Flat frames

[emyliano2000]

Hi guys.

I just finished making a lightbox.

I took a few flats and this is how the histograms look like. Is that ok? Why is the blue so far on the right?

Emil

 

 

[wxsatuser]

Either the light is quite blue or it's the CLS filter,

The CLS filter will give a lot of blue with daylight white balance.

Personally I would'nt worry about it as the important bit is the white luminance histogram.

[Guest Tuomo]

Care to show how you made this. Looks nice...

[emyliano2000]

4 minutes ago, Tuomo said:

Care to show how you made this. Looks nice...

http://www.astronomyasylum.com/flat_field_light_box.html

And my next project is this fan cooler.

http://www.hutchyweb.co.uk/astro/default.asp?blog=19

[emyliano2000]

When I get home from work I might attach one of the flat frames and the master flat, maybe somebody with experience can have a look and tell me if they are good. I've  been told that the http://www.365astronomy.com/Aurora-Flatfield-Panel-D220mm-with-12V-Inverter.html is one of the best but to be honest I think that £165 it's a bit too expensive. 

[Tim]

I made my own out of an A3 EL panel, so it works across all of my scopes, for a lot less than £165

Just one thing about yours, if you go to star parties you may want to mask the sides

[emyliano2000]

8 minutes ago, Tim said:

I made my own out of an A3 EL panel, so it works across all of my scopes, for a lot less than £165

Just one thing about yours, if you go to star parties you may want to mask the sides

? I  was thinking about that. I will prbably do it. The neighbours might start wondering what I'm doing with a lit up bucket.

[ollypenrice]

5 hours ago, emyliano2000 said:

When I get home from work I might attach one of the flat frames and the master flat, maybe somebody with experience can have a look and tell me if they are good. I've  been told that the http://www.365astronomy.com/Aurora-Flatfield-Panel-D220mm-with-12V-Inverter.html is one of the best but to be honest I think that £165 it's a bit too expensive. 

I've had three of those things and the thin rigid cables have always broken.

Olly

[emyliano2000]

9 minutes ago, ollypenrice said:

I've had three of those things and the thin rigid cables have always broken

Yes, I'm a bit worried about that. I had a look at the reviews and most of the people say that it's a great product apart from the cables that break very easy. There must be a way to take the pressure off the flimsy connections. I haven't found anything about it yet. I'm not gonna buy it until I find a solution for it.

[wxsatuser]

Just bought an Artesky 250mm panel, quite expensive but I did'nt have the will to build something.

It's seems well made, no leads to break and has a LED readout so you can go straight back to a set
level of light. I'm actually looking forward to doing flats.

 

[wimvb]

Your light box (bucket?) certainly looks nice. From your first image, I was worried that the illumination wasn't uniform, but the measurements on your website look good.

Great job

[ollypenrice]

1 hour ago, emyliano2000 said:

Yes, I'm a bit worried about that. I had a look at the reviews and most of the people say that it's a great product apart from the cables that break very easy. There must be a way to take the pressure off the flimsy connections. I haven't found anything about it yet. I'm not gonna buy it until I find a solution for it.

I won't be buying another one. It's one of the worst products I've ever met in astronomy. It is not the job of the customer to fix the mistakes of the maker. I tried hard not to stress the entry-exit points of the cables but I run commercial observatories and use equipment more intensively than private amateurs. The Aurora panels all failed. I can't recommend them.

Olly

[brrttpaul]

said it before, to take darks you put the scope cover on because its black and dark, so why not make a white fitting cover also

[Tim]

7 minutes ago, brrttpaul said:

said it before, to take darks you put the scope cover on because its black and dark, so why not make a white fitting cover also

The best AP scopes should come with an integrated flat panel in the cap, agreed!

A plain white cap wouldn't be so useful I dont think, and hard to get even illumination when and where you want it!

LED panels are the future I should think.

[ollypenrice]

12 minutes ago, brrttpaul said:

said it before, to take darks you put the scope cover on because its black and dark, so why not make a white fitting cover also

I cannot take darks this way. I've tried. This is with a Tak 106 with close fitting metal lens cover, an electric filterwheel with no obvious light ingress, no Off Axis Guiding port in the system and a CCD camera without viewfinder - but still a 30 minute 'dark' taken this way is simply not a dark when compared with a dark made using the metal screw-on chip window cover. They are a million miles apart. Where the light comes from I do not know, but come it does.

