SharpCap 2.9 - Polar Alignment

[Dark Matter]

Would this particular PA program work in the Southern Hemisphere? 

[SimmoW]

Yes! I'm using it all the time in Melbourne, it's fantastic!

im using a 1600 with a 430mm scope but am now wondering, could I use a cheapish webcam with a lens and Orion 50mm GS? I sold my asi120 the other day unfortunately! 

 

Thanks so much Mr Genius! 

[Roysten]

Hi guys, it looks like it's going to be a  clear night for awhile tonight so hoping to get out and try the polar alignment tool!

I know the best solution will be a guide scope or 0.5 reducer but for tonight do people thing that a FOV of 0.69 (0.85 diagonal ) will be ok for the alignment?

[alcol620]

11 hours ago, SimmoW said:

Yes! I'm using it all the time in Melbourne, it's fantastic!

im using a 1600 with a 430mm scope but am now wondering, could I use a cheapish webcam with a lens and Orion 50mm GS? I sold my asi120 the other day unfortunately! 

 

Thanks so much Mr Genius! 

The ASI120 would have been an excellent guide scope.

[wornish]

I have changed from using a Skywatcher ST80 as my guide scope with a Toupcam to just using the Skywatcher 50 x 9 mm Right Angle Finder with an adapter and the same Toupcam.    Sharpcap Polar alignment works great and it is much lighter.

[Crose01]

I have another question if for my AstroTrac I'm getting perfect PA could I use this to calibrate my AT polar Scope? I'm suspecting the answer is

no. The PA Scope would have to be perfectly aligned with the polar axis. I use it the other way to get me into the ball park with SharpCap.

[rwg]

Hmm,

once you have polar aligned with SharpCap, you have your mount axis well aligned with the pole. If you then set the correct orientation of the polar scope and then adjust the polar scope collimation to put Polaris in the circle I would have thought that you have then successfully aligned the polar scope correctly with the mount. Was that what you were thinking of?

cheers,

Robin

[Crose01]

Hi Robin

Yes I was thinking along those lines but I'm wondering if it may introduce a false positive if I do this process but the Polar Scope Arm doesn't have the same rotational axis as the AstroTrac Mount. I've seen this before doing a PA and then moving the arm and finding that after rotating the PA scope it's quite some distance out.

 

Regards

 

Chris

[spillage]

On 11/6/2016 at 17:33, Ant-33 said:

For guiding, I use an ST80 and QHY5l-IIc. The fov is a little over half a degree, so it's not wide enough for the Sharpcap polar alignment routine. I wondered, though, whether using a 0.5x focal reducer would work. It would bring the fov to over a degree, which is within the spec for the polar alignment routine. Does anyone have experience with this setup?

Robin - Sharpcap is a fantastic program, and I'd like to echo the appreciation others have shown here. Awesome  

i have tried several time and use the st80 and qhy5 mono. I just can get it to pick up enough stars. Will keep trying but for now an using php2 drift align.

[Ant-33]

14 minutes ago, spillage said:

i have tried several time and use the st80 and qhy5 mono. I just can get it to pick up enough stars. Will keep trying but for now an using php2 drift align.

Yes, I was suffering from the same problem. I've got a 0.5x focal reducer now, and with it the fov on the ST80 is pretty good for guiding. I'd recommend it if you don't want to change your guidescope. It doesn't have to be an expensive reducer if you're only using it for guiding.

Clear skies

Tony

[rwg]

@Crose01 I think it ought to work - a side offset of a few inches (or feet for that matter) isn't going to make any difference as the stars are effectively infinitely far away...

 

@spillage 2.10 (in beta) is better at picking up faint stars than 2.9, also there are tweaks to the star detection parameters that may help. Much more info here.

cheers,

Robin

 

[al-alami]

Am very interested in this.  

Actually very glad I found it, I was considering getting the polemaster, but now I have a good alternative.  If only the weather would cooperate and give me a clear night!

Am looking forward to trying it out

regards

Fakhri

[andyboy1970]

Used The Polar alignment function last night on my big Meade mount c.1980's which has no polarscope or Azimuth adjusters.

Using my ST80 & QHY5 with 8 second exposures it was detecting 15-20 stars.

Managed to get the mount aligned by slowly rotating the pedestal then adjusting Alt.

Very happy with the outcome.

Thanks Robin.

