Taking it to the next level with the AT8RC...

It has arrived!

What a fine piece of Taiwanese machinery!

Balancing was quick and easy, using a recent replacement of the Atlas counterweight shaft with a 20" version from Criterion Machine Company of West Virginia. Replaced the stock focuser with my Moonlite version. The most excellent Moonlite focuser employs a shaft lock on the focuser knob rather than on the drawtube or drawtube rail, as compressing these induces unwanted image and focus shift. Had enough of that nonsense.

This week, evenings will be spent evaluating the back focus and adjusting the optical train configuration in preparation for the upcoming dark period. May the weather favor my intentions!

Countdown to September dark skies

Nearing the end of the monsoon season with nine more days until the beginning of the next lunar dark cycle. Looking forward to good weather and clear skies!

Though the popular constellations for this period will be overhead, my attention will be a little to the east such that I can get sufficient exposures of deep sky objects throughout the evening. The regions of celestial interest in this September shoot being the constellations of Sagittarius, Capricornus, Pegasus, and Cygnus.

A new look!

A little extra time on my hands; trying out the new eBlogger template designer. Nice. I like the change. Hope you do, too.

Messier 8, the Lagoon Nebula remix

Okay, once again trying my hand at this beautiful deep sky object. Of all my shoots, this has seemed to be the most troublesome; my recent attempts thwarted by cloud pirates and processing gremlins. This time the odds are better with significant improvements:

• polar alignment using setting circles and computed transit time
• better dynamic range and less noise than previous DSLR
• IR-cut filter removed
• field flattener lens adapter
• images normalized prior to stacking
• new DDP algorithm rather than traditional "stretching"
• nearly doubled the number of exposures taken

You be the judge. 300 x 15-sec. unguided JPEG frames, nearly 75 minutes of overall exposure, modified-Canon XTi, field flattener, calibrated, and processed with DDP.

Messier 23

Back in Tucson under a beautiful night sky for the Fourth of July! Here is Messier 23, an open cluster in the constellation of Sagittarius; one more in my quest to capture every Messier object.



This is very close, cosmologically speaking, only a couple thousand light-years away and upwards of 20 light-years across. Taken with DSLR @ 1600 ISO, unguided, 190 x 15 sec. JPEG frames, calibrated 200/200 bias/flat, and finished processing without "stretching". Instead, out of curiosity, the Digital Development Processing (DDP) feature of Nebulosity was used.

From what I've read, DDP makes digital images more like film and was invented by Kunihiko Okano, a physicist and amateur astronomer. I compared my results with some manual stretching and found I preferred the DDP output. Threw in a some sharpening and color balance - voila.

Messier 82, Cigar Galaxy

A new personal record, 400 frames! The whole lot taken in just under 5 hours during a good night of extended darkness. This galaxy gets its unusual shape from an exceptionally high rate of star formation, a process called starburst [wiki].

To add to this one's mystery, in April of this year, radio astronomers in Manchester reported a strange new object in M82. A 'micro quasar' was suggested, highly luminous and fairly stable. Some associate this with a massive black hole system, but not at the galaxy's center. The object is several arcseconds off center and an apparent motion of 4x the speed of light!

Yes, you read right, FOUR times the speed of light....warp speed, Scotty!

Casitas de Gila

An astronomer's getaway, that's what it is. Many thanks to the proprietors, Michael and Becky, of this quiet mountain retreat just outside the small town of Gila, New Mexico. What a fantastic way to spend quality time with your telescope!

Large open areas to setup, easy access to power, and the basic comforts the casitas provide including refrigeration for your foodstuffs. If you choose to indulge in this experience, please plan to bring your perishables in with you as the nearest grocery is over an hour away. A small convenience store is 4 miles back in Gila...but that's it.

Arrived on Thursday the 29th and stayed through Saturday night May 1st. Though the timing wasn't so great for dark skies, the clouds and Moon were absent for a couple hours where I could try out my scope.

Decided to retake Messier 13, the Great Cluster in the constellation Hercules. Comparatively, I have to say even with only 152 unguided frames, the results of this location impressed me. Nestled in a location with a Bortle Dark-Sky rating of 2, we were somewhere around 6000ft. above sea level.

This photo is comprised of 152 x 15 sec. unguided JPEG frames at ISO 1600, taken with a modified Canon 450D and field flattener. Created new bias and flats for this outing, 200 apiece.

We'll be back here again soon!

M104 up close and personal...

Jeepers, the Sombrero Galaxy doesn't look so bad for bumbling around with this big tube, fair atmospheric transparency, and then rolling clouds coming in to keep me to just 150 frames rather than the 250 frames planned. Unguided, 156 x 15 sec JPEG frames at 1600 ISO, noise reduction enabled, modified Canon Rebel XSi. Just stacked and stretched. Will try a little bias preprocessing to see if it helps a bit on the noise, I pushed this one pretty hard.

Bigger is better...

Well, especially when it comes to telescope aperture. Decided to take
my 10" Dobsonian (Newtonian) optical tube and put it up on the Atlas
equatorial mount. A couple tube rings and Voila! Turns out I need a
little more weight to stay balanced, but once that problem is solved
we'll see if this monstrosity is up to the tracking challenge.

I'm excited to see what the impact to my unguided astrophotographs will be! All my shots to date have been with nothing larger than 6" aperture. Just need those counterweights...

Waiting on the weather...

Wow, since after Thanksgiving the weather has really not played nice
with timing of dark nights. Just entering a bright Moon period, now.
Anxious for a break, this is the season for galactic clusters. Let's
go, let's go, let's go...

