Wednesday, November 9, 2011

DIY Coronado SolarMax mount plate

I have always been interested in viewing the sun, even with my first telescope I had filters that allowed me to see sunspots, but there is so much more to see with the sun. So, I recently purchased a Coronado SolarMax II 90 from OpticsPlanet.
The scope came with a nice case, several eyepieces, a barlow and a clamshell mount with a solranger spotter. What wasn't apparent at the time of purchase was how it would mount to my CGEM, there was no mention of anything outside of the clamshell mount.

So here is what I did to mount the scope:
Purchased the following:
- Aluminum door threshold ($9.99)
- a pair of knobs ($2.00 for the pair)

I measured the maximum width the CGEM mount would accomodate and decided that 3 inches would be about the right size for the width of the mount plate, to ensure that the mount head screws were firmly seated in the mount, you wouldn't want them to pop out or strip while your scope is mounted. ;-)

Next I cut and removed burs from the mount plate:
As you can see above, I also drilled out two small holes at each end to hold knobs used to secure the plate from accidental slippage off the CGEM mount head. You can also notice three holes I drilled to mount to the provided SolarMax clamshell.

Above is a side shot of the bottom half of the clamshell mounted on the new mounting plate and I inserted the safety knobs as well. Note: the safety knobs were installed on the bottom of the mount in the final procedure, this makes them act as a safety catch in case the mount slips from the CGEM mount head, keeping your scope off the pavement.

I painted the new mount plate a semi-gloss black to kind of match the CGEM as well as the black parts of the scope. In the image below you can see it mounted to the CGEM and scope mounted on it. You can also see the placement of the knobs and see how they might be helpful if the mount starts to slip from the mount head.

The image below shows the mount and scope as it is tracking the sun.

Here is a link to my first light video I got from the setup:

I used an Orion Starshoot Planetary imager for this image, I will be creating a way to mount my other cameras that should provide a greater level of detail than the 640p image provided in this imager. I found that the level of detail provided in the video is about 100x less than what you are able to see visually. If you have never looked through one of these scopes... it will take your breath away.

As a final note: I was initially somewhat concerned about the stability of the choice of materials, but after hours of visual use, tracking for 3 hours and my first video, I believe the mount plate will prove to be a very acceptable part of this setup and at about 6x less cost than a mass produced mount plate.

Happy Photon Hunting!

Sunday, October 9, 2011

Bahtinov Mask and Imaging

One question that I get asked a lot is:
- How do you know when a star is perfectly focused?

When attempting to focus on a star, the range of focus can be somewhat large, meaning that the difference between perfect focus and out of focus can be very visually challenging to discerne. This is true of visual astronomy, but even more difficult and time consuming in astrophotography.

There are many ways to obtain a perfect focus, one of my favorites is to use a tool called a Bahtinov mask, which fits on the front of your telescope over the aperture.
If you are performing visual focusing with the mask, just point the telescope at a bright star and you will see diffraction spikes emanating from the star as you look into your objective lens. You can then adjust the focus of the telescope to create a perfect diffraction image, where the spikes are completely in alignment.
Here is an image of what the alignment should look like:

In the image above, you notice three diffraction spikes per side of the star, the objective is to align the center spike so it is equidistant from the two outer spikes. If it is closer to either side, then the image is out of focus. This is a very simple procedure if you are looking to focus for visual astronomy, however if you are attempting to perform this for astrophotography, this is where some challenges emerge.

Here are some tips that I use when attempting to focus with the mask on a live camera image:

Getting good diffraction spikes:
1) If you are attempting focus with a camera and Bahtinov mask, you will need to increase the time of the image to ensure that you capture enough photons to obtain a good view of the star and diffraction spikes. The image above was taken with 30 seconds of exposure, when I took images of 10 and 20 seconds, the diffraction spikes were almost not visible. Experiment to find the right time for your imaging setup to capture enough photons to enable you to see the diffraction spikes clearly, once you see them clearly, note the imaging time and move on. Spending more time per image than absolutely neccessary to see the diffraction spikes is not going to help you achieve better results.

Imaging focus:
2) If you choose a 'focus' routine in your imaging software (such as Maxim DL), the software will have the camera initiate a continuous loop of photos for the duration of imaging time you set (eg: 30 second images), spaced apart by a time roughly equal to the amount of time necessary to download the photo from the camera to the PC. I find this to be less than optimal in most cases as the loop doesn't allow enough time between photos and downloads to perform modifications to focusing. The lack of delay in focusing, may make you waste a bunch of time making 'blind' focus changes thereby increasing the time spent focusing.

