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Daring the Full Moon with Lodester + H-alpha Filter


Dom543

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It was a nice clear night yesterday. So armed with my H-alpha filter and Lodestar X2c I decided to dare the bright full moon. This time I used my old manual 135mm, f2.5 Asahi SMC Takumar camera lens and aimed at mid-sized hydrogen emission nebulas.All images are with a 6nm H-alpha filter.

My favorite observing settings in LodestarLive v.0.11 are Contrast=50, Color Saturation = 2.0 and Black Level moved up to the left foot of the histogram. I leave White level, Brightness and Color Hue at their default values. These, or small modifications of these values, work well for enjoying the views on the LL screen at the telescope.(All exposures were 60 sec.)

Unfortunately, images saved with these settings look too dark and faint when posed on the internet. I believe that the reason is the narrow dynamic range of the internet images. With the above settings too much of the total dynamic range is used only scarsely as a buffer to prevent blown out regions. Only a narrow band is actually used to display the image of interest. This is o.k. on the computer screen directly connected to the camera with band-width practically unlimited. But not for internet images and internet video channels with their narrow bandwidth, most of which goes unused with my settings.

So for the sake of posting the images, I chose more aggressive settings. Hoping that these will result in brighter, more enjoyable posts but at the cost of the danger of some blown out regions.

Below are two comparisons. The left images are at Contrast=60, Saturation=2.5. As you may note, this is already more aggressive, than my preferred settings and may result in some blown out regions. The right images are at the extreme settings of Contrast=70 and Saturation=3.0. This is too postery for my personal taste but may be what the internet prefers.

So here is the Heart Nebula with the two different settings. We plan to hand out the right image to visitors of our outreach events so that they can mail it to their Valentines...

post-26379-0-26953400-1423026616_thumb.j

And here is tha Baby, that may come as a result of all that love... As you see, the Baby is fainter and feebler, it accepts more aggressive settings. In fact, 90 sec exposures may have been preferred for this object.

post-26379-0-19896400-1423026709_thumb.j

The images are as I saved them from Lodestar live. Absolutely no processing, except converting them to JPEG and gluing together in MS Paint.

The choice of objects were motivated by Don Rudny, who sent his very nice mono images of the same objects. With my mono camera and beginner sills I will never be able to match the fine detail of his pictures.

I also tried some other objects but the four images exhaust my posting file size. So I stop here before my weak internet connection goes away.

Wishing you all similarly clear skies!
--Dom

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This post attempts to show one, to me unexpected, benefit of stacking. 

Look at the images clockwise. The upper left is with the settings that looked best during the observing session at night at the telescope: Contrast=35, Saturation=2.0. With this faster lens exposures of 30sec would have been sufficient for the bright Rosette. The lower than usual contrast setting is to compensate for the overexposure. The capture has nice detail for a single frame but, when saved and looked at in daylight or as posted on the internet, it looks too dim.

The upper right is a single frame with Contrast=50 and Saturation=2.5. It obviously looks overexposed with fine details blown out.

The lower right image is a stack of three with the same settings as the image above it. Interestingly, the finer details are coming back, while retaining the overall brightness and vivacity of color of the base single frame.

A stack of ten (lower left) makes the image smoother but doesn't make that much of an improvement over the stack of 3.

It was unexpected to me that stacking would "repair" a blown out image by bringing back detail that was believed to be lost.

By the way, I always use mean-stacking. My single frame captures are o.k. in the sense that I can see things that I couldn't see with the eyepiece. But they are very noisy, especially the background. Interestingly, they look just fine, when posed on the internet. The noise is not as pronounced as when looking at them on the screen. After a mean-stack of 3, the noise gets smoothed away and the images look nice.. The images are getting to the level of being a pleasure to look at after a stack of about five. I usually let the stacking run up to 10 but am not noticing that much of a change past the threshold of 5.

I know that other members have good success with sum-stacking. I have not managed of getting the hang of it as yet. The quality of my sum-stacked images look very much like single frames with longer exposures. Noisy to look at but fine, when posed on the internet. Hybrid stacking might be the dream, especially for users with less accurately tracking mounts.

Anyway, here are the promised four images of the Rosette. These were taken with the same 135mm f2.5 SMC Takumar lens and 6nm H-alpha filter, as the captures of the previous post. (A week or two ago I posted another image of the Rosette taken with a 200mm lens. It is in the LodestarLive v.0.11 thread. The 200mm lens provides perhaps the best image scale for the Rosette. But yesterday I didn't feel like switching lenses.)

post-26379-0-90344600-1423029373_thumb.j

Clear Skies!

