Guidescope or OAG

[Bosuser]

Hi

I'm sure this has probably been asked before many times; though I've gone back through this forum and cannot see any recent entries  for this topic.

I'm thinking of buying a Celestron NexGuide autoguider for my Celestron Edge 8 HD and was thinking of coupling it to either the Celestron 80mm guidescope or the Celestron off-axis guider.

Has anyone got any experiences, thoughts or advice on a Celestron autoguiding package or something else that would do the job better?

Also, if I go for the guidescope package how would that fix onto the Edge 8 HD?

Any advice will be very welcome because I don't want to get it completely wrong.

Thanks

Kevin

[ollypenrice]

I'd always guide a long FL reflector with an OAG. This is what we used on Yves' 14 inch ODK for two years here. You stop worrying about flexure and mirror flop. These might not happen with a guidescope but they can't happen with an OAG.

Olly

[bobmoss]

For the focal length of your scope you really need to be using an OAG.

[swag72]

I agree with an OAG at that focal length. Are you going to be using a focal reducer out of interest?

[Bosuser]

Thanks everyone for the advice, I'm not planning on the focal reducer just yet, it's quite pricey when added to the cost of the OAG and autoguider. That will probably be on my list for my next large purchase.

So, the OAG looks favourable - I wonder will the OAG work well enough with the Celestron NexGuide autoguider?

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[JamesF]

I'd perhaps be tempted to give your Skyris camera a whirl as a guide camera before going for the autoguider, unless you're trying to avoid using a PC?

James

[Bosuser]

Thanks James, I hadn't considered that. I've also got a Phillips 9000 which I could use.

What software would you recommend to use the Skyris as an autoguider?

Kevin

[Stu_2011]

Hi

I'm sure in read somewhere (maybe on Cloudy Nights??) that the Nexguide works best with a separate 80 mm scopes and not an OAG. I think this is recommended by Celestron as well. It was a while ago that I read this.

Thanks

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[ollypenrice]

Yes, with an OAG you do need a sensitive guide cam. The latest Lodestar should be a killer.

Olly

[JamesF]

What software would you recommend to use the Skyris as an autoguider?

I think phd would work with the Skyris.  Given that you have the kit I reckon it would be worth a go first anyhow.

James

[Steve 1962]

I've just converted from using a DMK21 618 as a guide cam through a 70mm guide scope to using a Lodestar V1 with a Starlight Xpress OAG - both using PHD2 - and I'd thoroughly recommend the OAG route.

Steve

[Bosuser]

Thanks Guys,

That's given me lots to think about.

I'll try out PHD with my Skyris to begin with and see what results I get.

Kevin

[Droogie 2001]

Hi,

As a follow up to the original post I was wondering whether the Celestron Neximage 5 would be ok to use with the Celestron OAG. The Neximage manual says it can be used for OAG so I guess yes... Has anyone tried using one? It would be nice to benefit from this feature rather than having the expense of purchasing a separate Guide camera.

Also any idea on whether the Neximage 5 is compatible with PHD?

Thanks

[ollypenrice]

The big firms are very casual in saying, 'This will work with this.' Celestron bundle big SCTs on mounts so tiny that it makes your eyes water. Folks on forums then say, 'Celestron bundle these so it must be OK.'

No, not necessarily. I'd wait for someone to come along and say 'Yes, I have it and it works.'

Olly

[JamesF]

I'd wait for someone to come along and say 'Yes, I have it and it works.'

I'd be inclined to agree.  The Neximage 5 has exceptionally small pixels.  So small that I'm really not sure what Celestron were intending when they chose it.  It does support binning which may help, but whether that's sufficient to make it genuinely useful as a guide camera I wouldn't like to guess.  As the poster already has one though there's probably little to be lost by giving it a whirl.

James

[Droogie 2001]

I certainly need to look at a OAG due to my focal length on my 8" SCT. I have read that the Nexguide is perhaps not suitable as a OAG. I think the poster had a Phillips 9000 and a Skyris so I guess still no direct comparison but just noticed on another Astronomy forum that someone has had a positive experience with the Neximage 5 so will check into this.

