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Guide scope for EgdeHD 8"


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Hi All,

It's been a while since i've last posted but been getting to know my scope and my over all kit and reading up on various bits and bobs in the mean time.

I'm back in the market again to make another purchase but this time i am on a tight ship.

I currently own a EdgeHD 8" on a EQ6 mount and am looking for a guide scope advise.

I did think about OAG but that's too much money and has to be complimented with a sensitive guide camera.

So, here's the thing, i need advise on which guide scope will be better? Not looking to spend any more than £200 on it.

As for the guide camera, i'm looking at ZWO ASI120 which is like killing 2 birds with one stone with the purchase.

Thanks

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humm, i know the guidescope can work, but its weight and at long fl with a eq6 it might not give satisfactory results, id really look again at OAG's and maybe save up a bit.

 

Edited by Earl
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If you're at 2000 mm then you will struggle to guide accurately with a short guide scope but if you have a reducer (1400mm) then you might get away with a finder guider or a used ST 80 maybe .Don'tt think there will be a ' budget' guiding solution for a C8 .

Good luck though 

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Cheers knobby. I am going to get the 0.7x reducer for sure.

I'm not looking to burden up my scope with a massive guide scope, was looking in to like a 50/60mm ones. Orion 50mm with helical focuser looks good so far but then again there's an APM one as well

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I use this package.  

http://www.altairastro.com/altair-80mm-maxi-finder-finder-scope-package.html

It comes with various extras and a really nice illuminated reticle eyepiece which is great for star alignment.  It is also a bit longer FL for a guidescope which may help a bit with your Edge 8" set up.  I got mine from Greenwich.  For the money its very good.

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I've very little hands on experience of guidescopes for long FL since the long FL imaging I've done has been via OAG. Testing a 10 inch Meade ACF recently at 2.5 metres FL I used the ST80 guidescope which i normally use with the dual Tak 106 rig on our Mesu 200. Using the same guide scope on the same mount but with the long FL SCT (with its mirror locked) the result was a mess. It wasn't working. The guide trace was, as ever with the Mesu, outstanding but the stars were trailing. Clearly the problem was differential flexure. Since this was only a quick test of the scope and camera I didn't try to get to the bottom of it but my only experience of guidescopes with long FL reflectors says 'no.' Your mileage may vary, as they say.

I remain convinced that the way to guide reflectors or long FL rigs is with an OAG but for shorter FL refractor guiding I prefer a guidescope.

Olly

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5 hours ago, Owmuchonomy said:

I use this package.  

http://www.altairastro.com/altair-80mm-maxi-finder-finder-scope-package.html

It comes with various extras and a really nice illuminated reticle eyepiece which is great for star alignment.  It is also a bit longer FL for a guidescope which may help a bit with your Edge 8" set up.  I got mine from Greenwich.  For the money its very good.

Which scope do you use this mate? Your 9.25"? with focal reducer i would imagine correct?

4 hours ago, ollypenrice said:

I've very little hands on experience of guidescopes for long FL since the long FL imaging I've done has been via OAG. Testing a 10 inch Meade ACF recently at 2.5 metres FL I used the ST80 guidescope which i normally use with the dual Tak 106 rig on our Mesu 200. Using the same guide scope on the same mount but with the long FL SCT (with its mirror locked) the result was a mess. It wasn't working. The guide trace was, as ever with the Mesu, outstanding but the stars were trailing. Clearly the problem was differential flexure. Since this was only a quick test of the scope and camera I didn't try to get to the bottom of it but my only experience of guidescopes with long FL reflectors says 'no.' Your mileage may vary, as they say.

I remain convinced that the way to guide reflectors or long FL rigs is with an OAG but for shorter FL refractor guiding I prefer a guidescope.

Olly

Cheers for replying Olly. I understand what you're saying but i seriously do not want to keep a leash on my spending as i'm trying to save up for a CCD package. Do you think introducing a reducer and bringing the native FL from 2032mm to 1400mm would help if i use a guidescope? Most of these 50mm guidescopes they say are better suited for FL under 1500 so i would be well within the range. If not then OAG i will have to think about. I'm not well versed with the OAG specifications but would you mind suggesting me one and can i make it work with the ZWO ASI120? I've heard people say that OAGs are most certainly good at longer FL but they have these issues where not many guide stars are available as compared to using a guidescope. Widescreen guys like i said did recommend me "Orion Deluxe Mini 50mm Guide Scope with Helical Focuser" so though i respect your knowledge and experience a lot, it has confused me even more because i do believe what you're saying but then the guys at Widescreen are saying the complete opposite thing. What shall i do :(

 

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In a fairy recent thread Steve Richards also said that OAG was the way to go for SCT imaging.  Guidestars are indeed harder to find with an OAG but with a sensitive guide camera we always found them in the 14 inch rig. I'm afraid I don't know the ASI camera at all so I don't know how sensitive it is.

