DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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Hi all,
There have been some great images posted over the last few days and I thought I would have a go myself, but I am struggling to get any decent detail. I am using a 0.8A 70 mm scope, which I realise won't show as much as a lower bandpass scope, but as you can see, my image is pretty poor. I am using a DMK21 at 60 fps, early in the morning so the seeing is pretty good and have paid attention to focussing. I have tried with a high gain and a low gain and using a 5X Powermate and also with 3X and 2X barlows. Am I just hitting the performance limits of my gear, or are there other tricks to try, such as better image processing? I'm hoping that because I have almost no idea what I am doing that there is still more I can do to get better images. Any advice from the expert imagers here would be most appreciated.
I've also thrown in an image of a prom, just because it was there and the suface imaging was starting to give me the woopsies.
Thanks,
David
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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And the prom
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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darkstar528
Postmaster
Reged: 03/06/07
Posts: 7446
Loc: Hodgenville, Kentucky, USA
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Nice shots!...Clouds here...
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Blue skies,
Stephen "Darkstar" Ames
PST(#96038), VIXEN 8-24mm,CEMAX 2x Barlow, Thousand Oaks White Light Filter and a Meade Elec EP
CFI, CFII, MEI, working on EIEIO!
BAA Member
My solar site:
http://seemysunspot.com
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robert_arnold
Carpal Tunnel
Reged: 11/08/05
Posts: 1601
Loc: Isle of Skye, Scotland
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I prefer less glass, so no barlow (others on this site can do wonders with them).
The first image looks to me like registax has lost the alignment point and has tried to stack several images out of sync. Worth redoing that stage I would think
Robert
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ED80 ED100 DMK31AF03 CaK-B600 LS75F/B1200
www.robertarnold.co.uk
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PeteLawrence
Carpal Tunnel
Reged: 02/07/06
Posts: 2438
Loc: Selsey, UK
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How many frames are you taking and how many on average are you stacking. What quality threshold are you using?
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Best regards,
Pete Lawrence
http://www.digitalsky.org.uk
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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I have been taking up to 4500 frames and have been stacking anywhere between 500 and 1500. I'd have to check the quality threshold, but for this image it was about 90% I think. Should I be much more strict on the quality and stack fewer images?
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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rumples riot
Carpal Tunnel
Reged: 07/01/04
Posts: 2515
Loc: South Australia
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Ok here is my tip.
In IC capture reduce your gamma if you can. Gamma reduction during capture produces great contrast in the surface detail.
Use fast exposures and adjust the gain to suit. Gain is not an enemy, it just produces more noise in individual frames. So if you collect enough good frames you will get a nice image. Using the histogram and keep it at about 240 in log mod will give you the right exposure for each frame.
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EARTH AND COSMOS
How to peltier cool a C14 SCT
SOUTH CELESTIAL POLE
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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The gamma set as low as I can on this camera (10), which I suspect is not very low. The best result I had was with the highest gain. With the gain set low, things were really bad. I will try stacking maybe the very best frames and see if that helps.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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PeteLawrence
Carpal Tunnel
Reged: 02/07/06
Posts: 2438
Loc: Selsey, UK
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Can you post one of the best frames from the AVI that the above image came from? The quickest way to do this is to open the AVI in Registax, cycle through until you find a good one and then do a screen grab (Print Screen). Paste the grab into PhotoShop or whatever and crop to just the frame.
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Best regards,
Pete Lawrence
http://www.digitalsky.org.uk
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robert_arnold
Carpal Tunnel
Reged: 11/08/05
Posts: 1601
Loc: Isle of Skye, Scotland
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I usually record 100 frames and stack 80-90, I am not convinced huge numbers add anything except to processing time.... just a thought to speed up experimenting
Robert
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ED80 ED100 DMK31AF03 CaK-B600 LS75F/B1200
www.robertarnold.co.uk
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Oldfield
Postmaster
Reged: 03/20/02
Posts: 5889
Loc: Hong Kong
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Take only 1000 frames at most... the sun is so dynamic that the feature actually changes over time and it could be the reason why it's not as sharp as it could be.
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The Home Astronomer from a city where most people are proud of the light pollution
Toys: Orion 100ED, Ranger with NGF-CM, SM40/BF10, TG-SP II, LXD55, DMK 31AF03, Lumenera LU070M, Canon 10x30 IS...
