PA fails on step 2

Using SharpCap's Polar Alignment feature
Post Reply
Prathab
Posts: 1
Joined: Sun Jan 31, 2021 2:08 pm

PA fails on step 2

#1

Post by Prathab »

I'm using a orion SSAG with orion 50mm finderscope. This is sitting on a eq5 pro mount. Here is the view of Polaris from where the mount is sitting.

Step 1 solves every time. Step 2 does not. I have tried both sides for 90deg movement. Also tried starting at 40deg on one side for step 1, but this causes step 1 to fail.

Based on the platesolving DB will sharcap do PA in my case? How many degrees of sky under Polaris do I need to be able to see for this to work?

Thank you!
Last edited by Prathab on Sun Jan 31, 2021 11:52 pm, edited 1 time in total.
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: PA fails on step 2

#2

Post by admin »

Hi,

you need to be pointing within 5° of Polaris for the plate solving routines to be able to identify the field of view correctly. The field-of-view should be an issue with your set up of an SSAG on a 50mm finder scope.

If you continue to have problems a good trick is to capture an image from the guide camera and upload it to nova.astrometry.net to get a full plate solving solution for it. Sometimes it can turn out that you are further away from the pole then you expected to be (which may be the issue).

Also, if you haven't already, check out the troubleshooting steps given here. https://www.sharpcap.co.uk/sharpcap/fea ... leshooting

Cheers, Robin
SonnyE
Posts: 9
Joined: Sat Apr 18, 2020 5:37 am

Re: PA fails on step 2

#3

Post by SonnyE »

The times I've had troubles with my MMAG SSAG, I usually find I need to check my focus.
It's rare, but sometimes correcting my focus helps Sharpcap snap right to it.
Rob Power
Posts: 1
Joined: Sun Aug 08, 2021 10:28 am

Re: PA fails on step 2

#4

Post by Rob Power »

Hi All,

Am jumping on this topic as I have a similar issues with step 2. (I have used PA before with no issues but had spent a few months away due to weather and work, so may be a little rusty).

I'm using a Skywatcher Evoguide 50 with a ZWO 120 mini, an EQ6 mount and Sharpcap version 3.2.6482. The geographical position, in settings under the PA tab, is showing the correct location and hemisphere (South and East)

I've attached two pdf files with screen shots gathered during the trouble shooting process. Hopefully these will provide insight to the narrative.

I attempted two alignments, but varied the exposure; first with two seconds exposure and then 4. Sufficient stars were captured and first step completed; however the second step was not completed.

I'm not sure if this is relevant or not, but the first step always shows the Centre Dec as North (but I'm in Brisbane and working with the SCP). Also of note is that on both attempts Sharpcap does not record any rotation (is this a symptom of not completing step 2?)

On attempt 3, I manually moved the mount so to place it close to the SCP. I ran the first step of PA to reconfirm it was completing step 1 successfully (I had to increase the gain to capture enough stars). I then ran the plate solve function and transferred the position in to Stellarium to cross check that I was close to the SCP. As can be seen in the screen grab, I was close to Sigma Octans (close enough I would have thought for PA).

Ran the PA tool again and failed at step 2. (Ran plate solve for info).

Attempt 4 I rotated the mount through 90º, but in the opposite direction - but still unsuccessful. (I also ran Plate Solve for info).

I'm not really sure where to go from here.

Cheers,

Rob
Attachments
Sharpcap Polar Align Issues - Attempts 3-4.pdf
(930.11 KiB) Downloaded 75 times
Sharpcap Polar Align Issues - Attempts 1-2.pdf
(533.37 KiB) Downloaded 64 times
User avatar
admin
Site Admin
Posts: 13177
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: PA fails on step 2

#5

Post by admin »

Hi,

sorry to hear that you are having trouble. The first thing I would suggest is trying SharpCap 4.0 - there are improvements to the polar alignment including better star detection, more logical UI layout and bug fixes. It's possible that somewhere in the journey from 3.2 to 4.0 the bug you are encountering has already been fixed. Note that installing 4.0 will leave 3.2 still working on your PC, so you can easily switch between the two versions.

Other things you can try include starting with the mount in the rotated position that you are having trouble with for step 1 and then rotating it back to the home position for step 2.

It's possible that if you are on the edge of SharpCap's plate solving zone (about 5-7 degrees out from the pole) and you have some misalignment between the mount and the guide scope that the rotated position could be giving an image outside the plate solveing zone. A good way to test this is to snapshot an image from the position that does not work and upload it to nova.astrometry.net to get a plate solving result for it.

If none of this helps then snapshot an image from both the stage 1 and stage 2 orientations and post them both here and I will investigate further.

cheers,

Robin
Post Reply