GOTO - Is it me?..

[Aikidoamigo]

I'm looking for a little reassurance please, I think perhaps I know the issues but just wanted to ask here just in case I am missing something...

 

last night i had the most perfect seeing, we had gone into a national park with amazing skies and no light pollution, it was Fab.

all set up and nicely aligned with the two star system, so off we go. We look at Mars... The scope misses, I fine tune and note the change in the handset... Next object same again.

so my questions / points are these:

my garmin handheld GPS tells me exactly where I am to the second and yet the GOTO mount only allows for degrees and minutes... Is the small detail having an effect?

Same with altitude... Do I need to record that from the Garmin at the height of the mount base or the height of the eyepiece? Would such a small difference in Alt make enough error to throw the scope off?

 

finally and perhaps most importantly - having fun (?!) with my GOTO handset and seeking out unusual objects is all well and good if you already know what the object should look like; for example when I look for any of the other Nebula (not Orion) then my scope seems to point to 'black nothing' has the GOTO worked? Or is my alignment off? Is my eyepiece right or wrong for the job??

hope you can follow my rambling questions... When I align and ask the scope to go to something I know, it's off... But It's close so I can find what I need; when I don't know what I am looking at... I have no chance and it's very frustrating.

 

as a footnote, when I do two star align often the handset tells me something which I think means 'stars used may be too close to each other' is that likely and therefore having an effect?

 

thanks in advance as always

[Mr Spock]

It's always best to use stars from different parts of the sky, and, three star alignment if you can. What mount are you using?

[Aikidoamigo]

It's the Mak Skymax 127 with the goto that came as a system package, not sure exactly what the mount is called... Can check later.

I don't believe the handset offers 3 star as an option only 2 star and polar, again I can check that later.

i tend to use one of the Orion stars and then Capella or Pollux... Are these all two close to each other to be effective?

[John]

With the exception of planetary nebulae and a few supernova remnants, many nebulae, even quite well known ones, are pretty faint and hard to see. M42 is an outstanding example and far more obvious than most of it's type.

On getting more GOTO accuracy, as Mr Spock says, pick alignment stars that are quite far apart in the sky.

 

[Ant]

If it's a skywatcher goto the three start alignment should be an option (I've never used more than two).

I'd be inclined to try a one start alignment close to your target and see how you get on. That's what i do when imaging, goto never failed (but that's a bit of a cheat really).

Ant

[Aikidoamigo]

I think it offers brightest star - which I guess I don't like as what seems bright must depend on light pollution / visible sky... 2 star and polar. But with two star it slews to within 40mmEP FOV on the second star and then I centre and confirm. Surely then when I say 'go to Mars' it should be fairly central, but it's not and sometimes quite a bit off; so if it's not very accurate for Mars what chance with DSO?

 

but then as I say, maybe it is bang on but I don't recognise what it is pointing to!

[dannybgoode]

Sounds daft but make sure you're aligning to the right star. 

Bear in mind for example is you have a target star and another close by you may be zeroing in on the other one-particularly because day the finder scope is inverted so you think you're going the right way when in fact you're not. 

A red dot finder helps enormously here as you can be sure you're on the right target. 

I'm struggling to goto align at the moment as well but I know that I'm not doing it right. The times I have got it right goto has been spot on. 

[cjdawson]

Just want to throw my 2p's worth in on this.

1. There are several systems for co-ordinates.  It's best to make sure that both the Telescope and GPS are talking the same co-ordinate language.  I believe that GPS uses something called WGS 84.   I'm not sure what telescopes use.

I do know that co-ordinates put into my Meade LX-90 mount work just fine.  It would surprise me if your mount is different, but it's work checking if you can.

2. Altitude.  Yes, this can make a difference, when you are talking about 100's of meters.   1-2 meters won't matter too much.

 

If the scope is always off by the same amount, maybe it's an alignment error or some sort.

[Nova2000]

Hmm. I think the stars in goto alignment should be in different hemispheres? Doesn't it increase the accuracy? 

