RASA, EQMOD and centering


#1

Hi All,
I have done extensive searches of this forum and other forums to resolve my problem before making this posting.

Recently acquired a RASA 8 mounted on EQ6-AZT mount using EQMOD.
I use Astroplanner for acquiring targets.
All software including SGP is current versions (including beta’s if available)
EQMOD is setup as recommended by SGP.
Astroplanner will slew target dead center (RASA is only 400mm FL)
SGP PS2 will solve every image…But!!!

Centering is always in the wrong direction. PS2 will always report successful centering even if the point on the image I have selected has moved out of the validation frame. In addition the “slew here” (that does not use platesolve2) are also reversed.

I have checked the location coordinates in the user platesolve2 (I assume south lat is negative and East long is positive). I note that the image fits header states that “flipped” is true irrespective of which side of the pier I am imaging. I have checked the reverse boxes in the telescope tab but all to no avail.

it just seems that SGP “sees” a reversed or flipped image compared to that actually displayed.

Is this an issue related to RASA and Hyperstar setups ( I do not have this issue with my other scopes)?

Any thoughts anyone?

Cheers
Paul

PS: forgive all the acronyms but hopefully all are well known!!


#2

If “Slew here” is not working I think your home coordinates in EQMOD is not setup correctly. My first guess.


#3

I have double checked this and both SGP and Astroplanner are connected to EQMOD andAstoplanner slews correctly so I don’t think this is the problem.


#4

Have you tried using the framing wizard to set a target then using the center here to see if that works? Just to rule out all these extra steps.


#5

I will give that a go.

I am wondering if any one else using a Hyperstar or RASA (that produce “mirrored” images compared to refractors and double reflected reflectors such as newtonions, cassegrains and schmidts) have had a simalar problem.

I have used SGP and EQMOD for sometime with other scopes with no problem but this is the first time I have used SGP with EQMOD and RASA. Maybe I should try to use my 50mm guidescope to test if I can center correctly but the plate scale might be to large.


#6

Paul,

once the image has been solved, the orientation of the frame (rotated or mirrored) has no relevance for the centering process. The plate solve returns the coordinates of the center of the image – this is just a point.

Kind regards,
Horia


#7

Horia, I am sure you are right that the plate solve returns the coordinates of the center of the image perhaps that is the reason that it would not distinguish between a rotated, reflected or mirrored image.

It is only when you select a point other than the center of the image that the process that SGP uses to identify that new point in relation to the solved center of the image and send slew commands to the telescope mount that the orientation of the image may cause the problem.

Since this issue affects the slew command (which doesn’t not use platesolve) I think the point I select to slew to is not the point SGP “sees”…it see a point in a diametrically opposite position on the image.

This seems to be supported by the fact that using the centering (not slewing) routine platesolve will verify that the point I selected is centered because that was the point SGP decided I had selected on the image. I am assuming that SGP uses the orientation of the image and its platescale to determine the magnitude of the slew commands it sends to the mount.

I believe the centering routine adds a platesolve at the end of the slew to determine how close the image is to the new selected plate center

Gosh that was a bit more long winded then I intended but I hope it makes some sort of sense!!!

Regards
Paul Sartory

paulsartory:

I am wondering if any one else using a Hyperstar or RASA (that produce “mirrored” images compared to refractors and double reflected reflectors such as newtonions, cassegrains and schmidts) have had a simalar problem.

Paul,

once the image has been solved, the orientation of the frame (rotated or mirrored) has no relevance for the centering process. The plate solve returns the coordinates of the center of the image – this is just a point.

Kind regards,

Horia


#8

Hi all,

I thought I would have another look at the “FLIPPED” status in the FITS header. I assume this is can only be added to the FITS header after platesolve?

“Slew Here” and “Center Here” are only available after platesolve

All the frames from my refractor are “F” (False) and from my RASA are “T” (True).

According to Jared (Forum Thread: Flipping Image Problems)

“FLIPPED(my capitals) indicates that your image is essentially mirrored with respect to the sky. This often happens when you have an odd number of mirrors. But it can also occur if your ccd writes bottom to top rather than top to bottom”

So this indicates that platesolve has identified that the image is “FLIPPED” as you would expect from a Hyperstar or RASA.

I have note determined if my ASI1600MC writes bottom up FITS or not but I did not have this issue using SGP with a refractor and this camera.

Since my planeterium program “Astroplanner” accurately slews the mount and centers the target I assume that Astroplanner and EQMOD are configured (for each other) correctly.

I have been clouded out since my first posting so I have not been able to test plate centering via the guide scope on the RASA. This would certainly confirm or otherwise if my SPG and EQMOD configurations are correct.

Paul


#9

Ok,

So the clouds cleared and I was able to test the centering with the guidescope and it worked flawlessly.

So I guess there is something about the flipped images from the RASA that is causing the issue.

Maybe I need to raise a bug report?

Paul


"Center Here" and "Slew Here" issue with Flipped Images
#10

This has been mentioned before and something which we need to correct when using PS2. I believe this works correctly for other solvers if you need this feature immediately.

Thank you,
Jared


#11

Looking into this now. If one of you can provide a FITs file that would help make sure I have the orientation and such correct.

Thank you,
Jared


#12

Hi Jared

See drop box link:

Jared

Jared

Shared with Dropbox

Regards
Paul Sartory


www.mainsequencesoftware.com