Updating Synscan alignment stars

[Don Walters]

I was setting up my Orion Sirius mount for the first time and what a mess! I go all the way down the list of alignment stars and see only a couple of stars that I recognize. It gets all the way to the end and loops around to the beginning of the same list. Notable stars that are visible tonight: Sirius. Regulus. Arcturus. These are the brightest stars visible in the night sky and none of them are listed as choices for alignment stars. Are you kidding me?!?!? I have less than an hour before the clouds start moving in and this is not something I should be struggling with on my first night observing with this mount. Meade got it right. What's your problem Orion???

Is there a way to modify the star list, or update the list to utilize more stars? Or modify so it will pick stars of higher magnitude? Or maybe type in the stars I wan to use for alignment?

[jambouk]

I only know the skywatcher synscan handset.

Have you entered roughly the correct time, date and coordinates? If not, it may not suggest stars which are visible to you.

What is your nearest city?

James

[jambouk]

In the handset, i think under "setup" next to "alignment" is an option called "alignment stars" - there are two options, one is to turn on or off an advanced filter (once you select the first alignment star it picks others which will give you the best possible alignment, rather than letter you pick two very close together like say castor and pollux); the other option to to order the stars by either magnitude or alphabetical.

James

[jambouk]

For your coordinates, try:

92 degrees, 20 minutes west

34 degrees, 44 minutes north

James

[Marky1973]

Thanks Don and James, was thinking the same thing last night when aligning - Vega and Capella were two very bright and prominent stars but only one came up on the handset. Will have another play!

[Don Walters]

James, I'm actually at 92 deg 33 min W by 34 deg 37 min N.    I have an iPhone and there is an app that gives me my exact coordinates.   I'm in central Arkansas, USA.  And yeah, I put in the correct date and time, however I will say that it offered me Deneb and Aquila which were both below the horizon at the time, so maybe I had something wrong with the daylight savings and it was off by an hour or so.

The stars it was offering me were in the night sky for my area, but they were dimmer than what could have been offered.  It always offered me the lesser magnitude stars in constellations that were visible.  Example:  It offered me Muphrid in Bootes, but Arcturus wasn't listed?!?!?   Other notable stars that were visible but not on the list:  Spica, Pollux and Castor.  Its almost like this system is TRYING to avoid offering me the brightest stars.  

I will try the setting you mentioned and see if that helps.   I've been doing some reading and it seems like most everyone is using Stellarium to control the mount, and by doing so they are able to pick a much wider variety of stars than what's offered on the hand controller.  I guess I will have to look into that too.  Maybe its the answer to all my problems.

[jambouk]

Make sure you have entered the latitude and longitude in the correct order.

Also make sure you have the correct time zone.

Had you already selected the first star? If so, if your version of the handset has an advanced filter, it might just want you to pick other stars which will give you the best possible alignment rather than simply ones which are bright and easy to find that might give a less accurate alignment.

Even if you have brought the kit indoors, you can still play and try and work it out as you will able to remember what sort of time it was and roughly where the stars were.

I bet is in human error... Sorry. I only say that as this is so common and i've done it myself.

Do report back.

James

[Don Walters]

Thanks James.   Yeah, maybe I'm doing something wrong and I just don't realize it.  I will look again next chance I get.  I thought I was entering the coordinates correctly.  When I got to the screens for that, it starts the line with "N" and gives some numbers that are wrong for me, but I can easily put in the correct ones for the "N" coordinate.  Then I hit enter and it starts the line with "W" so I put in the correct numbers for that coordinate.  Maybe they have to be put in a different order?  So I need to change the "N" to a "W" and put the W coords in first?  I really thought I did this part correctly.  I feel like if I had them reversed, it would be showing me constellations from the southern sky and my problem would be obvious?

[jambouk]

Don, if it suggested Deneb as a star to align on, and it was below the horizon, then something is amiss. I suspect it is something to do with the date (usually in the american format of month, day, year (which is very foreign for us in the uk as we do day, month, year)), time, time zone or co-ordinates. I suspect is it not to do with daylight saving as that would only put it one hour out, and if deneb was below the horizon then i guess it was more out than an hour as it would unlikely suggest a star which was 15 degrees or less above the horizon (in my experience).

As i say, i have not used the handset you have. You'll have to study the manual and enter all the data very carefully. I'm pretty confident it is operator error as i say, that is not meant as a slur on you, it is just a common error we all make, but luckily an easy one to resolve.

James

[ronin]

For 34N Deneb would have been up high enough, Vega would have been above it and better.

Arcturus again high and nice and easy, even Capella would have been prominent.

Did have a list of the alignment stars and they had seasons against then, just wonder if Arcturus is sort of not in season.

