My images suck !!

[allcart]

Ok so I am testing out the pst modded scopes and haven't quite got the focus arrangment for imaging right yet, but i tried a few things today and am getting closer. I did take a few avi's today and noticed this in every clip. I was using a DMK41.

Does anyone know what causes pattern across the image. I could see it on the laptop creen as well.

[DrRobin]

Hi Allan,

It is a diffraction pattern, caused by internal reflections between the Etalon and the Barlow/camera. Almost everyone gets them, but I have found that if you tune the Etalon slightly you can reduce them. The other way to get rid of them is to move your mount slightly during your image capture and then they average out during sacking.

Robin

[GlassWalker]

Flats will get rid of them, but you must take the flats without adjusting anything.

[allcart]

I could try flats, but how do you add them the a AVI for stacking. Will registax combine them?

[Photosbykev]

its the interference pattern caused by two internal glass surfaces being almost but not not perfectly parallel to each other. You can remove them by adding in a very slight tilt in the optical path, you could use flats but it is much better to remove the problem at the source rather than try to mend/hide the problem afterwards.

[DrRobin]

Kev is right much better to get rid of them or reduce them in the first place. However, if you want to try flats this is one way to do it.

After your imaging run, adjust nothing.

Move your mount until the frame is completely illuminated by the sun.

if possible choose a section of sun without too many bright surface features.

now defocus until you can't see the surface features, keep the Etalon tuning the same.

Record an AVI, say around 500 frames. It is better if your mount moves a little.

import the AVI in to Registax and then from the Flats, darks menu select 'Create Flat'

Let Registax create the flat and then save.

From the same menu select 'Load Flat' and then tick to use it.

Registax will now apply the flat to your pictures during stacking. I have noticed that it often reduces the contrast slightly, but it can be really useful if you are trying to create a mosaic.

I hope this helps.

Robin

[nytecam]

Flats will get rid of them, but you must take the flats without adjusting anything.

How do you do Ha flats through the 'scope on the sun free of any suface/ Ha features?

[GlassWalker]

How do you do Ha flats through the 'scope on the sun free of any suface/ Ha features?

Same way I do it for night sky: put a diffuser on front of the scope. In the case of the PST I use an old plastic bag loosely held in place by a rubber band. This does rather kill sensitivity though, so you do have to jack up exposures and watch out for hot pixels. To correct myself, the flat should be done changing nothing optical. Camera exposure settings are of course ok to adjust.

[markt]

Definitely a diffraction pattern going on there.

The other thing that is going on is the etalon assembly isn't orientated as good as it can with respect to the OTA - this is causing the washed out look to the image. You need to drop the gamma down on the DMK back to say 50 ish, then whilst watching the image live (use the middle of the solar disk) on the screen rotate the whole etalon assembly in the focus draw tube. What you will find is there is a point that shows maximum detail / contrast and no gradient across the frame. When you find this optimum rotation clock it in someway that you can easily return to it every time. Then you can use the etalon tuning ring as usual to fine tune.

I think doing this will shift quite a bit of the diffraction pattern you are seeing.

[allcart]

Thanks guys for sound advice. I'll try these flats soon if I can't solve the problem.

And thanks Kev and Markt..That explains it very well and gives me an insight into what I have to do to correct it.

[JamesF]

Interesting. Something to be aware of when I start imaging with mine...

James

[allcart]

Its certainly something I'll be watching for in future. I must admit, it was plain to see on the laptop screen, but I ignored it.