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Starting imaging


Neiman

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Hiya, I have a Celestron Advanced VX 9.25 scope and I’ve been looking to get a guidescope with camera and n imaging CMOS Camera. 

My question is do I need the guide scope ? Will it make things much easier, is it essential or advised ?

 

cheers

Neil

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2 hours ago, Freddie said:

You would be better served with an OAG on a 9.25

Thanks for the advice, don’t know a hell of a lot about them. What’s the downsides ? Are there any ? And what do you look for in a decent one ? 

Thanks

Neil

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I’ve found a Celestron Off Axis Guider. So am looking at that now. Seems it may be a bit fiddly trying to get the same focus, but I’m sure it’s somethkng I can work with. Didn’t realise I needed one. Now I do 🤩

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If you've never guided before an OAG can be tricky to set up, easier to start with a small guide scope and not worry about whether its perfectly matched to the scope focal length etc, in the past I've guided my 10" SCT successfully with all sorts of small refractors and converted finder scopes.

Whereabouts are you roughly in Kent

Dave

 

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4 hours ago, Davey-T said:

If you've never guided before an OAG can be tricky to set up, easier to start with a small guide scope and not worry about whether its perfectly matched to the scope focal length etc, in the past I've guided my 10" SCT successfully with all sorts of small refractors and converted finder scopes.

Whereabouts are you roughly in Kent

Dave

 

Hiya Dave - I’m in Herne bay. I’m happy to fiddle with the off axis guider. I just am unsure of the benefits of each ? I Understand that with an off axis guider it uses the whole aperture off the main scope to pull in light, that’s gotta be a good thing right ? 

Cheers

Neil

Edited by Neiman
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OAG only uses a small portion of the scope field of view, it is better for SCTs to match the focal length and help with mirror flop, depending on if your SCT has a mirror lock a more useful addition for imaging is an electronic focuser.

There are some regions of the sky aiming out of the Galaxy that are somewhat lacking in stars which can be a problem when using an OAG involving rotating the camera or off setting your target to try to find a guide star.

I use my 10" with and without the OAG.

Dave

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This is a case of "easy to learn" vs. "best results". At that focal length you will likely eventually get smaller RMS numbers with OAG but a small guidescope, rigidly mounted, will likely get you guiding more easily. You can probably reuse the camera for the OAG so the only sunk cost is the guidescope, which you can resell for half or better.

Having *any* guiding is likely to be a big enough improvement that a separate scope will serve you well (unless nonrigid mount, mirror flop, etc.). 

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On 01/10/2019 at 23:37, rickwayne said:

This is a case of "easy to learn" vs. "best results". At that focal length you will likely eventually get smaller RMS numbers with OAG but a small guidescope, rigidly mounted, will likely get you guiding more easily. You can probably reuse the camera for the OAG so the only sunk cost is the guidescope, which you can resell for half or better.

Having *any* guiding is likely to be a big enough improvement that a separate scope will serve you well (unless nonrigid mount, mirror flop, etc.). 

Cheers for that, still haven’t made my mind up. I know that the OAG is tougher to set up but I like the idea of it. 

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Another advantage of an OAG, is you should not have any differential flexure (which @rickwayne nodded to when he mentioned rigidity) 

Differential flexure is when parts of the imaging system shift, when others do not. This can lead to unreliable guiding. 

IMHO, an OAG is worth the hassle. You can also buy a helical focuser (if you go down the ZWO route) to make setting up easier. 

https://www.firstlightoptics.com/zwo-accessories/zwo-125-helical-focuser.html

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On 03/10/2019 at 20:12, Astro Buer said:

Another advantage of an OAG, is you should not have any differential flexure (which @rickwayne nodded to when he mentioned rigidity) 

Differential flexure is when parts of the imaging system shift, when others do not. This can lead to unreliable guiding. 

