solutions for 8SE to make long exposure possible
Posted 18 August 2012 - 11:55 PM
Posted 19 August 2012 - 01:39 AM
Posted 19 August 2012 - 02:15 AM
Get the CG-5 mount or CGEM if you can afford it. The SE mount just isn't up to the task of AP and the use of a wedge won't improve on that fact. The CG-5 will have firmware you are familiar with and it is a good progression from the SE mount.
Posted 19 August 2012 - 09:33 AM
The 8SE is on an Alt/Az mount which means that exposures over 20-30 seconds will show field rotation. You can add a wedge as you suggested to get around that limitations, but the mount also has spur gears with lots of backlash which also limits your exposures times to about the same range. Bottom line, a wedge will not improve your ability to do long exposures on this mount.
A CG-5 is a much better option, but is considered an entry level mount for AP (astrophotography). While there are those who use it with a C8, it is better suited to shorter focal length scopes. You would have much better results with a mount like an Atlas, CGEM, or iEQ45. Of course those cost considerably more too.
Posted 19 August 2012 - 03:41 PM
Posted 19 August 2012 - 05:11 PM
Posted 19 August 2012 - 07:37 PM
CGEM is bigger and heavier.
More importantly the bigger/heavier CGEM (or Atlas or EQ6 or iEQ45) is better able to give precision tracking & autoguiding at longer focal lengths and with heavier telescopes.
I use a CG-5 myself and I agree with what others said. A C8 on a CG5 is right on the edge of the mount's capabilities - not impossible, just a bit harder to get REALLY long exposures out of (like 5 & 10 minutes long). With the focal length of the C8 reduced to 1280mm using an f/6.3 reducer-corrector it is a bit easier so you should consider that a highly recommended addition.
So if money is tight get a CG-5 and a f/6.3 reducer-corrector for your 8SE. If you can afford it get a CGEM-class mount (and f/6.3 reducer/corrector) then you will have a slightly easier time of it and will know the mount is more capable of advanced AP down the road.
Either way, have fun with it!
Posted 19 August 2012 - 07:40 PM
Posted 20 August 2012 - 10:39 AM
Although the AP'ers I met at Stellafane agreed that the Atlas/CGEM would be an effective upgrade from the CG5 they universally recommended a used Losmandy G11 or Celestron CGE. These are a big step up in size, capacity and quality, at a cost only slightly higher than even a used Atlas or CGEM. Reportedly the G11 and CGE may be obtained used for around $1500, but I haven't found any bargains like that yet. Welcome to the crazy world of AP.
Posted 20 August 2012 - 02:58 PM
Don't you know it. I've seen an EdgeHD 8 OTA mounted on a Paramount MX. It looked perfectly happy there too.
Welcome to the crazy world of AP.