Good Morning Everyone!
It has been a while since I have weighed in on a discussion here. Darcy...a very interesting topic that raises some interesting questions/discussion. On the issue of using smartphones to image, I am going to get behind Paul on this one and say...in patient hands and with an inquisitive mind, a smartphone can generate some very good images. The caveat is...it will be limited by the size of the optics, primarily. Your ETX 80 setup has small optics so it will be limited to sun, moon, bright planets, bright double stars and some of the brighter Messier objects such as the Andromeda Galaxy (M31), the Orion Nebula (M42) and the Hercules Globular Cluster (M13). There are likely others, you will simple have to experiment. I am not sure what you are referring to when you say chromatic aberration, but the ETX has fairly good optics, albeit small, that should not generate a lot chromatic aberration. There is a possibility that your ETX has had an accident and the optics have been misaligned, or it may be an issue of the smartphone camera not being in proper alignment. One thing I would suggest is that you start with the longest focal length eyepiece that you can find. This will generate the wider field, thereby gathering more light and giving you brighter but smaller images....not and issue for sun and moon...but for everything else. If you can find someone with a 1.25" focal reducer, that should generate an even wider field. Borrow as much as you can to start, just in case the bits don't generate the results you want.?
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On the issue of a finder scope, an ETX can be easily fitted out with a red dot finder. I don't have an ETX in front of me so I am not aware of the mounting holes that may be available. I would suggest that you find a plastic version that is fairly light and can be mounted with some 2-sided tape. The only caution, some finders may have a limited range of adjustment so you will need to find a temporary way to attach the finder to see if it provides enough range for your setup. The 2-sided tape can work but you will need to be prepared to remove it if you need to add a slight shim to help the adjustment.
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Tim...on the issue of power supply, if you are a tinkerer, this thread from Cloudy Nights may provide your solution:
Darcy...do you have an owners manual for your scope? It would be very useful. According to my Sky Safari app, the older Meade ETX models can be controlled with it. I have a Meade LX200 and Sky Safari works flawlessly with it. I use Sky Safari with all my mounts...a joy to use. One note....I do all my Messier Marathons with a manual setup and a red dot finder. For my LX200 connection with Sky Safari, I use a SkyWire instead of the Wifi dongle.?
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One final note Darcy, you will be limited to short exposure, stacked images, given the Alt-Az nature of the ETX drive. Adding a field rotator is not a possibility for this scope I believe.
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With all astro-photography, there is a learning curve that can be overcome with patience and a little guidance. I wish you luck and don't forget to post your images and don't ever apologize for there quality!! :-)
Cheers, Chris.
Chris T