would be with a regular Nikon T-ring. If that does not solve the issue then it must be the F5 reducer. I noticed earlier already that images at F7 with the Nikon were a lot cleaner.

IC1805 or the Heart Nebula in Perseus. Image dedicated to my mom who passed way in September age 79. 

Imaging with ASI and Nikkor lenses

It would be nice to image through some of the Nikkor lenses with the ASI183mm Pro. In some cases you reach telescope fields and resolution.

As an example: the 300mm F2.8 Nikkor, attached to the ASI 183mm, delivers a field of 151′ on 100′ with 1,65″ pixelsize.

The Nikon FF D750, combined with the Esprit 120mm, delivers a field of 146′ on 98′ with 1,46″ pixelsize.

Comparing the combinations Esprit/D750 and ASI/300mm: the fields are almost overlapping

Actually the Nikkor 300mm can be seen as an 110mm F 2.8 Apo? The ASI will also use only the center field of the image circle, which avoids all image issues that might occur towards the edges of the field.

The next issue is connectivity! how to connect an ASI body to the Nikkor lenses? The Nikon F-mount backfocus is 46,5mm. The setup that works for me is the following:

  • Nikkor lens with F-mount
  • SI Nikon lens adapter. But ONLY the first ring that attaches to the lens. That ring has 11mm optical length and uses M57x0,75mm male thread. Link to TS.
  • TS Optics M57 to T2 adapter Link
  • Filter manual wheel ATIK Optical length 20mm (could be replaced by a motorized ZWO ASI FW)
  • ASI 183mm camera without the T2 F/F/ connector.

The total optical length of this setup is close to 46,5mm and gets me sharp images. The 1 “1/4 filters that are used might still stretch the focus further out.

Further possibilities to explore:

  • autofocus using a belt and a Pegasus FocusCube 2 or a ZWO MotoFocus
  • simultaneously imaging with ASI 300mm H-Alfa on F 2.8 and Esprit/Nikon RGB: given the faster optics of the Nikkor, all H-Alfa and O-III imaging can be done in the same timeframe as the Esprit/Nikon RGB.

Waiting for a clear night!!!!