My observation log and ideas My General Blog
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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Thanks for the advice everyone. Here is a capture of one of the better frames. It seems to me as if it is the quality of the raw images that is the limiting factor. I did a reprocess and the frames come in with a quality of ~65-75, as opposed to my prominence capture from the same day which has 90-95%. This image was captured with a 2X barlow and with the gain at the highest setting (hence the noisy appearance) because the low gain image was showing even less contrast. I just don't seem to be getting a decent image at a reasonable magnification, which is surprising given that people seem to be doing much better with a PST with a smaller aperture and higher bandpass. I am imaging at about 9:30 am, but perhaps I need to wait until the sun is higher, even though the seeing starts to drop off pretty quickly.
I'll have another go this morning.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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PeteLawrence
Carpal Tunnel
Reged: 02/07/06
Posts: 2438
Loc: Selsey, UK
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Hi David,
That's way too bright to be honest. Here's a raw frame from a previous run.
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Best regards,
Pete Lawrence
http://www.digitalsky.org.uk
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NickH
Post Laureate
Reged: 05/09/06
Posts: 3717
Loc: Wiltshire, UK (near StoneHenge...
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The other worrying thing in the image is the appearance of astigmatism in the shot. Are you finding focus a problem at F20 or higher? Not sure how the assembly on the Helios 1 works, but it looks a bit odd to me, not just a focus odd..
Probably nothing, but just curious
Like you say for a 70mm 0.8A setup, it's missing something..
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Oldfield
Postmaster
Reged: 03/20/02
Posts: 5889
Loc: Hong Kong
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I believe the focus can be better.
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The Home Astronomer from a city where most people are proud of the light pollution
Toys: Orion 100ED, Ranger with NGF-CM, SM40/BF10, TG-SP II, LXD55, DMK 31AF03, Lumenera LU070M, Canon 10x30 IS...
My observation log and ideas My General Blog
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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I had another bash today. The seeing wasn't quite as good, but I think the image is slightly better. Perhaps my focussing was a little better. The helical focusser on the Helios has just a little bit of play which makes focussing hard to get just right. I'm not sure if there is astigmatism. Does this mean different parts of the image would be in focus at different places?
I used a moderate gain setting these images, which I think helped (much less bright than the full gain image above). I captured 1000 frames and stacked about 50%.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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And the second. Thanks for all the help everyone. I might need to get a local expert to check out my setup to see that everything is in order.
I am only doing relatively straightforward processing at the moment (wavelets, then in Photoshop despeckle, unsharp mask and colourising). I'll check the how to guides see if there are more tricky ways of going about things.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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rumples riot
Carpal Tunnel
Reged: 07/01/04
Posts: 2515
Loc: South Australia
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I think your gain is getting close, but you need to follow the histogram. Use the fastest exposure possible to capture the frames quickly. This acts like the shutter on a camera. The faster it moves the quicker you capture the still moments.
You do need more than 100 frames though, good images have a lot more frames than that. You cannot work and image properly with only 100 frames. As also placing a defining limit on 1000 frames is not correct either. If you image for 35 seconds you want to capture as many frames as possible. Stacking 600 odd good frames has a big impact on the image.
I would try turning your blue shift knob (forward etalon) to near the middle too. I am not sure if the 70mm has these, but if it does, try using this more too. If it is all the way closed (ie dow hard and with no tilt)you will get this sort of look.
You might also consider getting a new camera. The USB DMK is a good camera and affordable if you are on a budget.
These last images are an improvement, but you could get a lot more out of that scope.
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EARTH AND COSMOS
How to peltier cool a C14 SCT
SOUTH CELESTIAL POLE
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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Hi Paul,
I'm leaning towards getting a new camera at some point. What would the main advantage be in getting say a decent Skynyx, apart from being able to change the gamma? Is there less noise than a DMK, or are the pixels smaller?
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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rumples riot
Carpal Tunnel
Reged: 07/01/04
Posts: 2515
Loc: South Australia
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Well the skynyx is a great camera. It has a multitude of advantages, but the main ones that I was concerned with are larger pixels which make it hold more charge and there for more data. Its well depth is correspondingly longer and this also means more data.
To boot the Skynyx has a lot less noise per frame than the DMK. If you buy the skynyx you will not be disappointed. They are superb. The best program to use it with is the Lucam recorder (cheaper than streampix)and this is written to include filter wheels if you happen to be into planetary imaging also.
