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2022-05-29: APP 2.0.0-beta2 has been released !

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windows 2.0.0-beta2

macOS x86_64 2.0.0-beta2

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Light Pollution Issue

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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

I used an IR-Cut Filter last night on M101. But the neighbors security light caused a lot of interference with my image. I can get about 50% of it removed using the LP tool...But just not enough. PS 2021 I use won't get it either, without losing some of the data from the object...

I put a check mark also in Tab 2 of the Calibration part of it...Didn't seem to have any effect. There was no moisture in the air either. But I did notice this morning pollens were on my collector plate. I cleaned this off already...See photo attached please...I don't know what these strange circles are either, any Ideas?

M101

 

Is there anything else I can do, short of me loading up and going to a dark site?

I may use my Optolong CLS Light Suppression filter tonight, with increased exposure time.

 

Thanks,

 

Rod


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Rod, did you use any flats and, if you did, were they taken with the same filter? There are a lot of dust bunnies in your image which seem to indicate either no or incorrect flats. I'd start with ensuring that that's OK before pursuing further attempts to correct for the light pollution.

Wouter


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

Yes, I used flats and bias frames, same Gain of 120 (unity gain) for my ZWO. There was a crap load of pollen on the collector plate I saw this morning. That may be some of it...

I also tried Astro-Flats which is an add on in my Photoshop 2021.

Thanks!


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod So, apart from taking another look at your flats and making sure they are correct, I don't know what to do. Removing light pollution depends on the smoothness of the background and with those dust bunnies the background is far from smooth. Are you using a OSC? Is the peak of the histogram far to the right but not clipped? Even with dirty optics, proper flats should remove those dust bunnies.


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  
starless M81
M81 123 Subs  Final One

 This is the same filter, IR-Cut the night before on M81, 120 second exposures...Quite a contrast. Both in the northern sky.

Only difference is I took 240 second subs on M101, and got the foggy stuff...I took my flat frames outside early morning with a T-Shirt, using the same Gain settings, and I had the Means set between 18,500-21,000 as recommended.

This post was modified 1 year ago by Rodney Bell

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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

I seem to forget what OSC is...I'll check the histogram...I just ran everything thru again. I've tried several types of integrations, all get the same result. This is before any processing at all. Just so you can see what Im seeing.

APP Screen Shot M101

 

This post was modified 1 year ago by Rodney Bell

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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Hi Rod,

OSC = One Shot Color camera. I assumed you were using one but now I am not so sure anymore.

Very strange that the flats don't work on M101 while they do on M81. Could you upload a few raw flats taken for both sessions to

https://upload.astropixelprocessor.com

in a directory called rockinrod_flats? Please use upload1 for both username and password.

 

Thanks, Wouter


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  
Posted by: @wvreeven

@rockinrod Hi Rod,

OSC = One Shot Color camera. I assumed you were using one but now I am not so sure anymore.

Very strange that the flats don't work on M101 while they do on M81. Could you upload a few raw flats taken for both sessions to

https://upload.astropixelprocessor.com

in a directory called rockinrod_flats? Please use upload1 for both username and password.

 

Thanks, Wouter

Oh drat, of course. My brain was so rattled I'd forgotten...I used an ASI294MC Pro cooled camera, yes, OSC...I'll see about uploading those files...

 

Thanks


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

For some reason that upload page does not like my login info...Using the same thing I logon on to ask my questions. To get it...Still trying to get in.

I changed my password, then tried to use it on the upload page. It's not working. There is also an image of a locked Lock in the Password Field. Not sure if that means anything

Screen Shot 2021 04 06 at 3.09.09 PM

 

 

This post was modified 1 year ago by Rodney Bell

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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4856
 

Hi Rodney, you can't use your own login there. Please use upload1 as the name and upload1 as the password (both are the same).


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@vincent-mod

I got ya. I misunderstood the login info...I uploaded 8 files there, 4 for M81 and 4 for M101...I used the same flats, with the same 120 Gain...

Wow, I think I see the problem...Nasty looking flats, yet why didn't it affect M81...That's a mystery

This post was modified 1 year ago 3 times by Rodney Bell

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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@vincent-mod

Got those files uploaded, but I can already see my flats stunk...!I'm redoing those now, and some new darks. I also used my CLS filter last night, at 6 minute exposures...Helped considerably but it needs more exposure time and data for this particular galaxy. Thanks for all your help!

I

M101 Test2 RGB session Good

 I'm about 50% of where I want to be with this....


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Thanks for confirming that my initial suspicion about bad flats was correct!


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

I'm trying to correct this now...One thing I found, at least on this particular object...The more flat frames used the worse it looks..I just ran everything thru 30 Lights, 30 Bias, 30 new Darks, and just 5 Flat frames...The result is much better...I think I will invest in one of those Flat frame Light panels which sits on top the scope. Stop using the T-Shirt method...

5 Flats Used

 This is with 5 flats...Big Diff...!


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Wow that indeed is a big difference. Are you taking all flats at the same exposure time or do they vary?


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

 

Same..I'm using nebulosity...Setting the gain the same as the lights, the "Means" values set at 21,350 at an exposure time of 0.04 sec. The problem I'm seeing here is using this 50Watt LED light is not uniform across the OTA...Causing Vignetting and for some reason this hazy appearance...

This post was modified 1 year ago by Rodney Bell

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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Could there be internal reflection in the telescope tube? If yes then that will change the properties of the optical system leading to unusable flats. Also, 0.04 sec is VERY short. Many modern cameras have rolling shutters with shutter speeds in the order of milliseconds. This may lead to uneven read out times for the pixels causing a lot of issues. You may want to aim for exposure times of at least a second. This can be easily achieved by adding more layers of white t-shirt to dim the light source.


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

I used two layers this morning. I saw a video on Flat Frames from one dealer, maybe OPT, maybe Starizona, can't remember, which said to shoot for a 19500 to 21500 Means number. So that's basically what I've been doing. Either moving the light closer or further away.

I know the Bias frames are very fast...I set the ZWO at .000032

I have an OSC ZWO...

I'm not sure how one would check for this internal reflection. First time I've heard of this. I used a Glare shield on it like always..


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1724
 

@rockinrod Take the camera off the telescope and shine the light source for the flats in it. Then look at the other end and try to determine of there are reflections could be a way to check.


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(@rockinrod)
Red Giant Customer
Joined: 2 years ago
Posts: 127
Topic starter  

@wvreeven

 

I'll give it a shot.


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