[Cosmic Geoff]

The 3-star align is not necessarily better. On the Celestron system, with 3 star the software identifies all 3 objects (helpful for beginners) while with 2 star the user has to identify at least one of them. The 2 stars should be a sensible distance apart, e.g stars in Orion & Gemini. It is essential to accurately level the mount (you don't mention this) for one-star and solar system align, and it seems this applies for 2-star and 3-star align too.  The Celestron doesn't have altitude (geographical) so it does not look like a major issue.

There are various GoTo 'gotchas' for the unwary user: wrong date, wrong date format (that one got me last night), wrong site, wrong Lat/Long format. Errors with planets suggest a date error.

A lot of nebulae and galaxies are beyond the reach of a 127mm telescope. 

[SkyBound]

12 minutes ago, Nova2000 said:

Hmm. I think the stars in goto alignment should be in different hemispheres? Doesn't it increase the accuracy? 

So we should start the alignment in the UK and then nip to Oz to finish it off......lol, I don't think so... :):)

[Nova2000]

10 minutes ago, SkyBound said:

So we should start the alignment in the UK and then nip to Oz to finish it off......lol, I don't think so... :):)

Not what I mean

If one chooses capella, second star should be in the West ie_mirach

Then in the north or south ie. Canopus, procyon, Sirius, 

This is how I do it

[happy-kat]

^ Only if you have an eq mount. The guidelines are different for altaz.

[ronin]

Quote

all set up and nicely aligned with the two star system, so off we go. We look at Mars... The scope misses, I fine tune and note the change in the handset... Next object same again. 

This partially makes sense.

You have asked it to goto Mars, it slews and as far as it is concerned it is on Mars (even if it is not). You slew to the actual Mars and the scope considers that this you moving away from Mars, and recalculates it's "new" position. That is how they estimate an object when you ask it. In effect although you have Mars in the view the scope is unaware of that. So when you ask the next goto it moves from where it thinks it is, not necessarily from where it actually is.

On a Meade there is a simple "synch" action which aligns your movement after the goto has done. As best I know there is one on your handset but it is not as simple.

I often wonder if the expected action is, or should be: Goto target, center target, press Enter to synch target and scope cordinates but that does not appear to be the prescribed action.

One option is to look for something called Precision alignment - not quite that but similar. You select a nice easy simple star and then the scope goes to it, you center it and then press Enter and the scope now uses the stars RA+Dec as its position and your movement is cancelled.

Not sure where you are doing this observing but have you changed time zones ? Just a location of European Traveller implies you are now on CET and the timezone may still be UK or something.

Generally do not worry about altitude, not sure why they added it in. Setting it to 0 seems the normal.

[SkyBound]

1 hour ago, Nova2000 said:

Not what I mean

If one chooses capella, second star should be in the West ie_mirach

Then in the north or south ie. Canopus, procyon, Sirius, 

This is how I do it

I know, was just kidding.... ?

[cloudsweeper]

Lots of useful tips here - I use two star (known stars), far apart, but not necessarily half the sky away!  Getting date/time/lat/long right is of course very important, but I now have a GPS Module which takes care of all that a treat.

Tried seven targets last night using GoTo, and all were virtually dead centre in the long FL EP.  

If you try GoTo on a well known star and see how it performs, you then have confidence for objects you can't easily see.  (But remember - they might actually not be visible!)

One other thing - I have Stellarium on the go on a laptop out there with me (well, in the shed), so I compare what I see with the star patterns around the hoped-for target just to make sure.

GoTo is great - saves a lot of viewing time.  But I also occasionally enjoy hopping with my frac.

Doug.

[alanjgreen]

For Celestron mounts, you can't beat "auto 2 star" for simplicity. 

You need to know two named stars before you start. ( with SkySafari or some other point and see system on a phone its dead easy)

as Ronin, says above, a red dot finder is best for goto alignments, you need to align to a star you can see. This is more easily done with RDF as you are certain to be looking at the star you can see. Using a 6x50 finder is harder as you look into the finder to see lots of stars that you could not see before then the doubt and time wasting starts...  