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EARTH AND COSMOS
How to peltier cool a C14 SCT
SOUTH CELESTIAL POLE
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DesertRat
Pooh-Bah
Reged: 06/18/06
Posts: 1042
Loc: Valley of the Sun
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It looks to me that there is an excess of striations in the image. It is quite possible, as Nick H stated, there may be some astigmatism in the image. There may be an analytical way to look at the image in frequency space via an FFT to see whether or not that is true. Possibly someone out there knows what processing packages provide this. It could also be that Registax is not registering the images correctly which would be an operator function since there are plenty of options available.
Glenn
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Brandon 94mm f7, Televue TV102 f8.6; GM8
Baader Wedge & Filters, Coronado SM90/BF30
IM715; C11 & C14; G-11 Gemini
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DesertRat
Pooh-Bah
Reged: 06/18/06
Posts: 1042
Loc: Valley of the Sun
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Hi David,
I performed a forward FFT using AIP4WIN (Enhance->Manual FFT Operations->Forward FFT) on two images. One from a better solar disk image posted here by Pete Lawrence on the left and another on the right you posted. I don't make any claims that this is conclusive proof of astigmatism. Halpha images of selected portions of the Solar chromosphere showing filamentary structure could present preferential directions which would exhibit similar results. But it is interesting and possibly a tool we could use in addition to a keen eye.
Possible causes could be a tilted optical element or poor tracking not locked onto by the stacking program.
Glenn
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Brandon 94mm f7, Televue TV102 f8.6; GM8
Baader Wedge & Filters, Coronado SM90/BF30
IM715; C11 & C14; G-11 Gemini
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pjstoker
sage
Reged: 04/21/06
Posts: 454
Loc: So. Calif, USA
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Glenn, very interesting analysis. However, I don’t think David’s problem is astigmatism. As Pete pointed out, the single frame image David posted is grossly overexposed due to the high gain setting. Here is what it looks like with the black and white points set and a little contrast enhancement. As you can see there is a lot of detail, albeit buried in noise due to the high gain setting. It also looks like possibly a little vignetting around the edges, which causes the darkness and actually improves the detail. This could also just be due to the brighter area around the active region. David, I would not mess around with various barlows for the time being, but instead would stick with the 2x and concentrate on getting the exposures correct. Whatever camera control software you are using I’m sure is giving you a preview on your computer monitor. With your DMK21 this is a real time image you are seeing on your monitor and whatever you see on your screen is what your avi images are going to look like. So, you don’t even have to take any images to work with the various camera settings like exposure, gain, gamma, brightness and contrast to see which combination is best. The other thing is to be sure and use the frame list in Registax and scroll through you individual images and pick one that has a high resolution for your reference image, and then set your quality based on that image. You shouldn’t have to stack more than about 200- 400 or so to eliminate almost all of the noise with the type of camera you are using.
Pat
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Patrick Stoker
http://home.earthlink.net/~pjstok/wp10_intro.htm
Edited by pjstoker (03/31/08 05:30 PM)
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NickH
Post Laureate
Reged: 05/09/06
Posts: 3717
Loc: Wiltshire, UK (near StoneHenge...
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Quote:
Well the skynyx is a great camera. It has a multitude of advantages, but the main ones that I was concerned with are larger pixels which make it hold more charge and there for more data. Its well depth is correspondingly longer and this also means more data.
To boot the Skynyx has a lot less noise per frame than the DMK. If you buy the skynyx you will not be disappointed. They are superb. The best program to use it with is the Lucam recorder (cheaper than streampix)and this is written to include filter wheels if you happen to be into planetary imaging also.
Costs 2.5 times as much though...
That's all that puts me off the Skynyx..
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DesertRat
Pooh-Bah
Reged: 06/18/06
Posts: 1042
Loc: Valley of the Sun
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Pat,
I would expect to see noise at this level when the image was stretched from this camera (I've got the DMK 21BF04, but I agree using a lower gain setting would help in general). I did not see the single frame as overexposed, maybe close but there is no wall on the high end of the histogram.
If there is not an optical aberration its got to be the stacking process. Maybe David could post the avi or a subset on a forum's ftp area (IceInSpace supports this from time to time) and let one of the experts analyze further.
