NGC 7822 and FUNKY FLATS

[ultranova]

 

 

Sorry guys not sure what happened , i went to put up another topic and some how 

it put this back on at the top of the page, apologies for that.

Admin if you are about could you move this post down the list or move it to the next page ,

as people have already seen this post.

Many Thanks 

Paul

 

Hi Every one,

Managed to get out for 4 hours on Saturday,

which gave me the opportunity to try out the ZWO EAF.

which was a first for me, the last 40 years I have been focusing manually and was 

very hesitant at letting something else do it.

worry unjustified as it worked a charm.

It was also a first using the optolong L-extreme filter for a longer session with the ZWO294mc pro

Anyway here's my take on it and the Flats that I can not use when staking,

As it makes processing  of the image near on impossible.

Would be interesting to here from any one else with a similar problem using 

that camera filter combination.

 

here is the master flat, never had a problem like this before with flats 

thanks for looking, 

clear sky's

Paul

 

 

 

Edited February 24, 2021 by ultranova
Problem putting up new topic,

[peter shah]

its really good result. your flats look almost like the filter wheel is off centre. Do you calibrate your flats?

[Craney]

There is quite a bit of discussion regarding this phenomena.
https://www.cloudynights.com/topic/653346-flats-not-working-as-expected-asi294mc-osc/

Not sure what the resolution was /is  ??.... whether it is a chip thing or a chip / filter thing.

Looks a nice camera as well.    I would be interested to see how it works out.

[ultranova]

3 hours ago, peter shah said:

its really good result. your flats look almost like the filter wheel is off centre. Do you calibrate your flats?

Hi Peter,

I have spent quite a few hours now going through what might be the cause of the strange flats,

what I have adopted to do is reduce the amount of time in the flat taking process by around 30%

In other words if I get a reading saying I need to take flats at 22000 adu I have  now been taking them at 16000/17000   

If I go to the recommended /  calibrated flat the red side becomes over powering to the point its almost black.

 

Strangely enough, I did think that my filter might be on the wonk a little, which might cause  the problem in hand

and it doesn't matter if its in the EAF or in the manual  draw, it always comes out the same.

regardless of filter of where the filter is on its axis, 

As long as I can over come the majority of the problem by the method I am now adopting with this filter

ill be ok with it but not ideal.

Thanks 

Paul

 

[ultranova]

3 hours ago, Craney said:

There is quite a bit of discussion regarding this phenomena.
https://www.cloudynights.com/topic/653346-flats-not-working-as-expected-asi294mc-osc/

Not sure what the resolution was /is  ??.... whether it is a chip thing or a chip / filter thing.

Looks a nice camera as well.    I would be interested to see how it works out.

Hi Craney,

Thanks for the info, I did chase up the links you sent me, very interesting,

I dont seem to be getting some of the matrix patterns some of those guy's are talking about,

I think Peter  might be on to something , when he said about the filter not being in parallax with the chip,

I have a pretty good even flat field across the the picture, stars a pretty good across the frame,

I shall keep experimenting and see what occurs.

if clear outside is correct on Friday i shall be  out having another round with the filter.

Thanks 

Paul 

 

[Craney]

I first picked the issue up when scanning through the Astrobin forums

https://www.astrobin.com/forum/c/astrophotography/other/flat-frames-l-extreme-asi294mc/

..... and this connected to a few lengthy discussions on CloudyNights.  ( there is much longer one somewhere than the one I quoted originally).

I have the 294mc on a wish list, so I was a bit surprised and concerned  to hear a few serious astrophotographers talking about potentially a physical reason within the camera that might be causing the chip to display this mottled coloured effect. ie.  the sensor is not set perfectly square against the fixing surface.  Although,  a few people commented that theirs were behaving perfectly OK.  (  shades of the DayStar Quark product ???).

As with most things on CN, the discussion then mutated into a verbal tennis match about how to take correct flats etc....  and you end up not knowing what the original problem was !!

I hope you find a solution that is exterior to the camera and which is easy to remedy.

It would be reassuring to know that the 294mc is as good as the specs say it should be.

Rgds,

Sean.

 

 

 

[ultranova]

1 hour ago, Craney said:

I first picked the issue up when scanning through the Astrobin forums

https://www.astrobin.com/forum/c/astrophotography/other/flat-frames-l-extreme-asi294mc/

..... and this connected to a few lengthy discussions on CloudyNights.  ( there is much longer one somewhere than the one I quoted originally).

I have the 294mc on a wish list, so I was a bit surprised and concerned  to hear a few serious astrophotographers talking about potentially a physical reason within the camera that might be causing the chip to display this mottled coloured effect. ie.  the sensor is not set perfectly square against the fixing surface.  Although,  a few people commented that theirs were behaving perfectly OK.  (  shades of the DayStar Quark product ???).

As with most things on CN, the discussion then mutated into a verbal tennis match about how to take correct flats etc....  and you end up not knowing what the original problem was !!

I hope you find a solution that is exterior to the camera and which is easy to remedy.

It would be reassuring to know that the 294mc is as good as the specs say it should be.

Rgds,

Sean.

 

 

 

Hi Sean,,

 If you push the Extreme filter to one side, the camera is good, On the rare occasion , the moon is not up and the clouds

are not about,  its a good all round camera for the price point.

there are other offerings not far off the price point, that don't show any artifacts in the dark frames, the 294 has quite a big

artifact in the top right in all of my subs, but easily calibrated out .,

The only thing that blows me away, is how sensitive it is in the green  channel, due more than likely to havin two green to every one red and blue 

matrix over every pixel,.

and almost looks like you have nothing in your picture to see when streched before back ground calibration,

But again it calibrates out.

Personally I would call this camera a middle of the road camera , a good all round work horse.

Paul