Having done EAA for 6 years now, I have always used an EQ mount and typically use my C9.25" or my C14" with Hyperstar. And I am very happy to continue using these with my variety of cameras from my first, a Mallincam Xtreme, to my latest a Starlight Xpress X2C.
However, I notice many who are either just getting into EAA and want to start with something relatively inexpensive, or just want something that is lightweight and easily portable. So, as my personal form of public outreach, I got hold of a Celestron SE6, a Revolution Imager 2 and a ZWO ASI224MC to demonstrate what could be done with a light weight setup that is easily transported assembled from the garage or house to the driveway or back yard. Others have posted with setups like these in a number of different threads (Charles comes to mind for one), but I thought it would be nice to have it all in one thread. Hopefully, in addition to pulling all the information into one thread (and I assume others will add their inputs) this can become a resource for many new to EAA.
Why the choice of the SE6? Well, first, it is an Alt-Az mount which represents a new challenge for me since I have only had the pleasure of using EQ mounts. Most already know that Alt-Az mounts don't track along the Celestial Equator like and EQ mount does, so field rotation becomes an issue for long exposures. How long? That depends on the focal ratio used, the Altitude and the Azimuth of the object being viewed, and the observer's latitude. At the north or south pole, no problem. At the equator, the worst case for rotation. Rotation follows the simple formula:
Field Rotation Rate (arcmin/min) = 15.04 COS(Latitude)*COS(Azimuth Angle) / COS(Altitude Angle)
So looking due east (90deg Azimuth) or due west (270deg Azimuth) there is no field rotation at any altitude because the Cos is zero. However, that lasts for a brief moment before the sky rotates and you aren't pointed due east or west any more. Looking due south or due north, field rotation will be the strongest. And higher altitudes cause more field rotation in a given time than object along the ecliptic. On my web site listed below you can find a nice graphic showing curves of field rotation for different Altitude and Azimuth angles.
But, as Charles and Astrojedi have pointed out and shown, using an Alt-Az mount with software which can rotate frames while stacking, one can overcome the field rotation problem to a great degree, i.e. take much longer exposures with this software than without.
Second, Alt-Az mounts are typically much less expensive than EQ mounts which goes to the low cost factor. The 6SE typically sells for $799 including accessories, but I believe it is currently on sale for $699.
Third, there is no requirement to polar align an Alt-Az mount which makes it much easier and faster to setup than an EQ. (You cannot polar align an Alt-Az mount even if you wanted to). The 6SE has a Skyalign routine which only requires one to go to three bright stars in the sky which are first aligned in the unity Red Dot Finder and then in the 6" scope and EP to get a GoTo alignment. You don't even have to know which stars you are pointing at, just that they are far apart in the sky. Once aligned, the hand control will even tell you which stars you aligned on. How easy a setup is that?
Fourth, the 6SE comes with a 6" SCT which I think is sufficient for observing all of the Messiers and many of the Herschel objects with either of the two cameras listed above. By showing what can be seen with this scope, one can reasonably guess how much more they might see with the bigger 8" but also portable scope if they are willing to spend a bit more.
Why the R2 and the ASI224? Simply cost. The R2 is $300 and the ASI224 is $349, which are two of the low cost options for EAA. The R2 is an analogue camera which comes as a kit with a 7" LCD, Li Ion battery, focal reducer, UV-IR filter and cables. It is a very good, reasonably sensitive camera which can be used with or without a computer. The ASI224 is a USB camera which comes with a USB cable, C-Mount adapter and an All-Sky lens for wide angle shots of the night sky. It requires a computer, but only a single cable. And, if you decide to move up in cameras later, the ASI224 can be used as an autoguider. And, given its very low read noise, it is very well suited, as others have shown, for stacking with software such as Sharpcap or AstroLive. Did I say AstroLive is free with the ASI224? Well it is.
So, over the next month I hope to post images with the 6SE with both cameras taken from my suburban back yard and from a dark site to give anyone interested an idea of what they might expect to see with one of these setups.
To get started here is a picture of the R2 setup with the 6SE. I'll post a picture of the ASI224MC setup this weekend.
Here I have the camera attached to the SCT visual back with a 1.25" diagonal to give enough space for the camera to clear the mount when pointed at the zenith. The Hand control is attached right at the back of the camera since I would be standing there to control the camera and view on the LCD. I bent the LCD mounting base to the curvature of the the optical tube assembly (OTA) and glued a piece of spongy material to the bottom of the mounting base to avoid scratching the finish of the OTA and held it in place with velcroe straps. I can change the angle of the monitor to compensate for different OTA orientations. I mounted the battery to the arm of the Nextstar SE mount and ran the power cable to the monitor and camera using the included power splitter cable. The mount can be run on its own internal batteries or with an external 12V battery using the cable you see on the EP tray. Excess video cable is wrapped around the LCD base to prevent snags.
With this setup, I can leave everything connected and stored inside my house and very easily carry it outside and set it up in under a minute. Plus, the SkyAlign feature allows me to align to 3 stars in less than 5 minutes. I did the SkyAlign with the video camera, since this is how I always align my EQ mounts, but it is a bit trickier since the object moves quickly across the LCD screen considering that this is an Alt-Az mount and the camera is equivalent to an 8mm EP. I found it easier to use a longer focal length EP to do the alignment, but it very much can be done just with the camera.
Hope this thread is helpful to the new folks or anyone considering a low cost (relatively), light weight, portable setup. Keep in mind that you can also use a smaller scope, including a refractor for even less cost or you can move up to a larger aperture or the Evolution mount for a bit more.