Advice Sought About SkySafari

[JK 31]

Fairly new to looking at double stars and found SkySafari Plus great for identifying possibilities but a couple of things are confusing me when trying to work out where the fainter double should be. If anyone could help with these points it would be most appreciated.

1. Because some doubles are orbiting each other I assume the position of the fainter star would change over time. My queries on this is how up to date is SkySafari Plus, Object Info, which sometimes provides photos and layout information of the double. Also, how up to date is the SkySafari Starchart which sometimes shows the position of the fainter double and do these two sources of information tie up?
2. Secondly I refer to the Object info. which gives the Separation reading and an angle in degrees. My query on this is; does the angle give a clue to where I should find the fainter double, because it doesn’t seem to tally with the SkySafari Starchart or what I am seeing (I mostly use an erect prism). Also, how accurate is this angle, given that the position of the fainter double must change over time?

3. Would an upgrade to SkySafari Pro help with this, is the Object info in SkySafari Pro much more up to date?

Hope this makes sense.

[Jiggy 67]

I’ll do my best but others please chip in

1 - SkySafari is completely up to date, it’s software based on mathematical science that runs constantly, it can’t be “out of date” as far as I’m aware, in fact, you can pick a date a thousand years in the future and the starchart for that date will be absolutely accurate. Many binary stars are actually many AU’s apart and so take many many years to orbit each other, some hundreds of years, therefore any movement of many of them will be indistinguishable to the likes of us. Even then, the program will follow it

2 - Not sure about this, but I imagine you have got to think in 3D with an up, down and all sides sideways. The angle and separation will be correct, but you have to consider perspective when it comes to angles in space

3 - No, the program is the same, there are just more objects in Pro

HTH

Edited August 10, 2021 by Jiggy 67

[Zermelo]

The object information does reflect the current state as far as it is known (for some doubles we don't know the orbital parameters, but that usually means they're moving slowly anyway and don't change). If you compare the separation value for fast orbiting doubles with a table that was produced a few years ago, you will often see a difference (which is why you should always check the latest data - I was very disappointed one session when I couldn't split a double in Bootes that I'd got from a list; when I checked it in SkySafari, the actual separation was 0.1").

3 hours ago, JK 31 said:

does the angle give a clue to where I should find the fainter double

It does - it's telling you the angle of the companion compared with north. So you need to know the direction of north in your eyepiece view. The usual method is to find polaris and gently tap the telescope tube in its direction, while looking through the eyepiece to see the direction in which your view moves (it takes a little practice).  Then you just need to decide whether it means clockwise or anticlockwise in your particular scope - it depends on the design. In my newtonian, the position angles are anticlockwise from north, but in my Mak with a diagonal it is clockwise.

Edited August 10, 2021 by Zermelo
posted incomplete by mistake

[Zermelo]

... and if you want a second opinion on the separation and angle, you could have a look here: https://www.stelledoppie.it/index2.php?section=2

[wookie1965]

There are a few double star resources out there. 

https://bestdoubles.wordpress.com/resources/

Is very good from starsplitters. 

[JK 31]

Thanks for your reply Jiggy I now understand that the SkySafari Skychart and the Objects info. data on the left of the screen are constantly up to date although the text on the right side of the screen is not. This would explain the occasional minor variations between the data and the text. 
Thanks also for the clarification between the SkySafari Plus & Pro versions

[JK 31]

Thank you for your reply Zermelo, I now fully understand the situation regarding the separation of doubles that you explain so well, especially after looking at the stelledoppie web site, where you can often find the history of a double stars relative movements over the years. I have found this web site fascinating. 
Thanks also for the clarification regarding the direction of the companion star. I need to work this through a bit but I think I have it. 

[JK 31]

One further thought on SkySafari. Can someone clarify whether the data required to update a double stars separation for example is embedded within the App at the time of downloading or does the App get updated through the WiFi?

[Stu]

7 hours ago, JK 31 said:

One further thought on SkySafari. Can someone clarify whether the data required to update a double stars separation for example is embedded within the App at the time of downloading or does the App get updated through the WiFi?

I’m not certain, but believe this is all embedded within the app and will only update when the app is updated.

The only database which is updated via WiFi is the Minor Body Orbit Database which covers asteroids and satellites. This updates automatically or you can trigger an update manually.

The double star info is very useful, and you can see the position change as you change the date. These images show the position of Sirius B in 1995 vs 2022. You can see why it used to be considered such a challenge, but is now ‘much’ easier. I say that having still not successfully split it! 🤣. As mentioned by @Zermelo, you can also see which direction it is in, and provided you have correctly identified that direction in your eyepiece based on the orientation ie left right reversed, inverted etc, can match up the position to confirm your observation.

[JK 31]

Thanks Stu for the information regarding SkySafari updating process and also the tip about changing the date to identify the changes to Separation distance and the angle of the minor double star. You’ve set me off looking for all the doubles with known and identified orbits that are shown in SkySafari. There are quite a few when you start zooming in to look. Brill.

[Voyager 3]

@Jiggy 67 I agree , but all features in SkySafari pro is not available in the free version . For example , one can't add eyepiece circle by adding equipment (s) . Also one can't measure the distance between two objects in the free version . Making observation list is also not possible . And as said , the database is HUGE compared to the free version and you can even download the Gala extension to add other objects down to 18th mag . 

I upgraded from the free version and I find the Pro version absolutely worth it . But if you are a beginner , the free version is more than enough for a great start . 

[Jiggy 67]

28 minutes ago, Voyager 3 said:

@Jiggy 67 I agree , but all features in SkySafari pro is not available in the free version . For example , one can't add eyepiece circle by adding equipment (s) . Also one can't measure the distance between two objects in the free version . Making observation list is also not possible . And as said , the database is HUGE compared to the free version and you can even download the Gala extension to add other objects down to 18th mag . 

I upgraded from the free version and I find the Pro version absolutely worth it . But if you are a beginner , the free version is more than enough for a great start . 

You are absolutely right, I have the pro version on the Mac and plus on the phone, I think I meant, in terms of the planetarium and how it’s updated or not updated , which is what the OP was asking, it’s the same program 

[lunator]

Hi JK 31

Sky Safari is an excellent bit of software.

I use it on my phone and tab. 

The database is pretty accurate but not totally upto date. Only the WDS catalogue and Stella Doppie are fully upto date.

It shouldn't be a major issue as Most doubles don't change quickly but where an observation is quite old then expect the parameters to have changed a bit. 

The advantage of SS is that it does get updated. I have numerous double star books and the data is quite inaccurate now. 

Cheers

Ian