Does anybody have any experience of making video sequences in "White Light" ???

[SlimPaling]

Hi Folks ...

 

Has anybody any experience of using a mono CCD camera on a "normal" refractor to produce video sequences in "White Light" at all? I have done quite a bit of research into this on the web and I can't spot anybody who has done it. It seems that everybody is doing video sequences in Ha light only.

 

I have been trying to produce video sequences on my refractor and I am having a few problems. Maybe somebody can give me some advice?

 

My set-up is as follows:

I am using an APM 123/780 f6 Refractor and I have fitted my DMK mono CCD camera to a Hershel Wedge. I have fitted the recommended ND filter along with a polarising filter ... (This system works well for visual viewing using an eyepiece instead of the camera) .... but when I try to take a sequence of video images the Sun's disc is wildly over exposed despite turning down the Gamma & Gain controls as far as they go and also reducing the exposure setting right to the fastest possible speed. Nothing seems to change despite me changing the settings in the software.

 

I am finding it impossible to reduce the over-exposure of the images so that I can do some fine focusing on the sun spots .... I just keep getting a massively over exposed view of the sun's disc :-(

 

I am using the software that came with the camera ... "Image Capture" which I have used successfully when imaging Jupiter in the past without any problems.

 

Am I trying to do the impossible here and wasting my time????

Or am I doing something stupidly wrong???

 

Should I be doing "single shot" images rather than trying to do video sequences?

 

Should I reduce the aperture of my objective lens by making a card cover with a circular hole in it in order to cut down the amount of light coming in .... or ..... do I need to get a darker ND filter???

 

Any help and suggestions would be very much appreciated.

 

Regards Mike

 

 

[Ibbo!]

You should be able to collect an avi with your set up.

 

i know its for ha but the workflow is the same.

 

have a look here

 

[GreatAttractor]

1 hour ago, SlimPaling said:

I have done quite a bit of research into this on the web and I can't spot anybody who has done it. It seems that everybody is doing video sequences in Ha light only.

 

Oh, come on, most of us here have :> There's plenty on Astrobin (see e.g. http://www.astrobin.com/users/GreatAttractor/collections/131/) and elsewhere. It's just that once you transition to Hα, it's hard to go back.

As for your overexposure issues, it could be due to the ND filter being too bright; at the same time, an f/6 refractor gives a very bright image at prime focus. Possible solutions:

- use the Baader ND5 film over the objective lens instead of the wedge (very cheap, practically the same image quality)

- add a Barlow

- add another 1,25" ND filter (like 25% or even darker; they're cheap too)

- add a green filter ("visual" or the Baader Solar Continuum); not only reduces brightness, but improves granulation contrast

 

Combinations of the above will also work.

 

Quote

Should I reduce the aperture of my objective lens by making a card cover with a circular hole in it in order to cut down the amount of light coming

 

Not recommended, as image resolution is proportional to aperture. The only reason for using a mask would be bad seeing (too bad for full 123 mm), and for white light I'd suggest keeping it at at least 80 mm.

[Pete Presland]

As has been said above a lot of the images you see will have come from video files, obviously H/A does offer a more ever changing view maybe. All my "white light" images are done with the video technique.

The green filter really does make a huge difference compared no filter or just a I/R cut filter. If your budget allows it I would go for the Baader Solar Continuum filter its excellent, the difference for me is not huge between the Green No58 filter and the Continuum though.

 

[SlimPaling]

On ‎17‎/‎06‎/‎2017 at 14:05, GreatAttractor said:

 

Oh, come on, most of us here have :> There's plenty on Astrobin (see e.g. http://www.astrobin.com/users/GreatAttractor/collections/131/) and elsewhere. It's just that once you transition to Hα, it's hard to go back.

 

Hi ... yes, you are totally correct and I was dead wrong! ... there is a lot of info on the solar imaging section. When I did a search for solar imaging in White Light I misread what came up on my screen ... in my haste I thought that it told me that there was zero matches !!!!

I have found a lot of info there now :-)

Mike

[SlimPaling]

Many thanks for all of the help and suggestions.

I now know what has been going wrong .... I have been using a 3.0 ND filter but it seems that I needed a darker ND filter to overcome the excessive overexposure. I managed to borrow an extra ND filter from a contact and stacked it with mine ... success at last :-) 

Please see my initial effort taken at 9am this morning of Sunspot Region 2663. Not the best seeing here in Nottinghamhsire as there seems to be quite lot of haze up there.

But I am happy with my first effort ..... still lots of experimenting to be done!  

I will be getting some of other filters that have been suggested in the very h=near future :-)

Again Many thanks .... Mike