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hectorbdn

Flats for QHY16200A

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Hello, I own a qhy16200A from like one year ago and I haven't been able to take flat frames that works well to me,someone I know who own a atik 16200 recommended me to target 45k adus, that adus works well for my Halpha but the same settings don't work for O3 and S2, the exposure time of these flats are = halpha (7 seconds), O3 (5 seconds), S2 (10 seconds), all three targeting 45k adus, anyways could anyone who owns this camera be so kind to tell me how many adus is targeting and exposure times for LRGB and narrow band? This is driving me mad 

Thanks in advance 

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I have a Moravian G3-16200, i always aim for 30k ADU and get perfect flats.
How are you taking your flats? Light source?

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26 minutes ago, Xplode said:

I have a Moravian G3-16200, i always aim for 30k ADU and get perfect flats.
How are you taking your flats? Light source?

Hello, thanks for your answer, I have a panel flat which I can regulate the intensity of the light, no luck yet, just in order to show the problem I will add a picture 

 

32326782867_4ef7a5239a_h.jpg

 

The bottom shadow is due to the OAG prism, already fixed that, please notice the flats are over correcting 

Greetings 

 

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I'm using a flat panel too, an Artesky USB 550mm panel.

Would you be ok with sharing a stack of uncalibrated files? Something like 10 of each would be perfect

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6 minutes ago, Xplode said:

I'm using a flat panel too, an Artesky USB 550mm panel.

Would you be ok with sharing a stack of uncalibrated files? Something like 10 of each would be perfect

Do you mean light frames or flat frames? 

 

Now I'm  not at home so I will upload them when I can and send the link to you 

Thanks for your help 

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It would probably be best with subframes

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4 hours ago, Xplode said:

It would probably be best with subframes

Hello Xplode , I just have snet you a private message with a link where you can download those frames :D

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There's almost no vignetting in your lights so it's definitely overcorrecting, i think you should try lower ADU to around 30k, but it's probably not the sollution to the problem.
I believe the cause is that you are taking the flats at room temperature, since they are several seconds long they have some dark noise in them at that temperature.
There's the possibility of using dark flats, but i'd simply recommend you take them att -20C as with darks and lights.

Slight overcorrection after calibration and stacking. 
image.thumb.png.b6ede466d56f17c463d6ca03d544bd10.png

I also got some comments on other stuff.
1) You should look at using dithering to remove noise better, it will remove collumn defects and hot pixels a lot better than cosmetic correction. I've never used cosmectic correction with the G3-16200.
2) Which scope do you have? Seems like you're using a flattener/focal reducer with the wrong distance to the sensor.

Edited by Xplode

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Hello, thank you very much for taking your time to answer , greatly appreciated !

 

I take the flat frames at the field , just i finished my sequence of lights while the camera is warming up, that might be the cause indeed , i will keep cooling the camera while i take the flat frames and try lower ADUs , as you said the vignetting is low and unitl now i just skipped the calibration with flat frames because they do more damage than good, but I could love to be able to take flat frames properly as I always did with my former camera (Canon 550D modded) 

 

about the other stuff:

 

1 - i use dithering indeed! SGP - High dither , which do you use if I may ask? 

2- that's other stuff is driving me nuts, I keep talking with the manufacter of the scope (TS-Optics 130/650mm imaging star apo) and the QHY , this scope has the flattener incorporated in the focuser , I have a adapter matching the exact distance they say I need, but as you correctly saw I dont have the field perfectly corrected, some say is tilt, some others say it shouldn't be, and blah blah blah , it¡s f**** driving me nuts! 

 

I can't thank enough for your help! 

 

 

 

Edited by hectorbdn

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1) Maybe the images i didn't receive weren't dithered? If they were dithered you should change dither scale in PHD2, i had to do that with an OAG. I choose scale 5.0 with medium dither in SGP.
I'm imaging at 1855mm with guidecam scale at 0.65"
2) It's definitely not tilt, it's in all corners. TS does unfortunately not give the exact numbers all the time, also filters can influence the distance. for 3mm thick filters 1 mm extra of extension should be added.


