Craig & Tammy's Astrophotography Blog

Finally a clear night...and we got The Crescent!

2010-06-15T10:44:00.000-07:00

With the sketchy weather these days, clear nights are rare it seems. We finally got an opportunity to see some stars, provided we were willing to stay up late. In addition, we agreed to help Mike Unsold with some beta testing on a new auto-focus routine he is developing. It all planned out fairly well. At dark (~9:00pm) we would begin the focus training and do a little testing. By 11:00pm, Cygnus and The Crescent Nebula would be well positioned to the NE. Focus training didn't quite go as planned, so by 11:30pm, we gave up and focused normally to get ready for imaging. Seeing wasn't very good, and no doubt had a negative effect on the focus training. We will try again next time out by adjusting the training parameters a little.

At 11:46pm, we were all ready to start capturing NGC6888, The Crescent Nebula. I think summer has arrived here in TN, as the temperature was 82ºF when we started our run. I ended the session just before we crossed meridian at 3:15am. At this time, the temperature had dropped to 78ºF. Click the image for a larger version with details and image data.

M13 in the AT8IN - finally!

2010-05-25T06:18:00.000-07:00

We were finally able to get some use out of our new MoonLite focuser with the Hi-Res stepper motor and MoonLite mini controller. Of course, when the focuser is changed-out, a full collimation is in order. We struggled with this a bit, since collimation is critical in fast systems, and the AT8IN is fairly fast at f/4. Then comes the live star tests. As of late, clear nights have been scarce! We would have a semi-clear night, test the scope, and see that we needed to adjust collimation again.

After several iterations of this, the skies finally cleared and gave us the opportunity to catch some photons. We zeroed-in on M13, The Great Globular Cluster in Hercules, especially since we were facing a near-full Moon. We went into it knowing we would try either an HDR or masked composite image, since it's easy to blow out the core. In the end, we went with a masked composite. In truth, this final image is the third revision working with this data. We're happy with the results! Click the image above for a larger view with complete details.

TPI Astro EQ-G Leg-spreader & shelf

2010-04-26T15:35:00.000-07:00

After having used the Orion Atlas EQ-G for a couple of years, Tammy and I came to realize that there was some room for improvement in the stock tripod. Although it comes with a “spreader”, it is more of an accessory tray than it is a spreader. The problem, we found, was stability. We were a bit disturbed that after setting up the mount and getting polar aligned, pressing hard downward would cause a little give. It seemed that we had to tighten the “accessory tray” a ridiculous amount to stabilize the tripod, but it never seemed to feel very solid.

We contacted Dave Yates at TPI Astro to inquire about an EQ-G leg-spreader. After several days, it arrived, along with a battery shelf. Our first impression was this was a very classy-looking piece of gear. Hand and CNC machined from 6061-T6 and 6063-T5 aluminum with stainless steel hardware and a brushed finish, it is an excellent visual complement to the Atlas. But what about the functionality?

Installation took all of about 10 minutes. The spreader is installed about ½ - ¾ inch above the black collar on the tripod “feet”. This allows the center of the spreader to “snap” when pressed down to lock into place. Since it is so low on the tripod legs, it provides much more leverage to stabilize them. Once the spreader is in place, the battery tray can be installed. This is very simple, and only has one thumb screw. It attaches to any of the 3 vanes of the spreader and centers over the spreader’s hub. For transporting, the spreader can be left attached (but you must remove the battery tray) and it will simply fold up with the legs. When you are ready to set back up, just spread the legs and press the center hub back down to snap it in place.

First light with a newly stabilized mount was the very evening we received the spreader. At dusk we began to setup, and removed the mount from the tripod so that we could level it. We realized right away some of the benefits. Before this upgrade, we would loosen the accessory tray and unscrew the bolt that holds the mount head to the tripod. Once removed, the lack of weight would cause the tripod legs to relax and draw inward slightly. While we understand that leveling perfectly isn’t necessary we like to get as close as we can. This was a challenge with the legs moving all around as we raise this one and lower that one. In addition, after it was finally leveled and we put the mount head back on, we could feel the tripod “give” a little when the weight was applied. Like that wasn’t bad enough, after putting a scope and counterweights on, we could feel it give again! Well, that is no longer a problem! With the spreader in-place, the legs remain tensioned even after removing the mount, so we can be assured that they don’t move with the removal or addition of weight. This has a sort-of “trickle-down” effect as well. After leveling and re-attachment of the mount head, we were never assured that polar alignment would hold very well. We could level, polar align then add the scope, weights, camera, etc. and if the tripod flexed any, things could be thrown off a bit. Not much, but if you are imaging for several hours, it is enough to show up as drift and/or stacking error. Again, this proved to no longer be a problem. In fact, we had been used to a little stacking error (sometimes more than just a little), and always cropped our final image to remove it. On one target, that we spent 3 separate nights on, the stacking error was noticeably reduced on nights 1 and 2, and there was essentially NONE on night 3! This proves that the flex in the tripod legs had a direct impact on our imaging.

