First Light – ZWO ASI 2600 color camera

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Pete
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First Light – ZWO ASI 2600 color camera

Unread post by Pete » Sun Aug 09, 2020 3:34 pm

My initial objective here was to capture astro photos without pulling my SBIG astrometry setup off the 14”. And since most folks are imaging with a small / medium size refractor the thought was to pick up a quality piggyback refractor and a medium-large format color camera.

The ZWO ASI 2600 MC Pro “C” format camera eventually purchased was twice as expensive as the 4/3 format ZWO ASI 294MC Pro. While the “C” chip is a bit larger (measuring 28mm diagonal) the deciding factor was that this brand new chip has no amp glow and is producing wonderful images with NO PROCESSING.

As for the mating scope, until camera operation is nailed down I’m going to attempt to mate it with the existing guide scope on the 14” – a 15 year old $119 Orion 80mm f/11.3 long tube achromatic with a focal length of 903mm. This being a cheap scope the focuser is a bit wobbly and crude, but if the optics work out Scope Stuff sells a sophisticated 2-speed Crayford focuser that fits the tube. With the long focal length even a crude objective is expected to have little color.

Although there was a 4-6 week backlog from China the scope arrived on Friday – less than a 2 week wait. The chip is, in my experience, HUGE. Spent Friday afternoon downloading appropriate drivers and misc software. And then trying to learn/understand the SharpCap control software. Powered up the camera using the new fast laptop and the camera does indeed connect.

On Saturday the camera was attached to an Orion 80mm short tube so as to achieve an image, and most of the day was spent experimenting with SharpCap.

Image

Subsequently on Saturday night the ZWO was attached to the Orion long tube mounted on the 14”.
The 42mm T thread to 1 ¼” barrel doesn’t have a safety grove, and at 1.5# camera weight that’s a concern. Before mounting I fabricated and attached a safety wire.
Image
Attached the camera to the laptop. Powered up the cooler with an available 12VDC power supply left over from my last imaging 10 or more years back. All systems go. Even though cloud is rolling in.

Centered and calibrated the mount using the SBIG camera. The 80mm focuser is a bit wobbly and crude but Rasalhauge comes easily to focus. As expected, the SBIG on the 14” is far more sensitive. Slewing Rasalhauge to the edge of the SBIG FOV barely moves it on the laptop screen. The new FOV is HUGE.

Slewed to M102 as it’s relatively large. Can easily see it in the 14”/SBIG at a 6 second exposure, but no joy with the 80mm at 3 min binned 1X1. At 3 min binned 2X2 there’s the very faintest suggestion of a galaxy. But the screen is blue, not black. Due to light pollution reflected off of the cloud I’m working through.

Shorter exposures will null light pollution so a 1X1 binning 30 second life stack was tried. And 102 showed after the 2nd frame stacked. I love auto-stack, where the image builds on itself as you watch. Working thru cloud 28 frames were taken before the camera started rejecting them for lack of object.

Here’s the very first ZWO learn-as-you-go and working-thru-cloud image:
Image

Normally in the 14” the galaxy would fill the frame with its 21 arc-minute wide FOV. Here I’ve got 1.5° left to right. Hmmm. Lots to learn but First Light’a a milestone in itself.
Pete P.
Bruce D
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Re: First Light – ZWO ASI 2600 color camera

Unread post by Bruce D » Mon Aug 10, 2020 1:01 am

Nice Pete!
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Pete
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SECOND LIGHT

Unread post by Pete » Mon Aug 10, 2020 3:47 pm

9 Aug 2020 ZWO camera night 2

Attempted comet NEOWISE and found it took a 3 minute exposure to get it faintly. Guiding with the SBIG and the Y axis is jumping around pretty seriously, to the point where the SharpCap auto stacking was rejecting frames after the first 3 were stacked. Gave up on the comet as its sinking in the W.

Back to last night's M102. After a couple of unsuccessful attempts with the drive jumping around I gave up on guiding with M102. Experimented with ever increasing exposure trying to capture the faint galaxy. Eventually ran a stack of 12 5 minute images. (15 actually as 3 were rejected by the stacking routine).

