Out at 17:30 powering up computers, cameras and the 14” with its Hyperstar. Tough and frustrating night.
NGC 1275 aka the Perseus Cluster and C24 Initiated imaging and SharpCap kept dropping out. Did so 5 or 6 times. SoftCap wouldn’t align stars for live stack. Severe vignetting with L side light red. Managed to capture 10 frames. Stacked & processed in ImagesPlus. And PS of course.
- NGC 1275 10x3m f2 1x annotated.jpg (1.61 MiB) Viewed 1170 times
10 X 3 minutes, unbinned, -20°C, gain at 200, guided at 3 sec.
While there are dozens of galaxies in this wide field image only a handful are obvious. Flats were discarded as they buggered up the vignetting more than if not used.
IC 405 – aka the Flaming Star Nebula and C31
- IC 405 1x 116G -20cm 41x3m.jpg (174.89 KiB) Viewed 1170 times
This time around SoftCap was picking alignment stars but the software dropped out after 2 hours and the stack wasn’t saved. So stacking of individual frames and subsequent processing was run thru ImagesPlus. Flats were worthless and couldn’t be used. Vignetting was horrible and this small image is very tightly cropped.
In at 23:30.
Conclusions and lessons learned:
Nice to be out under the stars but imaging difficulties made it a wee bit frustrating. Flats just aren’t working. With the Hyperstar, the ASI2600 is severely vignetted. Live stacking is hit or miss as SharpCap frequently won’t find alignment stars.
Both images are cropped and obscene processing was necessary to get them where they are. See problems above.
I'm beginning to better appreciate imaging at long focal length. Using wide field (at 700 mm) the stars are pinpoint but there just aren't that many large DSOs compared to a FL of 3500mm.
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Dropping back
4 Jan 2021 Dew shield modified and mounted over the Hyperstar. Weight added to the backplate counterweight bringing it up to 18#. With the dew shield new flats are necessary..
Flat frames were taken (as I normally do with the SBIG) using the T shirt frame at twilight. 3 sets run at 1s, 2s and 4 as there’s some talk on the ASI facebook about longer exposures being necessary. These were unbinned and run at a gain of 100.
These flats didn’t work on Jan 7. Light is fading fast at twilight and over the course of stacking 15 or 50 frames the histogram brightness drops from 10% to 20%. You can see the curves marching across the screen from bright to dark. Is this creating a problem?
A long series of dark frames was run at a gain of 100, as 100 may be the setting to use. Can’t use a lens cap with the Hyperstar mounted. So got a ladder and covered the top of the dew shield with opaque cloth. Ran long series and afterward discovered that they were all junk. Even in the closed dome at night with the dew shield covered the center area was gray while the corners were black. Unusable.
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Subsequent action
8 Jan 2021 corrective actions taken.
As for the drop out situation, it’s either the camera or the software. Rather than remove and reload SharpCap 3.2, SharpCap 3.3 Beta was downloaded. This Beta runs with the 2600 and compatibility was tested by running the new flats noted below.
The only workable flats taken for the 2600 were on the 14” at prime focus. (At prime focus there’s no noticeable vignetting). These were run under early morning black cloudy sky with the old T shirt frame after adding another 2 layers of fabric. Perhaps there’s a need for the sky remaining at constant brightness?
So on the 8th yet another series of flat frames were taken with the Hyperstar & dew shield. This time at mid-day after adding 4 more layers of white T shirt to the existing wooden framework. ¼ sec exposure is the longest exposure possible. Fine tuning of the histogram was done using gain. Set white average curve at 45% saturation, leaving the R and B curves down at 30% and G at 70%. To be tested.
hgp 9 Jan 2021
