Do these flats look ok after changing down to 1.25" filters?

[tooth_dr]

I picked up another EFW2 with filters today, to see if 1.25" filters will work ok with my Atik 383L+.  I've attached flats taken tonight of Ha and Oiii with the new carousel of 1.25" filters installed.

Do they look like they will calibrate out the vignetting ok?

 

Thanks in advance!

Adam.

 

MF-ISO_gain_0.0-exp_9.0s-5subs-ARTEMIS_CCD__ATIK-383L__588_-3354x2529-NR-noBl-avg-NoSt-HA_FLAT_125FILTER.tiff

MF-ISO_gain_0.0-exp_11.5s-5subs-ARTEMIS_CCD__ATIK-383L__588_-3354x2529-NR-noBl-avg-1-NoSt-FLAT_OIII_125FILTER.tiff

[geordie85]

You may get more replies if you upload your flats in jpeg or PNG format so we can see them without downloading them

[MarsG76]

3 hours ago, geordie85 said:

You may get more replies if you upload your flats in jpeg or PNG format so we can see them without downloading them

+1

 

[tooth_dr]

6 hours ago, geordie85 said:

You may get more replies if you upload your flats in jpeg or PNG format so we can see them without downloading them

I didn’t think a jpeg would be useful in this context? 

[RichLD]

25 minutes ago, tooth_dr said:

I didn’t think a jpeg would be useful in this context? 

JPEGs will be fine if we are evaluating the differences in illumination between the centre and edges of the frame. Just give them the STF treatment in PI or equivalent stretch in another app so we can see it. It might also be worth checking the adu values at the centre and edges of the frame in the linear state and posting those as well.

HTH

Rich

[tooth_dr]

Here are the Jpegs.  I used DDP on APP to stretch them.

 

 

[tooth_dr]

What’s the verdict guys?

[Jkulin]

Hi Adam,

For me you are pushing it with that amount of Vignetting, I don't think the 383 likes 1.25" filters

[geordie85]

Are the un-stretched images showing the same amount of darkness in the corners? 

[alexbb]

You should take more than 5 flats for each filter. I applied a 5px blurring. 

The Ha flat contour plot looks like this:

And for OIII:

 

For both you have an ~87% ratio of high/low. I measured one of my flats and I have ~89% with the Ha filter on my ASI1600 and SW72ED.

[steppenwolf]

Using my Esprit 150, 1.25" Ha filter and a QSI camera with the same sensor (8300) as you I am getting a 90% ratio of high to low so the 87% that Alex has calculated above should give you workable flats.

[tooth_dr]

7 hours ago, Jkulin said:

Hi Adam,

For me you are pushing it with that amount of Vignetting, I don't think the 383 likes 1.25" filters

Cheers John. I phoned Atik. They told me F6 will yield correctable vignetting. But advice on the forums is conflicting.  Hence this thread. The proof if it works will be in the data my setup produces.

[tooth_dr]

4 hours ago, moise212 said:

You should take more than 5 flats for each filter. I applied a 5px blurring. 

The Ha flat contour plot looks like this:

And for OIII:

 

For both you have an ~87% ratio of high/low. I measured one of my flats and I have ~89% with the Ha filter on my ASI1600 and SW72ED.

Of course. I take 30-50 flats usually. This was purely a quick sample. 

87 seems close to your 89%?

 

 

[tooth_dr]

7 hours ago, geordie85 said:

Are the un-stretched images showing the same amount of darkness in the corners? 

The unstretched images look pretty much evenly grey, slightly darkening. Nothing like the stretched ones. 

[tooth_dr]

7 hours ago, geordie85 said:

Are the un-stretched images showing the same amount of darkness in the corners? 

Screen shot of above unstretched tiff

 

[RichLD]

I have a QHY9 that uses the 8300. I don't use a FW, instead using a Geoptik lens adapter. I can use 1.25" filters with this at f2.8 without issue but suspect I am getting my filter closer to the chip than you.

[RichLD]

1 minute ago, tooth_dr said:

Screen shot of above unstretched tiff

 

That looks fine to me mate, I'm sure your subs will calibrate fine. Have you tried calibrating a single flat with your master flat? That is a good test to see if calibration will be effective (I think!?)

Rich

[tooth_dr]

2 hours ago, steppenwolf said:

Using my Esprit 150, 1.25" Ha filter and a QSI camera with the same sensor (8300) as you I am getting a 90% ratio of high to low so the 87% that Alex has calculated above should give you workable flats.

Thanks Steve for taking time to reply. Is there a minimum ratio? And what does this mean?

[tooth_dr]

1 minute ago, RichLD said:

That looks fine to me mate, I'm sure your subs will calibrate fine. Have you tried calibrating a single flat with your master flat? That is a good test to see if calibration will be effective (I think!?)

Rich

I did not know this was a test! I’ll run a decent number of flats off, and try this. 

[RichLD]

7 minutes ago, tooth_dr said:

I did not know this was a test! I’ll run a decent number of flats off, and try this. 

Well, my logic tells me it's a good test and it works for me but others may disagree. The resultant calibrated single flat should show no signs of vignetting when stretched. It may be worth creating a special frame with a much lower adu than the flat and calibrate that as well but this is just a thought. HTH ?

[alexbb]

Just 13% decrease in the amount of light should present no issues. Maybe I should have set more contour lines, but it was 5AM in the morning, I woke up only to pack some gear and bring them inside, sorry for being cheap with the words.

I believe you will seamlessly calibrate the lights. I think others have a significant higher amount of vignetting and still manage to correct it.

[steppenwolf]

7 minutes ago, moise212 said:

Just 13% decrease in the amount of light should present no issues. Maybe I should have set more contour lines, but it was 5AM in the morning, I woke up only to pack some gear and bring them inside, sorry for being cheap with the words.

I believe you will seamlessly calibrate the lights. I think others have a significant higher amount of vignetting and still manage to correct it.

I think you are right, Alex  @tooth_dr should find these flats to be more than adequate. I was up at 5am because the clouds had spoiled my imaging session again and I was by then so awake that I did some SGL-ing!

[steppenwolf]

1 hour ago, tooth_dr said:

Thanks Steve for taking time to reply. Is there a minimum ratio? And what does this mean?

There must be a minimum usable ratio but I don't know what that ratio is - I guess it is the point at which NO light falls in the corners!! All the ratio is indicating is the difference in light intensity of the background between fully illuminated and maximum shadowing and the 13% drop off from the centre fully illuminated section that you are getting here doesn't seem to be too bad.

[tooth_dr]

Thanks guys, you are all great!

 

I now have another dilemma --> sell my second EFW2 with 2" filters, or buy another CCD!

[tooth_dr]

19 minutes ago, moise212 said:

Just 13% decrease in the amount of light should present no issues. Maybe I should have set more contour lines, but it was 5AM in the morning, I woke up only to pack some gear and bring them inside, sorry for being cheap with the words.

I believe you will seamlessly calibrate the lights. I think others have a significant higher amount of vignetting and still manage to correct it.

Alex, thanks for taking time to answer.  I was lazy and should have done it properly!  Thanks for pointing that out :D:D