Image

All stars are being dragged at a slight angle. The angle is believed to be associated with the camera not being squared and the severe declination jumping is probably associated with a severe imbalance situation. That’s a 1.5# camera hanging way out past the back of the scope. In fact slewing on the declination axis from the comet to M102 was intermittent with the drive motor/motors making an RRRRrrrrrRRRRrrrr sound and occasionally stopping for a second. Note that while guiding was problematic on the comet I gave up on guiding with M102.

Conclusions & lessons learned.

Good night actually. Debugging problems are expected.

The scope MUST be balanced to properly track. Way out right now.

This setup requires LONG exposures. M102 was quite clear with 6 seconds exposure thru the SBIG on the 14”. Not sure where I’m going but it’s a fun trip.

Since the camera’s front illuminated chip is supposedly highly efficient is the problem f/ ratio or aperture related? Here’s a quickie S&T writeup on the topic:

The total brightness of a star or other object is determined by the telescope’s aperture, also called light grasp. The focal ratio (also called f/number, that is, the focal length divided by the aperture) has nothing to do with it.
The f/number does affect a telescope’s magnification (with a given eyepiece), and the magnification determines the surface brightness of the view: the amount of light per square arcminute as presented to your eye. But that’s different. In fact, no telescope can ever increase surface brightness beyond your naked-eye view.
Confused? Here’s how it works. A telescope can’t funnel more light into your eye unless it also magnifies the view — that’s the way optics function. You collect more light and you see the object bigger. But with the light spread out in a magnified view, the surface brightness is diluted back down to what it was before magnification, or even less. If surface brightness was all you cared about, you’d skip the telescope!
If two telescopes have the same aperture and magnification but different f/numbers, their views will be essentially identical.
— Alan


OK. Cameras with mechanical lenses change aperture when they change focal length so a wide open f/2 image will be brighter than a restricted aperture f/8 image. It’s the wide open aperture that makes the difference and the FL is simply a by-product. And the experience with using a faster f/ ratio on a DSLR or SLR doesn’t carry over to telescopes. Think I’ve got it.

It would appear that once the drive balance is sorted out an aperture larger than the current 80mm might be helpful. However. How do people get lovely astro-images from 60mm short focal length scopes? An ongoing puzzlement…..
Pete P.
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mark.m
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Re: First Light – ZWO ASI 2600 color camera

Unread post by mark.m » Tue Aug 11, 2020 11:10 am

Hi, Pete:
Congrats on the camera.

That camera has adjustable gain, with an automatic shift to "high gain" mode when you select a gain >= 100. What gain setting did you use for First Light and for Second Light?

It looks like the lower gain settings are appropriate for situations where you're trying to avoid overexposure (and want highest dynamic range) and the higher gain settings when your primary concern is noise due to low light levels.
- Mark
Mark M
Portsmouth, RI
10" Meade SCT
SBIG ST-9E
GM2000 (10Micron)
American Association of Variable Star Observers (AAVSO) observer code: MMU
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Pete
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Re: First Light – ZWO ASI 2600 color camera

Unread post by Pete » Tue Aug 11, 2020 12:46 pm

There are many adjustments that I've not yet played with Mark. The neat software provided this comprehensive set of data within the imaging folder for that particular set of M102 images:

[ZWO ASI2600MC Pro]
Debayer Preview=On
Pan=0
Tilt=0
Output Format=FITS files (*.fits)
Binning=1
Capture Area=6248x4176
Colour Space=RAW16
Hardware Binning=Off
High Speed Mode=Off
Turbo USB=100(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=142
Exposure=300
Timestamp Frames=Off
White Bal (B)=95
White Bal (R)=57
Brightness=85
Anti Dew Heater=On
Temperature=-2
Cooler Power=57
Target Temperature=-2
Cooler=On
Auto Exp Max Gain=350
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1
Notes=
TimeStamp=2020-08-10T03:06:27.9609344Z
SharpCapVersion=3.2.6396.0
TotalExposure(s)=3600
StackedFrames=12

Settings were left untouched from 1st to 2nd light runs. And I see that gain is set at 142, probably a random setting as at 1st light I was making adjustments to get a feel for them all.

There are many basics, such as "how do I terminate a long exposure in the middle of the exposure", that I have yet to learn. It's time for a second reread on the SharpCap instrucions. And yes, we're having fun yet.
Pete P.
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