Instead I choose to shoot a single photo, see what focus modifications need to be made, make the adjustments and shoot another single photo. I find that this process is generally much faster than trying to work within the 'focus' routine.
For example, using the 'focus' routine I will spend roughly 15 minutes attempting to gain perfect focus, when using the single shot method, I usually have focus within 5 minutes. (given 30 second image captures)

Reducing setup time:
3) Once you find great focus on your camera, you may want to remove the camera and insert an eyepiece with a focusing ring into the telescope. The concept here is to move the eyepiece around until you have a very clear picture of the stars without changing the actual focus of the telescope, essentially giving you the same image visually that you had while taking photos. Once you obtain focus, you then lock the focusing ring in place around the barrel of the eyepiece. This makes the eyepiece parfocal with the camera, allowing you to use your eyepiece to move between objects to image without having to repeat the focusing of your camera.
When you have a parfocal eyepiece, it can be used to gain an initial setup for your telescope without moving your focus, making it faster to get to the fun stuff and away from additional setup time.

In summary:
The Bahtinov mask can be a very effective tool for obtaining great focus, leaving you with very tight round stars and clear shots of your intended target. Taking the time to learn how to most effectively use it in your setup routine can shorten time to imaging, which is time well spent in my book.

1) In order to facilitate removal of the mask after focusing and not getting fingerprints on the primary objective lens of my SCT, I placed a couple of small zip-ties on the edges of the mask, they are not in the light gathering path so they do not affect the images and they make the removal of the mask a very simple task in the dark. (Photo below)

Saturday, June 25, 2011

Homebrew: Dew shield (day 1)

I decided to build a new dew shield for my telescope.
Why you ask? Because I thought it would be an interesting project and I didn't have one for my CGEM.
I plotted out what I would need to buy to complete the project, here was my shopping list:
- 24 inch wide aluminum flashing, this is a very light and flexible material (not sure if it will be rigid enough, but a good first try :-))
- flat black spray paint, for both the inside and outside of the dew shield
- pop rivet set (black pom / hand rivet tool)

At a minimum this should give me a very light, dew shield that will protrude about 24 inches from the primary objective lens. Offering a good amount of both dew and ambient light blockage.

I am a little worried about the rigidity of the aluminum, but getting it cut and formed will tell me a little bit more about the material and it's weaknesses.

Happy Photon Hunting!

Wednesday, June 15, 2011

Any night is a great night for Astronomy

Tonight is June 15th, the moon is in the Waining Gibbous phase, meaning that it is illuminated at about 99.73 (or so) percent, pretty much a full moon to most people. That means that there is so much light in the sky that you can only see a handful of stars. The moon is also so low on the horizon that it is pretty much unable to be viewed in my telescope.

About now you might be asking yourself, so why is Ken saying that any night is a great night for astronomy? He can't even see a thing through his telescope because of all the light of the moon and can't even see the moon due to tree coverage.

Let me let you in on a little secret... Shhh, don't tell anyone, but...

Astronomy is a hobby that requires instruments, some that are as in expensive as a set of binoculars, while other instruments may be as (or more) expensive than an automobile, but they are all instruments and just like musical instruments or other scientific instruments, they take practice and sometimes tuning to ensure optimal performance when you need them.

So being the boring guy that I am, I took this evening to do a couple of fun tuning activities for my scope, here is what I did:
1) I checked mechanical zero against my mounted optics to make sure that everything was aligned and operating as it should.

2) I tried out my brand new dew shield, one that I designed and fabricated myself out of lightweight aluminum (worked as expected, but saw some areas of improvement that I will work on this week).

3) tested my optics for collimation, which to my surprise was remarkably aligned, about as close as one could reasonably expect, can't ask more than that. :-)

4) tested the new bhatinov mask that I fabricated for this scope, the legs of the stars came out brightly, slowing for pinpoint focus of the stars.

So even though I wasn't able to see some of the skies wonders tonight, I was able to dial in my instruments to a fine level of precision, ensuring that when the moon and the atmosphere provide me more optimal viewing opportunities, I will be ready and able to take in the beauty of our universe, one object at a time.

Happy Photonic Hunting!

