The Night of the Comet

We finally got a short break from monsoon weather and I had a clear, moonless night. I had intended to use it to get RGB data for the Helix Nebula (see below), but the Helix doesn't clear the mountain to my southeast until about 10:30 PM so I needed to start with a different target. I set up my scope for the Helix (no focal reducer, using a nebula filter--the Baader UHC-S), and thought I might try the Bubble Nebula in RGB for an hour or two first. But then I remembered that Comet Jacques is in a good part of the sky for me and decided to try to find it. I googled its position and found it was in Cepheus midway between two of the brighter stars in the asterism. Finding the comet was pretty easy because I could see a fuzzy patch with 1 sec exposures in my guide scope. About then the fun began.

Well, actually the fun began several days before, when my trusty laptop decided to give up the ghost. After giving me no problems at all for 3 1/2 years, it just abruptly froze and refused to reboot (while I was on a trip, of course). After a couple of frustrating days of waiting for the computer guys to look at it, the report came back that the mother board had died, so I've got an order in for a brand new, retina display, high end MacBook Pro. It's my work machine, and they only replace them every 4 years, so I always try to get the very best I can buy because in 4 years it will be massively obsolete. In the meantime, I've resurrected my ancient Core 2 Duo and a loaner i5, both of which are horribly slow and which required a couple of days of moving files and installing software before I could really get back to work.

So back to the comet.  This was my first night out trying to use these old laptops to run my imaging session. I knew VMWare+Windows 7 would be slow on either of these laptops, because neither has the solid-state drive I've become accustomed to. I tried both the Core 2 Duo and the i5 and had massive problems with both of them hanging and not connecting to my USB cameras and USB-Serial connector. Eventually I got the older machine, the Core 2 Duo, working, found the comet, and started imaging. I guided on a star, but kept having problems because the USB transfers from the cameras were slow so the guiding would keep pausing. I never did get the i5 to work right, but eventually (when I switched targets to the Helix Nebula) I stopped the Core 2 Duo and rebooted both the host and guest operating systems. Things ran fairly smoothly after that, but I can't wait for my new machine to get here so I can really put things right.

If I had this to do over, I would use a focal reducer and no filter. The proper motion of Jacques is pretty large (I understand it was at minimum distance from Earth about the time these images were taken), so a shorter focal length would make my optics faster and I could also make my subs longer because the motion would not be as apparent. As it was, I was limited to 60 seconds; any longer, and the nucleus was clearly blurred. I'd also try to guide on the comet nucleus rather than on a star; I think my guide camera is sensitive enough it would probably work. The UHC-S filter probably was not the best to use with a comet. 

I had all kinds of fun trying to stack the comet images. I first tried Deep Sky Stacker, which has a comet stacking option. You have to select the comet in each subframe, then you can stack on the comet only (streaked stars), on the stars only (no comet), or on stars and comet (both sharp, but essentially this does two passes and superimposes the images). The stars+comet option is what I wanted to use, but it has a bug in that it messes up the color. I tried separating the R, G, and B and stacking separately, then recombining in Photoshop. That works, but is a massive pain and kills your resolution. So finally I stacked on the comet nucleus only in Nebulosity (translation only rather than translation+rotation, which I usually use). I post-processed in StarTools pretty much in my normal way, just with less stretching. This picked up a little bit of tail.  Here it is:

Date: 28 Aug 2014
Subject: Comet C/2014 E2 (Jacques)
Scope: AT8IN
Filter: Baader UHC-S
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider+DSI Ic+PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc, chiller at 2.50 A, 12.5 °C
Acquisition: Nebulosity 3.2.1
Exposure: 47x60 s
Stacking: Neb 3, bad pixel map, extract NEB, normalize, de-Bayer & square, trans align on comet nucleus, 1.5 SD stack
Processing: StarTools 1.3.5.289 Crop; Develop 74.99%; Wipe; Develop 55.61%; HDR: equalize; Color: scientific 300%; Track: 7.2 pix. Photoshop CS6 Astronomy Tools levels, AstroFrame.

After that I switched to the Helix Nebula. As the nearest known planetary nebula to the Sun, it has the largest angular size and is one of my favorite objects to image; some call it the "Eye of God" because of its appearance. Finding the Helix manually has always been a bit of a challenge in the past because there aren't any nearby bright stars to use in positioning my Telrad finder. But amazingly, I was able to get Cartes du Ciel and the PicGoto to work on the old computer and this time I just synched on Fomalhaut and the goto was right on. My guiding performance was very poor; I guess I should have paid more attention to balancing my mount for this part of the sky. Overall, I was happy to pick up some of the outer shell of the nebula (in the upper left part of this image), but I'm sure I can do better and get a sharper image if I guide better. This would also probably be a good H-alpha target.

