AstroBrian

7 hours ago, Budgie1 said:

Is that image the stacked 24x 5min subs or is it one sub?

If it's the stacked image, do you see the noise in the single subs?

Are you guiding and do you use dithering?

It looks like "Walking Noise" caused by not dithering, but I'm not 100% sure so hopefully others will be able to assist.

Thanks so much. It is stakced 5 minute subs x 24 so two hours total intergration. Do you know how I can dither in SharpCap? Walking noise thats the word I was looking for!

3 hours ago, Whirlwind said:

As noted above this looks like "Walking Noise".  It's caused by fixed pattern noise on the CMOS camera that can't be corrected using dark frames.  Again as noted you have to use aggressive dithering to remove it.  This 'blurs' the noise across the image in an areas rather than rely on slow drift to remove it during processing which was more commonly relied on for CCD images.  I speculate that that the difference between a 2min / 5min exposures is that for some reason 2 mins is more heavily dithered and/or is generally more noisy so hiding the issue (rather than not being there).  For the 5 min exposures other noises sources will be lower (relatively) and/or there will be less images being dithered because of the longer exposure and hence more aggressive dithering is required. 

I dont do darks, probably should but have trouble taking darks. Two minute subs seem to do the trick. Walking noise is the word for it and dithering. I am not sure is there a way to do dithering in sharpcap function? I'll have to test all this Sunday night  Thanks for the reply!

Hey everyone. I have a ZWO294 MC PRO using Sharpcap Pro and I am doing 5 minute subs and I get these odd streaks... 2 minutes doesn't show any but the 5 minute has. Does anyone know how I can stop this from happening? I know theres a word for this but I doni't know a fix. Image of M106 processed shows the streaks. You can see what looks like noise ribbons. This is about 2 hours worth of data. 24 images of 5 minute subs. Thanks for any help offered

On 10/12/2021 at 21:00, robin_astro said:

You also need to watch what gain you run with some of these CMOS cameras if you are stacking a lot of short subs. You can generally get away with more shorter subs with CMOS compared with CCD as the read noise is lower but if you look at the specs for this camera the read noise suddenly shoots up to a poor figure at lower gain settings

https://www.firstlightoptics.com/user/products/large/zwo_asi294mc_read_noise.jpg

Robin

Hey Robin cheers! So for the 4 seconds per sub I am at anywhere between 460-500 on the gain. It seemed to be okay.  Heres a stacked 4 second x 30 (2 minute exposure total) of M33 galaxy. I am assuming the grey is okay for the background. I did the 1 hour on this and got the next result. Would you say I did good?

On 05/12/2021 at 18:54, vineyard said:

It sounds to me like you're trying to do lucky imaging on DSOs, which I think folks have done.  I've never tried that so can't help you w details I'm afraid, but this might be a helpful thread to start? 

You bet I am, amd I know a ton of people who have successfully gotten mind blowing results too. I think I am getting better at it. I including the latest 36 minutes on M81 Bodes Galaxy below on this post. Thank you!

On 05/12/2021 at 22:22, tomato said:

You might want to try a brighter DSO, this is M27, mag 8.1, 150x5 secs so 12.5 minutes total integration  with a 150mm F7 refractor and ASI 178MM, Bortle 5 Sky. Note it is the best 150 frames from over 1800 taken.

Thanks! Yes last summer this year I did do M27 test for 30 minutes in Bortle 4-5 sky. 4 seconds per frame total 2 minutes per image x 15. This was my result.

On 05/12/2021 at 22:50, vlaiv said:

There is significant difference between:

Stacking 2s subs to get 1 minute sub and then using 60 of those to get 1h total exposure

and

using long exposure length and getting again 1h of total exposure.

Two approaches would be the same if one had camera with 0 read noise, but since such thing does not exist - we must take into account read noise.

In your case - you took 30 x 60 subs and stack those - that is 1800 subs.

In normal case, one would use say 2 or 3 minute subs - let's say 2 minute subs - so stack would contain 30 of those.

You made a stack containing 1800 "doses" of read noise when you could have done the same with only 30 "doses" of read noise. Remember - each time you read out sub, even short one, it will contain some read noise.

On top of that - you are using very long focal length scope and you are sampling at very high sampling rate - you are "zoomed" in much more than your skies / mount / scope support - look at this:

That is size of stars when you look at image at 100%.

When you look at your image at 100% - you want your stars to be point like - here is example:

See the difference?

Moral of the story:

- Use better software for image capture - try NINA for example.

- Use ASCOM driver, capture in 16bit format and not 8bit

- Set gain and offset properly

- Use calibration frames

- Expose for at least 2-3 minutes if not 5

- Learn about binning and sampling rate. Aim for 1.2-1.4" if your sky and mount can support it.