I can recommend you try to change the distance with 1mm increments and lastly 0.5mm for fine tuning.
To not have to pay a ton for extensions/spacers that migt be uneeded i can recommend you find someone with a 3d printer to print 1mm, 2mm spacers.


I would print them for you, but i'm in Norway so it would probably take a while for them to arrive. I'm sure you can find someone in Spain that can do it pretty cheap.
I have actually printed a 25-30mm M78 extension with threads for a Takahashi TOA150 for a friend, it worked great so he ended up using it and it's been on his scope for over 1 year 😂

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24 minutes ago, Xplode said:

1) Maybe the images i didn't receive weren't dithered? If they were dithered you should change dither scale in PHD2, i had to do that with an OAG. I choose scale 5.0 with medium dither in SGP.
I'm imaging at 1855mm with guidecam scale at 0.65"
2) It's definitely not tilt, it's in all corners. TS does unfortunately not give the exact numbers all the time, also filters can influence the distance. for 3mm thick filters 1 mm extra of extension should be added.


I can recommend you try to change the distance with 1mm increments and lastly 0.5mm for fine tuning.
To not have to pay a ton for extensions/spacers that migt be uneeded i can recommend you find someone with a 3d printer to print 1mm, 2mm spacers.


I would print them for you, but i'm in Norway so it would probably take a while for them to arrive. I'm sure you can find someone in Spain that can do it pretty cheap.
I have actually printed a 25-30mm M78 extension with threads for a Takahashi TOA150 for a friend, it worked great so he ended up using it and it's been on his scope for over 1 year 😂

well... i know someone with 3d printer ... but it might take ages cuz he has 3 children now lol 😂 , I will ask around , do you sell them anyways? I could buy them from you because I'm not in a very hurry , I have been having this problem for over a year so one month more...... , no problem 😅😆

1 - yes they were dithered , at least that's what SGP told me , if it's not lying to me! 😆 I am indeed very noob with phd , I have being using maximDL from 5 years ago until now and I don't know very well how it works yet , Im using an OAG at 2.9" (zwo290mm mini) , i will try changing the scale to 5 as you said! 

2 . I use astronomik filters that in spec they are 1mm thick , yeah I know I should add 1/3 of the thickness of the filters for calculate the distances for the adapter , i was supposed to do just that, increase the distance by 1mm and further, it didn't even cross my mind about doing it with a 3d printer (im old school) lol 

 

thank you again! 

Edited by hectorbdn

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Your dither is prboably way too small then. Test with a scale of 5 and see if it dithers enough for it to be easily visible.
A larger dither will not only help with removing noise, but also fix small inaccuracies in flats if dust were to move a little or focus were bad.

I would not recommend 3D printed adapters/extensions for permanent use, especially not in smaller diameters.
For spacers 3D printing is ok, but they might not be accurate enough so they can make a small tilt.
I can make you a few rings and ship them to Spain for something like 10-15€.
Which size would you need them?

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1 minute ago, Xplode said:

Your dither is prboably way too small then. Test with a scale of 5 and see if it dithers enough for it to be easily visible.
A larger dither will not only help with removing noise, but also fix small inaccuracies in flats if dust were to move a little or focus were bad.

I would not recommend 3D printed adapters/extensions for permanent use, especially not in smaller diameters.
For spacers 3D printing is ok, but they might not be accurate enough so they can make a small tilt.
I can make you a few rings and ship them to Spain for something like 10-15€.
Which size would you need them?

We got a deal then🤝

 

M68 

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Great, i already got models for M68 spacers.
Do you have a small extension that can be removed if you need to shorten the distance?

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4 minutes ago, Xplode said:

Great, i already got models for M68 spacers.
Do you have a small extension that can be removed if you need to shorten the distance?

what do you mean? if i can shrink the distance instead of extend it? if so , no I can't , the only way could be sawing it up! 

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Lets hope you need to extend it then because i can't 3d print a working saw 😂

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1 minute ago, Xplode said:

Lets hope you need to extend it then because i can't 3d print a working saw 😂

crossing fingers 🤞😂

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