- time is an issue, the longer you take to move to the next star, the more inaccurate the scope will be at guesstimating where it is

- take too long, alignment failure guaranteed  

With auto 2 star, you align the scope manually on a known star, let's say Polaris for arguments sake. Then it picks the second star for you. A good thing is that you only need pick Polaris in the handset when you have it nicely centered in the eyepiece so you can take your time, it's not a race against the clock  

if you want to choose a different 2nd star, then up/down to the one you want. Note that it has picked "the best" co-star for the one you started with (so ideally you stick with that one), the star it picks will be another quadrant at a different altitude - if you swap to one of your own choice make sure it is in a different quadrant at a different altitude (for higher accuracy alignment) . You may have to switch if the one it picks is not visible from your location!

The scope then slews to where it thinks the second star will be. It will miss by some small amount.

Again, if you have a Red dot finder, then you can easily see which bright star it was aiming for (as it will be pretty close). If you have 6x50 then you have a much harder job to get this right, you look in the finder and oh no where did all these stars come from  

finally you centre the star (it missed) in red dot finder and then eyepiece, job done.

 

to conclude:

1. the sky is split into 4 quadrants - north, south, east , west. Pick stars in different quadrants, so at least 90 degrees away.

2. Red dot finders work great with goto. 6x50 finders do not as they add a load of stars that you don't care about into the equation. They also confuse you by reversing the view. And you may have to roll on the floor to see through It if it's the standard straight through kind  

3. Do yourself a favour and buy a red dot finder (££) OR even better... 

4. Buy Celestron starsense (££££££££) and sit back and enjoy the 2 minute wait for a perfect alignment every time  

- you don't even need to buy the red dot finder so knock the cost of the starsense

- think of how much money astronomers "with goto" waste on 8x50 finders of many variations and red dot finders  when starsense will do it all for you

- if you watch starsense in action, it picks first star in the same quadrant where you decide to start from, first star will be at mid height (say 45 degrees). Then it moves to next quadrant along and picks 2nd star at the same height. Finally, it moves to the third quadrant at an increased height of 75 degrees. The objective of all this is to make a nice wide triangle shape (in the sky), the wider the shape the better the alignment. If you use 3 star alignment then this wide triangle shape should be your objective too!

- of course starsense is even more accurate as it is not picking single stars but "plates" of up to 100 stars each.

 

If you are wanting to hit a faint DSO on a Celestron mount with high accuracy, use Precise Goto ( look for it in the manual). Scope will take you to a bright star near the target DSO, you centre the star and Enter. The scope will find the DSO dead centre every time.

 

[alanjgreen]

It's also best to avoid solar system align, unless you are after a quick alignment just to look at specific planet or the moon.

its the least accurate alignment by a long way, you are unlikely to get anything coming up dead centre unless it is right next to the alignment planet/moon.

[Aikidoamigo]

3 hours ago, alanjgreen said:

 

4. Buy Celestron starsense (££££££££) and sit back and enjoy the 2 minute wait for a perfect alignment every time  

It says sky sense only works with celestron and I dont have that brand PLUS it's 300 quid!

[Flyingfuzz]

I use Syscaninit a freed app on Android it gives all the correct info to input into the handset in the right format.

If you are just missing the object check time and W or E in the cords

[alanjgreen]

29 minutes ago, Aikidoamigo said:

It says sky sense only works with celestron and I dont have that brand PLUS it's 300 quid!

It's available for skywatcher too...

https://www.firstlightoptics.com/celestron-mounts/celestron-starsense-accessory-for-sky-watcher-mounts.html

yes, its expensive but it works!

it can be used on multiple scopes too, you store a "profile" for each scope.

you can spend £100 on a decent finder, then still spend 20 mins getting a poor alignment.

you pays your money and you takes your choice  there is always second hand for cheaper price  

 

Do you use red dot finder or 8x50 finder?

[Aikidoamigo]

Thanks for suggestion but I have made sure I'm  correct for date and times as I made that mistake initially.

 

what could be wrong is the time; I enter Spanish time correct as it is... And then put +0.00  for GMT. Would thy be the right way based on the fact I have put the correct local time in? If I put UK time in then I put +1 but as I used correct local time an I correct in also using +0?

[alanjgreen]

Put the date in American format. Month,day,year

[cloudsweeper]

44 minutes ago, Aikidoamigo said:

It says sky sense only works with celestron and I dont have that brand PLUS it's 300 quid!

Plus manual almt. is easy, plus Starsense can be limited by what's visible.

[Flyingfuzz]

Here in the UK daylight saving is no