Date: 29 Aug 2014
Subject: NGC 7293, Helix Nebula
Scope: AT8IN
Filter: Baader UHC-S
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider+DSI Ic+PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc, chiller at 2.50 A, 12.5 °C
Acquisition: Nebulosity 3.2.1
Exposure: 47x300 s
Stacking: Neb 3, bad pixel map, extract NEB, normalize, de-Bayer & square, trans+rot align, 1.5 SD stack
Processing: StarTools 1.3.5.289 Crop; Wipe; Develop 75.13%; HDR: equalize; Color: scientific 249%; Deconvolute 2.4 pix; HDR: optimize; Life: moderate; Track: 2.2 pix; Magic: shrink 2. Photoshop CS6 Astronomy Tools several cycles of layer mask space noise reduction; lighten DSO; more noise reduction; levels, AstroFrame.

Cheap Electronic Focusing

I was recently asked a question on Astrobin about focusing, which got me thinking about posting something. Adding an electronic focuser to my rig definitely improved both the quality and frequency of my focusing. Focusing is acutely important for lunar/planetary work, and probably just as important (but easier) for deep sky astrophotography. I started out with a really terrible focuser on my old Meade department-store level scope, and thought I had hit the big time when I got a Crayford-style, dual-speed focuser on my Astrotech Imaging Newtonian. I've heard some people complain about the stock Astrotech focuser, but I guess I don't know any better and it is certainly way better than anything I had used before. After using it a while, I decided I wanted an electronic focuser. With my wobbly mount it is hard to focus by hand because the image jiggles all over the place whenever you touch the scope. I started shopping around and decided the Orion Accufocus was about the cheapest commercial setup that would do the job (you could put together a stepper motor and some gearing for less, but that started to look like too much bother to me). So I bought the Accufocus and started using it with the handcontrol/battery box supplied with it. I had to jerry-rig the attachment a bit, because the Accufocus is not designed for use with the stock Astrotech focuser. I attached the bracket that holds the stepper motor to the focuser via the two screws that set the focuser tension and locking; I replaced one of these screws with one that was a bit longer, on which I could thread nuts so I could independently attach the bracket and set the focuser tension. The pictures hopefully show what I did:

Although the handcontrol works fine, because the winters are cold in Utah pretty soon I decided I wanted USB control of the focuser so I could work on focusing from the warmth of my living room couch rather than sitting out in the snowy back yard. I picked up a FCUSB unit from Shoestring Astronomy. It works well with the Accufocus. Stark Labs has Mac-native software to run the FCUSB (called Shoestring Focus), and Shoestring provides Windows software. I started out with the Mac software, but after I started controlling my mount with PicGoto I had to run Windows anyway, and I found Shoestring's FocusPal works a little better than the Mac-native Stark program. So I now use FocusPal. FocusPal lets you run the focuser at variable speeds either as long as a button is pushed or in fixed-duration pulses. Typically I get the Moon or a bright star in my field of view and do rough focus with that. With stars, I use the diffraction pattern from my secondary mirror mount for rough focus; I just focus to get good spikes. Once I'm on my target, I pick a star with intermediate brightness and use the "fine focus" feature of Nebulosity, my imaging program, to get as good a focus as my patience allows. "Fine focus" provides two focusing metrics: intensity (which you want to maximize) and "half-flux radius" (essentially the size of the star, which you want to minimize). Both are shown graphically, so it is easy to see the effects of adjusting the focuser, even when the seeing is messing with your star.

So was it worth the cost of adding these upgrades? Yes! I get much better focus in much less time and stay warm while I'm doing it. I really couldn't use "fine focus" at all until I started doing electronic focusing. Now it is no problem to stop and refocus in the middle of an imaging run, and focus on my scope does drift a little (probably thermal expansion/contraction of my optical tube). Now I can correct for that.  There are, I'm aware, automated routines for focusing with these electronic focusers, but I haven't got any working yet.

HαHα, More Fun with Hα Images

We got the hoped-for gap in the monsoon clouds this past weekend, so I got more Hα data.