IMHO, an OAG is worth the hassle. You can also buy a helical focuser (if you go down the ZWO route) to make setting up easier. 

https://www.firstlightoptics.com/zwo-accessories/zwo-125-helical-focuser.html

Hiya - thanks for that, must admit I’ve never heard of a helical focuser before ! ! But being new to the hobby I’ll forgive myself lol. 
many thanks for the help

Neil

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Are there any negatives to using an OAG ? It does use some light from the main scope so does that pose a problem ? Are there any other problems it does cause or any other negatives ?

cheers

Neil

Edited by Neiman
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Doesn't steal any light from main scope, what can be a nuisance is getting a target nicely framed as you need to keep the sensor long edge, assuming it's not square, aligned with the prism so you can lower the prism as far into the light path as possible without encroaching on the image, this means rotating the whole camera filter wheel assembly to frame your target.

The only other problem is lack of suitable guide stars in some parts of the sky at long focal lengths, a sensitive camera like the Loadstar helps.

I use an Atik OAG with Loadstar, it has adjuster to raise / lower the prism and a rotating ring to raise / lower the camera to focus but still requires that 1.25 extension to reach focus.

Dave

Just had it apart for a spring clean so took a picture

Atik-OAG.png.d6cd5e9899bddc8fa460431d93906179.png

Edited by Davey-T
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On 07/10/2019 at 18:48, Thalestris24 said:

Hi

Imaging life would have been much easier with a shorter focal length scope but too late now... You'll certainly want a focal reducer e.g https://www.firstlightoptics.com/reducersflatteners/celestron-f63-focal-reducer.html (if you don't have an Edge model).

Louise

Hiya Louise OR anyone else, what will the focal reducer bring to the table ? Also if I had a hyperstar would I need this then as a corrector / flattener ? 

Neil

 

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3 hours ago, Neiman said:

Hiya Louise OR anyone else, what will the focal reducer bring to the table ? Also if I had a hyperstar would I need this then as a corrector / flattener ? 

Neil

 

A focal reducer would widen your field of view and reduce your pixel scale. More sky will land on each pixel. In a perfect world this would reduce the level of detail in your image but in the real world your image scale in a C9.25 is almost certain to be unreachable because tracking errors and atmospheric seeing will be the factors which limit your real captured detail. The reducer will be a big help.

Many will assert that the reducer would also reduce exposure times but this is not as simple as it seems. Beware of the Hyperstar website which is misleading. 'Exposures that take an hour at F10 take mere seconds with the Hyperstar lens.'  In my opinion this sentence implies that they are the same exposures - that is exposures of the same target - but they are not because a galaxy which fills the frame at F10 will be a tiny thing surrounded by stars and sky with the Hyperstar. If that's what you want, fine, but there is no free lunch. The F6.2 reducers are widely available second hand. And the idea that an F2 system can ever be 'easy' will find few takers in imaging circles.

I'm agonizing over whether or not to say this but... you are about to devote a fair amount of cash to set up the C9.25 for deep sky imaging. If you later regretted this you wouldn't be the first and I've had the same regrets over a similar SCT. Modern cameras are getting smaller and smaller pixels which means that longer focal lengths are becoming unnecessary and even counter-productive in some cases. And they do make life difficult.

Olly

PS The reducer does not work with the Hyperstar. They are alternatives.

Edited by ollypenrice
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6 hours ago, ollypenrice said:

A focal reducer would widen your field of view and reduce your pixel scale. More sky will land on each pixel. In a perfect world this would reduce the level of detail in your image but in the real world your image scale in a C9.25 is almost certain to be unreachable because tracking errors and atmospheric seeing will be the factors which limit your real captured detail. The reducer will be a big help.

Many will assert that the reducer would also reduce exposure times but this is not as simple as it seems. Beware of the Hyperstar website which is misleading. 'Exposures that take an hour at F10 take mere seconds with the Hyperstar lens.'  In my opinion this sentence implies that they are the same exposures - that is exposures of the same target - but they are not because a galaxy which fills the frame at F10 will be a tiny thing surrounded by stars and sky with the Hyperstar. If that's what you want, fine, but there is no free lunch. The F6.2 reducers are widely available second hand. And the idea that an F2 system can ever be 'easy' will find few takers in imaging circles.

