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kirkster501

Which OAG for SCT please ???

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Hi guys, recommendations please for a OAG for a Celestron C9.25 for close up DSO ? I am not just buying this scope for DSO AP but also Planetary AP and visual too. However, I am going to try out DSO AP as well on my NEQ6 to complement my ED80 rig in sig.

I see there is a Orion OAG and some used Celestron OAG's on ABS.

Interested to here stories and pros and cons of each.

Rgds, Steve

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I do have one only used it once :(, I attached it to my 6" SCT and my thoughts were that it did not give me anything and it just added extra to the visual train, sorry for the negativity.

Jim

Edited by The Sailor

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The SCT gives you loads of back focus so you can get away with the big celestron and meade OAG but I wouldn't recommend it. Go for the TS 27mm one or if you have a starlight express filter wheel - use their OAG thats designed for it.

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good point themos - if you are using a focal reducer you need to put your camera a fixed distance behind the reducer to get decent reduction and star shapes. This generally means a thin OAG is best - TS do a 9mm one.....

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I've got the Orion OAG and have been very pleased with it. I've used iit with my RC at both prime focus and with a focal reducer. I've had no problems locating a guide star when using a Meade DSI 1 OSC as the guide camera - the ability to rotate the guide camera around the scope axis made it possible to locate a suitable star with not too much effort.

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The SCT gives you loads of back focus so you can get away with the big celestron and meade OAG but I wouldn't recommend it. Go for the TS 27mm one or if you have a starlight express filter wheel - use their OAG thats designed for it.

...but be aware that the earlier SX ones have this wonderfully waggly turret that pivots merrily on the lock screw and has more differential flexure than the worst guidescope you ever saw. I gather that the latest ones have this sorted and a simple brace solves the problem on the earlier ones. Just watch out for it.

I would only guide an SCT with an OAG. I love guidescopes on shortr FL refractors but at long FLs and with movable mirrors it has to be OAG.

Olly

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I use the Celestron OAG. I am yet to see/use one that comes close in terms of quality, adjustablility, ease of use. and reliability. Not only can you rotate the prism around, you can also tilt it. You wont be short of a guide star with a decent guide camera, guaranteed.

If you use it with a proper 0.63 reducer on your SCT the spacing will be correct with a DSLR.

I have a TS 9mm OAG as mentioned in the thread and I use it a lot, but like a lot of TS products, it is a poor relation in comparison to the Celestron OAG's, for instance the prism is of lower quality and smaller, it is not tilt adjustable, only marginally rotatable, and the camera fitting leaves a lot to be desired, and the supplied screws cut into and damage the alloy stalks, making future fine adjustments awkward. Furthermore it is NOT 9mm, usually coming out at 13.2mm in a typical setting.

There was a Celestron OAG in the classifieds just recently, I dont know if it is still available, I was thinking of getting it myself as a spare.

Cheers

Tim

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PS, I've been where Jim was once, make him an offer :D

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I bought a Orion delux off axis guider over a year ago,I got to say it has been the worst piece of equipment i have ever bought,Trying to find a guide star is a joke and thats with qhy5,one of the locking grub screws broke off and the locking ring to dslr slips on thread when locking total junk,thrown in cupboard to ashamed to sell it on.

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This is the OAG I have:

http://www.wexphotographic.com/buy-meade-off-axis-guider-777/p13521?cm_mmc=googlebase-extension-_-astronomy-accessories-_-camera-adapters-_-meade-777-off-axis-guider_13521&utm_source=googlebase-extension&gclid=cmpkolwcgrucftdmtaod6iaaja

Found it chunky, resides in my camera case, might ressurect it when the new observatory is open for business, see what all the fuss is about :)

Jim

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That last OAG from Meade, I've tried it but the spacing is wrong for the Antares f/6.3 reducer.

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I've only used a Celestron Radial guider. Very happy with it, nice and solid, a decent amount of movement on the guide camera arm to rotate it around to help find a guide star. I'd buy the same again, though I can't compare it to other OAGs.