A couple of years ago I was playing with the free planetarium program Stellarium (which I love because it really can mimic what the sky looks like, because it is free, and because it is available for Windows, Mac and Linux), and noticed a patch of nebulosity right on the spine of Cygnus. After a little googling, I realized it was the Tulip Nebula, an emission nebula about 6000 light years away. I tried to image it and was happy to get something, but it was a pretty difficult object for me at the time.  You have to use a little imagination to see a tulip in this (opening toward the bottom left corner). I thought I was also getting Cygnus X-1, the famous X-ray source that is due to a black hole in a binary system, but it's actually right off the left edge of the frame and is nothing to look at anyway. Here's the image:

Date: 14 Aug 2012
Subject: Sh2-101, Tulip Nebula
Scope: AT8IN + 0.5x Antares telereducer
Filter: none
Mount: CG-5 (Synta motors)
Guiding: Orion ST80 + 0.5x Antares telereducer + DSI Ic + PHD
Camera: DSI IIc
Acquisition: Nebulosity 3.1.0
Exposure: 33x240 s
Stacking: Neb 3, bias included, normalize first, trans+rot align, 1.25 SD stack
Processing: crop, color balance, levels & curves, one layer GreyCStoration, unsharp mask another in N3. Layer mask combine the layers, star color enhance, GradientXTerminator, star size reduction, saturation boost all in CS6. 

The Tulip Nebula seemed like it would be a good Hα target because it is mostly Hα emission. It was an easy find after synching on Sadr with the goto dead on. The sky was quite clear and conditions were good save for a bit of gusty wind. I initially had balance issues with the mount and had to rebalance after getting an unsatisfactory PHD2 calibration. The Tulip does show up quite well in Hα (opening toward the upper left corner), with a lot fewer stars and a lot more detail visible in the nebula. I don't think the old RGB data are good enough to bother with combining.

Date: 15 Aug 2014
Subject: SH2-101, Tulip Nebula
Scope: AT8IN+0.5x Antares telereducer
Filter: Baader Planetarium 7 nm H-α
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc chiller at 2.50 A, 14 °C
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 22x600 s
Stacking: Neb 3, bad pixel map, bias included, extract R, normalize, square, trans+rot align, 1.5 SD stack, resize 2x (Bilinear).
Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 75%; Develop 75.54%; HDR:Equalize; Deconvolute 2.7 pix; Life:Moderate; Track RNC 0.01%; CS6 AstronomyTools B&W to Hα; deep space noise reduction; Astro Frame.

That same night I actually started by imaging IC 1275, at one edge of the Lagoon Nebula complex, through the Hα filter, but IC 1275 is pretty close to my southern horizon and I got a late start so I only got about an hour's worth of data before it moved behind my neighbor's trees. This was definitely not enough. So the next night I took more Hα of IC 1275. I got started as soon as it was dark. I synched from λ-Sag and aligned the field of view with the previous night's image. Conditions were excellent: very little wind. I combined the previous night’s data with the new subframes. For now, I'm still converting to false-Hα color, as seen below, but I'm wondering if you can't actually see detail better in these images in greyscale.  I'll have to think about that.

Date: 15, 16 Aug 2014
Subject: IC 1275
Scope: AT8IN+0.5x Antares telereducer
Filter: Baader Planetarium 7 nm H-α
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc chiller at 2.50 A, 16 °C
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 22x600 s
Stacking: Neb 3, bad pixel map, bias included, extract R, normalize, square, trans+rot align, 1.5 SD stack, resize 2x (Catmull-Rom).
Processing: StarTools 1.3.5.279 Crop; Develop 74.99%; HDR:Optimize; Deconvolute 2.7 pix; Track RNC 0.01%; Magic:Shrink 1; CS6 AstronomyTools B&W to Hα dark space; Astro Frame.

Finally, I combined the Hα with an image taken through the UHC-S filter on 22 July 2014. I’m learning more about HαRRGB combining. Interestingly, the scale was slightly different in the Hα and the RGB because in the RGB image I removed the Meade IR cut filter, putting the focal reducer slightly closer to the imaging plane of the camera than it was in the Hα image, where the IR cut filter pushed it away slightly. (I know I don't need the IR cut when using the Hα filter, but I didn't want to change my optical train so I left it in). So I had to translate, rotate, and scale align the Hα and the RGB in Nebulosity. The choice of stars in this alignment is critical; they need to be bright enough to show up in the Hα image, but not bright enough to bloat badly in the RGB. I mainly followed Starizona method 1 for this image, with one major modification: after replacing the original R with HαR, I boosted the red channel using the Photoshop Channel Mixer by 175%. This prevents the image from looking really blue (especially the stars). After that I used the HαR for luminosity, used local contrast enhance, and boosted the saturation a bit. I like the result. The bright Hα emission area at right center looks a lot like a leaping rainbow trout to me, and shows nice contrast with the blue reflection area just below the trout.

