PHD2 and Star Adventurer

[Ken Mitchell]

Hi,

Couple weeks ago I've received my guide setup for the SA. Bad weather here didn't give me the chance yet to test it in the field. Next week there will be a (couple) of clear nights so hope to give it a go soon. I want to be sure that I have everything set up correct though.

This is what I did until now, I hooked up everything and launched the software. I can get a capture image on screen through the software so I believe it's recognizing the camera. I'm not sure if it is recognizing the SA mount as I can't find a way to test it. I tried to move the RA by the use of 'manual guiding' in phd2 but nothing happens. 

Is there a way to test this during the day and see if the SA is connected correct?

Do I need to connect the SA with USB to the laptop or just connect the SA-ST4-CAMERA and CAMERA-USB-LAPTOP?

I know there are members here that uses the SA with guiding so I'm hoping they could share their setup.

Thanks in advance.

Ken

 

PS.  my gear if it would help. TS72 with nikon ff, TS 50mm guidescope with zwo asi120mcs

[Davey-T]

Hi Ken, I've got a guider setup for my SA but have never got around to trying yet, you only need the ST4 cable connected.

Are you sure it's not moving manually ? it is hard to see it moving, you could stick a laser pointer on it aimed at the wall to check if it's moving.

Personally I'd use PHD1 as it is simpler and has all you need as long as it works with your computer.

Dave

[kens]

If you use ST4 you need to set the mount to On Camera. The further away the easier it will be to focus.

To test during  the day aim at anything you can get into focus on the camera. Turn on the cross hairs or grid  (View > Bullseye or View > Fine Grid). Set the manual guiding Guide Pulse Duration to its maximum (5000). Tools > Manual Guide to get the popup dialogue.

Click the various buttons and you should see the image move a small amount. The grid/bullseye makes it easier to detect the movement.

[Ken Mitchell]

5 hours ago, kens said:

If you use ST4 you need to set the mount to On Camera. The further away the easier it will be to focus.

To test during  the day aim at anything you can get into focus on the camera. Turn on the cross hairs or grid  (View > Bullseye or View > Fine Grid). Set the manual guiding Guide Pulse Duration to its maximum (5000). Tools > Manual Guide to get the popup dialogue.

Click the various buttons and you should see the image move a small amount. The grid/bullseye makes it easier to detect the movement.

When I set the mount to On Camera, it says mount connected. But no matter what direction I click in the Manual guide screen, it doesn't move.

Should it work with the SA as it only guides in RA?

What else can I do to make it work? When I try to use calibrate functions in the tools menu it says, no calibration data available. Does this mean something?

 

Ken

Edited November 11, 2018 by Ken Mitchell

[Ken Mitchell]

Thanks Dave,  now I know everything is connected correctly.

I will try with phd1 to see if it changes things when testing at daytime.

Ken

[kens]

Looks like the Star Adventurer will only accept guide commands whilst in celestial tracking mode so you can't test it in daylight.

PHD2 will start calibrating automatically when you start guiding. For RA only guiding you need to turn off Dec guiding as shown below. Also, you can find the PHD2 manual at https://openphdguiding.org/manual/?section=Introduction.htm

Personally I would not recommend using PHD1 as it has not been supported for many years now

 

[Ken Mitchell]

On 11/11/2018 at 21:50, kens said:

Looks like the Star Adventurer will only accept guide commands whilst in celestial tracking mode so you can't test it in daylight.

PHD2 will start calibrating automatically when you start guiding. For RA only guiding you need to turn off Dec guiding as shown below. Also, you can find the PHD2 manual at https://openphdguiding.org/manual/?section=Introduction.htm

Personally I would not recommend using PHD1 as it has not been supported for many years now

Managed to get it up and running and had some decent guiding results I believe.

Got up to 5 min without startrails. Did a few tests yesterday night to see how well it reacted to a good or bad PA. I've heard people say you can do a rough PA and still get good guiding. Maybe that's true for a mount that guides in both axis? but from what I've tested it seems that it's pretty important you have a good PA with the SA as it doesn't guide in dec. 

My PA was slightly off and got trails even with 2 minutes. I could see the guidestar drifting, as with a good PA the guidestar stays in the middle. Probably because the SA can't compensate for dec.