Glenn
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Brandon 94mm f7, Televue TV102 f8.6; GM8
Baader Wedge & Filters, Coronado SM90/BF30
IM715; C11 & C14; G-11 Gemini
Edited by DesertRat (03/31/08 08:07 PM)
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pjstoker
sage
Reged: 04/21/06
Posts: 454
Loc: So. Calif, USA
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Glenn, when I looked at the histogram I saw it was shifted to the white with most of the pixels showing counts between 172 and 255 with the peak about 220. We know that there are black areas in this image with the sunspots and long filament and that there should be a broad histogram distribution with counts close to 0 for those areas. When I saw the stacked image, my first impression was that the frames were misaligned during the stacking process. However, even if only a single point alignment box was used, there should have been a pretty good alignment because Registax had a lot of the high contrast features to lock on to. Of course if there was a poor alignment on the mount and quite a bit of drift during the time the avi was shot, then even with high contrast features the program would have a hard time getting a good alignment.
Pat
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Patrick Stoker
http://home.earthlink.net/~pjstok/wp10_intro.htm
Edited by pjstoker (04/01/08 01:30 AM)
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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Thanks for the in-depth look at what might be going on. I believe I can set the exposure and gain settings much better now, though there seems to be a fair bit of slop before the main peak on the histogram approaches either end of the range.
After playing around with things today, I have noticed that the focus is absolutely critical and that being a touch either side of perfect introduces a strong linear element or 'lean' to the image. I think this is what caused my prom images I posted separately a couple of days ago to slant one way or the other. This is presumably the cause of the striations on some of the images, which are only enhanced when wavelets are used, and is the cause of the linearity of the FFT analysis. This revelation is somewhat horrifying, as it is very difficult to get the focus absolutely spot on. Does anyone know what might cause the image to warp like this as you go in and out of focus? I have a long train of gear for imaging (extension tube, hanging out a little from the OTA, barlow and camera), and I think there is a bit of 'droop' in the setup. Could this cause things to go wrong?
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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rumples riot
Carpal Tunnel
Reged: 07/01/04
Posts: 2515
Loc: South Australia
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Droop is almost certainly the cause of your problem. Why not use a 2.5x powermate? Or like I do and use a 5x powermate. You have the diameter and focal length to do this.
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EARTH AND COSMOS
How to peltier cool a C14 SCT
SOUTH CELESTIAL POLE
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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It's never good news to hear that droop is your problem...
I'm not sure how to fix this with my setup. Back to the drawing board I guess.
I am using a 5X Powermate for my close-up prom images, which seems to work well. My other options are a 2X and 3X barlow. I have been favouring the 2X at the moment for disk images, just because focussing at higher mag is proving such a problem.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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rumples riot
Carpal Tunnel
Reged: 07/01/04
Posts: 2515
Loc: South Australia
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Achieving focus is a practiced thing. I can now focus with the Solarmax 60 which has the same helical focusor as your scope in about 30 seconds.
I use a 3x a lot but don't really use my 2x very much. For full disk I need to get a camera adapter so that I can use my DSLR. Certainly something I need to take a look at.
Having discussed the idea of some flexure in your imaging train, it might be prudent to give us some images with the 5x powermate. This will verify whether it is flexure or astigmatism. I am leaning more to the former, but it might be worth checking. Did you buy the scope new? You may have told me on the other site, but I cannot remember.
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EARTH AND COSMOS
How to peltier cool a C14 SCT
SOUTH CELESTIAL POLE
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DavidM
sage
Reged: 03/25/06
Posts: 235
Loc: Sohar, Oman
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The prom shots I have posted on this forum were done with the 5X Powermate, but I presume that I will need a surface shot to verify flexure or astigmatism. What are you looking for to decide between the two? Does the higher magnification make the flexure distortion more pronounced?
Do you use aperture masks to focus? I have been doing it using the sharpness of features as a guide, but given I can actually get sharp (albeit slightly distorted) images just out of focus, I wonder if there is a better way.
I bought the scope second hand a couple of years ago. The seller was a respected astronomer who considered the optics to be very good, and from my dealings with him, I would trust his assessment (though I guess that was a while back). I must say that visually, using a daigonal and eyepiece, I have always thought the images looked really good, though I have nothing to compare it with. I'm off to the South Pacific Star Party this weekend and can hopefully do a visual comparison with a PST or Solarmax60, if there are any about.
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David
16" Meade Lightbridge
70 mm Coronado Helios 1 H-a scope
8" Celestron 8iSE
80 mm Orion EON
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