It’s clearing around 18:00 and while I’m looking to make pretty pictures the technical focus is upon Hyperstar vignetting and upon the SharpCap frequently refusing to “see stars” so as to align and stack a live image.
On Friday I’d gone through yet another set of flat frame captures. These flats were run in the daytime rather than at twilight, so the histogram peaks remained in position rather than drifting to the left. Dimming histograms could be the cause of the flats problem. Here’s a flat capture screen from Friday.
- 45 histo.jpg (316.84 KiB) Viewed 2037 times
- 45histo flat.jpg (155.1 KiB) Viewed 2037 times
Looks pretty good. Let’s see if it works…..
Messier 74 – (also known as NGC 628 and Phantom Galaxy) is a spiral galaxy in the constellation Pisces. It is at a distance of about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a grand design spiral galaxy. It is estimated that M74 is home to about 100 billion stars.
Experienced extreme vignetting with the Hyperstar. No darks or flats applied as vignetting with this setup vignetting is only exacerbated. THE NEW FLAT IS NG. Here’s an example:
- flat not working.jpg (316.56 KiB) Viewed 2037 times
I’d asked about my star detection problem on the SharpCap online forum, and had 4 pages of responses with different things to try. None worked.
- giide star fail.jpg (306.53 KiB) Viewed 2037 times
Not to say I didn’t capture something……
- M74 annotated.jpg (895.86 KiB) Viewed 2037 times
The image is only mediocre rather than horrible due to intense post processing.
It was necessary to reduce chip captive area to 3120 X 2088 pixels to avoid the worse of the vignetting. At 10.5 X 9.5 arc-minutes in size M74 is better suited for the higher magnification of the 14 without the Hyperstar.
IC 405 (also known as the Flaming Star Nebula or Caldwell 31) is an emission and reflection nebula in the constellation Auriga, surrounding the bluish star AE Aurigae. It shines at magnitude +6.0. The nebula measures approximately 37.0' x 19.0', and lies about 1,500 light-years away from Earth
- IC405 annotated.jpg (3.95 MiB) Viewed 2037 times
Playing more with SharpCap’s align settings and changing the digital gain from the maximum 8X to none there are hundreds of stars now being detected. Think I’m getting the hang of this.
Experienced extreme vignetting with the Hyperstar. No darks or flats applied as vignetting with this setup vignetting is only exacerbated. It was necessary to reduce chip captive area to 3120 X 2088 pixels to avoid the worse of the vignetting and allow processing.
Looking back, here’s what the same object processed out on the 7th when darks and flats had been applied. First here's the super vignetting:
- IC 405 super vignette.jpg (105.55 KiB) Viewed 2037 times
- IC 405 1x 116G -20cm 41x3m.jpg (174.89 KiB) Viewed 2037 times
Shut down and inside at 23:25 hrs. It’s 26°F and after being out for the better part of the night the warmth feels good.
Observations & Lessons Learned:
It’s pretty certain that the C format chip is too big for use with the Hyperstar. I've gone thru all combinations of flat imaging and none have solved this problem. Had been considering the purchase of an illuminated flat screen but will give that a pass as it’s doubtful that it’d help.
There was no obvious vignetting with the ASI2600 mounted to the 80mm Orion long tube so it looks like I’ll revert to using the Orion or a similar refractor for wide field imaging.
Next step is to remove the old Hyperstar (that worked will with small format CCD chips 11 years ago) and see what happens with the 2600 mounted to the Orion when flats are introduced.
The SharpCap star detection problem isn’t completely solved. But I’m getting the feel for it.
To some degree, tonight's images were salvaged so the night wasn’t a total loss.
Early in the evening SharpCap started dropping out again, even with the new beta version software download. Turns out that the 86x 64 bit version of the software is a bit hidden on the download page and I’ve been working with 32 bits. Found/Loaded the 64x beta and no subsequent problems.
And stargazing is supposedly a peaceful serene fun hobby???
