NexStar+ control / 8SE Mount questions

[Solanum]

I've used my 'new' 8SE a few times now and I'm starting to really miss my Argo Navis! It'd be good pick the brains of those of you with experience with this scope.... Apologies for the length of my rambling.

1) Alignment and tracking are not spot on, OK, but not close to the AN standard. Unfortunately, there is no three star alignment mode.... Is this likely to be due to inaccuracies in positional information?

I'm in Adelaide, so am picking 'Adelaide' from the menu, but presumably this is the CBD location and I'm about 10 km away, also the 9.5 timezone can't be set, so I add on half an hour and use 10, is that a problem?

I'm starting to think that a GPS would make the set-up a lot easier/quicker, does it help improve tracking/reduce set-up time in practice? If so, how does the StarGPS compare with the Celestron SkySync?

2) The ease of accessing common objects from the database is no where near close to that of the AN and the 'sky tour' is utterly rubbish compared with the AN, it is unbelievably N hemisphere heavy, with little other than Omega Centauri in our sky. More importantly, not even objects like Eta Carina are in the database, which means NGC numbers etc. have to be entered. That means more preparation before I head out....

I appreciate there isn't much that can be done about this (I assume?), so is it worth getting a bluetooth/wifi accessory to easily control from a smartphone/tablet? Or do people find the bright screen/faffing around no quicker...?

3) Any other tips to get the best (visual) use out of this scope/mount, particularly in minimising non-observing time?

Thanks!!!

[BeanerSA]

Have you updated the firmware in the controller?

[Solanum]

Yep, although second hand the scope is only a few months old + I did an update check with it a week or two ago. They don't appear to update the NexStar+ firmware very often either...

[BeanerSA]

Okay. Is there any useful info in this thread from SGL?
http://stargazerslounge.com/topic/107834-celestron-nexstar-6se-aligned-but-not-aligned/

Having just done a bit of googling, your problem doesn't seem to be uncommon. Most of the problem can be easily resolved, except for the time zone part. There must be a workaround for that.

[Solanum]

Thanks I have seen one or two other threads similar to that, but not that one - the pertinent link in that thread seems to be: http://stargazerslounge.com/blog/832/entry-810-celestron-nexstar-6se-learning-how-to-align/

Which does suggest that an accurate GPS position may be the main factor here.... Which leaves me with the query about GPS devices in my original post. Anyone tried both?

[Camelopardalis]

For your star alignment, use a mid-high power eyepiece (10-12mm or so) or reticle eyepiece (better) and make sure the star is centred in the FOV, you can use a trick like defocusing the star to a donut to make this easier. You will need a decent finder scope and have them accurately aligned to make this easier. The star alignment can be quite accurate with practice.

I have the GPS and rarely use it...I typically observe from the same few sites and have more or less memorised the coordinates at this point. You can use google maps or similar to zoom in on your location and determine your coordinates (just remember that many sites will give you the coordinates in decimal, not the Degrees:Minutes:Seconds required by the handset). The GPS doesn't really reduce the setup time as it can take a couple of minutes to lock on to the satellites.

When it comes to the time, you can set it to timezone 0 and enter the time as UTC to avoid having to convert local time.

To improve your user experience you can interface the handset with other software...a common one is to use a serial dongle such as SkyFi and the corresponding SkySafari app on a smart phone, tablet or computer, but other combinations exist.

The 8SE is a great portable combo IMO. Hope that helps...

[Solanum]

I don't think (hope!) it is getting the star into the right place that is the problem, I was used to doing this with my AN and after alignment the AN always put me spot on, even with a high power eyepiece....



OK, thanks, I will have a go at putting in a precise location from Google/my phone and using UTC, hopefully that improves things without the expense of the GPS devices....



I'll have a look at that app and how it works, thanks again!

[Camelopardalis]

It usually won't get the alignment stars in the FOV, at least the first one. The purpose of doing the centre and align steps during the star alignment is that you're showing the software what the offset is between where it thinks the star is and where it really is. That's how it gets its bearings, and calculates its model of the sky.

The accuracy can also be affected by your choice of alignment stars. It's best to choose your alignment stars carefully, using these rules as a guide:

altitude: alignment stars should be between 20 and 70 degrees in altitude and around 30 degrees difference in their altitude
azimuth: alignment stars should be between 90 and 120 degrees apart in azimuth, and not close to 180 degrees

If you're going to be observing primarily on one side of the meridian, pick both alignment stars on that side. And for particularly faint objects, there is the Precise Goto function, where you would goto a star near the object you're after and sync on that. That improves the accuracy of the goto in that area of the sky.

And I haven't even touched on approach directions...which can affect your alignment if your scope suffers from significant backlash...most do, but it's a tricky thing to explain, so best to digest this lot first ;)

[julianh72]

Does the 8SE have the option of SkyAlign, where you do your initial alignment using any 3 reasonably bright stars or planets? I have found this to be remarkably quick and accurate on my 130 SLT and 5 SE - and you don't need to be ultra-precise with location or time.

[Solanum]

OK, thanks for all the comments. Just to clarify:

The 8SE has an automatic alignment procedure using position and date (SkyAlign), I haven't used this as I don't have those accurately (see earlier posts), this uses three bright objects. Also when I did try it a couple of times it failed (N hemisphere centric database I suspect being the problem).

It has a semi auto two star align (Auto Two-Star Align), where you pick one star, centre it and then it picks and moves to a second. This isn't always visible (obstructions etc.) and I heard it can fail regularly, so I don't use that either.

It has a solar system align, but there haven't been enough visible objects in the sky to try it.

Finally, it has a manual two-star alignment (Two-Star Alignment), which is analogous to the Argo-Navis system, which is what I have been using. I pick a suitable star and then a second one on the opposite side of the sky and centre these. So when I talk about objects not being in the field of view, I'm talking about after alignment, not the alignment stars themselves.

The Argo Navis uses three stars for alignment and does a much better job, even without accurate positional information. Sadly, that is what I am used to!

The alignment isn't massively off, but it doesn't always put an object into the field of view, which is obviously a problem for less bright objects. I appreciate that backlash etc. can be a problem and I have yet to optimise that, but this is bigger than that I think.

So I'll try better location/time info and using the precise goto function if necessary, which I haven't tried yet either. The latter being a function the AN doesn't have or need....

Then I'll have a play with the anti-backlash and see how I go.

Thanks again for the advice and I'm happy to hear more of it!

[julianh72]

Seriously, try the SkyAlign routine - it REALLY works!

Level the mount, set your location (it will remember this next time you fire up), and set the date and time. Surprisingly, location, date and time don't need to be super-accurate - location within 50 km or so is good enough, and time to within 5 minutes or so is fine. Remember that for Southern hemisphere observers, latitude is negative, and remember that it uses USA date format yy/mm/dd . For Coromandel Valley, just using "Adelaide" from the database in the handset will probably be good enough.

Pick three bright naked - eye objects for the alignment - you don't even need to know what they are, but they should be well-spaced, and not in a straight line. I understand that it actually only uses two objects for the alignment, and the third is a cross-check / calibration, which adjusts for slight levelling errors, and can therefore get better accuracy than the 2-star alignment.

[Amaranthus]

Once you've done the star alignment (I find the auto-2-star to be the fastest and as accurate as manual 2 star of course), make use of 'local sync' for high pointing accuracy in a specific region of sky.