The things that are most difficult in the guide process is locking onto a guidestar and getting focus right with that particular scope. I now wish I'd payed 50$ more and get the one with the microfocuser. The one I have now is push and pull and find it a bit hard to operate. 

Any tips on choosing/acquiring a good guidestar? It seems like it's not always the best option to choose the brightest in the sky, or am I wrong? 

How important is it to choose a star in roughly the same area you're imaging in?

 

Ken

[Davey-T]

Well done getting it working Ken.

Too bright a guide star will not work very well an " ordinary " looking one is best, it doesn't need to be perfectly focused.

A good idea to calibrate around the dec that you're imaging at.

Dave

[kens]

9 hours ago, Ken Mitchell said:

Managed to get it up and running and had some decent guiding results I believe.

Got up to 5 min without startrails. Did a few tests yesterday night to see how well it reacted to a good or bad PA. I've heard people say you can do a rough PA and still get good guiding. Maybe that's true for a mount that guides in both axis? but from what I've tested it seems that it's pretty important you have a good PA with the SA as it doesn't guide in dec. 

My PA was slightly off and got trails even with 2 minutes. I could see the guidestar drifting, as with a good PA the guidestar stays in the middle. Probably because the SA can't compensate for dec.

The things that are most difficult in the guide process is locking onto a guidestar and getting focus right with that particular scope. I now wish I'd payed 50$ more and get the one with the microfocuser. The one I have now is push and pull and find it a bit hard to operate. 

Any tips on choosing/acquiring a good guidestar? It seems like it's not always the best option to choose the brightest in the sky, or am I wrong? 

How important is it to choose a star in roughly the same area you're imaging in?

 

Ken

If you are not guiding in Dec then you do need very good PA. As a guide the amount of drift you get will be equivalent to the PA error over a period of 6 hours. If you want less than 1 arcsecond of drift on a 5 minute exposure your PA needs to be in the order of 1 arcminute. You can use PHD2s drift alignment tool to adjust your PA.

Getting a good focus on the guidescope will help a lot. Is there a focus ring near the objective lens you can use? Also, since you have the ASI120 you may be able to use a threaded connection. Then you can use spacers to adjust the focus.

To choose a guide star you can either let PHD2 choose one (Tools > Auto select star) or if you do it manually, display the star profile and ensure that it does not have a flat top. You can adjust the camera gain if there are no suitable stars. Also, when you connect the camera, select 16 bit mode. It tends to give better profiles for guiding.

Since you are not guiding in Dec the guide star does not need to be very close to where you are imaging. Obviously not pointing 90 degrees away or anything like that but within a few degrees wont make much difference. 

[Ken Mitchell]

16 hours ago, kens said:

If you are not guiding in Dec then you do need very good PA. As a guide the amount of drift you get will be equivalent to the PA error over a period of 6 hours. If you want less than 1 arcsecond of drift on a 5 minute exposure your PA needs to be in the order of 1 arcminute. You can use PHD2s drift alignment tool to adjust your PA.

Getting a good focus on the guidescope will help a lot. Is there a focus ring near the objective lens you can use? Also, since you have the ASI120 you may be able to use a threaded connection. Then you can use spacers to adjust the focus.

To choose a guide star you can either let PHD2 choose one (Tools > Auto select star) or if you do it manually, display the star profile and ensure that it does not have a flat top. You can adjust the camera gain if there are no suitable stars. Also, when you connect the camera, select 16 bit mode. It tends to give better profiles for guiding.

Since you are not guiding in Dec the guide star does not need to be very close to where you are imaging. Obviously not pointing 90 degrees away or anything like that but within a few degrees wont make much difference. 

Thanks for the information. Where do I choose 16bit mode? Can't seem to find it.

Would you happen to have any advice on guiding while imaging targets close to the celestial pole? Obviously you can't choose Polaris but even stars in the vicinity don't work. Calibration fails because the star didn't move enough. And when I choose a star somewhat off axis from where the main scope is aiming I get startrails. I don't think it's because "bad" PA but rather because the guide doesn't compensate correctly for the guidestar is off axis. Could that be?

My target is ngc 7822  if that helps.

