Monday, 16 July 2018

Slight delay in the release of the next version of AstroDMx Capture for Linux

Nicola is making great progress with the implementation of the Atik 314L in AstroDMx Capture for Linux as previous posts have shown. However, she has also been trying to resolve a problem over the QHY cameras giving unreliable exposures at certain long exposures. This is a problem with the QHY SDK.

The problems have been reported and new SDKs have been released. However, with each new SDK release, a number of other serious, deal-breaker problems have been introduced. These in turn are being reported, and the hope is that the QHY SDK developers will soon resolve all of the problems. In the meantime, it may be necessary to produce a release of AstroDMx Capture for Linux that implements the Atik 314L (and possibly others) before the QHY issues are resolved.

This is unfortunate and disappointing, but it is important to realise that the problem is not with the AstroDMx Capture code, but rather, with the SDK that has to be used to call the camera functions.

I will make sure that when a new release is made, the information will be posted here. Nicola will implement a hack that should improve the exposure situation for the QHY, but that is no substitute for a reliable SDK.

Sunday, 15 July 2018

Testing a new display function in AstroDMx Capture for Linux with an Atik 314L camera

An Atik 314L camera was placed at the Newtonian focus of a Skywatcher 130 PDS 130mm, f/5 Newtonian, mounted on a Celestron AVX GOTO mount. 16 x 48s exposures were captured of M8, the Lagoon nebula and 5 matching dark-frames using AstroDMx Capture for Linux. The images were dark-frame corrected and stacked in Deep Sky Stacker running in Wine. The final image was processed in Fits Liberator, running in Wine and the Gimp 2.10.

The problem with 16 bit imaging is that the image being captured has to be rendered in 8 bits so that it can be viewed on the computer screen. Moreover, the interesting parts of the data are very dim and with a simple scaling of the results to 8 bits, much of the object being image will probably be invisible. What is needed are transfer functions that will brighten, in a non-linear fashion, the image data, so that the fainter parts of the object are revealed. These transformations are only made to the displayed image, leaving the saved data untouched. AstroDMx Capture for Linux has been given a number of controls to optimise the visualisation of the data being captured. Here we were testing a gammalog display function to help reveal the object whilst being captured.

Final image of M8, the Lagoon Nebula

The images were captured while testing the new gammalog image display function in AstroDMx Capture for Linux.

The preview image can be brightened or dimmed using the other non-destructive controls of gamma, brightness and contrast.
Additional display transformation functions are being implemented now and will be tested as soon as possible.

Tuesday, 10 July 2018

Occultation disks and streetlights

To the astronomical imager, streetlights can be such a problem as to make imaging all but impossible. I don't mean the general problem of light pollution in the sky caused by streetlights, I mean the glare from nearby streetlights that can shine directly into the telescope and ruin any results.
We have a streetlight right outside the front of the house. The council fitted internal baffles to the lamp on request, which reduced it in brightness a little, but it is still able to cast its bean of light onto our scopes that we have to use at the front of the house in order to image objects lower in the sky. This problem is solved by mounting a blackened occultation board on a sturdy tripod and placing it so that it casts its shadow onto the scope. This solution works very well and occultation disks or boards can help problems with more distant street lights that are in the general direction of where the scope is to be pointed.

The streetlight can be seen very close beyond the occultation board.

From the point of view of the scope, the street light is completely obscured and does not cause a problem.
Smaller occultation boards, strategicall placed, can deal with problems caused by more distant lights.

Saturday, 7 July 2018

First Light for the Atik 314L implementation in AstroDMx Capture for Linux

An Atik 314L camera was placed at the Newtonian focus of a Skywatcher 130PDS, 130mm, f/5 Newtonian, mounted on a Celestron AVX, EQ, GOTO mount. 16 bit Fits images were captured of  M16 (40s), M17 (40s) and M13 (35s) using AstroDMx Capture for Linux. For each object, the best 26 frames were stacked in Deep Sky Stacker, running in Wine. The images were post-processed in Fitswork (running in Wine), The Gimp 2.10, RawTherapee and Neat Image.

M16 the Eagle nebula and cluster

The Pillars of Creation

M17, the Swan or Omega nebula


 Nicola hasn't quite finished the Atik 314L implementation. When it is finished, it will be present in the next release; which has been delayed by problems with the latest QHY SDK. QHY have been made aware of the problem and are currently working on it. In the meantime, the Atik 314L implementation goes ahead.