...the man in the Moon

New MoonLite focuser rig

The old Astro-Tech Crayford focuser that came with scope had issues when it came to keeping the drawtube square with the focusing assembly. Off-center position when locked down induced coma-like effects, made star alignment difficult, and fine focus was problematic. In short, it was just a cheap focuser.

Enter the new MoonLite focuser. In addition to being a solid piece of machined hardware, the primary benefit is that the drawtube is locked in position by applying pressure to the focusing shaft, not the drawtube itself.

Tried it out and focusing was a pleasure! Looking forward to using this from now on.

Camera mod successful!

Yes!! I've done it, muwaaahaaahaahaaaaa! Below is a shot of the remnants from the offending filter...

Many thanks to Gary Honis and his great instructions from which I was able to successfully remove the IR cut filter from the Canon 450D in just under 3 hours. As I only intend to use this camera with telescopes, I decided to just remove it outright. If certain shots require some filtering, there are always premium front-mounted filters available.

Busy making new flats and master bias...next dark period is in a week or so.

Messier 35

Filling another empty slot in my Messier portfolio, here is the open cluster M35. There is actually more stars to this as it spreads across an area almost the size of a full moon. Limited by my f/9 prime focus though, I kept the view centered on the bulk of the members.

Close Up on Alcyone, brightest of the Pleiades

Since I don't have a focal reducer for the AT6RC, the f/9 focal length
gives a bit more magnification than with the Newt. The night was so
dark and clear, thought I'd try pick one of the lights in the Pleiades
before catching up on my sleep.

Wonderful stuff.

Unguided, 1600 ISO, 250 x 15 sec. JPEG frames, noise reduction enabled, with bias/flat calibration.

NGC 7789, one of the oldest open clusters

1.6 billion years old, this cluster is one of the oldest.

Unguided, 1600 ISO, 225 x 15 sec. JPEG frames, noise reduction enabled, 250/173 bias/flat calibration.

Messier 103

All right, back in the game! With cooler nights and cleaner workflow, its getting better. Here's a nice take of M103, the last I-am-not-a-comet object recorded by Charles Messier. Some 8,000 light years distant, Charles apparently never observed this open cluster. It was included in his work based on a report received by Pierre Mechain in 1781 of whom he became friends with in 1774.

Looks like it is time to collimate this RC scope, coma is apparent in the left and upper left bounds of the image. Gasp!

Messier 76, Little Dumbbell Nebula

One of the faintest Messier Objects, a planetary nebula discovered in 1780 near the 4th magnitude star 51 Andromedae. 243 x 15 sec. JPEG frames at 1600 ISO, noise reduction, unguided, bias/flat calibrated.

Started taking this a little too early, as neighbor's outdoor lights came on and off a few times before going to bed. Some remnant remains. Shouldn't try starting before 9 or 10pm.

Messier 29, the "less impressive" cluster

As quoted by the SEDS organization on its Messier Catalog site, "Messier 29 is a rather coarse and less impressive cluster."

Huh.

Kind of took that as a challenge, so I captured what I think is pleasing view of this simple open galactic cluster of blue giants, 7,200 light years distant. Charles thought enough of it in 1764 to write it down.

250 x 15 sec. JPEG frames at 1600 ISO, unguided. 250 bias, 173 flat calibration frames.

This image taken without field flattener and only flat/bias calibration. Rather than post-process dark frame calibration, the camera's built-in noise reduction (dark frame subtraction) was applied to each exposure, shortening the post-process time.

Creating a new master flat

New camera, new master flat.

After crawling numerous blog and forum postings regarding flats, I never came across anything that really explained how simple creating a master flat calibration frame can be. After some personal research coupled with trial and error, I eventually understood the purpose of and how the calculation works. In addition, it became exceedingly clear to me that a common recommendation to point the telescope at various regions of the blue sky before twilight is collectively bad advice.

I want to correct this now!

What you want is a calibration image that will scale your pixels consistently to normalize individual pixel intensity - removing the variation in detected energy due to curved optical plane, the effect referred to as vignetting. Key phrase here, "scale your pixels consistently."

What does that mean? It means record a neutral image of your optical curvature. What does neutral mean in this context? It means without preference to any color channel (i.e., grayscale, folks). If you still don't get it, find a new hobby or just follow the instructions below and don't worry about it.

So, here's a simple recipe for creating flat calibration frames for DSLR prime focus astrophotography:

1) On a bright, sunny afternoon bring out your telescope and attach the camera exactly as you would for shooting
2) Ensure the camera is "focused", this will require some thinking on your part (suggestion: lock the focuser down from a prior night's shooting when the camera was focused on a star)
3) Tape a white sheet of paper without wrinkles across the opening of the telescope (see picture above)
4) Set the camera to aperture-priority mode and ISO 100 (best dynamic range/low noise), this will record our "white" light in the median range of the combined color channels - forming our grayscale image. Afterwards, look at the histogram readings from the images and you'll see what I mean.
5) Take as many shots as you can, I strongly recommend over 100 to get good saturation and signal coverage. This shoot I'm taking 250 as I tend to go for 200+ image frames on any good outing.
6) Once you've collected them, use your favorite stacking program to apply a standard distribution.

You'll also want to adjust the RGB channel offsets, so they are right on top of each other (this is a one-click operation in Nebulosity called Adjust Color Background). This will account for the slight fluctuations of the channels we recorded and then you'll have your wonderfully neutral master flat!

Good luck!