Data wise check the Longitude, people have had problems getting the correct number of leading zero's in, yours should be 092 but I suspect that is a bit doubtful.

One other is that if entering your own location then you will have to give it a timezone, the software likely defaults to Pacific. Which is UTC-8 you are on Central which is UTC-6 (I think that is right).

So you could have your Long+Lat correct but the timezone defaulted to elsewhere.

Arkansas does use DST so when asked that is Yes.

I know others here have commented on the alignment stars they are offered, so I suspect the criteria they use is not obvious.

[Owmuchonomy]

For 34N Deneb would have been up high enough, Vega would have been above it and better.

Arcturus again high and nice and easy, even Capella would have been prominent.

Did have a list of the alignment stars and they had seasons against then, just wonder if Arcturus is sort of not in season.

Data wise check the Longitude, people have had problems getting the correct number of leading zero's in, yours should be 092 but I suspect that is a bit doubtful.

One other is that if entering your own location then you will have to give it a timezone, the software likely defaults to Pacific. Which is UTC-8 you are on Central which is UTC-6 (I think that is right).

So you could have your Long+Lat correct but the timezone defaulted to elsewhere.

On the contrary. Both would have set by 9pm.

Arkansas does use DST so when asked that is Yes.

I know others here have commented on the alignment stars they are offered, so I suspect the criteria they use is not obvious.

[Don Walters]

At the time I was setting up, around 9pm, Vega and Deneb were not up yet.  If they were up, they were hidden behind the trees and I couldn't see them.  I checked Distant Suns on my ipad and it showed that Deneb was definitely below the horizon at the time.  It showed that Vega was right on the horizon.

Arcturus was high in the sky, and it was the first star I saw that evening, and it was conspicuously missing from the alignment list.  Capella was offered to me, but was obscured, so not a good choice.  Regulus was also high in the sky and missing from the list.

Before I upgraded to this mount, I was using a Meade with Autostar, and it would ALWAYS choose the brightest stars first.  Sirius and Arcturus were almost always used for the Autostar alignment unless I asked for something different.  

I really feel like I put in the coords correctly.  I put 092 because the defaults that were there when I started was something like 111.  I also used the -6 as my timezone, and put DST=Yes.  For the time, I put in 21:00 hours, and when I finished entering it, the handset showed "9:01 PM".

[ronin]

I was looking at Vega and Deneb at 10:00 and Vega was obvious and quite high as you are further south would have thought it was more pronounced for you.

Even if an hour earlier you are 18 degrees further south.

Meades will go for Arcturus if it is at all visible, and I suspect sometimes if it is not, they like Arcturus.

I recall one person being asked to align on Algieba which they were unsure of, whereas it did not off them Regulus or Denebola both of which are brighter. So I guess the selection and offer criteria are a bit strange.

Sounds like all the data was OK, it was just having read of similar thought I had better ask.

One odd thing to check.

I think that when you power up the display gives the Lat, Long and maybe Time Zone, check the values displayed.

There was a fault on SKywatcher Software, and Orion use the same basic setup, whereby the timezone got changed - you entered UTC-6 and it changed it to UTC+6.

Recall someone in Aus fell foul of this.

[Lonestar70]

Hi Don,

Just a thought... is your phone app set to give your location in Degrees, Minutes and seconds or are you actually entering decimal degrees by mistake.

92.33 deg W is 92 deg 19minutes  48 seconds W.... which is pretty close to 92 degrees 20mins W.

Similarly 34.37deg N would be 34 deg 22minutes and 2 seconds N... it's an easy error to make and many off us have made it.

This could account for some of the error you are getting.

Best regards.

Sandy.

[jambouk]

As long as the degrees was within a couple, it should be OK, as the suggested stars won't move much.

He needs to try again, even in the house and repeat the data entry for the time he was setting up and see what happens.

James

[Don Walters]

Well tonight was better. The first thing I noticed is what Ronin said. The keypad had me at +6 so I quickly corrected that. I changed the star listing to sort by magnitude and tonight Arcturus was on the list along with Regulus and Pollux which was different than i experienced last night. Only one I noticed that was absent from the list was Spica. But by the time I got my three star alignment I was satisfied and moved on with my life. So I guess the answer is it's possible I was 12 hours off without realizing it, which seems a bit doubtful because if that were the case, it would only offer me stars that were not visible? Or perhaps sorting by magnitude made a big difference. Either way, I think I'm good now. But this is only my second time using the mount, so time will tell. I will reply again if I see any more funny business. Thanks to all for your replies.

[Marky1973]

Don, I've had similar confusion. Playing last night I noticed that some stars seemed to come and go as I was scrolling and, from the 1st alignment, to the second, Vega suddenly appeared so it may be constantly 'thinking' about available stars? Or perhaps thinking of different ones in relation to the first.