- Process images in 32bit format

Thank you so much for that. That makes alot of sense. Although I don't process at 32 bit, I process at 16 bit as it seems thats whats best in photoshop at least. I heard from other sources exporting to 16-bit is better than 32 bit for these? I did however do a test shot at M81 and for 36 minutes exposure and a .67 reducer I am pleased with the results. I did BIN 1x1 this time with 470 gain. One stack every 4 seconds total exposure per image 2 minutes x 18 of these. NO DARKS. Fairly pleased! Would you say this is about where I should be? SharpCap seems to be working in my favor. I see what you mean though! Im going to reshoot NGC 7217 again tomorrow night (at least try to) Its a huge difference and my tracking seemed to have been better with the reducer on. Is there any proof of reducers increasing the tracking performance?

9 minutes ago, Stuart1971 said:

Basically you have a total image integration time of 1 hour, made up of 2 second exposures, (you need to forget the 1 minute part as it has no bearing) which is just not enough at all, now if you were taking 3 minute exposures, and take say 3 hours worth, then you will get a much better image, or even 1 minute exposures for 2 hours will give a better image…, but 2 seconds ain’t gonna cut it I’m afraid…☹️

Just because you are stacking 1 minutes worth of 2 second exposures and then stacking all the 60 x 1 minute stacked images together, it still only means you have 1 hour of 2 second exposures….I’m not sure how else I can explain…

Okay thank you! I think I understand what you mean. I'll try and get my LX850 to track better.. It really is difficult in the observatory because the opening of the observatory just doesn't seem to be enough for the starlock tracking lol. I will do an experiment at 2 minute exposures and take 30 of them and see if there is a difference. 

33 minutes ago, Stuart1971 said:

No, each photo is not 1 minute, each photo is made up of 2 second exposures, for a total integration time of 1 minute, that is different 

Thanks, but what about the 1 minute total time x 60 of them? Its 1 hour total stacked. Does that mean nothing?

13 minutes ago, Stuart1971 said:

Hi,

Taking 2 second exposures for 1 minute is just not enough light gathering at all, you need to be taking several hours of say 1 min or longer exposures, all the excellent images taken with you camera will consist of much longer exposures than 2 seconds and many more of them, I’m sure someone who owns this camera will be along to give you a better insight into this than me…👍🏼

11 minutes ago, scotty38 said:

I'm far from an expert but I posted some of my latest pictures in the imaging section and they were 5 minute exposures (admittedly with an l-extreme filter) at gain 121. A few seconds for DSOs is nowhere near enough I'd say.

Hi there thanks for the reply. What I mean is each photo is 1 minute exposure and its about 60 minutes on the target. But to combat poor tracking I would do 2 seconds per snap and the program live stacks it for me until it hits 1 minute total stack image and saves as a total of 1 minute stacked file. So instead of 2 seconds per image its really just a bunch of 2 second images stacked into a 1 minute final image. I would do this 60 times to get 1 minute each. Hope that helps! Thanks!

Hi, this is my first post! Thank you for having me. I am Brian, American moved to England. I own an Lx850 12" MEADE in my family observatory. I have a ZWO294MC PRO. Its a fantastic camera but I think I'm making a mistake somewhere. I might have found the issue but i'll let you know my setup. First off, I don't take longer than 5 second exposures (I heard the camera has no shutter so taking tens of thousands of exposures is okay and not like a DSLR with a limit. So how I do this is I enter SHARPCAP program and I focus the camera at the highest gain possible. Then I will put down the gain to 450-480 level and set the live stacking to 2 second exposures for 1 minute. After 1 minute it takes the live stacked image and thats the result. (Attached) the object is NGC 7217. A very interesting galaxy in Pegasus. Now, my issue is.. I take 60 total images like this and put it into DeepSkyStacker. I get the final TIFF 16BIT file saved to my computer and process in photoshop. I get the final image. To me I thought I would get more detail after an hour. I am in Bortle 4.5 zone as well. 

So, based off this method. Am I doing something wrong? My processing is good, there is no denying I can process because my DSLR photos were very decent but this Camera seems to lack photon intake or gathering details etc. Should I put the gain down to 200 regardless of how bright the sky is? I know my raw stacked 1 minute image has a bright sky. Is this the issue? Below is my Camera Settings and yes I do realize i've been shooting at RAW8 (Might be a significant issue). Thanks!

[ZWO ASI294MC Pro]
FrameType=Light
Debayer Preview=On
Pan=0
Tilt=0
Output Format=PNG files (*.png)
Binning=2
Capture Area=4144x2822
Colour Space=RAW8
High Speed Mode=Off
Turbo USB=80(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=473
Exposure=2.000s
Timestamp Frames=Off
White Bal (B)=95
White Bal (R)=52
Brightness=15
Cooler Power=12
Temperature=-5.3
Target Temperature=-5
Cooler=On
Auto Exp Max Gain=285
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Background Subtraction=Off
Planet/Disk Stabilization=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
Display Black Point=0
Display MidTone Point=0.5
Display White Point=1
Notes=
TimeStamp=2021-11-28T19:22:57.5416930Z
SharpCapVersion=4.0.7976.0