Meade LX200 De-rotators

[thunderchildobs]

Are Meade de-rotators good enough to do the following.

Place galaxies on a ST-7 chip at f/6.3 from LX200 Classic 10 inch, and allow for unguided 60 second exposure, with no or minimal tracking or rotation errors?

Are the de-rotators reliable?

I am looking at de-rotators rather than a wedge because the clearance on the scope only allows scope to reach about 70 South when on a wedge. I need to image galaxies between 70 South and the south pole. For galaxies north of 60 South, I will be using my observatory, wedge mount 12inch LX200. Due to trees, I cann't image 70 south from the observatory. I will be moving the 10 around the yard to image areas that I cannot see from the observatory.

Brendan

[jase (Jason)]

If you're using an ST7 that is extremely sensitive, why not simply lower your exposures so no rotation or drift is present. Simply stack many short exposures.
I have assumed you are doing this for research purposes as if you intended to take pretty pictures you'll want much longer exposures than 60 seconds (unless your talking about an NABG chip) to give a greater S/N ratio - especially for faint galaxies around the pole. Still think the wedge is a better option and reduce the size of your imaging train so it will fit between the fork arms.

http://www.allaboutastro.com/Article...vsrotator.html

[rogerg (Roger)]

Hmm, I haven't used one and would be curious to hear how reliable people find them, but, some thoughts..

Using my ST7 with NGFC on 12" LX I can only get a focal ratio of around F/7 becuase of the increase in the imaging train. I suspect if you throw a field rotator in there you're going to not get below something like F/7.5. But just guessing based on my experiences.

You can shorten your imaging train by placing the focal reducer inside the draw-tube of the focuser. I'm not sure how much further south that would mean you could get. I would tell you if my LX was on it's pier, as I just had such a fitting made prior to my LX being taken out by lightning. I'm sure you've probably already considered this.

If you need to get that far south, do you have any option? That or mount the OTA on a GEM.

[Gama]

Dont waste your time and money on a rotator.
There are so many reported issues, that its best to stray away.
They are notorious for bad engineering, so you will be spending more time fixing rather than using.
Only a thimble full of people have reported it working good, not great, but good, but after mods to the rotator.
As suggested, lower your exposures to a point where rotation cant be seen.


Theo

[thunderchildobs]

Thanks for the info.

Shorter exposures will probably do, as the images are not being taken as pretty pictures, some trailing / rotation shouldn't be a problem.
Will need to take some pratice shots.

I was probably going to get a wedge, but just wanted to check on the de-rotators.

Brendan

[Gama]

Wedge, by all means. The best of the 2 options. Then you only have 1 axis to worry about.