What I did find is the alignment was still out and I ran through the PAE facility a few times until it was slewing accurately.

Glad you are getting sorted, it really does get easier! ☺

[jambouk]

Glad it's sorted Don.

[jambouk]

Marky,

Are you doing a three star alignment?

Is your advanced filter turned on? If not i would have it on.

If the filter is on, it will alter which star to use after you select one; it is trying to get the best possible combination of stars to get the best possible alignment, so it makes sense if stars were appearing or disappearing from the list after you made the first, then second selection. If you have a limited patch of sky available then turn the filter off, but try and pic stars which are reasonably far apart in both RA and dec if possible.

If your GOTO was subsequently off, there are a number of possible causes:

- you tried aligning on the wrong stars (say the mount wanted castor but you went to pollox)

- the filter is off and you picked stars which were all reasonably close and maybe on the same side of the meridian

- you have significant cone error

- the scope or mount got accidentally moved after star alignment

Depending on how your scope is attached to the dovetail, it can be very easy to reduce the cone error. Lots of info out there on this; you don't need to get to zero cone error, but if there is lots i've found it does improve go to accuracy if you can get it reduce physically. Yes a three star alignment helps to reduce the impact of cone error, but doesn't fix it altogether.

What scope were you using in which you noticed GOTO was off? And how much do you think it was off by? Was it off more in one part of the sky than another?

James

[Marky1973]

Hi James

I meant to check the filter last night but forgot, until I was half-way through the alignment process! I went for Vega in the East, Cappela which was over on the West and Kochab which was sort of North-East - the alignment wasn't massively out, so I think I was on the right stars. I then slewed to a few stars and adjusted in the PAE routine and, after 3 goes, I slewed back to capella and it was dead centre on the crosshairs in APT... when I slewed to M13 though, that was not in the centre - but at least it was on screen! I just need more practice and playing around with the equipment - I haven't even thought about cone error yet - I am working my way through the Astronomy Shed Tutorials and that is coming soon so will have a look at working on that next - baby steps for me - had about enough time to set up and align, take half an hour of  images, and then the clouds came back!.

I was using the 70ED, the first alignment was out by quite a bit, but the next two were fairly close, so I just presumed that was usual for fine tuning.

Onwards and upwards!

[Earl]

Can you use EQmod? that way you choose the alignment stars you want to use rather than the utter garbage handsets offer.

[Marky1973]

So, just to be clear Earl, you don't like the handset? 

I am planning to go down that route, but having only had the mount for a couple of weeks, i just want to get familiar with the way it works before I complicate things (in my head) will probably switch over in a month or so...

[jambouk]

Marky,

That scope and 1100d gives you a lovely wide field of view

http://www.12dstring.me.uk/fov.htm

[Marky1973]

But some of my targets are sooooooo small! 

I need to get a modded camera as well next... need to power up my wallet first.....

[jambouk]

So if targets are within a degree or so from the dead centre of the FoV, then you are not doing too badly. The PAE corrections are useful, but only appear to influence any target in the constellation you've made the PAE for, so to get it bang on, you'd need to do 20 or so PAEs for the various constellations on show at any given time. Better to do a better alignment in the first place.

Sounds like you are doing the right things by working your way through the videos. People dismiss cone error, but if it is significant, reducing it can make a big improvement in your GOTOing.

The other thing to think about, and which you'll come on to is backlash. When you lock the clutches, how much play is there in either axis? You can sometime semi-quantify this by looking at the setting circles and see how much movement there is. There are other way described to assess the backlash such as looking at a distant object on the horizon and putting the slew rate on the slowest and slewing and observing the position recorded on the handset at the start, and when you first see the distant object move. Again there are ways to correct electronically for backlash using the handset, but much better to physically reduce it.

In keeping with backlash, when doing any of your alignments, it is always good to end using the up and right arrows, so it meshes everything in the same way each time. I drop the slew rate right down to one or two and then do the final movements with up and right, else just press them a few times until I see it move a bit and I know it's meshed.

An illuminated reticle eye piece also helps, as you know you are always getting the star bang on in the centre of the FoV. Again I often found when it was pitch black, I couldn't tell if a star was in the centre of the FoV as I couldn't tell where the edge of the FoV was. There was a reticle eye piece on ABS for £25 or so, but you can get them for a similar price on ebay - you only need the cheapest one going, and you can stick it in a Barlow or Powermate and turn what is usually a 12.5mm reticle eye piece into a 6mm one and get it even tighter

I've never used EQMOD as I can't be arsed with even more leads and relying on yet more technology which invariably goes wrong in my hands. I've always managed to find stars which work from the handset.

James