Olly

[emyliano2000]

OK, here are the flats.

1st one is a raw file

IMG_1360.CR2

and the second is the master flat

.MasterFlat_ISO400.tif

If somebody with more experience could have a look at them and tell me if they're good, I would really appreciate it.

 

 

[Davey-T]

Seems to have an average pixel value of just over 6000, I think it needs to be nearer 25000.

If you want to buy an expensive panel FLO do one.

https://www.firstlightoptics.com/flat-field-generators/artesky-premium-250mm-flat-field-generator.html

Dave

 

[emyliano2000]

10 minutes ago, Davey-T said:

Seems to have an average pixel value of just over 6000, I think it needs to be nearer 25000.

If you want to buy an expensive panel FLO do one.

https://www.firstlightoptics.com/flat-field-generators/artesky-premium-250mm-flat-field-generator.html

Dave

 

Is there anything I can do to change that on my box (bucket)?

I have no idea what you just said :-)

[wimvb]

2 hours ago, ollypenrice said:

I cannot take darks this way. I've tried. This is with a Tak 106 with close fitting metal lens cover, an electric filterwheel with no obvious light ingress, no Off Axis Guiding port in the system and a CCD camera without viewfinder - but still a 30 minute 'dark' taken this way is simply not a dark when compared with a dark made using the metal screw-on chip window cover. They are a million miles apart. Where the light comes from I do not know, but come it does.

Olly

How close? If it pinches in a few places it may feel close fitting, but doesn't need to be. And if the inside of the lens cover is as bright as the outside, it will reflect any light leaking in.

[wimvb]

2 minutes ago, emyliano2000 said:

Is there anything I can do to change that on my box (bucket)?

I have no idea what you just said :-)

Quadruple the exposure time?

It seems that on a scale from 0 to 64000 (16 bit image), the average pixelvalue of your flat is at 6000, whereas the recommendation is to have it at about 25000. Making the exposure time 4 times what you currently use, should fix this.

[emyliano2000]

27 minutes ago, wimvb said:

Quadruple the exposure time?

It seems that on a scale from 0 to 64000 (16 bit image), the average pixelvalue of your flat is at 6000, whereas the recommendation is to have it at about 25000. Making the exposure time 4 times what you currently use, should fix this.

Ok, I'll give it a try, I thought you were joking, that's how much I know about this stuff. Is there any chance that the average pixel value to increase if I remove one layer of thacing paper? It's double on one of the rings inside the box. 

What software do I need to find out the average pixel value?

[ollypenrice]

25 minutes ago, wimvb said:

How close? If it pinches in a few places it may feel close fitting, but doesn't need to be. And if the inside of the lens cover is as bright as the outside, it will reflect any light leaking in.

Well, you know, it's an overlapping thingy.

I don't know where the light gets in but I know that it does, certainly for my attempts at thirty minute darks. Atik give their camera buyers a thick screw-on metal chip window cover and I can easily tell the difference between darks using this and darks done on the scopes.

Olly

[Davey-T]

25 minutes ago, emyliano2000 said:

Ok, I'll give it a try, I thought you were joking, that's how much I know about this stuff. Is there any chance that the average pixel value to increase if I remove one layer of thacing paper? It's double on one of the rings inside the box. 

What software do I need to find out the average pixel value?

Remove some tracing  paper.

I use Maxim but there must be something free out there that can do it.

Dave

[wimvb]

20 minutes ago, emyliano2000 said:

Ok, I'll give it a try, I thought you were joking, that's how much I know about this stuff. Is there any chance that the average pixel value to increase if I remove one layer of thacing paper? It's double on one of the rings inside the box. 

What software do I need to find out the average pixel value?

I would say PixInsight, but only using it for that would be serious overkill. Otoh, it also does a decent job stacking and processing. 

If you use the histogram tool in your processing software, you should be able to get an estimate, at least. Otherwise, if you use the eye dropper tool that most image processing software has, and set the area of the tool to a large value, you should be able to get a good estimate. Even if you can't get exact statistics (pixel values), 25000 out of 64000, is about a third of the histogram x axis from the left edge. I don't think there is a scientific article that says that 25000 is the holy grail.

[emyliano2000]

The only not free software that I have is startools. I'm thinking of making a subscription for photoshop for £8.25/month. Pixinsight is a bit too expensive to pay it all at once.