--Dom

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Magnificent images, Dom, and especially considering the full moon! Nice side-effect of the H-alpha.  

On my monitor the right-hand Heart and Baby look best as the sky background appears darkest. For the Rosette I'd be very happy with the top left version for similar reasons. 

Mean stacking is still my default mode in spite of the better results I've managed with sum, but that was in v0.10 when sum stacking meant chasing the black and white levels. Since v0.11 was released I've had wall-to-wall cloud and now we're in the grip of week-long bout of full on winter (not complaining -- I like snow!). 

I read somewhere that using very narrow band filters with fast systems can be problematic (something about ending up with the narrow pass band not looking at the H-alpha region). So I'm interested to see that you don't appear to be suffering from this with your 6nm passband + f2.5 lens. Anyone know more about this issue? I've been holding off getting an H-alpha filter with my f4 mirror until I can be sure which bandwidth to go for.

I hope you can post your other captures. The outreach visitors are going to love these!

cheers

Martin

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Hi Dom

Absolutely stunning images - great to see what can be achieved with the X2-C!

How do you mount your Lodestar and camera lens - a picture of your set up would be great?

How do you find achieving focus using the focusing ring on the lens - is this a big issue?

I'm not sure that the internet images have any less dynamic range (although I'm not sure what the dynamic range of your average lap top is these days, it always used to be 8bit per colour - 24 bits per pixel).

The differences you see at the scope and later on the web might be down to ambient lighting washing out the image?

Clear skies

Paul

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Excellent, Dom! I agree with Martin on which looks best, but the viewing monitor can make a difference. I think you have opened up a whole new avenue for NRTV. Having DSO's in color makes a big difference to some, especially in outreach programs. And you did this just in time for Valentines day.

Martin, I don't think you will have any problem with F4 optics and Ha. Here is a link that explains how faster optics shifts the bandwidth on narrow band filters. You may lose some transmission, but nothing really significant until F3. They even have examples of good results with F2 Hyperstar. Not sure this applies to all makes of filters, though.

http://www.astrodon.com/Orphan/astrodonfaqnarrowband/#h13

This entire link is very helpful in understanding narrow band filters.

Don

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Thank you for all the kind words!

A few quick answers.

Martin:
As the histogram changes with diffring contrast settings, the position of the black level relative to the histogram may also change. This can cause a difference in the darkness of the background.

I also used to use sum stacking witd LL v.010 and when my mount was poorly aligned on a balcony, where the view of Polaris was blocked by the wall. But that's no longer needed with LL v.011 and a well aligned mount. Mean stacking literally eats the noise as one goes from stack of 1 to 5. It's an added pleasure to see the noise going away as new frames come in.

I asked the same question about the use of narrow band filters with fast optics in this CN tread:
http://www.cloudynights.com/topic/485764-h-alpha-filter-bandwidth-for-fast-optics/?hl=%2Bnarrow+%2Bband+%2Bfilter#entry6360006
The last reply by Samir Kharushi sums up the situation well. As one goes faster than f2.5, one starts to lose some light. But still the loss is outweighted by the benefit of drastically reduced light pollution and skyglow by the narrower band filter.

Paul:
I will post a description and image of my setup.I need to take some photos.

I use the lense's focusing ring to finalize focus. I place the camera a bit closer to the lens so that infinity focus is achieved at around the 90% setting of the ring. Fast focal ratios mean shallow depth of field and very fine adjustment is needed to achieve exact focus. But these old Japanese lenses are masterpieces of craftsmanship and have excellent mechanics. It takes some patience but is not difficult.

I like to use Bakhtinov masks to verify focus. But with the Ha filter it is not feasible. I go to Sirius and visually minimize the size of the dot on the LL focusing screen.

I have just noticed the difference between the images displayed on different web sites. Images displayed on SGL look almost as good as directly on the computer screen.  On the other hand, lots of detail and brightness gets lost on CN images. I suspect that sites might use their own compression software to reduce space requirements of images. I agree that ambient lighting also makes a difference.

Don:
Thank you for the inspiration and your example images that help to choose the best targets. Images posted by you and by nytecam motivated me to buy the Lodestar last fall.

My apologies for all the typos. I am a poor typist in general and am now composing my posts under the constant danger of loosing my internet connection.

