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View Full Version here: : Celestron C9.25-Connecting DSLR-Advice Please


Tamtarn
24-06-2008, 09:33 PM
OK we've taken the plunge :scared: Now we need some advice from the experts

We're getting a Celestron C9.25 XLT OTA in a few weeks and we will be mounting it on our EQ6. We're going to be using our Canon 40D prime focus.

We will be using a William Optics SCT Crayford focuser and a Meade 6.3 Focal Reducer.

We need to know what other adapters we may need to attach them together.

Here is our system

Celestron OTA - WO SCT Crayford Focuser - Meade 6.3 Focal Reducer - Cannon 40D

In which order do we connect them and what extra T Adapter? joiners etc ? will we need in order to reach focus with the DSLR.

I would appreciate any feedback

Thanks David

g__day
24-06-2008, 10:51 PM
David,

I believe focal reducers always attach first, then your focuser, then a Canon DSLR specific adapter then your camera.

The Canon EOS adapter should be available from many good telescope shops.

A C9.25 (did you go for the carbon fibre - mine almost never has to be refocused as temperature changes to maintain focus) has a tremendous focal range - so I would adjust the WO focuser so its almost all the way in - focus the C9.25 till say the moon is sharp in your 40D then fine tune with the WO focuser.

Consider a power adapter for your 40D if you have a mains power source near by and a ShoeString astronomy USB -> Canon bulb cable attachment to take shots over 30 seconds from your camera (controlled by say DSLR Shutter (www.stark-labs.com - free software).

Final a focus lock or a FeatherTouch 10:1 Micro focuser is a great addition to minimise mirror shift or flop in the SCT and I reckon you need something alot better than a standard CG5 dovetail to carry that scope reliably - I went with Losmandy D bars.

Eventually add a GSO 8*50mm finder scope (under $100 at Andrews Comms) and maybe Bob's Knobs to aid collimation (and try the 30 day evaluation of CCDWare's CCD inspector to really improve your optics alignment.

Good luck - where did you purchase from out of interest?

Zuts
24-06-2008, 11:22 PM
Hi,

I am not sure this is correct? On my TV85 the reducer screws into the T-Ring and acts as a 2 inch nosepiece. So focusser, reducer, T-ring, camera.

On my C11 i dont have a Crayford, so its Giant Easy Guider, 2 inch nosepiece, T-ring, camera.

Not sure about the celestron 6.3 reducer though?

Anyway, good luck with the 9.25, that should bring those galaxies and planetaries much much closer :)


Paul

Merlin66
25-06-2008, 01:25 AM
The x0.6 focal reducer is designed to sit, from memory 120mm inside focus ie 120mm from the CCD chip.
The Canon with a T-ring adaptor is 54mm deep, so you need about 66mm.
If the focusser is longer than that, then the reducer must be placed after it and a T2 to T2 spacer (66mm)used to position the camera.
No sure about the WO focusser... is it a 2" or does it give SCT threads at the eyepiece end??
If it's 2", then an 2" ORION prime focus adaptor is a good thing to have; this gives both the option of a 2" to SCT male, and a 2" to T2 male.
Most (??) good camera shops still sell T2 spacers. Worst case, Baader do a complete range but are rather expensive in Oz.

citivolus
25-06-2008, 01:26 AM
You'll need something similar to the attached.

It is supposed to provide the "optimum" reducer to focal plane distance. On the right is a 2" threaded adapter, next is the focal reducer, followed by the Meade T-adapter (#62), followed by a Canon t-ring. Celestron has identical items to any of the Meade ones above.

If you mess with the reducer to focal plane distance, you end up changing the reduction factor, and can additionally introduce astigmatism.

I've got the C9.25 and WO Crayford focuser as well, so the above items sit on my desk pre-assembled for when I need them.

Regards,
Eric

Merlin66
25-06-2008, 01:32 AM
In Eric's photo, the ORION Prime focus adaptor provides the 2" to SCT thread section at the RHS.....

citivolus
25-06-2008, 01:33 AM
Bingo :)

Omaroo
25-06-2008, 07:01 AM
I'll take a leap of faith here and assume that the C9.25 is going to behave the same way my C8 does with a Meade FR attached.

I had great difficulty getting my 350D to come to focus with the f/6.3 FR attached unless I shortened the image train significantly from the Meade tube's 110-odd mm. The Meade adapter was still too long, and the one that Bintel sells which can be separated into a shorter length is very hard to find. Bintel is out and has been for a while.

I discovered that even better than the Meade t-adapter tube was Bintels' SCT diagonal's screw-on tube (removed). It creates a total length of 76mm between the rear element of the FR to the sensor plane within the 350D and reaches focus perfectly - even for visual.

If you contact Michael Chaytor at Bintel he'll know what I mean if you mention it to him. I showed him my fix using this section of tube and he showed be a box of these tubes that he had on his shelf which were "I don't know what to do with these" spares. They work very well and he'll sell you one at a nominal price. He agreed that the Meade tube did not work for me and was too long. Maybe the 9.25 is different, but I don't think so.

