Poor Contrast of Images from New ASI071

mslehv

In January, 2018 I purchased a newly upgraded ASI071 Pro. The camera captured excellent images but two weeks ago the cooling section stopped working. As per Sam's instructions, I sent it back to my dealer who shipped it back to China for repair. Because I didn't want to be without a camera for 2-3 months waiting for the repair and because I really liked my ASI071 Pro, I purchased a second ASI0171 Pro.

I was operating the original camera and capturing images with The SkyX Pro using the X2 drivers with absolutely no problems. When I sent back the original camera, I simply disconnected the USB and power cables, covered the open extension ring to the camera and shut down the system.

Once I received the new ASI071 Pro about a week ago, I simply reversed the process, screwed the new camera onto the extension ring, connected the cables and started up the system. I changed nothing in the optical train and changed no settings in The SkyX.

However, the images from the new camera lack the contrast, number of stars visible and background blackness of my original ASI071 Pro. I tried changing some of the camera settings such as gain, offset, gamma with no improvement in the background blackness or number of visible stars. In fact, even increasing the exposure time doesn't seem to have much effect.

Below are images from each camera of exactly the same star field, under similar seeing and transparency sky conditions, similar sky locations, same gain of 50 and same offset (brightness) of 12 and exposure time of 120 sec. There are considerably more visible stars and a blacker background in the image from the original camera than from the new one. The difference is even more apparent in the actual FITs images than in the down-sampled attached images. The images were taken only three weeks apart.

Did the camera hardware or firmware change from 01-18 to 10-18? This seems to be a problem with the new camera because nothing in my optical train or software changed.

What can be done?

Thanks.

Michael Lehv

Support@ZWO

Could put original *.fit documents on dropbox and tell us the link?

images from old camera and new camera.

We will check what happened.

mslehv

Hello Sean,

I've looked into this issue further. It seems that the problem is with the FITs files that are downloading from the new ASI071. I'm using PixInsight and its STF to view FITs files. I never had a problem with viewing images from the original camera. However, when the STF is used to view FITs files from the new camera, the images don't display properly due to a light background and fewer stars visible. The background ADUs (from CCD Inspector) are over twice as high from the new camera as from the original camera.

It is possible to improve the appearance of the images from the new camera but it requires considerable manipulation of the sliders on the STF to adjust the blackpoints and midtones balance. The normal STF settings don't work and adjusting the sliders for each image from the new camera is too time consuming.

So it seems that the problem is with the histograms of the images from the new camera. They are very different from those from the original camera and don't display properly with PixInsight's STF default settings. This isn't a problem with seeing or focus because the images from the new camera actually have better (lower) FWHM values than from the original camera.

The scope is an SW150 with a field flattener and ZWO IRCUT filter. I made sure all the optical surfaces were clean. The settings for all images were: Gain 50, Offset 12, Gamma 50, Raw 16, Hardware and Mono Bin=0, X2 Driver 17.4.25 Version 2.000, ASI SDK V1,13,0,16

Here are Google Drive links to the FITs images at 120 secs from each camera. It's the same star field but the new camera images are rotated about 90 degrees and the images from the original camera are at ambient temperature because the cooling section wasn't working.

Original camera 120 secs. https://drive.google.com/open?id=1Rq36AtZD9b-JqVVkBHJAtQvYZt23GAS3

New camera 120 secss. https://drive.google.com/open?id=17Cczu3iUnx6L9kjATGsjBwD0bVmCFLJ0

Here are two more images from each camera with the same settings but 300 secs exposures.

Original camera 300 secs https://drive.google.com/open?id=1x3W-Kk2eSU0rw0vWEk7FYm0U5yYM4Mve

New camera 300 secs https://drive.google.com/open?id=1Q-SiKskHStGCU9r43bKFasK9EoMvXBH4

Thanks in advance for your assistance.

Michael

mslehv

Hello again Sean,

After further experimenting, there appears to be something seriously wrong with the new camera. I took 30 dark frame images and stacked them in PixInsight as a dark frame master. When viewed with PixInsight's STF, the single dark frames and the Master Dark images appear as uneven shades of gray rather than black.

However, this is not just a problem with how the images appear in PixInsight, it is a problem with the underlying raw data. I was unable to utilize the dark master for calibration of 26 light frames that I imaged of M30. The calibration process produced numerous errors preventing proper DeBayering, star alignment or final integration. The final image was just a mess of noise with a few blotchy stars.

Here is a link to a single Dark Frame:

https://drive.google.com/open?id=1AVT4txu4cXUTiTRBnQuVdnXGuYZ9AXRP

Here is a link to the PixInsight Master Dark Integration from 30 dark frames

https://drive.google.com/open?id=15XjD8OmNOOExgHntC9kQW4aoEVsvA1EG

Since the dark frames don't depend on anything other the camera output, having the same gray images directly from the camera eliminates any possible optical or seeing issues. It seems that the camera's dark images cannot be viewed or processed in PixInsight.

This is actually the fourth ASI071 I've had. I had no imaging problems with my original ASI071, my upgraded ASI071 Pro that had to be returned due to sensor dust or my ASI071 Pro that was returned because of the broken cooling system. So out of four cameras, only the new camera that I received two weeks ago has had these imaging problems. All four cameras have been running under the same SkyX Pro and PixInsight settings.

Please see if you any ideas about correcting these issues.

Thank you,

Michael

chad

Hi Michael，

Can you take some flat fields?

When you take it, please move the lens, and use the natural light.

Thanks

Chad

mslehv

Hi Chad,

Before I get to the flats, I wanted to see whether this issue was somehow related to capturing the images with the SkyX Pro (TSX). It's been too cloudy for sky images but I did take 25 dark frames using Sharp Cap. Both the single dark frames and master dark show the same problem as with TSX - shades of gray, not black and very few hot pixels showing. So, this problem doesn't seem to be related to anything in TSX. Here's a link to the Sharp Cap darks master integration created in PixInsight. https://drive.google.com/open?id=1rHOVQKnys6p3XZ8O3a-61B48mTlDlFcp

I actually did take some Tee Shirt flats yesterday. The scope was tracking at the sidereal rate so I was "moving the lens" while the sub frames were being acquired. These were taken at an ambient temperature of about 20C, 50 Gain, 12 Offset, 0.03 secs X 100 subs. I tried to calibrate the flats but I was unable to do so properly because the PixInsight calibration process using the the master dark integration produced an error with each flat frame sub. Here is the best I could do in producing an integrated Master Flat (for the West sky).

https://drive.google.com/open?id=1pOG3DF2LWTDGjWnbQgo_iUtl9qfQf9JD

Thanks.

Michael

chad

Hi Michael,

1, Can you check your filp setting? According to your images, the first pixel is Blue, but usually it should be red. I am not sure if it is the flip caused. And I think this is the reason caused the lack the contrast.

2, Can you send me the single flat fits file?

Please send email directly to me: chad.cao(at)zwoptical.com

Thanks

Chad