Trying to Get the Best of Both Worlds: Combining Hα with RGB

I wish I could claim I have figured out how to combine Hα images with RGB so as to retain the detail and contrast of the Hα and get reasonably good color from the RGB, but I'm still learning. As I mentioned in my last post, I've been using the tutorial on the Starizona web site as a guide for doing the combination in Photoshop. In my hands, the Starizona approach usually seems to result in blue stars or at least loss of the star colors (and if you've seen many of my images, you know I tend to favor a lot of color in the stars, perhaps more than most people would like).  A couple of nights ago, while trying to combine my Hα image of the Bubble Nebula with RGB, I finally pushed one of the buttons in StarTools for the first time, the LRGB button. I loaded the Hα into the luminance channel, and then used an old RGB image I had previously aligned with the Hα in Nebulosity to load the R, G, and B. On the first try I got a better result (I think) than I had been able to produce after hours of messing around in Photoshop. Here are the Hα, the RGB (flipped so it has the proper orientation), and the HαRGB composite. The stars are still a little blue, but it's my best Bubble so far.

I've also reworked the Crescent Nebula using StarTools and some Photoshop layer masking. Here is my best Starizona-method 1 result (layering Hα on R (a little more R than Starizona recommends), using that for luminance, and also using an Hα with R blend in place of the original R channel), and my best StarTools result (which involved loading Hα into both the luminance and the R channels, and layer masking and playing with the colors to try to get them approximately right). As you can see, the StarTools image is also stretched a bit more. I think I like it better. If the monsoon breaks so I can get more Hα data, I'll continue to play with this.

Full Moon (Even Super-Duper Full Moon)? No Problem!

My foray into Hα imaging using an inexpensive one-shot color camera continues. One of the things proponents of narrowband imaging usually mention is that you can do it from heavily light polluted skies and even when the Moon is full. My light pollution isn't horrible (technically, according to the light pollution maps that go with the clear dark sky charts, I'm in a Bortle orange-yellow transition area), but the Moon was definitely full last night. It was even the brightest so-called "super Moon" of the year (a few percent larger and brighter than normal because full Moon occurred at perigee this month). Anyway, over the last 2 nights I've been testing my ability to do Hα imaging under bright sky conditions, and it does work. So far, I'm continuing to stick to using a focal reducer to speed up my optics and to make the guiding very forgiving (we keep having gusty wind every night, so I need it to be forgiving).

Here's the Crescent Nebula in Hα from a couple of nights ago. Even under cloudy, hazy conditions it turned out OK I think. Conditions were terrible: a very bright Moon (which really doesn’t matter for Hα but matters for finding things) and lots of clouds combined with lots of haze. I tried to start on the Elephant's Trunk Nebula but could not find any asterisms nor could I see it after 300 s) so I came back to the Crescent where I knew I could see the parallelogram of stars. It was even a little bit difficult to find Sadr to sync (clouds and haze being the main culprit). 600 s subs are still barely sufficient. Warm; started at 24.5 °C and the chiller got it down to about 14-17 °C (it was drifting down through the night). Did a meridian flip and continued. The power of Hα is evident in that I got anything useful out of such poor conditions. It will be nice to get some Hα on a good night!

Date: 8 Aug 2014

Subject: NGC 6888, Crescent Nebula

Scope: AT8IN+0.5x Antares telereducer

Filter: Baader Planetarium 7 nm H-α

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)

Camera: DSI IIc chiller at 2.50 A, 14-17 °C

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 23x600 s

Stacking: Neb 3, bad pixel map, bias included, extract R, resize 2x, normalize, trans+rot align, 1.5 SD stack.

Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 75%; Develop 74.99%; HDR:Optimize; Deconvolute 2.7 pix; Life:Moderate; Track RNC 0.25%; Magic:Shrink 1 pix.  CS6 AstronomyTools B&W to Hα; layer masked deep space, space noise reduction; Astro Frame.

I'm having a terrible time trying to do HαRGB or HαRRGB combinations with this. The problems come with replacing the RGB R channel. The Starizona method says you should combine Hα with an extracted R and use that to replace R. However, that always seems to leave the resulting RGB quite blue, especially the stars. I don't know how to fix it. Part of the problem may be that in this particular case my RGB is really not full RGB, it was taken through a UHC-S nebula filter. Anyway, here's the best so far. I'm not sure it's any better than the RGB I started with.