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[MartinB]

Your OAG will be working at the same long focal length as your imaging camera.  This means that your FOV will be small.  Also focus will need to be pretty tight.  You are best to sort out getting the guide cam par focal with the imaging cam in daylight.  Also it is a good idea to use planetarium software that gives an FOV indicator which allows you to show both the main camera and the guide cam.  The Sky does this very nicely but I guess there are plenty of alternatives which are cheaper and do a good job.  Finding a decent guide star can be a real pain in the neck at this focal length, planning in advance and knowing the best rotation for picking up a good star helps.

You are unlikely to find this easy Kevin so prepare yourself for a lot of frustration but if you are the persevering sort it should eventually start to come together.  2000mm F10 is a formidable challenge and OAG, whilst technically the right choice, is going to add to your headaches.  Good luck, it is doable!

[Wolfman_55]

I wouldn't rule out a guidescope:

I've used this set up for some time and I'm now using it with my C11. The only real problem I have is for long exposures, more than 5mins, there is some differential flexing/mirror flop coming into play. I've now got an OAG to try out, but setting it up is a bit challenging, much more so than the guidescope.

Here are some of my images mstly suing the ST80 guidescope with a QHY5L:

http://www.astrobin.com/users/wolfman_55/

Either way, good luck,

Dave

[JamesF]

I have to admit whilst I know it's probably not the best way to do it, I am also about to attempt something similar with a C9.25 and ST80.   Mainly because I have all the bits to set that up, whereas I don't at the moment have an OAG.

James

[Droogie 2001]

Martin. Apologies for what maybe an obvious answer but further to your comment regarding running a 2000mm Focal Length tube with F10 being a big challenge. How would a 8" running at F6.3 be affected I assume this would be easier to setup as the FL is reduced down to around 1260mm?

Thanks

[MartinB]

Martin. Apologies for what maybe an obvious answer but further to your comment regarding running a 2000mm Focal Length tube with F10 being a big challenge. How would a 8" running at F6.3 be affected I assume this would be easier to setup as the FL is reduced down to around 1260mm?

Thanks

Yes, you will have a bigger FOV so easier to find a guide star.  Also you will have less magnification which is more forgiving of small guiding errors.  1260mm is still a decent magnification and extra resolution beyond this is usually limited by seeing conditions.  A focal reducer isn't imaging nirvana though, you have to get the spacing right to maintain a flat field (especially relevant for APS+ sized chips) and the 6.3 Celestron reducer requires around 110 mm spacing which is enough to flex if there is much weight to the imaging train.  However, at this stage, these are relatively minor points and I think you will have a much happier time using a reducer!

[fwm891]

Both. options, why because things like galaxy's are fine with OAG's because it doesn't matter that the subject is not in the OAG's field of view. Try that with a comet and you need the guide scope as the comet unless really slow moving needs to be the object your guiding on. Even relatively short guide scopes will guide long fl's well

[Bosuser]

Thanks everyone for the advice,

I've taken the plunge and today received my Celestron OAG - thanks FLO for the very speedy delivery.

I note what Martin says and, yes, I am the persevering sort so will find a way of making the Skyris work as an autoguider on the OAG ... and as I may be saving a few quid on not having to purchase an additional autoguider I think I could well splash out on Celestron's 0.7 focal reducer. The blurb says that it increases the FOV by 46%.

Kevin

[ollypenrice]

I wouldn't rule out a guidescope:

I've used this set up for some time and I'm now using it with my C11. The only real problem I have is for long exposures, more than 5mins, there is some differential flexing/mirror flop coming into play. I've now got an OAG to try out, but setting it up is a bit challenging, much more so than the guidescope.

Here are some of my images mstly suing the ST80 guidescope with a QHY5L:

http://www.astrobin.com/users/wolfman_55/

Either way, good luck,

Dave

But, to be honest, at F10 five minute exposures are snapshots. You want to be guiding for 30 minute subs at F10. Skyglow rules, of course.

Olly

[Bosuser]

Okay guys, thanks for all the advice.

I've heeded all of your comments and now ordered the Celestron 0.7 800 HD focal reducer.

So, with the off-axis guider, Skyris camera used for guiding and the focal reducer I should be in a better position to get some decent long exposure DSOs after a bit of practice and tinkering.

Bring on autumn and some good dark skies.

Kevin