[alcol620]

Hi folks

I thought I would take my time last night and check polar alignment using the sharpcap software. It all seemed to go to plan, after a fair number of adjustments to the up/down/left/right the software indicated that I was within a few seconds on being spot on. I have a ED80 scope, AZEQ6 mount on a Pulsar pier.

However, when I did a check on star trailing, ie running a 120s sub with no guiding, PHD not running I get quite long star trails.

I have been under the impression that if I get polar alignment spot on, star trails would be a thing of the past, especially those of only 120s??

 

Ideas welcome, am I doing something wrong?

[rwg]

One case where there was a similar problem was tracked down to a mechanical problem causing the view to shift as the scope is rotated - this led to inaccurate results. The user's view of polaris as they rotated the mount was like this

As you can see at a certain point in RA, something shifted which then ruins the calculation of where the telescope's axis is pointing.

Another (unconfirmed so far) suspicion is that there may be flexure in some mounts due to weight distribution changes when moving the telescope from the pole pointing position used for alignment to a more ordinary position for imaging. This might be a particular problem if you are using a tripod on soft ground.

cheers,

Robin

[alcol620]

Hi Robin

Thanks for that. Obviously with the mount being mounted on a Rigel Pulsar pier, movement from this should be minimal or non existent. Are there any other factors like data that I have to enter that I might have got wrong. I was disappointed as Sharpcap Polar align seemed to be working fine, Finding stars, giving me adjustment distances etc etc.

Regards  Alec

[rwg]

Other possible causes of error that I am aware of

* Bad plate solve on either the first or second stage - this could throw out the whole process - I think this is very unlikely and haven't encountered a case yet

* Atmospheric refraction - only significant below 30 degrees of latitude, probably not going to be a problem in NE Essex!

I would advise that if you are having problems, then at the end of the PA process (once adjustment complete), spin the RA axis again and watch the screen - the stars in view should appear to move around the point marked as the NCP. 

If none of this helps, then I am (for now) baffled. It would be helpful to have an image captured (saved using the snapshot button in SharpCap, not a screen grab) for each orientation of the PA process and also if possible an estimate of the PA error from an independent measurement such as PHD drift alignment.

cheers,

Robin

[alcol620]

Thanks Robin

I will try what you suggest next time out and report back.

Regards  Alec

[al-alami]

Hi,

I tried to use it last night, but ran into some problems.  I'm using a QHY5II Mono + 9x50 Finderguider, for some reason I can never get more than 2 or 3 stars.  Any suggested setting to work with? I did check that the stars are in focus, and in PHD I can count at least 20.  I'm assuming its my fault since it works for people, so what am I doing wrong?

Thanks in advance.

Fakhri

[rwg]

@al-alami

Have you turned up the gain? That's usually necessary to see a decent selection of stars with 2-3 second exposures.

cheers,

Robin

[al-alami]

10 minutes ago, rwg said:

@al-alami

Have you turned up the gain? That's usually necessary to see a decent selection of stars with 2-3 second exposures.

cheers,

Robin

Am sure I tried, but will try again as soon as the clouds give us a break.   How different would the exposure time be compared to PHD?  In PHD I can't even go to exposures that are longer than 1 sec, everything gets washed out.  But like I said before, its probably my fault.

Thanks,

Fakhri

[rwg]

PHD does a strong stretch on every frame before displaying it which can make it's brightness onscreen misleading. There is a way to turn this off somewhere in PHD, but can't recall where.

cheers,

Robin

[alcol620]

There is a slider at the bottom of the screen.

[frugal]

I managed to fiddle with the settings to get SharpCap to recognise about 26 stars last night by tweaking exposure time, digital gain, noise reduction and some others. After a few failed attempts (I know I am trying this at twice the recommended focal length, so I was chancing my arm), I got the image to Plate Solve. Then when instructed, I moved the RA axis 90 degrees and it Plate Solved again. Woot!. Then I clicked Next as told... "Guided Alignment is only available in SharpCap Pro"... [removed word]

This is with the latest beta version. Having a look at the website it says that the beta versions will have all of the licenced features until the end of the beta period. Has this changed?

Does the Polar alignment feature work well in 2.9? Is it worth uninstalling 2.10 beta and installing 2.9?

[rwg]

If you look on the beta download page there is a license that you can use with the beta for now. This will continue to be available and updated during the beta period. So yes, you can still use the features for the beta period, but we've got to the point that the license entry/checking code needed to be turned on to make sure it didn't have bugs in it!

cheers,

Robin