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For best results a proper guide camera is a must. The lodestar is excellent, but pricey, but one of those items which is worth paying the extra for. The qhy5 is not sensitive enough to find the kind of stars you need to guide on.

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Hi thanks everyone. Does anyone know how I would get my Hutech 2" IDAS LP filter into the lightpath somehow please with an OAG - I presume it would need to come AFTER the prism pick off point but I cannot see on the radial guider pictures where it would screw in? I can't see where the filter could be inserted? I do not want to have to buy a "clip" type of filter now that I have shelled out for a IDAS.

Because of the longer exposures required with the SCT I would think that a LP filter of some description is pretty much mandatory for UK use of this setup....?

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Does anyone know how I would get my Hutech 2" IDAS LP filter into the lightpath somehow please with an OAG

Two ways seemed to work okay for me but I am not an expert on spacings. I just tried them and was happy with them for me:

- A low profile SCT to 2" adapter with filter thread between the Celestron 6.3 reducer and a 2 inch adapter on the visual back. I think it was this one:

http://www.firstligh...ct-adaptor.html

This was okay until I wanted to use a 2" Ha filter, which would have made the guide stars too faint for the guide camera after being savaged by the Ha filter, I think. So I bought some bits from the ROT system from Teleskop Service to go between the DSLR and OAG:

https://www.teleskop...OS-bayonet.html

Edited by Luke

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On 24/01/2013 at 20:37, r3i said:

I've got the Orion OAG and have been very pleased with it. I've used iit with my RC at both prime focus and with a focal reducer. I've had no problems locating a guide star when using a Meade DSI 1 OSC as the guide camera - the ability to rotate the guide camera around the scope axis made it possible to locate a suitable star with not too much effort.

What spacer did you use between the DSI and the OAG, im having trouble getting the DSI to focus.

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1 hour ago, Lenny said:

What spacer did you use between the DSI and the OAG, im having trouble getting the DSI to focus.

Lenny all credit for looking but you have asked a question in a thread over 6 years old, I'm not even sure if the poster you are asking of is still doing astronomy, you may well do better to ask the question from scratch.

Alan

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Posted (edited)
On 26/06/2019 at 12:19, alan potts said:

Lenny all credit for looking but you have asked a question in a thread over 6 years old, I'm not even sure if the poster you are asking of is still doing astronomy, you may well do better to ask the question from scratch.

Alan

It's okay, I'm still alive and kicking.

I didn't use any spacer with the DSI, I just used it without the 1.25" eyepiece adapter and screwed it directly onto the top of the OAG. I did however have a 7.5mm spacer between the back of the OAG and my QHY8L camera.  I've attached a pic showing it connect to the back of Star71. 

Hope this helps.

Star71 with OAG.jpg

Edited by r3i
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10 hours ago, r3i said:

It's okay, I'm still alive and kicking.

I didn't use any spacer with the DSI, I just used it without the 1.25" eyepiece adapter and screwed it directly onto the top of the OAG. I did however have a 7.5mm spacer between the back of the OAG and my QHY8L camera.  I've attached a pic showing it connect to the back of Star71. 

Hope this helps.

Star71 with OAG.jpg

Very pleased to hear though I have not seen you for a good while, I am fairly new to AP but do look through most stuff. I am sure you can understand my reasons for saying what I posted.

Alan.

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On 27/06/2019 at 18:50, r3i said:

It's okay, I'm still alive and kicking.

I didn't use any spacer with the DSI, I just used it without the 1.25" eyepiece adapter and screwed it directly onto the top of the OAG. I did however have a 7.5mm spacer between the back of the OAG and my QHY8L camera.  I've attached a pic showing it connect to the back of Star71. 

Hope this helps.

Star71 with OAG.jpg

Thanks a million for the reply I had tried a 7.5mm spacer between the oag and the DSI. It looks like I need about 22mm so I have spacers on order. 

Thanks again for the reply 

Lenny 

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