In short, this is a very worthy upgrade to an otherwise great mount. It is obvious that some thought was put into the design and manufacture of this product. The materials are high quality and the fit and finish are impeccable. TPI makes a couple of versions of the spreader, to fit the Atlas EQ-G, EQ-6, CGEM, and CGE. We are believers!

Clear skies!
- C&T

As a side note, you might be wondering, why we don’t use the bubble level that is installed on the mount head? Simple - we have verified that it is wrong therefore don’t trust it.

Telescope Service TS-OAG9

2010-04-18T09:00:00.000-07:00

After a couple of years in this hobby, Tammy and I, like many others, have begun to get “picky” and notice shortcomings in our images. We have determined that one of the biggest contributors is differential flexure. This led us to the conclusion that we needed to start looking for an off-axis guider (OAG). Since we have several telescopes of various types (SCT, refractor, Newtonian) we wanted to find a model that would work with all of them. The problem with using an OAG on a Newtonian is that they typically are so large, that they move the camera too far back in order to achieve focus. Often, there is very little room to add thick accessories to these scopes and hope to still reach focus. We knew we needed an OAG that was very thin. After a recommendation from another CN member, we researched and purchased the TS-OAG9 made by Telescope Service.

This OAG is only 9mm thick and is the thinnest one we have seen! The camera side has a T2 adapter for attaching just about any camera that has T2 threads. Of particular interest to us, however, was the Canon EOS bayonet adapter. In effect, this allows the TS-OAG9 to replace the t-ring. This would therefore solve the problem of moving the imaging plane so far past the focal point that focus cannot be achieved. The telescope side of the guider has M48 threads which can accept a variety of adapters. An M48 to 2” barrel and an M48 to T2 threads are the two we found necessary for our own application(s). The M48 to T2 threads allows the attachment of an MPCC, a William Optics 0.8x reducer/flattener as well as an Astro Tech 2” zero-power flattener (all of these attach via T2 threads). The M48 to 2” barrel allows us to insert the OAG (after it is attached to a DSLR) into the 2” external focuser on our Celestron C8. These two adapters cover all of the applications necessary for us at this time. Many other adapters are also available.

One thing of note, most OAGs have the ability to rotate around to assist finding a guide star. The TS-OAG9 essentially has 3 locations for the guide cam, at 120 degrees apart. For our particular application, we cut out some thin cardboard spacers to insert between the OAG and the EOS adapter. This allowed us to locate the guide cam at the bottom of the camera (6 o‘clock), where there is the most clearance, and the most space to adjust the prism radially. Other locations were not desirable: at the top (12 o’clock) the guide cam would bump the DSLR flash and to the right side, it would bump the “grip”. Even though the OAG cannot be rotated “around” to locate a guide star, it can be moved “radially” - that is, in-and-out to give more possibilities for finding guide stars. That being said, you can rotate the entire camera + OAG in the focuser to give more possibilities.

Our first light with the new OAG was a “get familiar” night. We had two goals that we wanted to accomplish. First was to focus the guide camera. Second was to learn how to find a guide star. In preparing to focus the guide camera, we first focused the main camera. This is important as doing so will insure that once the guide camera is focused, any further focusing of the main camera will also adjust the guide camera in tandem. Focusing the guide camera is done by sliding it up and down the prism stalk of the OAG. There is a separate thumb-screw for this. Once we had both cameras focused, we were ready to find a guide star. That turned out to be remarkably easy! In fact, one was already visible in the PHD Guiding window. This helped us make short work of locating a guide star the next night out when we were ready for a night of serious imaging.

The result of using this OAG is no different than using any other - your exposure times are no longer limited by differential flexure problems and so you can expose as long as your skies will allow. However, the TS-OAG9 has many benefits all to its own. The biggest of which is this: if you are using a Canon DSLR as your main imaging camera and have a Newtonian or any other scope with limited inward focus travel, then this is the OAG for you. This is a great product and it works very well! Gone are our days of differential flexure causing egg-shaped stars. Clear skies!

- C&T