2nd Attempt at White Light Sun

[David Smith]

My second attempt to capture the Sun in white light. This time I took around 70 frames with the 1100D and then stacked the best of them with Registax. The I tweaked the result very slightly in GIMP. First time I have ever used Registax and many thanks to Roger (aka Bizibilder) for his tutorial which was invaluable.

I am using an undriven mount and I think this is causing the shadowing effect at the limb ( I had to GIMP out a similar, opposite, effect on the opposite side of the disk). I will need to try and keep the sun centred better in the view finder in the future. Suspect a new mount may be on the shopping list in the future. I am still getting to grips with GIMP. Some of it translates quite well into "photoshop language" but some doesn't.

Not a top of the line image when compared to some of the great work seen on these Forums, but I am pleased with the step forward from my last attempt (see Flickr link below for last image).

Edit: Why do I always spot the spelling mistakes after I hit post

[DrRobin]

Hi David,

Nice pic, possibly slightly over-expossed, but for a full disc you have recorded a lot of detail of the main sun spot. I took some white light solar images using an ST80 and fixed mount and recorded mages whilst the full disc was visible, stopping the record once the sun had moved to the frame edge. In a low powered scope it works well enough if the skies are clear.

I then tried a motor drive on an EQ1 mount which was okay, but required a fair about of fiddling to keep the speed right. Just recently I have switched to my EQ6, which is a bit overkill for an ST80 or PST, but works really well. I have just bought a second hand EQ3-2 with motor drive, which will become my mount for solar observing.

I have found that if it is rally clear, you don't need a driven mount, but if there is cloud, it means that your scope is always aligned, ready to capture what is available.

How are you getting on with your PST?

[Bizibilder]

That is a really good image David. I think your processing problems may be with GIMP being only 8 bit which may be responsible for the "banding" you are getting. Keep on going as there is no substitute for practice - which is a bit of a joke with the current weather we're having in the UK!!

[michael.h.f.wilkinson]

Nice images. I think Bizibilder is right. You could try ImageJ for 16bit or 32bit processing

[David Smith]

Thanks all for your words of guidance and encouragement.

Robin - Interesting you have imaged with an undriven mount and got good results. I will persevere. I love the PST, just a shame I do not get to use it very much with this weather. I do need a better mount for it though, as my old photo tripod is not up to holding the weight at the angles required. More weight to the "I need a new mount" arguement . I am also trying to mod a webcam to have a go at imaging through the PST, but that's another story.

Roger - Image below is the stacked but not yet GIMP'd (?) image. This shows the banding (more like arcing really but whatever) before i attempted to remove it. My guess is that if it is not due to the undriven mount, and it is evident before it even gets as far as GIMP, that it must be something I am doing in Registax?

This was a stack of approx 20 frames (1/2000 sec each). I took something like 70 frames but when I tried to stack this the results were very poor. So I picked out what looked like 20 frames that were free of cloud and where the sun appeared to be in a reasonably consistent spot.

[David Smith]

Micheal - thanks for the tip ref Imagej.

[sologuitarist61]

Good image David - well done, I bet you are pleased.

[Astrokev]

Nice image David.

Interesting artefact in the upper part of the disk. I presume you're referring to the arc shaped darker edge. To my eyes, this looks like a stacking artefact rather than anything else, since the radius of the arc looks to exactly match the arc of the solar disk itself. I've sometimes experienced a similar thing when stacking, depending on which method I use to centralise the images. Through trial and error, I now always use the "align using centre of gravity" tick box, which automatically and perfectly aligns whole disk images. I may be way off here, but I'd try this option before you stack and see if it cures the effect.

Good luck.

[David Smith]

Thanks Kevin. Definitely a stacking issue as I have just tried the process again with the same frames but used the manual align option. I selected the largets spot in each frame and the result is much batter (see below). Will try the centre of gravity trick with the full 70 frames and see what happens.

The above has been stacked and cropped in GIMP.

[DrRobin]

Hi David,

I imaged with an ST80 on a fixed mount and used an Xbox camera with focal reducer. If I started with the sun on the left hand side, I could get about 700 frames before it drifted through the field of view. If there are no clouds then you can get exposure all sorted out and just go for it when focused.

I then used Registax 5 which tracked and stacked the moving image quite nicely. BTW I can't seem to get Registax 6 working on solar images at all.

Requiring webcams on a PST, I can just get my Xbox camera to come in to focus, but it is so far out of the eyepiece that the small exit hole in the PST means that the frame is very badly illuminated.

I managed to solve this by unscrewing the Barlow lens from a TV 3x Barlow and drop this into the eyepiece holder first, then put the camera in on top. The Barlow lens used in this way gives a much lower magnification but importantly fools the PST in to seeing the camera much closer in. The result it is possible to focus and the the frame is correctly illuminated.

Astro Engineering sell a 1.6x 1.25" screw in Barlow, so I have ordered one to give it a try as I would rather not keep dropping my Televue barlow in. The AE is only £23, so it doesn't break the bank. Hope you find this useful?

I haven't tried my PST unguided, the higher magnification would mean that the sun/sunspot drifts out of the FOV too quickly.

[David Smith]

Thanks Robin. My Logitech Quickcam in it's original case comes nowhere near to focus in the PST! My plan was to remove the main board and then mount it in some sort of plactic housing but with the sensor very close to the aperture I cut in the box. Will see how this pans out but may try the barlow trick you mention at some point too.

I am using Registax 5.1 as recommended on here, seems to stack quite nicely if i use the manual align option. Early days yet, I had never used it prior to yesterday!!

[Astrokev]

Thanks Kevin. Definitely a stacking issue as I have just tried the process again with the same frames but used the manual align option. I selected the largets spot in each frame and the result is much batter (see below). Will try the centre of gravity trick with the full 70 frames and see what happens.

The above has been stacked and cropped in GIMP.

That looks spot on (forgive the pun!). Using "centre of gravity" should achieve the same result but without the faff of needing to manually select targets.

[DrRobin]

My Xbox camera sits just outside the eyepiece holder and will just come in to focus on a PST. However, without the Barlow, only about the centre third is correctly illuminated with the rest rather dark. With the Barlow and the camera in about the same place it easily focuses and most of the frame is correctly illuminated, so I would definitely recommend a Barlow.

I did until recently have a MS Lifecam and the body of these is circular and smaller than a 1.25" eyepiece. Therefore it would slide inside a PST and might be the ultimate webcam. I think I might buy one again and see how it goes.

[michael.h.f.wilkinson]

That reprocess is much better

[Montana]

Super work David I'm sure you will get all the little things sorted for more cracking images.

Alexandra

[David Smith]

Ok, I think I have gone as far as I can go with this data set. I have tried various combinations of stacking methods, input files and GIMP processes. The image below is still the original 20 frames stacked using manual align and then just a slight tweak of curves and color balance in GIMP.

I have tried re-stacking with a higher number of frames but the results a of lower quality. Need some more Sun now so I can get some more frames to play with! Was sunny today but I was at work.

Thanks all for your guidance / encouragement

[michael.h.f.wilkinson]

Really nice result. Shows a lot of subtle detail.