Bringing the FL down will clearly reduce the required guiding precision but I gather you'll be using a DSLR at first? I don't know which one, but if we take one at random, a Canon 1100D, you'd be imaging at 0.79"PP. This is a very tall order indeed. Both the guiding and the seeing are going to be against it. An NEQ6 can, perhaps, be cajoled into giving this level of accuracy but I wouldn't bank on it, nor would I bank on the seeing letting you get anywhere near that. This is such a tall order that you are going to need all the help you can get and using a short FL guidescope will simply not do that. It will compund the diffiulty.

If your guiding fails to meet the needs of your pixel scale you might still get an image with round stars. (This merely requires your guiding errors to be random on both axes.) However, you will not be making any use of your scope's focal length. You would obtain the same level of final resolution and a much wider field of view by using a shorter focal length instrument.

Once you go to CCD (it would have to be monochrome) things start to look up because you can bin your pixels up till you have a more realistic pixel scale. (An Atik 383L binned 2x2 would give you a perfectly possible 1.64"PP.) That would be something I'd be happy to try on an NEQ6. I've plenty of experience of using these mounts at that kind of scale and they thrive.

Olly

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Many thanks for replying Olly. I totally understand that to a sensitive guide camera is required and I will also need to watch out for the spacing etc which I really really need to look in to when and if (i tell you why i used "if") i choose to go down the OAG route. DSLR is out of the question, i might still use it but only for planetary but it's not a given. I'm looking to find out exactly what i need to prepare myself for the CCD route and funny enough i was most certainly looking at the ATIK 383L (monochrome of course with the complete LRGD and narrowband filter set) which as you mentioned brings me nicely within the 1.64"PP range.

Back to the point on using "if", i don't know if this would work but I'm getting one of my minion to try this out (sort of like a DIY) jobby. Put a barlow at the guidescope and see if that works lol ok I'm no genius but I'm letting my mind go wild on this guidescope business for the FL.

In short how i understand is that introducing reducer will bring the FL down to 1400mm and most guidescopes work up to 1500mm FL so for now it should work but to make full use of my 2m FL, OAG is the way to go with it.

To be honest I'm more than happy to go down the OAG route (i like to dive in to the deep end with everything to begin with) because sooner rather than later i will have to use OAG any way but dishing out nearly £450 on a guidecam, i just can not justify myself the price. I'm not looking to produce super perfect round stars and get my image published in a magazine or anything. I just need something that will find me something to guide on.

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No, I have used it with a 4" frac and my 130 PDS. DSO imaging with my 9.25" would not be advised even reduced. Don't get me wrong it can be done but the results with my kit wouldn't meet my expectation. I'm following Olly's venture into long FL imaging though.

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1 hour ago, Owmuchonomy said:

No, I have used it with a 4" frac and my 130 PDS. DSO imaging with my 9.25" would not be advised even reduced. Don't get me wrong it can be done but the results with my kit wouldn't meet my expectation. I'm following Olly's venture into long FL imaging though.

Cheers for clarifying this for us mate. Much appreciated. I think OAG is the way i'll have to go. Now just need to find out from your good selves a less heavier on the wallet guide cam

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I'm back to square one. I called in one of the sellers to find out what they can do for me if I buy a bundle deal and their answer completely set me back.

They suggested me against an OAG route , why? their words were "Forget about the OAG because living in light polluted area will find you nothing from the 1 sq inch of prism even with lodestar", I don't know why but I sort of believed him. Instead suggested me go via the guidescope (60mm or 80mm) route and use ZWO ASI224.

Now I'm stuck ... HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!! :(

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The specs on the Edge HD reducer says it can't be used with a DSLR and Celestron's own OAG which is a pretty deep piece of kit. I *think* it might work with a SX filter wheel and OAG which is a lot thinner.

Here: at the bottom of the page

https://www.firstlightoptics.com/reducersflatteners/celestron-reducer-lens-7x-edgehd-800.html

And their OAG

https://www.firstlightoptics.com/off-axis-guiders-oag/celestron-off-axis-guider-sct.html

Compare with the SX OAG

https://www.firstlightoptics.com/off-axis-guiders-oag/starlight-xpress-off-axis-guide-head.html

Edited by DaveS
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22 hours ago, souls33k3r said:

I'm back to square one. I called in one of the sellers to find out what they can do for me if I buy a bundle deal and their answer completely set me back.

They suggested me against an OAG route , why? their words were "Forget about the OAG because living in light polluted area will find you nothing from the 1 sq inch of prism even with lodestar", I don't know why but I sort of believed him. Instead suggested me go via the guidescope (60mm or 80mm) route and use ZWO ASI224.

Now I'm stuck ... HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!! :(

WellI 'm in some of the worst light pollution in West London (Chiswick) and my Lodestar always has plenty of stars to chose from. Have stuck my Altair Astro Mini-guider in the cupboard.

Peter

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