Quote:
Originally Posted by Craig_L
Very nice shot Bill.
What software are you using to guide the LXD-75 mount? And did you have much trouble getting it to guide? I have a LX55 mount, model before yours and have pretty well given up trying to autoguide. Any advice would be welcome.
Craig
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Cheers, Craig.
I use the guide function of MaxDSLR software to autoguide the LXD-75.
For this image I used an ED80 (focal length=600mm) as the guidescope with a x2 barlow and a Mintron video camera running at around 0.5 second exposures. Guiding aggression setting was around 7/10. The imaging scope was the SN-8" (Focal length =812mm).
With this setup I can guide well (stars at 100% resolution are nearly round) if I get the balance of the scope correct in both DEC and RA. Using the SN-8 to guide images taken through the ED80 also works well.
A good polar alignment is very helpful. A bad polar alignment makes it harder for the autoguider to keep up. If you have to make a lot of DEC adjustment then the mount won't be able to respond quick enough, the autoguider will send it more DEC adjustments and when the mount finally catches up it will overshoot. Good balance really helps.
Not knowing anything about your mainscope/guidescope, etc. makes it hard to suggest a fix for you, however you could try imaging with the shortest focal length scope and use a guidescope of the same focal length. Use a "non-aggressive" (5/10) setting on the guider to smooth the small/medium tracking errors. This won't do anything about the big bumps which cause the system to lose the guidestar.
If the LXD-55 has PEC (Periodic Error Correction) I'd give that a shot to try and smooth out those bigger bumps.
Also if you sent a video feed to a TV you could supplement autoguiding with a bit of manual guiding to assist the system when it needs it (this requires practice and is a pain).
There's a do it yourself hypertune (
www.lxd55.com) for the LXD-55/75 where you get parts and video which shows you how to strip down the mount and rebuild it. The marketing blurbs (and some users on the forums) say that it works great for the LXD-55 and I've heard/read that it can also help PE/tracking on the LXD-75.
Other things that can help:
a) Change your autoguider software so that you make only RA adjustments (switch off DEC adjustments [you'll need a good polar alignment (or image only near North DEC=0 degrees) for this to be feasible]);
b) Change autoguider software to make its RA adjustments in one direction only ( depending on how "fast" the mount is tracking maybe try +x only and switch off -x [or vice versa]);
c) Set telescope weight balance in RA (WHILE POINTING AT THE TARGET) so that the RA balance is 50/50 and then add a very slight imbalance so that weight presses down on the east side of the mount (i.e. the RA motor is always working to lift a weight on that side) so that the gear teeth are always meshed/engaged.
d) Test guiding at North azimuth and zero degrees declination so that the only guide corrections needed will be RA corrections.