Ken

[Maxrayne]

Following intently as you're exactly where I'm at atm with this ?

[kens]

1 hour ago, Ken Mitchell said:

Thanks for the information. Where do I choose 16bit mode? Can't seem to find it.

Would you happen to have any advice on guiding while imaging targets close to the celestial pole? Obviously you can't choose Polaris but even stars in the vicinity don't work. Calibration fails because the star didn't move enough. And when I choose a star somewhat off axis from where the main scope is aiming I get startrails. I don't think it's because "bad" PA but rather because the guide doesn't compensate correctly for the guidestar is off axis. Could that be?

My target is ngc 7822  if that helps.

Ken

When you are connecting click the settings button as shown and you'll get the options for 8bit and 16bit

NGC7822 is at dec 67 which is not very extreme although PHD2 recommends against it. At that declination the RA pulses need to be 2.5x longer than at the equator for a given movement. In the step size calculator make sure all the values are correct and enter the maximum 60 degrees declination. Then manually add 25-30% to the calculated value.

When you are very close to the pole (say > 85 degrees) you can turn off RA guiding 

You'll also want your guide star to be close to your target as the relative motion difference between the two will be greater if they are at different declinations. You also want to be sure not to chase the seeing as your mount will be making large movements in RA to correct for small star movements on the sensor.

[Ken Mitchell]

9 hours ago, kens said:

When you are connecting click the settings button as shown and you'll get the options for 8bit and 16bit

NGC7822 is at dec 67 which is not very extreme although PHD2 recommends against it. At that declination the RA pulses need to be 2.5x longer than at the equator for a given movement. In the step size calculator make sure all the values are correct and enter the maximum 60 degrees declination. Then manually add 25-30% to the calculated value.

When you are very close to the pole (say > 85 degrees) you can turn off RA guiding 

You'll also want your guide star to be close to your target as the relative motion difference between the two will be greater if they are at different declinations. You also want to be sure not to chase the seeing as your mount will be making large movements in RA to correct for small star movements on the sensor.

These are the default values, I only changed the FL. What values should I change here?

Do you suggest I try to turn of guiding for that target and see how well it performs?

Ken

[kens]

At Dec 67 I'd still use guiding. Since you are ST4 guiding: in the calculator you need to manually enter the declination (default is 0). You wont be able to set it higher than 60 so use that to calculate the Calibration step size. Then manually increase the step size by 25-30% to make up the difference for dec 67.

[Ken Mitchell]

Ok gotcha. I understand now.

I assume you can consult the dec degrees with Stellarium or similar SF? So for every target I image it is best to change the dec degrees in phd2?

Ken

[kens]

Correct. The main thin is to enter the correct declination when you calculate the calibration step size.

There is also an option PHD2 to set the Aux Mount to "Ask for coordinates". When you use this option, each time you start guiding, PHD2 will pop up a window asking you to enter the declination. If you calibrated with this option on, you can reuse the calibration like with an ASCOM controlled mount.

[Ken Mitchell]

Thanks a lot for the help!

Last question(for now), even if the Star Adventurer doesn't guide in dec it is still important to enter the correct dec degrees? Will these values be taken into account when correcting for RA?

Would you happen to have some information on how this operates, just to have an idea what phd is doing.

Ken 

[Ken Mitchell]

Out of curiosity I did a stack from last night's subs without calibration frames and simple edit in photoshop. Total was just over 3hours.

At the bottom there is a 100% crop to see the trails caused by the guiding.

Should I give this another go? With double the exposure how much more detail should I get on this target.

Or is it best to wait and do this with my modded cam and 7nm Ha?

Ken

 

 

Edited November 16, 2018 by Ken Mitchell

[michael8554]

4 hours ago, Ken Mitchell said:

 even if the Star Adventurer doesn't guide in dec it is still important to enter the correct dec degrees? Will these values be taken into account when correcting for RA?

As Ken said, lacking feedback from the mount about where it's pointing, putting the approximate Dec into PHD2 will enable it to tweak the RA corrections you obtained at zero Dec for any Dec you use.

Michael 

[kens]

5 hours ago, Ken Mitchell said:

Thanks a lot for the help!

Last question(for now), even if the Star Adventurer doesn't guide in dec it is still important to enter the correct dec degrees? Will these values be taken into account when correcting for RA?

