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Does a sky simulator exist for testing a telescope?

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#1 adamchicago

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Posted 15 July 2020 - 04:25 PM

Hi All, I have settings that I need to test and few clear nights to test them on and was wondering if there was a sky simulator you can bring up on a large screen or projection screen tv (or maybe a laser projector that moves at the sky's normal rate) that would simulate the movement of the sky so you can test PHD2 tracking and dithering settings (amongst other tests).  So I'm talking about actual star-like objects that show on the screen and move at the same rate that the night sky would move so your mount and tracking scope would be able to track it like the real thing (so not a phone or PC app such as Stellarium or similar...unless you can project them as I was describing).

 

Thanks

 

Adam


Edited by adamchicago, 15 July 2020 - 04:27 PM.


#2 Richard O'Neill

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Posted 15 July 2020 - 05:01 PM

Have you considered using Venus?



#3 TOMDEY

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Posted 15 July 2020 - 06:07 PM

The short answer is no. The closest few similars I can think of are:

 

Planetarium used to research migratory birds sensing earth's gravitational field and/or stars for navigation.

Flight simulators for pilot training... like Al Nagler's work re' space missions.

Flight simulators for camera suites... like my US Patent >>>

 

The challenges are focus, distortion, and parallax. The screen that you visualize would have to be too close, creating/exacerbating all three problems... way out of focus, severe distortion, and terrible parallax. I'd love to be proven wrong, but have been steeped in these challenges for quite some time, and would be rather astounded if someone has come up with a truly working solution... other than what I have mentioned.    Tom

 

~click on~ >>>

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#4 adamchicago

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Posted 15 July 2020 - 06:24 PM

Thank you very much for providing those options but it sounds like there really isn't an option which is a bummer:(  Well they say patience is a virtue...guess I'm a bit short on that:) 

 

 

 

The short answer is no. The closest few similars I can think of are:

 

Planetarium used to research migratory birds sensing earth's gravitational field and/or stars for navigation.

Flight simulators for pilot training... like Al Nagler's work re' space missions.

Flight simulators for camera suites... like my US Patent >>>

The challenges are focus, distortion, and parallax. The screen that you visualize would have to be too close, creating/exacerbating all three problems... way out of focus, severe distortion, and terrible parallax. I'd love to be proven wrong, but have been steeped in these challenges for quite some time, and would be rather astounded if someone has come up with a truly working solution... other than what I have mentioned.    Tom

 

~click on~ >>>

 



#5 adamchicago

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Posted 15 July 2020 - 06:26 PM

You raise a good point as Venus will probably be seen through light clouds, will keep that is an option...thank you!

 

Have you considered using Venus?

 



#6 kel123

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Posted 15 July 2020 - 06:32 PM

Have you considered using Venus?


Even Venus does not penetrate cloud covers.

#7 han.k

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Posted 15 July 2020 - 11:38 PM

If you want to add the mount in the loop, you could use a planetarium program with an refresh rate of one second for plotting the sky on a projection screen/monitor. The only problem is that you have to keep the monitor at a large distance (20 meters?) from the scope to be able to get in focus. Due to the distance (20 meters?) the mount RA tracking will move the scope away from the screen in minutes. So you will need a large screen and a short distance as possible otherwise the simulation will end in a short time.

 

An other possibility would be a laser mounted on a second equatorial mount. Laser pointing (safely) to a wall/roof.

 

So it is probably better to simulate the mount in software making the simulation less real.

 

Your best option is to wait for clear sky.

 

Han



#8 han.k

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Posted 16 July 2020 - 05:29 AM

As an experiment I have added tracking error simulation to the "Sky simulator for Ascom".  This allows to experiment with PHD2 in simulation with a cyclic error of 20 arc seconds with a period of 5 minutes and a random error of 3 arc seconds. It will create artificial tracking images based on the RA, DEC position of the mount modified by an artificial cyclic and random error.

 

Caution it will cause a reset of your PHD2 settings, calibration and darks since an artificial Sky camera has to be selected!!

 

Han

 

PHD2 with Sky Simulator for ASCOM

PHD2 guiding simulation.png

 

Settings Sky simulator:

PHD2 guiding simulation-2.png


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#9 adamchicago

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Posted 16 July 2020 - 01:07 PM

Thanks for sharing those options...I actually have a projection screen in the basement where I store my equipment and while I don't have 20 meters I do have about 10-15 so can experiment and see what happens. BUT I really like the laser pointer attached to another mount suggestion, which I am definitely going to try.

 

At least for this round of settings tests I won't be able to use the Sky Simulator software because I need to physically connect the PC/PHD2 to a mount because it's likely a USB or some sort of PC communication error I'm having...but good to know the simulation software is available.

 

And the best news of all is clear skies are forecast for tonight:)

 

As an experiment I have added tracking error simulation to the "Sky simulator for Ascom".  This allows to experiment with PHD2 in simulation with a cyclic error of 20 arc seconds with a period of 5 minutes and a random error of 3 arc seconds. It will create artificial tracking images based on the RA, DEC position of the mount modified by an artificial cyclic and random error.

 

Caution it will cause a reset of your PHD2 settings, calibration and darks since an artificial Sky camera has to be selected!!

 

Han

 

PHD2 with Sky Simulator for ASCOM

attachicon.gifPHD2 guiding simulation.png

 

Settings Sky simulator:

attachicon.gifPHD2 guiding simulation-2.png

 



#10 han.k

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Posted 16 July 2020 - 02:29 PM

With a projection screen you have to figure out the correct zoom factor of the planetarium program . If zoomed in, the stars will move in meters/sec faster for you.  If you zoom out the star movement in meters/sec will decrease. You better do some calculations in advance.

 

Assuming the distance to the screen is 10 meter then a circle around the mount can be drawn of 2*pi*10m is about 62.8 meters equivalent to 360 degrees. So you will need to use a zoom factor for the planetarium program such that you have a range of 360/62.8= 5.7 degrees/meter on the screen. The stars have to move about 62.8meter/(24 *60 minuten) equals or 0.046 meter/minute for the distance of 10 meter.

 

Furthermore you have to present stars near the horizon assuming your screen is near the horizon and your using an equatorial mount otherwise the stars will move the wrong direction.

 

So the setup will be (very) tricky and I assume you have to experiment a little with the zoom factor till the movement is about correct.   A good start will be having the Moon at the correct size as in reality.

 

 

The laser on a second mount will be much easier to setup since the angular speed will be automatically correct.

 

Han



#11 OldManSky

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Posted 16 July 2020 - 07:08 PM

I think you'll have a heck of a time getting your main scope and guide scope to focus on something (a screen, wall) a few feet away, when they're setup and optimized for infinity focus...and usually don't have enough focus range to focus that close.

But good luck.




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