dont laugh, at least not too much! 16 pane mosaic

[Pete Presland]

another small step taken today, a few more to go still!

actually i think it was a 20 not 16 pane mosaic, stitch with Autostitch, usual set up Coronado PST/DMK21au618 & X2.5 Powermate.

each pane is 1000 AVI's stacked around 400 per run.

a pretty poor end result, in terms of brightness balance. but absolutely delighted to actually get a mosaic stitch together for the first time! the advice about the "overlap" needing to be at least 25% seems to have helped hugely.

not sure what i can do about the brightness variation other than adjust each image before stitching. i did think maybe producing duller images when capturing, but i was worried about the lack of contrast in the final image.

next stop - a more balanced image and then proms with it! any advice gratefully recieved as always!

[JamesF]

Even with the short focal length of a PST, using a DMK21 and 2.5x barlow is going to make a really tough job of a solar image, so I think you've done well getting enough to stitch together to form a single image.

You may find that if you create a copy of the image, blur it so you lose all the detail and darken it and then subtract it from the original that you're left with a more even image (after you've merged them, that is, not before).

James

[Beulah]

No laughing here.  That's a fabulous effort for a first stitch. You've noticed all the things that need tweaking, there'll be no problem next time.

[Luke]

Great detail, Pete, well done getting all those tiles to stitch. I've had trouble getting four to join!

[DrRobin]

Super stitching job and a great capture. It is certainly a great start. Mosaics need everything to be just right, the same detail in the overlaps and a reasonably good brightness balance across the frame.

As you dont need any help in capturing the detail, you have got that nailed, a couple of suggestions to help you get better brightness balance. Did you adjust the gain and/or exposure at capture on the frames to balance it on the histogram? If you did then this might be the source of some of your variation if you went too far. The centre is naturally brighter than the limbs, so set gain and brightness on the brightest part and leave them as is. Unless of course you get a bit of haze come across in which case upping the settings will help. I used to tweak mine on every frame and spend ages getting the alignment and overlap consistent. Now I don't make any changes and try to get through my captures as fast as possible, before something changes on the sun.

The main reason for the bright patches in the stitch is probably the variation in brightness across the frame coming from a variation in the tuning across the frame, a so called sweetspot. You have a couple of options here, one crop the images, but this might mean more frames. Two try adjusting the tuning to balance out the bright spots, three use flats or four try post processing to reduce the gradient.

I would say either cropping or flats will give you the best and easiest solution and possible couple this with slight adjustments to tuning. I normally detune slightly to get a more even frame, you lose a bi of detail but it looks better overall. You can take a flat by either defocusing and take an image in the centre of the sun, or by putting a supermarket bag over the front. Reg AS! will do flat subtraction and Firecapture will do them on the fly, so the file you record is already corrected. The only problem I have seen with flats is that they seem to reduce the contrast and possible as a result the detail slightly and it is for this reason I prefer cropping, but they may mean a lot more frames.

I hope that helps.

Robin

[Montana]

I agree with Robin or you could spend a while using the lasso tool, feather the selection and raise the brightness in the areas that are dark. Gradually with painful selection and blending, will really help this image a lot. I do this plenty of times for my images, it takes time but is worth it.

A fantastic start :)

Alexandra

[Pete Presland]

Even with the short focal length of a PST, using a DMK21 and 2.5x barlow is going to make a really tough job of a solar image, so I think you've done well getting enough to stitch together to form a single image.

You may find that if you create a copy of the image, blur it so you lose all the detail and darken it and then subtract it from the original that you're left with a more even image (after you've merged them, that is, not before).

James

thanks for the tips, i gave it a go in my clumsy way it seemed to help a little so a bit more experimenting will be the way forward on this image.

[Pete Presland]

I agree with Robin or you could spend a while using the lasso tool, feather the selection and raise the brightness in the areas that are dark. Gradually with painful selection and blending, will really help this image a lot. I do this plenty of times for my images, it takes time but is worth it.

A fantastic start :)

Alexandra

is this in Autostitch or Photoshop?

[Montana]

Photoshop but I am sure any other program would do the same.

Alexandra

[Pete Presland]

Super stitching job and a great capture. It is certainly a great start. Mosaics need everything to be just right, the same detail in the overlaps and a reasonably good brightness balance across the frame.

As you dont need any help in capturing the detail, you have got that nailed, a couple of suggestions to help you get better brightness balance. Did you adjust the gain and/or exposure at capture on the frames to balance it on the histogram? If you did then this might be the source of some of your variation if you went too far. The centre is naturally brighter than the limbs, so set gain and brightness on the brightest part and leave them as is. Unless of course you get a bit of haze come across in which case upping the settings will help. I used to tweak mine on every frame and spend ages getting the alignment and overlap consistent. Now I don't make any changes and try to get through my captures as fast as possible, before something changes on the sun.

The main reason for the bright patches in the stitch is probably the variation in brightness across the frame coming from a variation in the tuning across the frame, a so called sweetspot. You have a couple of options here, one crop the images, but this might mean more frames. Two try adjusting the tuning to balance out the bright spots, three use flats or four try post processing to reduce the gradient.