Hα of the Bubble Nebula turned out pretty well; it's my best Bubble so far. Full Moon (in fact Super Duper Moon if you believe the media!). You really can do this Hα stuff under a full Moon. There's still lots of haze in the air, but when I went out to check the sky, things looked good enough to try so I did (besides, I left my gear out from the night before so I didn't have to set up!). There was also quite a bit of gusty wind again. Anyway, the Bubble was easy to find from α Cas with the PicGoto and easy to recognize even with short exposures of a couple of seconds even with the filter. 2.5 A on the chiller has the CCD at 16 °C. I like the way the filter picked up lots of detail in the nebula and a lot of surrounding gas I couldn't pick up otherwise. And all this under the Moon as full as it gets.

Date: 9 Aug 2014

Subject: NGC 7635, Bubble Nebula

Scope: AT8IN+0.5x Antares telereducer

Filter: Baader Planetarium 7 nm H-α

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)

Camera: DSI IIc chiller at 2.50 A, 16 °C

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 24x600 s

Stacking: Neb 3, bad pixel map, bias included, extract R, normalize, square, trans+rot align, 1.5 SD stack, resize 2x,.

Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 75%; Develop 70.97%; HDR:Equalize; Deconvolute 2.7 pix; Life:Moderate; Track RNC 79.41%; Magic:Shrink 1 pix.  CS6 AstronomyTools deep space noise reduction; B&W to Hα; Astro Frame.

I'm Cheap, but the Hα Filter Was Worth the Money

As I mentioned in my last post, I finally succumbed and laid out $160 for a Baader Planetarium 7 nm Hα filter. Last night was my first time out using it. Conditions were marginal at best; it's monsoon season so there were clouds and wind gusts as there were thunderstorms around. Synced on λ Sag and easily found M8 with the PicGoto; use of the PicGoto is becoming routine. Focusing with the Hα filter was interesting; the stars are so small that it is hard to use the half flux radius as a focusing metric, so mostly I just eyeballed it. M8 did turn out to be a good target for this first try. Because it is so bright, 300 s subframes were sufficient (and actually just about right) for the Hα. While waiting for clouds to clear, I did take a 300 s shot of the Crescent Nebula through the filter, and that was not enough for this dimmer object. Clouds rolled in after only about an hour, so this session was cut off prematurely (though I did get a few more subs through "cheater holes" in the clouds), but even with these problems I captured a lot more contrast in M8 than I got unfiltered. Here's the unfiltered version for comparison:

Date: 30 Jul 2014
Subject: M8, Lagoon Nebula
Scope: AT8IN+Antares 0.5x focal reducer
Filter: Meade IR cut
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc chiller at 2.50 A, 15 °C
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 55x120 s
Stacking: Neb 3, bad pixel map, bias included, normalize first, trans+rot align, 1.5 SD stack.
Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 81%; Develop 80.11%; HDR:Core reveal; save; undo; HDR:Optimize; Color:Scientific, 250%; Deconvolute auto mask 1.5 pix; Life:Moderate; Track RNC 1.47%; Magic:Shrink 1 pix; to the Core Reveal image: Color:Scientific, 250%; Deconvolute auto mask 2.5 pix; Life:Moderate; Track RNC 1.72%; Magic:Shrink 1 pix; CS6 Astronomy Tools layer the HDR:Optimize image on top of the HDR:Core Reveal with 85% opacity; Increase star color; Astro Frame

Processing Hα data involves a lot of new tricks. You begin by doing normal preprocessing of the images with darks (a bad pixel map in my case), flats (taken through the Hα filter), and bias frames. Next, you have to extract only the red channel from the CCD because the G and B channels are mostly just noise; Nebulosity has a batch tool for doing that with a whole set of files. Next, I normalized the intensities. Next, I needed to square the pixels (since my camera has rectangular pixels, and the RGB image I want to combine with has already been squared when it was de-Bayered); again Nebulosity has a batch tool for dealing with that. Then I stacked the Hα images as I normally would: I aligned them using two stars, saving each aligned image, then stacked the aligned images with 1.5-σ clipping. A quick visit to Photoshop let me double the number of pixels so I'd be at the same scale as my RGB image when I'm ready to combine. I next took the stacked Hα into StarTools and processed much as I would an RGB image, except I skipped the "wipe" step since I didn't need to do any color fixing. Finally, back to Photoshop where all I did was false color the image and put a frame on it. Here's the result. The increased contrast in the nebula, even on a first attempt under poor conditions, is amazing. The Hα image makes the nebula look almost 3-dimensional (which of course it really IS):

