14" EDGE HD Scope endless issues

[ceefna]

Hi all I wonder if anybody has ever come across such terrible flat field images? I initially thought it was mono camera/filter related reflections but these 2 pictures are one mono and filters and the other is OSC no filters. Both cameras are Atik 490EX and I have tried a flats led panel, panel with white 't' shirt over the scope and these two images are pointed up to a cloudy sky. I cant see any dust, the optics look clean and i have had the scope from new but hardly used it. I am rapidly falling out with this scope and finding it impossible to get a decent image through it.

Any help would be greatly appreciated.

Ceefna

 

[Stub Mandrel]

28 minutes ago, ceefna said:

Hi all I wonder if anybody has ever come across such terrible flat field images? I initially thought it was mono camera/filter related reflections but these 2 pictures are one mono and filters and the other is OSC no filters. Both cameras are Atik 490EX and I have tried a flats led panel, panel with white 't' shirt over the scope and these two images are pointed up to a cloudy sky. I cant see any dust, the optics look clean and i have had the scope from new but hardly used it. I am rapidly falling out with this scope and finding it impossible to get a decent image through it.

Any help would be greatly appreciated.

Ceefna

 

Don't blame the scope for those. The small doughnuts are probably on the camera's front plate and the big one at the bottom on a filter.

At least, if I get doughnuts that size, taht's roughly where they would be in the imaging train. Dust can be the very devil to see.

[ceefna]

Hi Neil thanks for the reply, so much dust on both cameras? I have had a jewlers loupe on them and I cant see any dust at all. I had got to thinking it was on the HD correcting lenses inside the baffle tube?

I will give them a good clean and see what happens.

thanks v much

Ceefna

[Peter Drew]

They look like classic images of "dust bunnies", they will usually be found close to the focal plane of the camera so probably not on the telescope corrective optics.

[ollypenrice]

Hmm....

Let's think about  terrible looking flats. Flats always look terrible, which is why we need them. If they looked flat we wouldn't use them. The flat below went into the image which was runner up in the International Astrophotographer of the Year competition. In fact it went in many times because the image was a thirty-odd panel mosaic.

When you look at a stretched flat it has been - obviously - stretched but have you measured the captured ADU values of the darkest and lightest parts? They may not be very different at all.  Deep sky imaging is not about taking flat flats, it is about creating flattened images. A good flat is one which perfectly captures everything wrong in your light path and, as in the flat I posted above, there may be a lot wrong with it, but that will be dealt with by division.

Another thought: an Atik 490 in a C14 at native focal length is going to be working at about 0.19 arcseconds per pixel, I think. This is beyond optimistic for deep sky imaging, it is plain impossible and the scope-camera combination is, to my mind, questionable. But that's a different question.

Olly

[ceefna]

Questionable is an understatement! I have a hyperstar for the scope which I will be using with the 490. I have built a new observatory so I was just trying to get things working together. If I can guide it nicely at f11 then anything else is a piece of cake!

Ceefna 

[ollypenrice]

28 minutes ago, ceefna said:

Questionable is an understatement! I have a hyperstar for the scope which I will be using with the 490. I have built a new observatory so I was just trying to get things working together. If I can guide it nicely at f11 then anything else is a piece of cake!

Ceefna 

OK, so this is only a question about flats. There seems to be nothing wrong with yours so far as one can tell. You'll only find out whether or not they are good or bad when you apply them to your lights. What you are seeing in your flats is perfectly normal. As long as the same anomalies are present in your lights they'll be corrected. With a CCD camera you should calibrate your flats by subtracting  a dark-for-flats (AKA flat dark) but this is easy: just use a master bias as a flat dark. It will work perfectly and save you a lot of time.

Olly

[Shibby]

Hi. I'm partly commenting to agree with others about your flats, these dust rings are almost certainly from the camera's sensor window judging by their size and they should calibrate out no problem. You can always take a blower to the window to try and reduce them. The first flat does seem to have a separate issue, though. Is it the refresh of your LED panel?

Secondly, I just wanted to say that your observatory is a real beauty!

[ceefna]

Thanks for all the replies I had no idea dust would cover the entire image thats why i wrongly assumed it was reflections( as its all different intensities) always learning!

The first flat is with my colour 490ex so I think that's the Bayer matrix showing up. 

Very pleased with my obs. The dome has a real industrial look and all handmade at home out of cheap 0.5mm galvanised steel sheet. I may ask very basic questions but I am a car mechanic that will never be an optician! 

Thanks for your help 

Ceefna

[Stub Mandrel]

You made that dome from scratch? I'm impressed!

[ceefna]

From 10 sheets of steel. Not including the rolled base of course. Funny how I completely understand the bits I've made it's all the bits I've bought that are confusing.

Nothing more rewarding than making something yourself.

 

 

[ollypenrice]

Gorgeous observatory! Well done x 100...

Olly

[sloz1664]

That dome is a work of art. Any Tinsmith would be proud of the quality of workmanship involved in making it.

Regards dust....You cannot eliminate it, however hard you try. All you can do is clean the best you can, without damaging any optics and, as all have explained, use flats.

Steve

[JamesF]

I don't want to drag the thread off in a completely unrelated direction, but please do post more pics of the observatory build in the DIY Observatories forum.  That dome is a gorgeous piece of work.

James