Clear Skies!
--Dom

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Hi Dom and All,

I want to thank Dom for his efforts in experimenting and successfully developing a technique for using a NB Ha filter with the color Lodestar. His results are very impressive, indeed. After a few nights with trying it myself and some advice from Dom, I finally got some decent results. If you're interested I have posted them in my SGL gallery. Here is a direct link.

http://stargazerslounge.com/gallery/album/3621-nb-ha-and-lodestar-x2c/

Let me know what you think, and any advice is always appreciated. I'll still in a learning process. Probably always will be.

Thanks,

Don

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Yesterday night I was experimenting with capturing different size of objects with different sizes of lenses.

Here is the first one that was a pleasant surprise to me. The Heart and the Baby in one field with an 85mm portrait lens. I didn't know that they were so close and have not seen this wide of a field with a small 1/2" EAA sensor. I estimate that diagonally I have about a 5 degrees FOV, which is in the binocular territory.

Please also note that the exposure times are a mere 30 seconds. And this is with a narrow-band H-alpha filter. I have mean stacking running all the time while I am observing. It improves the signal/noise ratio. The improvement is noticable up to about the 5th stacked image, after that it just keeps running. Mean stacking doesn't change the brightness if the image. The first frame was just as bright as the one I am posting.

Returning to Martin's question from yesterday, focusing at these fast focal ratios, and with an Ha filter, requires some patience. First because one has to wait for 30 secsonds between each iteration to see, if one got an improvement. Second, because one has to move to a very bright star that can shine through the filter and still provide a sufficiently large image circle. The range of acurate focus is very narrow for fast optics. That's why they use them for portrait photography.

Anyway, the full equipment and settings info for this shot is as follows. Lodestar X2C with LodestarLive v.0.11, Asahi SMC Takumar 85mm f1.8 manual focus lens, 6nm H-alpha filter. 30 sec exposures mean stacked, Contrast=.70, saturation=2.5, Balck level at the foot of the histogram bulge, and all other settings at their LL defaults (incl. Scaling=Linear).

post-26379-0-43480400-1423168213.jpg

The second shot for todays'post is of the Flame and Horsehead nebulas with a much larger 300mm lens. This lense is one of the earliest examples of the Asahi Takumar series from the 1960's and one of the most beautiful of my collection. It would deserve its own photo.

The shot below is of the Flame and Horsehead nebulas taken with Lodestar X2C with LodestarLive v.0.11 software, Asahi Takumar 300mm f4 lens and 6nm Ha filter. Exposure=30sec with mean stacking running, Contrast=0.70, Saturation=2.5, Black level at the left foot of the histogram and all other settings at their LL v.011 defaults.

post-26379-0-44736300-1423168290.jpg

If you have any good suggestions for H-alpha objects that would be suitable targets for the 85mm and 300mm lenses featured in this post, I would appreciate them. I have many targets for the midrange 135mm and 200mm lenses but fewer for the extremes.

Clear Skies!
--Dom

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Hi Dom,

Your 85mm gives you about a 4.4 degre FOV with the Lodestar. According to my SkySafari, that should be enough to get Orion, the HH and the Flame in one view. I think it will be hard to beat Heart and Soul. You should do a YouTube with the song as background.

Don

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Two more captures with the 85mm SMC Takumar lens from two nights ago. One night past full moon.

The Seagull Nebula IC2177 near Sirius. Thanks to Don for suggesting this object for a wide angle target. I suspect that those were the medieval Arab astronomers, feeling swell after giving Arab names to most stars, who placed the head of a laughing camel on this celestial bird...

post-26379-0-78482400-1423354576.jpg

The Flaming Star and Tadpole Nebulas in one field (IC405, 410 plus little no-name nebula IC417 near the left border).

This framing also includes the chain of brighter stars 14, 16, 19 Aurigae, which show the challenges of achieving accurate focus with sub-f2 optics (Or of the limits of Dom's patience). Especially with an Ha filter that forces a 60 sec wait between each tiny modification of the focusing ring.

post-26379-0-27715500-1423354698.jpg

Clear Skies!

--Dom

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Martin, I don't think you will have any problem with F4 optics and Ha. Here is a link that explains how faster optics shifts the bandwidth on narrow band filters. You may lose some transmission, but nothing really significant until F3. They even have examples of good results with F2 Hyperstar. Not sure this applies to all makes of filters, though.

http://www.astrodon.com/Orphan/astrodonfaqnarrowband/#h13

This entire link is very helpful in understanding narrow band filters.

Don

Thanks Don for that really excellent link. I recall now that it was Starizona's site that mentioned the possibility for issues for scopes faster than f/4

http://starizona.com/acb/ccd/advimnarrow.aspx

Since I'm on the cusp (actually f/3.9 it turns out) I was a little concerned about investing in the narrower bandwidth, but your link suggests a loss of only 15% at f/3.