Date: 2 Aug 2014
Subject: M8, Lagoon Nebula
Scope: AT8IN+Antares 0.5x focal reducer
Filter: Baader H-α 7 nm
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc chiller at 2.50 A, 20 °C
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 24x300 s
Stacking: Neb 3, bad pixel map, bias included, extract R, normalize, square B&W, trans+rot align, 1.5 SD stack.
Processing: StarTools 1.3.5.279 Crop; Auto Develop; HDR:Optimize; Deconvolute 2.5 pix; Life:Moderate; Track RNC 0.74%. CS6 Astronomy Tools double the pixels; H-α false color; Astro Frame.

The next task was to combine the Hα data with the RGB data. There's a nice tutorial on Starizona's web site about how to do this in Photoshop (google it). They describe two methods. The first preserves more of the stars from the RGB image, while the second emphasizes the detail in the nebula. I show both results below. You can judge for yourself, but for this image I like the "Method 1" HαRRGB better than the "Method 2" HαRGB combination. I think the rich star field adds to the image and Method 2 pretty much wipes that out, and looks a bit overprocessed to me. Of course, this is all in the hands of a first-timer, so maybe I'll get better with practice. Here are the two images. Both show a lot more nebula than the RGB alone did. So even though the Hα was a big investment for me, I think it is worth the money. I'm looking forward to using it some more.

Lobster, anyone? (and an Astrotortilla!)

I've run across a very cool piece of software called Astrotortilla. I love Mexican food, and Astrotortilla just sounds yummy! It's a Windows wrapper (hence the tortilla) program that works in conjunction with your imaging and mount control programs (via ASCOM, hence Windows-only) to do plate solving, automatic syncing, and automatic correction of your gotos. It's supposed to work fine with Nebulosity and PicGoto. I have it working OK for saved images with a simulated mount, but I still can't get Astrotortilla plate solves to work live. After watching the Astrotortilla log I think this is because the image file is not getting passed correctly from Nebulosity, and I seem to remember seeing something in the manual about that so I'll have to have another look. The capabilities of this program sound wonderful, and there are plenty of reports of happy users. I hope to add my voice to that.

But back to the imaging session.  I probably should not have tried to image at this scale (my full 800 mm focal length at f/4) with the wind issues and late start I had last night, but decided to do it because of the sky’s clarity and darkness. Synced on λ Sag and had an easy goto. It was another warm summer night; the camera started at 24 °C and with the Peltier running at 2.5 A I got the CCD down to 15 °C. The wind gusts made my guiding performance terrible, so besides starting late I threw out a lot of subframes and the result is noisy. In addition, I had issues with DEC motion; it seems like the mount is sticking. 

This is another target I can use for adding H-α later when the Moon is more full. So as you may deduce, I did succumb and bought a Baader Planetarium 7 nm H-α filter, which I'll start using when there is more Moon (tonight, if the sky is clear; I just can't resist doing full RGB imaging when the sky is dark). So hopefully soon I'll have some H-α data to play with and try blending with some of these RGB images. I'm slowly sliding down the slippery slope into narrowband imaging, I'm afraid. Another "not cheap" thing, too!

M17 is another beautiful deep sky object in the rough direction of the galactic core. Rotated 180° from the view below, it definitely looks like a swan, but in the orientation I've chosen, it looks more like a lobster to me. He's facing to the left. Can you see the lobster claw in the center on the left side? The bright part is the lobster's body.

Date: 1 Aug 2014

Subject: M17, Swan (or Omega or Lobster) Nebula

Scope: AT8IN

Filter: Meade IR cut

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)

Camera: DSI IIc chiller at 2.50 A, 15 °C

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 20x300 s

Stacking: Neb 3, bad pixel map, bias included, no flats, normalize first, trans+rot align, 1.5 SD stack.

Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 80%; Develop 78.49%; HDR:Optimize; save; undo; HDR:Core reveal; Color:Scientific, 250%; Deconvolute auto mask 2.5 pix; Life:Moderate; Track RNC 1.47%; Magic:Shrink 1 pix; to the Core Reveal image: Color:Scientific, 250%; Deconvolute auto mask 0.49 pix; Magic:Shrink 1 pix; CS6 Astronomy Tools layer the HDR:Optimize image on top of the HDR:Core Reveal with 85% opacity; Increase star color; Less crunchy more fuzzy; Reveal all layer mask cut through in bright places; Astro Frame