SharpCap Forums

I just bought an ASI662MC. It's tough to get my target into frame. I use an 8SE with AutoGuide on my stock alt/az mount and first set it up as instructed and then do a 4-star alignment. It does that flawlessly. My SharpCap app is sync'd with CPWI and I have the slew & focuser connected. When I select Saturn as a GOTO. I get pretty close, but not close enough and it's a real problem to get Saturn into the ASI662MC camera frame, even with max POI. The ASI662MC has a sensor about 1/2 the size of most other ZWO cameras and I guess that is a problem for me & my system. Anyone have any pointers? I've tried adding reference alignments all around Saturn and it still does not land within the camera frame when I refresh the GOTO. I have everything cabled so that my laptop is inside and I really don't want to make trips outside to fiddle with getting Saturn into a reticule eyepiece before I place the camera in; kinda defeats the purpose of cabling everything to inside. The hand controls on the mount don't work anyway when I have SharpCap engaged, so that's pretty much out. TIA. Maybe I need a wedge?

Hi,

it's a tricky one to handle without going to the telescope - your field of view with just the C8 and the camera is about 0.16 by 0.08 degrees, which is tiny. If you add a 2x barlow then half that in each direction. On top of that, my experience with the 8SE is that the GOTO movements are always a bit sloppy - not really the pinpoint movement to an exact spot that you would hope for

I don't think a wedge would help here - you would still be only getting the same GOTO accuracy from the SE mount and you would have to worry about polar alignment and balancing.

The field of view is probably a bit too small to plate solve. SharpCap's plate solving engine (SharpSolve) goes down to about 0.12x0.12 with the 'ultra high resolution' catalog installed. It might just work at 0.16x0.08 if you can get enough stars to show up, but it would be right on the edge. If you do get plate solving to work then that should solve your problem as it can tell the mount where its true position is and allow it to make a (hopefully accurate) small correction.

If you have a camera with a bigger sensor then you could plate solve and center Saturn using that, but then you have to go outside and swap cameras which you want to avoid. Another option that involves going outside but is more convenient to use is to get a flip mirror - it replaces the diagonal with a hinged mirror that can either divert the light by 90 degrees into a crosshair eyepiece or let it straight through to the camera on the back of the mirror body. Make sure to get one that has collimation adjustment screws on the body to allow it to be set up so that the two views perfectly align (I think the Vixen one doesn't have adjustment). I used to use a flip mirror when my setup was an SE8 and a small sensor camera.

You could also try the spiral search feature in SharpCap, but that is a really old feature due for an update, so it may not work as well as you would like. Set the goto movement speed to something low (2x, 4x, 8x) then press and hold the spiral search button and let go when you see saturn. The spiral movements are timed, so if it moves too far on each step select a slower speed and vice-versa.

Hope there is something here that helps,

Robin

Thanks for the reply. Your comments are in line with what I unfortunately have come to believe is true - I should swap this 662MC camera with one that has a larger sensor to give a wider field of view for plate solving, GOTO and slight inherent inaccuracies in the 8SE. That is probably the single best solution to my problem, since I'm doing everything else correctly.

I appreciate your well-worked-out reply.

Thanks again,

Tim