Celestron 6SE alignment question - Vega missing from alignment choices

[matsey]

Hi,

Quick question... last few times I've been out and tried to align with the Two Star Align, Vega has been missing from the list of stars to use as alignment stars.

My suspicion is that it is because Vega is currently pretty close to the zenith, but I don't really understand why that would be a problem?

If someone knows and could explain, I'd really appreciate it... and also, does that mean that if I chose a star that moved into the zenith position later in the evening, would that affect pointing accuracy when that happened?

Thanks

Matsey

[brantuk]

Do you have it set to the correct hemisphere? (i.e. North) and with the correct time zone, date, lat, long, etc? I see no reason for zenithal stars to be missing from the list. Are you mounted in alt/az mode or eq mode on a wedge?

[matsey]

Thanks for the response. Yes, all the settings, location, datetime, etc are set correctly and it's an alt/az mount I'm using. In fact when I chose other stars the alignment works just fine (last time I chose Dubhe and Altair).

Weird...

[brantuk]

Hmm.... I do know the Celestrons and SW's work most accurate with two or three well spread stars in the same third of the sky. Goto accuracy usually improves over the session across the whole sky through use of the pointing correction facility available on both makes. But why a zenithal star is missing from your list beats me...

Maybe someone else has an idea...

[valleyman]

I have seen on some Goto's that you can set the quadrent that you are viewing.

ie: N NE E SE S SW W NW so if yours is set to one of this quadrants that Vega is not in at the time of aligning...it will not name the star.

I think there might be something in Utillities that alows you to set your viewing quadrant, but am not to sure on that......sorry.

[matsey]

Thanks for the replies.

I've just checked through the manual, and there doesn't seem to be an option to set the viewing quadrant.

I also can't see anything in the manual or on the Celestron website about avoiding stars in the zenith position, so it is starting to seem very odd. I'm actually starting to wonder if I'm going a bit crazy and have maybe just forgotten where Vega appears in the alphabet !

Skies looking promising for tonight (actually I take that back, don't want to jinx myself or anyone else... I seem to recall saying that last night and then it starting raining!).... I'll give it another go with Vega with the different alignment methods, see if I can work out what's going on.

Anyone else though with the 6SE, if they've successfully used Vega in the last week, that would be really helpful to know...

Thanks again,

[Uranium235]

Vega will only pop up once you get to the calibration stage since your alignment stars are in the west by default, and your calibration stars are in the east (depending on what time you set up of course).

[matsey]

Hmm... I do wonder if Vega has never been in the alignment list, and I've only just noticed? I've definitely used it as an alignment star in the past though, but maybe I was using SkyAlign then so didn't actually have to pick it from a list ...

And it definitely wasn't there in the list last night, but having said that I had probably the most accurate alignment I've ever achieved using Altair and Alkaid with Two Star Align, so I guess it's not a big deal... lol as long as more stars don't start going awol !!

[Donkeiller]

Have you tried "filter settings"?: the SE mount will exclude stars below and above a certain altitude. Vega is very high at the moment so may well be excluded.

You can adjust the filter settings to suit your requirements.

[matsey]

Hi Donkeiller... I think you have the answer there in that it does seem like it is being excluded because of it's altitude. I have also had a similar response from Celestron support:

if it is circumzenithal, the mount may be filtering it out MENU > SCOPE SETUP > FILTER LIMITS

However, it's not my altitude filter limit that's the culprit... that is set to the max for altitude, so what looks like is happening is that it's being automatically excluded anyway because of its position at the zenith. In fact, I've just done a little bit of testing, which does seem to confirm this theory... eg, if I set the date to a month in the past to do the alignment, or even today's date but at around 3.00am, then Vega magically reappears, but if I set it to around 10.30pm (the time I've been doing the alignment normally and when Vega is directly overhead) then it goes missing again.

I guess there must be a reason why stars at the zenith position are bad for alignment purposes, maybe someone has a proper scientific explanation for why this is, but at least I think now that my scope is behaving "as expected", even though it does seem to be somewhat undocumented !

[asteria]

I noticed the same thing last time I used the alignment on my CG-5. I was expecting Vega to appear in the list but it didn't. It seems like such an obvious choice at this time of year.

Hope you sort it out.

Ed

[Ags]

I've noticed that my SE mount typically does not offer alignment stars near the zenith. Earlier in the year I could indeed align on Vega.