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!

Canon T1i mod gone bad...

Well, attempted to mod the T1i by removing the IR cut filter. Got into the point of removing the sensor plate, only to discover some special torque screws (for which I have nothing to get them out). Put it back together, apparently a little too quickly, only to discover that it will no longer take a picture - "temperature too high." Great. Something is shorted...could be one of a hundred contacts that were involved in various ribbon cables or even the aluminum shield plate.

When I have more time, and patience, I'll look into trying to bring it back. For now, I've decided to continue the DSLR path and when convenient, pay someone to do the mod. A new Rebel XSi has arrived, a couple hundred cheaper than the T1i, lighter and less noise (see previous post).

Cheers!

Noise and more noise

After a few months of taking additional photos with the new Rebel T1i (500D) DSLR camera at various high speed settings, there really has not been any improvement in eliminating high end noise as compared to the early generation Canon Rebel XT. In fact, after some comparative study of detailed reviews carried out by professional camera webzines, the T1i fares slightly worse than the model its intended to replace, the Rebel XS (450D). And my test photos support this, too.

The good news is that noise reduction modes at ISO 1600 perform comparably with the 450D.

It is not a complete loss. Where the Rebel XT was an 8 mega-pixel camera, the T1i is 15!! Longer battery life, and more importantly no battery amp glow!! There is still much I would like to accomplish with DSLR astrophotography. In the near term, I am looking forward to eventually replacing the IR cut filter with a wider band version designed for deeper reds and extended UV.

Messier 30

Back at it...a couple great dark nights are upon us! Here we have another in the Messier marathon series, M30, a globular cluster in the constellation Capricornus. This will be the last photo taken at 12,800 ISO setting for a while. Even though much has been removed from the shot, the noise is a bit excessive. Taking this last super high gain shot also allowed me to test my flat I created.

Worked great. Vignetting go bye-bye.

This unguided photo taken with the Canon T1i as 104 x 15 second JPEG frames, long exposure and high ISO noise reduction enabled, and calibrated with 200 bias, 100 dark, and 200 flat subs.

Below is my exciting new flat used in the calibrating the photo above. Created it by placing the telescope under the patio in this bright Arizona afternoon sun and taping a white sheet of paper across the telescope opening. Made sure the sunlight was indirect and bright across the entire surface of the paper. Set the Canon into AV exposure mode and ISO 100, proceeded to collect 200 frames!

After calibrating with bias, the frames were stacked together creating this master flat. The histogram in the camera showed it nailed dead center and the red, green, and blue curves aligned right on top of each other. Don't think I could get it any closer to grey than that!

IC 4665

A break in the weather and finally able to test out my workflow changes. Turns out the camera built-in noise reduction really needs to be enabled for this kind of photography. In this case, both long exposure (dark frame subtraction) and a new enhanced high ISO speed noise reduction is enabled. Successfully eliminated the mysterious banding I was seeing in post-processing.

This image was taken with 180 x 15 sec. JPEG frames at 3200 ISO, field flattener, strong noise reduction, and of course, unguided.

So much for the TI-89

Apparently, the data I/O output signal has been changed in the TI-89. Frequently, an extra "pulse" is detected by the camera. This utterly screws up the whole mirror lock up routine. Without putting a scope on it, I suspect the TTL level changes are not as long as in the older TI-83 model. Guess I'll keep the TI-83 and give up the shiny new TI-89.

Monsoon Season is upon us...

Well, so much for stargazing...can at least enjoy the evening light show when the storms roll through. In the meantime, I will be preparing for the next outing. A new TI-89 programmable calculator is on order, and this one includes a real-time clock for more accurate shutter control timing. This will consume a little extra time to revise my ASTROTMR TI-BASIC program with improved settings.

A short focuser extension tube and a Lumicon broadband filter are also on order. The short extension tube should permit me to put the diagonal back in, now that I'm committed to using the field flattener in my astrophotography. The broadband filter will help reduce the additional sky glow, especially when imaging more toward that part of the sky with the Tucson "light dome."

Since I've made progress using the field flattener and corrected my process to create darks and bias frames, thinking about going all the way and experimenting again with 12,800 ASA! I've already taken 100 bias frames set at that speed. Will plan on taking 100 darks at this extreme when the next clear night arrives and maybe shoot for the Lagoon Nebula, again. Pretty exciting stuff!

47 Messier objects and counting...

...only 62 to go.