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. 

Using the PegasusAstro FocusCube 2 on an Esprit APO 120mm

There are good reasons to switch the a motor controlled focusser:

  • automating sequences in Sequence Generator Pro
  • Autofocus
  • Automated focussing after a filter wheel switch
  • Getting comfy inside while able to fully control your telescope
  • Go to sleep while your equipment takes care of image acquisition
  • no more slipping of the focusser with heavier loads

Why the PegasusAstro focuscube? I actually ordered the Lacerta motofocus first, however there were delivery problems. It first took two months to deliver, after which nothing happened. On inquiry I learned that it would take another two months. I decided to change to the PegasusAstro, and a few days later it was on my telescope, mounted and working…

Both these brands could demonstrate that the motors would actually fit on an 120mm Esprit. That was my main reason, other considerations were the strict requirements of connecting to a PC, working with SGP and similar software, and the ability of attaching a handbox. The PegasusAstro FocusCube was standard delivered with a temperature sensor (option with the Lacerta).


It was not difficult fitting the FousCube to the Esprit standard focusser. The only challenge was to shift the L-frame so that the two bolts could fit the focusser body, while a the the same time the axis and the connecting cylinder were also aligned. The two screws were part of the assembly of fixation material delivered with the FocusCube. They fit the smaller screws of the Esprit focusser.

The two bolts fit the smaller sets of predrilled holes, which have tiny little hex screws inside. They are easily removed and replaced with two bolts that are part of the material send along the FocusCube.
The FocusCube attached to the Esprit standard focusser.

Getting autofocus working with Sequence Generator Pro, and the FocusCube was also a matter of trial and error. After two nights the autofocus works very well.

This is the full set of settings that work with my equipment:

  • when you cannot get a nice ‘V’-curve when autofocus runs, try to increase the exposure time. The image statistics should give you at least 50 stars. Below that value, the HFR values become erratic and unreliable. I use 20 seconds for a 7 nm H-Alfa filter.
  • remember that autofocus is intended for small corrections, so you should already be near focus before you can run it
  • always run autofocus before a filter switch. In theory the filters are parfocal, however in practice they rarely are
  • I only run autofocus per degree Celsius. If the temperature doesn’t change, there is little reason for focus. The whole autofocus process takes time, maybe 5 minutes or so, time that you loose imaging.
This is an actual screenshot of my first run with autofocus, based on the above settings.