Would you happen to have some information on how this operates, just to have an idea what phd is doing.

Ken 

PHD2 has an option on the Guiding tab of the brain to Auto-restore Calibration. If this is ticked then PHD2 will use the existing calibration when you start guiding. Otherwise it will start calibrating when you first start guiding. (This option can be overridden by holding down the shift key when you click the guiding button to force a recalibration). When PHD2 uses the existing calibration, it divides the RA correction duration by the cosine of the declination - or what it thinks is the declination. Or more correctly it multiplies by the cosine of the calibration declination then divides by the cosine of the current declination. So its important that it knows both the declination used at calibration and the current declination or it will issue RA corrections of the wrong duration. With a ST4 guided mount you use the "Ask for coordinates" driver at both calibration and when you guide on your target to achieve this.

[kens]

4 hours ago, Ken Mitchell said:

Out of curiosity I did a stack from last night's subs without calibration frames and simple edit in photoshop. Total was just over 3hours.

At the bottom there is a 100% crop to see the trails caused by the guiding.

Should I give this another go? With double the exposure how much more detail should I get on this target.

Or is it best to wait and do this with my modded cam and 7nm Ha?

Ken

The trails are in declination so they are actually caused by non-guiding  This illustrates why you need very good PA when not guiding in declination. Its a bit hard to tell from a JPEG but it looks like you've got about 3 pixels of drift per subframe.The pixel scale is 8.6 as/pixel so that's around 25 arcsec of drift. You didn't mention the length of the subs but assuming 5 minutes that means your PA error was in the order of 30 arcmin which is quite large. Now that you've got PHD2 running I'd suggest using its drift alignment tool to improve your PA. That will help you get more detail since they wont be smeared.

I'm not familiar with using a DSLR with HA filter but I imagine you'd want to take a set of subs with no filter to make up a synthetic lum channel and another set with the Ha filter for the nebulosity. For the no-filter case, doubling the integration time will improve SNR by the square root of 2 (1.4x). With the Ha filter you'll get light on only 1/4 of your pixels. Plus at 7nm even the red pixels will be getting just a small fraction of the sky background - in the order of 1/14th. That will affect how long you need to expose each sub. 

 

[Ken Mitchell]

On 16/11/2018 at 21:58, kens said:

The trails are in declination so they are actually caused by non-guiding  This illustrates why you need very good PA when not guiding in declination. Its a bit hard to tell from a JPEG but it looks like you've got about 3 pixels of drift per subframe.The pixel scale is 8.6 as/pixel so that's around 25 arcsec of drift. You didn't mention the length of the subs but assuming 5 minutes that means your PA error was in the order of 30 arcmin which is quite large. Now that you've got PHD2 running I'd suggest using its drift alignment tool to improve your PA. That will help you get more detail since they wont be smeared.

I'm not familiar with using a DSLR with HA filter but I imagine you'd want to take a set of subs with no filter to make up a synthetic lum channel and another set with the Ha filter for the nebulosity. For the no-filter case, doubling the integration time will improve SNR by the square root of 2 (1.4x). With the Ha filter you'll get light on only 1/4 of your pixels. Plus at 7nm even the red pixels will be getting just a small fraction of the sky background - in the order of 1/14th. That will affect how long you need to expose each sub. 

 

Short follow up and thanks.

Sorry for the late reply, had some issues with my guiding laptop. It gave up on me so had to get me a new one for guiding.

Also still waiting for the new desktop to arrive in able to do post processing.

Neither did I had the opportunity to do more testing with phd2 or the SA. When all is back to order I will definitely continue this to improve my imaging and acquire more knowledge on the topic in general. 

Ken

[Hax1993]

On 11/11/2018 at 21:59, Ken Mitchell said:

Thanks Dave,  now I know everything is connected correctly.

I will try with phd1 to see if it changes things when testing at daytime.

Ken

Hey ken 

im in the same situation as you got a guide scope and a star adventurer, did you manage to move your mount using the manual guide?
i tried alot but cannot move it in any direction. my mount is in tracking position and i can see movement on the screen but cant see any big movement when i click on the manula guide buttons.
thanks

Hax