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Bresser EXOS-2 goto mount query


Graham Fletcher
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Hi guys

Can one of you knowledgeable guys help me on this one.

If I were to roughly point my mount at North and approx set the latitude at my location.

If I were then to go through the setup procedure:

inserting the date and time

setting to BST

Then doing a 2 star alignment and adjusting to get both stars in the middle of the field of view.

Then selecting a target and the mount would slew to that target.

Would the resultant target be in the centre of the FOV seeing as I would not have done an accurate polar alignment?

regards

Graham

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In theory I think yes, but the closer the better.  Using a 2 star alignment (both stars on the same side of the meridian) the mount should be able to calculate where it thinks the RA axis is pointing so if your target is on the same side of the meridian as the alignment stars it should go to the correct location. If you do a meridian flip to the target then all bets are off and a 3 star alignment is required to adjust for any cone error.

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Pretty much Graham

As Clive says your target would have to be on the same side of the pier as your alignment stars.

If this is for visual you will get away with a single star alignment so long as it is close to your target.

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At 10pm BST. Am I right in thinking that if Regulus had gone past due South by 10pm BST then it is the other side of the meridian than Arcturus is?

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Yes, at 22 hr BST last night, from my location (NW Leics), Regulus had an azimuth of 203 deg and Arcturus had azimuth of 116 deg. 

 

I'm not familiar with the EXOS mount but my SkyWatcher mount for that date and time offers Arcturus (Az 116) as the 1st choice for the 1st alignment star and Vega (Az 51) as the 1st choice selected by the mount for the 2nd alignment star, so are ideal for a target East of the meridian.  If I scroll down through the list of choices offered for the 1st alignment star (they are listed alphabetically) the first I find west of the meridian is Capella (Az 302) and then the 1st choice for the 2nd alignment star selected by the mount is Procyon (Az 243) so ideal for targets West of the meridian.

 

If your target is to the east of the meridian, you could still select alignment stars west of the meridian and the force the mount not to do a meridian flip before you slew to your target, but just be careful your scope will not end up colliding with one of the tripod legs as it slews!

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Thanks for that Clive.

one thing I have noticed with this mount is that it only gives you 3 maybe 4 alignment stars to choose from!!

I would have thought that there would have been many more than that.

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Yes, that does seem a small quantity of stars. For my mount here are just over 200 named stars that can be chosen as the first alignment star.  50% are probably only visible from the southern hemisphere and about 50% of the remainder are below the horizon so leaving a choice of about 50 stars.  And then you've got local sky obstructons so the number of 1st alignment stars is further reduced.

 

Since the difference of the RA and DEC between the 1st and 2nd alignment star has to be within certain limits, the number of 2nd alignment stars choices is even further reduced.

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Posted (edited)

I wonder if any of you guys can help me with the initialisation of the handset.

I insert the name of my town : Telford

Then enter my latitude : 52 degs 42 mins 16 secs  N

Then enter my longitude 2 degs 31 mins 38 secs W

Then it asks for my “Zone” . What should I enter against this?

Edited by Graham Fletcher
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Thanks Clive

I think it has to be in the format W- - or E- -

so I guess I should put in :  W00

what do you think?

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2 hours ago, Graham Fletcher said:

Thanks Clive

I think it has to be in the format W- - or E- -

so I guess I should put in :  W00

what do you think?

Probably as good a guess as any, but I'm a bit concerned if you can only enter hours if it is actually asking for the local time zone. Does the mount also ask if Daylight Saving Time is in force?

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Zone does appear to refer to the local time zone and it also appears that it does only accept integer hour values. (Perhaps they dont sell any mounts in India (E5:30)!). So either E00 or W00 should work.

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I have followed Astro Baby’s procedure for polar settings. Adjusting the RA scale and the date scale to 23.00 hrs and 10th Oct when Polaris is at its highest point (shows Polaris position on the reticule at the bottom due to inverted image.) Everything okay. My question is that when I want to adjust the RA scale(for the time I want to polar align) in line with todays date, do I use GMT or BST for the time I wish to polar align?

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Since the local hour angle is based upon UTC and the local longitude then I would say use GMT rather than BST

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Thanks Clive. That was my thinking too. So to summarise , if I was to go out with the intention to polar align at 22.00 hrs this evening I should set the RA time to 21.00 hrs?

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I haven't seen the Astro Baby's procedure for polar alignment and have never used the setting circles for polar alignment, so to be honest, I haven't a clue!

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