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ISS Overhead: Viewing/Tracking Fast Objects

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#1 RMay

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Posted 20 September 2019 - 09:15 PM

I downloaded the ISS app that shows the location of the international space station over the user’s location. It’s been rather interesting these past few days, as the station’s been covering a wide swath of sky with magnitudes in the range of -1 to tonight which will be about mag -3.7, for around 6-7 minutes.

I’m wondering if any of you have ever tracked the space station through a Questar. I think it would be near impossible to see it, other than perhaps if it passes through the field of view while the scope is stationary.

Any thoughts on this? Have you ever tracked anything moving quickly with your Questar... even an airplane?

Thanks,

Ron
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#2 jayrome

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Posted 20 September 2019 - 10:53 PM

It all depends on how quickly you can track the ISS during a pass. Yes, the app is critical if you want to be ready for it. I've tracked ISS numerous times with my 10" dob, which is nice and manoeuvrable. I've seen it at 127x magnification and can clearly make out the solar panel array. You can practice too with other satellites. I'm always seeing many through the eyepiece  on nights out under the stars.


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#3 Erik Bakker

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Posted 21 September 2019 - 12:20 PM

Ron,

 

Unless on a specialized mount, the Questar is not wel suited for this type of observing.



#4 RobertPettengill

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Posted 22 September 2019 - 07:26 AM

The Questar images of the space shuttle Columbia starting to break up over New Mexico were made with a special external tracking mirror, light and fast.

What I’ve done to catch the ISS is to catch it at a well known place. Transits of the Sun or Moon work well. So will an occultation or close approach to a bright star.

Get the Q tracking the spot where the ISS will be with the proper exposure and lie in wait. The ISS will cross the field of view of the Questar In well less than a second; don’t rely on clicking the shutter. Use video, 4K will show twice the detail of HD and keep the shutter time short.

Here is one I shot in 2016 with details
http://astronomy.rob...blog160904.html
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#5 munirocks

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Posted 24 September 2019 - 04:21 AM

I once managed to see the ISS twice in the same pass. (Actually once with me at the eyepiece and once with my daughter at the eyepiece.) I did it with a manual ETX 90 RA which has similar controls to a Questar. 

 

I was having a nice quiet observing session. Little did I know that things were about to turn frantic. My daughter came home late from the lab, came out into the back yard where I had the scope set up, and happened to mention that the ISS was passing overhead tonight. I asked when? and she went inside to check the web site. She came running out of the house and said "Now!", and pointing to the sky yelled "There it is!" and sure enough a bright dot above the western horizon was moving higher.

 

Fortunately I already had in a low power 26 mm eyepiece. Quickly as I could, I swung the scope around and caught the moving dot in the right-angle finder. I put the cross-hairs ahead of the moving dot (where I thought it was going to be), looked through the main scope, and watched a tiny square of solar panels zip through the field of view. Nabbed it. No time to bask in the glory of a good capture, I immediately did the same thing again and let me daughter look through the main scope, and she nabbed, too. Turned out to be a social occasion and nice memory for both of us. 

 

It seems to me that you could try the same thing in a Questar. Against you is the fact that the Q finder mode has no cross hair but you could try it with an eyepiece that does, as long as it focuses in the finder. In your favour is the Q's quick-switch lever between finder and main scope so you could make many attempts in a single pass. 



#6 RMay

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Posted 24 September 2019 - 10:38 AM

Thanks for the comments and feedback. I happened to be out viewing with CN member Old Don at Chabot Space and Science Center a few nights ago when the ISS was passing overhead. Using the pan head on my Gitzo 501 tripod I was able to see the space station, but frankly, it was moving quickly and I was trying to shift the focus from ‘planetary’ to ‘near earth’ viewing of the satellite and caught it, but I have to admit with all of the sweeping and refocusing it was a bit frantic. But a good primer for next time...

Ron

#7 pbealo

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Posted 24 September 2019 - 01:43 PM

Thanks for the comments and feedback. I happened to be out viewing with CN member Old Don at Chabot Space and Science Center a few nights ago when the ISS was passing overhead. Using the pan head on my Gitzo 501 tripod I was able to see the space station, but frankly, it was moving quickly and I was trying to shift the focus from ‘planetary’ to ‘near earth’ viewing of the satellite and caught it, but I have to admit with all of the sweeping and refocusing it was a bit frantic. But a good primer for next time...

Ron

Focus should really be the same.



#8 Optics Patent

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Posted 24 September 2019 - 05:10 PM

Focus tip:  If focused at infinity, everything closer will have a blur from each point (seen at the scale of the object being viewed) of the objective diameter (e.g. 3.5").

 

That means that the beak of a bird on a wire (or sparkle from the sun glinting off a glass insulator) will be blurred to the size of a small bird.  If a 1 arc-second blob is effectively seen as a point, then the 3.5" aperture is effectively at infinity at 18+ km. 

 

At orbital distances infinity is the correct focus.




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