I'm agonizing over whether or not to say this but... you are about to devote a fair amount of cash to set up the C9.25 for deep sky imaging. If you later regretted this you wouldn't be the first and I've had the same regrets over a similar SCT. Modern cameras are getting smaller and smaller pixels which means that longer focal lengths are becoming unnecessary and even counter-productive in some cases. And they do make life difficult.

Olly

PS The reducer does not work with the Hyperstar. They are alternatives.

I have already bought the f6.3 focal reducer. I’m unsure as yet whether to get the OAG or a guidescope. I’m just going to take it slowly and research the bits before I buy them. 
Thanks for your advice and thoughts, I enjoy my scope and even though you may be right about the points you make, I am going to go through the journey and see where it may take me. . . . . 
many thanks

Neil

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On ‎29‎/‎09‎/‎2019 at 07:59, Neiman said:

Hiya, I have a Celestron Advanced VX 9.25 scope and I’ve been looking to get a guidescope with camera and n imaging CMOS Camera. 

My question is do I need the guide scope ? Will it make things much easier, is it essential or advised ?

 

cheers

Neil

I agree with using a guide scope if possible . Celestron sells a Guide Scope package for $99.00 USD that is perfect for the 9.25 .  

https://www.celestron.com/products/80-mm-guidescope-package

The OAG for that will run you $259.00 USD which is 2-1/2 times price of guider scope . 

https://www.celestron.com/products/off-axis-guider

Watch this video on YouTube , this guy uses a the celestron guide scope with his 9.25 . It's just informational for how he uses the guide scope with a mono camera .  (This is not me myself , just a YT video ) 

 

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2 hours ago, Neiman said:

I have already bought the f6.3 focal reducer. I’m unsure as yet whether to get the OAG or a guidescope. I’m just going to take it slowly and research the bits before I buy them. 
Thanks for your advice and thoughts, I enjoy my scope and even though you may be right about the points you make, I am going to go through the journey and see where it may take me. . . . . 
many thanks

Neil

Sure. The advantage of the OAG is that it allows for mirror movement in the SCT. This is usually called 'mirror flop' but the term is an exaggeration. It does't flop, it may just move a bit. I would use an OAG with any reflector for this reason alone.

Olly

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44 minutes ago, celestron8g8 said:

I agree with using a guide scope if possible . Celestron sells a Guide Scope package for $99.00 USD that is perfect for the 9.25 .  

https://www.celestron.com/products/80-mm-guidescope-package

The OAG for that will run you $259.00 USD which is 2-1/2 times price of guider scope . 

https://www.celestron.com/products/off-axis-guider

Watch this video on YouTube , this guy uses a the celestron guide scope with his 9.25 . It's just informational for how he uses the guide scope with a mono camera .  (This is not me myself , just a YT video ) 

 

Hiya, thanks for all the info above. I’ve seen the video before but thanks for locating it for me again to watch. I’ve been debating the guidescope / OAG for a bit now. I believe the guidescope has been discontinued ? ? Not sure if that’s true. I can get one from a shop online for £99. But then I’d need to buy a dovetail ( got to be the orange one ) another £40/50.

So I literally just bought the OAG lol. 

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5 minutes ago, ollypenrice said:

Sure. The advantage of the OAG is that it allows for mirror movement in the SCT. This is usually called 'mirror flop' but the term is an exaggeration. It does't flop, it may just move a bit. I would use an OAG with any reflector for this reason alone.

Olly

Lol, thanks Olly, see the post above , I have been busy lol

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2 minutes ago, ollypenrice said:

Sure. The advantage of the OAG is that it allows for mirror movement in the SCT. This is usually called 'mirror flop' but the term is an exaggeration. It does't flop, it may just move a bit. I would use an OAG with any reflector for this reason alone.

Olly

This is true with older SCTs' about mirror flop but if the OTA is a recent build in the last yr or so I believe Celestron has improved MF with their new SCTs' .  Can't remember exactly where but I was just reading few days ago how Celestron improved the focuser  to virtually eliminate MF . Now how correct this info was I can't prove it since I can't find my history where I read this . It maybe somewhere on Celestrons main website . But if his scope is new this should be something the OP doesn't really have to worry about now . 

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