Martin

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I asked the same question about the use of narrow band filters with fast optics in this CN tread:

http://www.cloudynights.com/topic/485764-h-alpha-filter-bandwidth-for-fast-optics/?hl=%2Bnarrow+%2Bband+%2Bfilter#entry6360006

The last reply by Samir Kharushi sums up the situation well. As one goes faster than f2.5, one starts to lose some light. But still the loss is outweighted by the benefit of drastically reduced light pollution and skyglow by the narrower band filter.

--Dom

Thanks Dom. That's a very helpful thread. The consensus seems to be: go narrow!

Martin

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Dom - inspirational stuff, wonderful images.

My X2C arrived recently, although work and family commitments have prevented much playtime, but an Ha filter is now definitely on the shopping list!

Your results, plus Don's excellent NB images, should give hope to anyone trying to cut through LP. They certainly give me hope! Street lights around our house have been "upgraded" a few months ago - instead of the pleasantly predictable yellow glow, they are now a harsh white light. Not far off the brightness of flame-thrower insecurity lights. Naturally, the effect seems much worse when your eyes are dark adapted!

The Ha road beckons. And thanks for the further proof that it's a technique well worth trying with the colour X2.

Cheers

Simon

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The past two nights I had my 200mm f3.5 Takumar lens mounted. I find this lens the easiest to use. Partly because it has its own mounting bracket but also because it is easy to focus. The latter is probably the result of its more modest f-ratio. It also has a good field with the Lodestar for many mid-size H-alpha nebulae.

My settings are similar to what I described in the earlier posts. This is easy and works for me. "Don't fix that's not broken..." If you are interested in the more exact setting for a given capture, they are included in the file names. "c" refers to contrast and "s" refers to saturation I don't change other options.

Here is a retake of the Rosette Nebula with the 200mm lens. You can compare it to the earlier capture with a 135mm f2.5 lens.

post-26379-0-75415600-1423598541.jpg

Here is a retake of the Flaming Star Nebula just by itself with the 200mm lens. This can be compared to an earlier composition with the 85mm f1.8 lens that includes both the Flaming Star and Tadpoles nebulas.

post-26379-0-99034000-1423598825.jpg

Finally the Jellyfish Nebula. I like to look at this on the screen, it really shines like a jellyfish in the sunshine under the surface of the water. This, unfortunately, doesn't come out quite as nicely on these internet posts. If you feel like taking a break from the realities of February and dream of a swim in some tropical seas, then you may consider of downloading the image and looking it that way.

post-26379-0-12883500-1423599378.jpg

Clear Skies!

--Dom

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Thank you for all the positive feedback. Credits should go primarily to Paul, who created LodestarLive that transformed the Lodestar guide camera into a real-time observing tool. Based on my experience with it, I believe that LL v.0.11 is ready to be released as release version 1.0. I also owe personal gratitude to nytecam and HiloDon, whose posts motivated me to buy the Lodestar camera in the first place and whose posted images gave me guidance about settings and object selection.

As the moon is now in its last quarter phase and not rising until midnight, it is time to conclude this "Daring the Full Moon" thread. My last image is a first in two respects. It's my first use of the 35mm f2.0 Super Takumar wide angle lens that I bought last fall with the intention of using it for Milky Way shots. It's also a first regarding the target that I have never seen before and was not even sure, if it was visible in real time with an eyepiece or camera.  As I wanted to test this lens at the end of the observing session yesterday night, I was scanning my memory for suitable wide field targets. I vaguely remembered that there was some large faint arc of nebulosity around Orion. I aimed the telescope (the lens) in that area and there it popped up right away.

Barnard's Loop with a 35mm f2.0 Super Takumar lens and a 6nm H-alpha filter.

post-26379-0-51994700-1423645611.jpg

This is a huge and faint formation, as it can be seen in comparison to the Horeshead and Flame nebulas at the top center of the image. (There is a capture of the HH+Flame earlier in this thread with a 300mm lens. The scale of that and of the current image compare almost as 1:10.) To make the loop bright enough, the HH & Flame area needed to be overexposed and a framing be chosen that excluded the extremely bright M42.

This concludes this thread as, in the absence of the bright moon,  we intend to move on and explore objects of more complex colors.

Thank you for your patience to look at all my images and for your encouragement as I was trying to learn my way to use the new version of LL and the Ha filter.

Clear Skies!

--Dom

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