SharpCap Forums

After polar alignment I would like to slew the scope to a target in order to begin live stacking for EAA. What is the next step in the workflow that allows SharpCap to be able to know the current alignment so that it can slew to a target with some accuracy? After completing the PA and manually moving the scope to roughly the home position, SC can't possibly know the alignment. I've searched extensively but haven't been able to find this very basic and no doubt simple information.

Thanks in advance!

Waid
---------------
Explore Scientific iEXOS-100 mount w/azimuth adjuster, Beelink U59 mini-PC
Astro-Tech AT80ED refractor, ZWO ASI178MC camera
Orion Mini 50mm guide scope, ZWO ASI120MM Mini guide camera
Apertura Portable Telescope Power Supply 155WH
ASCOM, NINA, Sharpcap, PHD2, ASTAP, ExploreStars
Ancient Celestron C90 Mak reflector, Orion 6" Dob

Hi Waid and welcome

After polar alignment (PA), your mount indeed doesn't know anything yet besides that it's pointing towards the Polaris area.
So after PA, you should enter the object you want to view into your mount software or app and let it go to there. Or indeed do that manually with slewing. Your mount now is roughly pointing to the right area.

To make it know precisely where it is, you now have to do some plate solving: a capture is taken and that is compared with a database of captures of the sky and thus it knows where it is pointing and where to move to get the object in view.
That whole procedure is explained here: https://www.sharpcap.co.uk/sharpcap/fea ... te-solving and in more detail here: https://docs.sharpcap.co.uk/4.0/#Plate%20Solving%20Tab

But before doing all that, you need to install the ASCOM software. ASCOM is simply put the software that is connected to SharpCap and your mount software and let both communicate with each other. You can find it here: https://www.ascom-standards.org/Downloads/Index.htm (upper right corner).
And install one of the plate solving tools mentioned in the first URL above. All Sky Plate Solver is used a lot by others.

As with a lot of things in our hobby, plate solving can be kind of confusing when starting with it. My learning curve with it was with trial and error. But with just following the manuals, looking at some YouTube videos and asking questions here, it's now a piece of cake

Menno

Menno, thank for your excellent advice!

I've actually used the PS procedures. I thought I was missing something in SharpCap like a 2 or 3-star align (using plate solving) so that SC would know where the scope is pointing BEFORE attempting to slew to an object. This is the method used by the ExploreStars app that Explore Scientific provides for the iEXOS-100 mount.

Another question - immediately after completing PA if you tell SharpCap to slew to an object in its database does SC assume that the scope is pointing at Polaris when it starts the slew?

I've watched several videos about using SharpCap for EAA and AP. Sadly, they all skip the steps required to get an initial alignment done after completing PA. They go from PA directly to viewing some object and plate solving to center it. How they got the scope pointing near the object is left to the imagination.

I've had little opportunity to experiment with the equipment and software because of bad weather and other factors. Looks like a clear (cold!) spell coming -- maybe a chance to play!

Waid

Dressed for the Arctic, I was finally able to do some observing/learning last night. After a couple of PAs in SharpCap and with Polaris visible in the guide cam the Goto Coordinates function in SC slewed nicely to Procyon. Plate-solving using the main cam (ASI178MC) and scope failed so I tried using the guide scope cam (ASI120MM Mini), which worked perfectly to solve and resync. Fortunately, before dark I had carefully aligned the guider with the main scope. Using the guider to slew and sync brought the target into the main scope's FoV every time. I got a good look at Comet 2022 E3 (ZTF) among other objects.

Over the course of the night I tried plate-solving (using ASTAP) with the main scope using various exposures and gains but was never able to get it to work. More research is needed.

Waid

Hi Waid

Good to hear you are making progress.
When SC fails a plate solve with your main camera, what is the message it's giving?
Below a screenshot with 3 indications to pay attention to.

1. When using multiple camera's, it's best to set the Focal Length to Do not use.
2. The Star Detection Threshold is set to 50 by default. You can try to set it to 30 and see what happens. If that doesn't help, try 80 (I always forget which way to go, so I try both )
3. Try and see what happens when you check the Downsample checkbox.

Over here for plate solving with my ASI071MC Pro, I set my Gain to the highest and then a capture of 2 seconds. But when I use my planetary camera (ASI482MC), I make captures of around 6 seconds. This because it has a much smaller FOV and especially in areas with fewer stars, it sometimes has troubles to get enough stars to plate solve.

Menno

You may have diagnosed the problem ASTAP was having. In the FITS files I saved, the focal length in the file headers is 160 (the guide scope). It should have been 560 for the main scope.

I installed ASPS. It solves the FITS files (ignoring the file header) quickly and correctly.

Thanks!
Waid