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

[alexbb]

2 minutes ago, tooth_dr said:

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

I don't understand your dilemma...

[tooth_dr]

Just now, moise212 said:

I don't understand your dilemma...

You dont understand my wife ?

[alexbb]

1 minute ago, tooth_dr said:

You dont understand my wife ?

I understand now

[tooth_dr]

19 minutes ago, moise212 said:

I understand now

Lol that’s not really fair on my part though, my wife is very understanding 

[Jkulin]

2 hours ago, tooth_dr said:

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.

That's why they would be no good for me as the Esprits are F5 and F5.5, personally I want to remove all possible conflicts with producing the right image and won't cut corners (Excuse the Pun)

[tooth_dr]

9 minutes ago, Jkulin said:

That's why they would be no good for me as the Esprits are F5 and F5.5, personally I want to remove all possible conflicts with producing the right image and won't cut corners (Excuse the Pun)

They actually said they will work down to F5, any vignetting will be correctable with flats.   Below F5 they said they wont work.

[Jkulin]

I know where you are coming from Adam, but personally why cause yourself more grief, I just wouldn't do it.

I am saving to buy some Chroma's but won't compromise by buying the 1.25's I'd rather wait and get the right item to alleviate any possible chance of my images failing, it really just isn't worth it IMHO.

[tooth_dr]

On ‎24‎/‎10‎/‎2018 at 07:39, RichLD said:

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

Here are two FITS of flats I've taken with 1.25" and 2 filters, with the respective ADUs displayed (using APT) for the whole image.

Also I manually assessed the ADU value at the centre and four corners:

1.25" filter
centre = 34082
corners = UR 26228 / UL 29976 / LL 31213 / LR 28462

 

2" filter
centre = 32538
corners = UR 28799 / UL 28675 / LL 29227 / LR 29172

 

I would appreciate any input based on these figures.

Thanks in advance

Adam.

 

 

[RichLD]

4 minutes ago, tooth_dr said:

Here are two FITS of flats I've taken with 1.25" and 2 filters, with the respective ADUs displayed (using APT) for the whole image.

Also I manually assessed the ADU value at the centre and four corners:

1.25" filter
centre = 34082
corners = UR 26228 / UL 29976 / LL 31213 / LR 28462

 

2" filter
centre = 32538
corners = UR 28799 / UL 28675 / LL 29227 / LR 29172

 

I would appreciate any input based on these figures.

Thanks in advance

Adam.

 

 

If we take the average of the corner values and use that figure to get a percentage of the centre illumination, the 1.25" filter gives us 85% and the 2" gives us 90% (both rounded). Very acceptable in both instances I would say! 

[tooth_dr]

Well I got a few Ha subs last night with the 1.25” filter. So I’ll get some new flats later and post up the calibrated results to let anyone interested cast their eye over them. That would be much appreciated. 

[ollypenrice]

All you need to do with flats is open them, unstretched, in a programme that will give you the ADU values when moused over. I use AstroArt for this but, doubtless, others will do it.

I look at the corners and the middle, naturally enough. My centre will be at about 23,500 ADU when my corners are down at maybe 19,000 on our older fluorite Tak FSQ106Ns with full frame Atik 11000 CCD cameras. That is a big drop-off in illumination, around 20% (it might be worse) so far worse than Steve's 10% - and it causes no difficulty whatever. We do lots of multi-panel mosaics with these rigs, including the 30-odd panel Orion, where you need the component panels to be well flattened in order to merge seamlessly - and they do.

What is the limit in drop-off? I don't know, but 20% is working for us.

On the TEC140/Atik 460 it's about 200 ADU! Nice but not, in practice, very important.

Olly

[tooth_dr]

On 25/10/2018 at 20:01, tooth_dr said:

Here are two FITS of flats I've taken with 1.25" and 2 filters, with the respective ADUs displayed (using APT) for the whole image.

Also I manually assessed the ADU value at the centre and four corners:

1.25" filter
centre = 34082
corners = UR 26228 / UL 29976 / LL 31213 / LR 28462

 

2" filter
centre = 32538
corners = UR 28799 / UL 28675 / LL 29227 / LR 29172

 

I would appreciate any input based on these figures.

Thanks in advance

Adam.

 

 

@ollypenrice I did this in a APT. There is an offset adjustment with the EFW, so I could prob centre the filter better too.