Sunday, January 23, 2011

CGEM Telescope leveling made easy

If you have a telescope and it isn't on a permanent pier, chances are you have had to worry about leveling the scope at one time or another. Due to a somewhat less than clear viewing area in my tree-filled backyard, I need to move my scope and scopebuggy into different spots in order to view the entire night sky. This normally implies that each time I move the scope, I need to re-level it to compensate for the different terrain.
As my scope and mount offers about 80+ lbs sitting atop the tripod, this poses some interesting challenges:
1) Do you remove the scope each time, prior to adjusting the tripod?
(This takes a huge amount of time,but it can be done.)
2) Do you try to lift each leg independently to adjust it while the scope is attached?
(It is pretty heavy and dangerous for one person to perform this action, but using some simple tools it can be accomplished, but not without a lot of work and perspiration.)

So what to do?
Well for my fork mounted Celestron CPC it was a cinch, Dave Yates at had just the solution, levelers for the CPC. When I bought my CGEM, Dave unfortunately had no answer for me, so I just continued the laborious leveling routines I have always done. Then one day Dave reached out and told me that they had some new levelers available for the CGEM! I told him to send me a set right away, I couldn't wait to finally have the simple leveling experience that I did on the CPC!

Here is what the unit looked like right out of the box, nicely built and finished. It appeared that he may have used some of the suggestions I offered from my experiences from the CPC levelers to modify the design.

Putting them on was very simple, I removed the scope and mount from the tripod, then proceeded to use a flat screwdriver and a small hammer to knock off the cap that was lightly glued to the bottom of the tripod leg.

Once the caps were off, I inserted the tubular portion of the unit into the shaft of the tripod leg. I could have chosen to mount it much further inside the shaft, but opted to place it into the shaft with a little over an inch of the unit exposed below the tripod shaft (note the brushed aluminum in the photo). I figured that if I needed to ever remove the leveler, it would be necessary to have a surface area large enough to get a good grip on the unit to prevent turning inside the shaft.

Here is a shot of the unit installed on the tripod and sitting on top of my scopebuggy. There are a couple of things to note about the scopebuggy + leveler combination that I will share below in the bold area named 'scopebuggy'.

This is a photo of the tripod and levelers mounted on the scopebuggy, note a couple of other good upgrades to the tripod and scopebuggy. First is the aluminum spreader that is mounted on the tripod, it is also made by TPIAstro. This creates a consistent and stable tripod, for some reason the CGEM doesn't ship with a spreader, so this was a necessary accessory for the scope. The next I built myself, I added the shelf onto the scopebuggy, making it large enough for all my supplies including power supply, hair dryer, power receptacles, etc.

So, you see the levelers... but what exactly does it do for you?
Prior to adding the levelers, the leveling process took about 10-15 minutes of trial and error (sometimes more), just to ensure complete level. Think of how frustrating this is if you need to do this a couple times a night; you lose about 30+ minutes of viewing opportunity to level the scope.
With the leveling system, it took me a whole 30 seconds to level the scope... 30 seconds, that is all, super simple. Once I document the exact movement characteristics using my bubble level, it will be even easier and faster!
Cannot wait to gather first light with the new additions, will write more after I get some field results.

There are some peculiarities to be aware of when combining the scope buggy with the levelers.
- TPIAstro normally ships 3 inch pads for the levelers, these WILL NOT work with the scopebuggy, all of the tripod stays on the scopebuggy can handle a maximum of a two inch pad. If you tell Dave about your application, he can get you some 2 inch (need to recheck for exact size, will modify this if necessary, later) pads for you. With my CPC he shipped me two sets of pads, one that was about 1 inch as well as the 2 inch pads, after much work I settled on the 2 inch pads and advised Dave of the better scopebuggy fit. It is apparently a difficult task to get these pads, but Dave will eventually get them to you.

- The levelers increase the tripod width, if you own a scopebuggy that is set on the lowest mount size, it will NOT work with the levelers (initially), the scope legs will no longer fit. This can be fixed by increasing the size of the scopebuggy, not a big deal to do, but if you weren't aware that you needed to do this, you would spend a couple minutes scratching your head attempting to figure out how to get it on your scopebuggy. Be prepared to have your scope buggy width increased by about 4 inches in all directions in order to correctly fit the tripod with levelers.

- The leveler pads are not an exact fit for the scopebuggy tripod stays, they are pretty close but not exact. I will likely put some circular (metal) cutouts on the base to offer a completely flat surface. I haven't seen any stability issues with the 'out_of_box' levelers on the scopebuggy, but think that it would be best overall to have one completely flat surface when moving the scopebuggy around.