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Old 07-11-2012, 03:00 PM
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Help with Auto Centering and Plate Solving

Hi,
I've been evaluating various software that can slew to targets, plate solve,
sync and auto centre.
So far i've tried Maxim, Sequence Gen Pro but have not had much luck. Plate
solve in Maxim just keeps trying and then fails. SGP gives me various Windows errors.
The exposure is set to 1sec and the stars are clear in the 1 sec image.

Have any of you'll been doing this successfully and if so what's your normal
workflow and what software do you use?
I just have an HEQ5Pro with a GPUSB cable.
I use stellarium for scope control using EQASCOM and a QHY8.

This is not for an observatory, but for the field, just thought that this would
make the whole sync and pointing model a lot easier if the sync is based on a plate solve. That'll give me more time to image rather than trying to centre and correct pointing errors.
I polar align by drift aligning in PHd before all this.
I've been wanting to try PolarAlign max as that uses plate solving for PA, but
haven't had a clear night in a while.
I noticed that GRAS uses Maxim for the same sequence.

Thanks
Alistair
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Old 07-11-2012, 03:51 PM
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I use Maxim/Pinpoint (Pinpoint LE is the plate solver that ships with Maxim) and it works fine for me.

Check that the Pixel Scale parameters on the plate solve dialog are correct and also that the RA and Dec are approximately right.

You don't mention your focal length but assuming it's not huge you should be able to get away with using the GSC 1.1 (corrected) catalog.

I don't think I've changed the parameters from the default. I use stars from mag -2 to mag 20, search area is 256% of image and I set "Search outward spiral." Detection parameters are Brightness 0, Std Dev 3 and Number of stars used to solve is 500.

One second is maybe a bit short for the image capture. Have you tried longer? I use 18 seconds on my FSQ setup which is good enough to get stars down to mag 18 from the city.

Poor focus sometimes confuses plate solving too. Make sure your focus is reasonably good.

Cheers,
Rick.
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Old 07-11-2012, 05:22 PM
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Thanks, I haven't tried those settings. will try it again.
But do you use it in an observatory where you can sync and build on your pointing model, so that way the goto's aren't too far out?
I use an 8inch F4 and 10inch F4, so FL is not too long.
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Old 07-11-2012, 06:06 PM
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I often forget to alter the site configuration after swapping scopes or forget to connect to the mount and then maxim won't resolve. But if it knows what the scope is and can talk to the mount it seems able to calculate image scale and it all works fine, even with 1sec exposures binned x2.

I don't bother building a pointing model in eqmod, I just plate solve, sync then slew to target and repeat.
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Old 07-11-2012, 06:41 PM
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Quote:
Originally Posted by alistairsam View Post
Thanks, I haven't tried those settings. will try it again.
But do you use it in an observatory where you can sync and build on your pointing model, so that way the goto's aren't too far out?
I use an 8inch F4 and 10inch F4, so FL is not too long.
You should be fine with the GSC 1.1 catalog at that FL.

I don't have an observatory. I set up from scratch every time and don't use a pointing model.
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Old 07-11-2012, 07:22 PM
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Cool, that's exactly what I want to do as well
Will give it a shot
Do you use maxim for choosing targets or other planetarium software for scope control?



Thanks
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Old 07-11-2012, 08:52 PM
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I use 2 different programmes for plate solving.
If your aim is just "telescope pointing" then elbrus works well
see
http://tech.groups.yahoo.com/group/StarLocatorElbrus/
When I was using an EQ6 with EQDIR this was all I used.
I would slew to a known star and take a 5 sec image with autodark. I then save the image and elbrus will plate solve it within seconds. You then press the "sync" button and this tells the mount exactly where the scope ia aiming.
You need to have worked out the image scale first but once you have done this then it doesn't change.
If you don't move the camera orientation then you only need to be within 5 deg of correct pointing for it to plate solve. If you change the orientation then you need to be within 2 deg. Still this isn't terribly difficult.
sometime sit will fail to plate solve if there is a very bright star in the image with diffraction spikes. You get around this by selecting a box around the star and telling it to solve outside the box. This usually works.
I use TSXP for platesolving now as I have a differnet mount and a permanent setup but still use elbrus to check the accuracy if TSXP fails.
Cheers
Terry
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Old 07-11-2012, 08:56 PM
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Remember, you've got to have the mount synced to Maxim so it know "roughly" where it is pointing, and the correct focal length data in Site configuration so it knows what "scale" the image is. These give it a starting point for the calculations.

DT

Last edited by DavidTrap; 07-11-2012 at 08:57 PM. Reason: Clarity
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Old 07-11-2012, 09:22 PM
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Quote:
Originally Posted by alistairsam View Post
Cool, that's exactly what I want to do as well
Will give it a shot
Do you use maxim for choosing targets or other planetarium software for scope control?
I use Maxim's catalog to find targets some of the time and other planetarium software (TheSkyX and StarryNight Pro) as well.
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Old 07-11-2012, 09:32 PM
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Have you considered using The Sky X with T-Point? I've had very good success with plate solves and automated T-Point runs. In addition after collecting 41 points (automated) a very accurate polar alignment report is generated.
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Old 07-11-2012, 09:47 PM
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I have been using Elbrus within SG Pro nd found it tot be excellent. Plate solves, centering to the previous nights image and meridian flips all work perfectly. The deal with Elbrus is that you have to have your arc sec/ pixel exactly calculated but don't rely on the manufacturers details as they are generally incorrect in relation to fl of your scope. My SCT runs at 2905 mm FL and not 2500mm as specified by Meade.
Allan
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Old 07-11-2012, 10:03 PM
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Thanks
I will try Maxim and SGP again. I used 2.01arcsec/pixel for the QHY8 at 7.8x7.8micron at 800mm.
I might switch to TSX and Tpoint with my permanent set up,
Just want to do away with manual sync's for now with SGP or maxim.
if the scope is connected to maxim or SGP, how would it also be connected to a planetarium software? would I have to use the ASCOM POTH hub?
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Old 07-11-2012, 10:33 PM
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Quote:
Originally Posted by alistairsam View Post
if the scope is connected to maxim or SGP, how would it also be connected to a planetarium software? would I have to use the ASCOM POTH hub?
My mount's ASCOM driver allows multiple apps to connect to it. No special magic required...
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Old 08-11-2012, 06:36 AM
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For maxim to solve (because I use the fits header to tell pinpointle the ra and dec) I need to manually do my first sync. I slew to a bright star and sync to it, then I take an image of it again and clear that first point I put in the model. This way the rough point is not part of the final pointing model but maxim knows where the first image was taken. Solving the first star shouldnt take more than a few seconds. I then use the "zoom" function to star hop around to lots of bright stars solving and syncing them to the model.

If you find a nice piece of automation to do this please let me know as that would be useful to me.
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Old 08-11-2012, 03:00 PM
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Quote:
Originally Posted by allan gould View Post
I have been using Elbrus within SG Pro nd found it tot be excellent. Plate solves, centering to the previous nights image and meridian flips all work perfectly. The deal with Elbrus is that you have to have your arc sec/ pixel exactly calculated but don't rely on the manufacturers details as they are generally incorrect in relation to fl of your scope. My SCT runs at 2905 mm FL and not 2500mm as specified by Meade.
Allan
Hi Allan,
What do you use to select targets and issue goto's? do you use a separate planetarium software that displays your scope position with SGP running to do your centering?
Thanks
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Old 08-11-2012, 08:47 PM
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I use Earth Centered Universe. Simple and cheap and works perfectly for goto has no fancy photo-image like overlays but really practical. CDC also works well.
Allan
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