I would say either cropping or flats will give you the best and easiest solution and possible couple this with slight adjustments to tuning. I normally detune slightly to get a more even frame, you lose a bi of detail but it looks better overall. You can take a flat by either defocusing and take an image in the centre of the sun, or by putting a supermarket bag over the front. Reg AS! will do flat subtraction and Firecapture will do them on the fly, so the file you record is already corrected. The only problem I have seen with flats is that they seem to reduce the contrast and possible as a result the detail slightly and it is for this reason I prefer cropping, but they may mean a lot more frames.

I hope that helps.

Robin

it certainly is down to the "sweetspot" i have the gain set quite low, because it gives better contrast to my eye. i suppose its a trade off between a duller more uniform image and the blotchy image like the one i have produced. i like the idea of Firecapture producing flats while capturing, i am using the Imaging source capture software at the moment.

[Pete Presland]

Photoshop but I am sure any other program would do the same.

Alexandra

is this done after stitching or prior to the mosiac being made?

[DrRobin]

I only started using Firecapture a couple of months ago and initially I preferred IC Capture from IS, but since I have to use it for my ASI120MM I have started to get used to it and quite like it now. With an ASI120MM, and many other cameras, it will let you set any exposure you want and automatically adjust the frame rate to suit. Sadly with a DMK you are still stuck at the pre-programmed exposures and frame rates. It also gives you ROI and binning, again not sure if the DMK series support this, but they probably do.

I haven't tried the 'flats' feature but with your narrow FoV that should work very well. I am guessing there are instructions somewhere on how to use it.

Alexandra is clearly a lot more dedicated to post process fiddling than me, I have seldom had any success in blending frames, I am guessing practice helps, but clearly it is successful as the images she gets from her PST are superb.

Robin

[Montana]

After you have done the mosaic, however mine aren't usually as bad as this one but it will improve is visually.

Alexandra

[Montana]

It needs a bit more time but my tea break is over, need to get back to my cells.

Alexandra

[todd8137]

Nice work

Pat

[Pete Presland]

It needs a bit more time but my tea break is over, need to get back to my cells.

post-5271-0-09447300-1408907306_thumb v2.png

Alexandra

  very nice Alexandra, that is very impressive! what technique did you use, i dont supose you know of a tutorial explaining it?

[Montana]

Thank you, it is rather a quick express version Just open your image in photoshop and click on the 'Lasso tool'. Then just crudely click round a dark patch to make a selection, then go to the top menu bar, drop down the 'Select' menu - Modify - Feather (5 pixels). Then go to the 'Brightness/Contrast' and raise the brightness a little to match the surrounding. Unselect your region and start again. Keep going round and round until you get a blend. It is best to do this with the image at low zoom as the eye can see the dark patches better, if you zoom right in you will not see the variances as easily. Like I say, this is a very crude fix, it is much better to start out with better gradients to put together, but sometimes this method can rescue an image. Once taken and the moment is past we are stuck with the image so we can't just say I'll go and take a better one as this hasn't worked so sometimes this can help

Kind regards

Alexandra

[Pete Presland]

Thank you, it is rather a quick express version Just open your image in photoshop and click on the 'Lasso tool'. Then just crudely click round a dark patch to make a selection, then go to the top menu bar, drop down the 'Select' menu - Modify - Feather (5 pixels). Then go to the 'Brightness/Contrast' and raise the brightness a little to match the surrounding. Unselect your region and start again. Keep going round and round until you get a blend. It is best to do this with the image at low zoom as the eye can see the dark patches better, if you zoom right in you will not see the variances as easily. Like I say, this is a very crude fix, it is much better to start out with better gradients to put together, but sometimes this method can rescue an image. Once taken and the moment is past we are stuck with the image so we can't just say I'll go and take a better one as this hasn't worked so sometimes this can help

Kind regards

Alexandra

thank you very much Alexandra for taking the trouble to explain so thoroughly, i will defintely give this a go later and post my result. if i do manage to produce a better balanced image next time, this will always be a "back up" plan.

[Pete Presland]

had a play with this tonight, much happier with the end result! added some false colour which i do not normally bother with, but even that seems to have come reasonably to my eye.

massive thanks to all who have offered advice     much appreciated      

[Space Cowboy]

Great effort Pete! Very encouraging for those of us considering imaging with a PST and planetary cam!

[Pete Presland]

Great effort Pete! Very encouraging for those of us considering imaging with a PST and planetary cam!

having seen your planetary imaging results Stuart, i dont think you would have too much trouble with the solar stuff

[Helen]

There are some great tutorials here which might help http://brierleyhillsolar.blogspot.co.uk/p/imaging-tutorials.html

Helen

[Pete Presland]

There are some great tutorials here which might help http://brierleyhillsolar.blogspot.co.uk/p/imaging-tutorials.html

Helen

what an excellent resource Helen  "bookmarked" thank you very much!

[kev]

Just like to say, really nice image. Reading through the posts on this thread is very educational.

Sent from my iPhone using Tapatalk

[Pete Presland]

Just like to say, really nice image. Reading through the posts on this thread is very educational.

Sent from my iPhone using Tapatalk

i am glad other readers found it educational as well. imaging is a never ending process, there are far better imagers on here than myself and thay freely admit the are still learning. especially with the processing side of it.