Here's mine. Good luck!

Merlin66
25-06-2008, 12:04 PM
I've just rechecked on MAPUG, Doc G quotes-
"
Focal reducers are designed, optically, to work at a fixed and specified distance from the film or CCD imager. They are best corrected for this one distance. For the Meade 0.63 focal reducer this distance is 87 mm from the rear of the lens (96 mm from the exit pupil) and for the Optec MAXfield 0.33 it is 29.5 mm. (from the rear of the lens structure) In practice the MAXfield distance of 29.5 mm is measured from the rear element of the reducer but is actually about 35 mm from the nodal point. The MAXfield is a very thick optical system. Note that all measurements are slightly approximate since the the focal reducers are thick lenses and do not have their nodal point marked on the lens mount. In this discussion, I am using the simple thin lens formulas so approximate locations for the lenses and images are sufficient. Additionally, the 0.63 reducers have considerable variation allowed for their placement. The 0.63 reducers work well from about 80 to 110 mm but with slightly different reduction ratios."

g__day
25-06-2008, 12:17 PM
I stand corrected - good to know although I a puzzled now over where I read connect the focal reducer first?

ozstockman
25-06-2008, 02:36 PM
Hi Dave,

I don't have 9.25" scope but I used to use almost the same combination(meade f6.3 reducer, Canon EOS, GSO Crayford 10:1 focuser) with my Celestron 8" SCT.
If 9.25" OTAs have the same visual back thread as 8" ones have it will be easy to connect.

You will need to remove a visual back adapter from your OTA and screw your reducer in the visual back of your OTA. Then simply screw your crayford focuser in the reducer and it's almost done. The only two things you will need are a T-Ring for 40D and a T-adapter.

I was using this one as a T-adapter with my Canons

https://www.bintelshop.com.au/Product.aspx?ID=7472

It has 2" thread to attach filters and you can use it with 1.25" eyepieces.

If you don't want it to use with 1.25 eyepieces this one would be better

https://www.bintelshop.com.au/Product.aspx?ID=7403

It has a wider diameter which means less vignetting.

They are both have M42 thread to add a T-Ring.

you can see it all connected on the first picture in my add at
http://www.iceinspace.com.au/forum/showthread.php?t=33240

There is a QHY5 shown there instead of Canon. However QHY5s have the same female 42mm thread as a T-Ring for your Canon. Thus T-Ring is missing on the picture.

cheers,

Mike

Tamtarn
25-06-2008, 03:59 PM
Thanks for the quick response with info and photos guys. I knew someone would steer me in the right direction :thumbsup:

We will take the info and advice from Eric as he is using exactly the same equipment we will be using.

Thanks for posting the pic of your set up Eric it made it easy to see what I needed.

I already have a T Adapter on order so I will just have to add the Orion 2" camera adapter and connect everything as you have.

Thanks again :thumbsup:

David

By the way have you taken any images with your set up Eric ??

Tamtarn
25-06-2008, 04:31 PM
Matthew we're not getting the Carbon Fibre OTA just the aluminum OTA.
We have much of the other equipment you mentioned already as we use the 40D on our Skywatcher 200mm Newt.

We already use a Power adapter, shoestring USB, PHD guiding and use the Canon software for long exposures and live view for focusing. And also on order Losmandy Dovetail Bar and Bob Knobs.

I'm sure there will be many more bits and pieces we will need as we get going with the SCT. It's seems a never ending spending spree once you upgrade to something different :)

Thanks for your input

David

Dennis
25-06-2008, 07:32 PM
Hi David

On my C9.25 I had the following set up:

C9.25 OTA -> Celestron x0.63 reducer -> JMI SCT motorised focuser -> Pentax *ist DS with a 2” to T-2 adapter. I haven’t tried the 40D on the C9.25 yet, but it should follow the same configuration.

Cheers

Dennis

mick pinner
25-06-2008, 08:12 PM
hi guys, why the change from the newt?

Tamtarn
25-06-2008, 09:56 PM
We will still use the Newt for a wider field Mick and the Celestron with its longer focal length we hope to image smaller DSO's such as galaxies and PN

citivolus
26-06-2008, 01:16 AM
Looking at my setup again, my distance is 105mm, which is the distance some say the 6.3 reducer was designed for. Others calculate it out as 85-87mm.

I can't help but wonder if the claim it was designed for 105mm stemmed from the fact that the #62 adapter conveniently gave that distance. The math does seem to more strongly support the 85mm number, which would require a 2cm shorter adapter, which Meade does not make.

In the end I doubt that it is absolutely critical.

Meade obscures this further by stating on their own web pages that the "optimal focus position 45mm". WTH?

I'd be interested to see a series of shots done at varying distances to see how it impacts edge sharpness, but this is more likely to be a resolvable issue with the newer designs than the classic SCT anyway.

Regards,
Eric

montewilson
26-06-2008, 05:00 AM
This should be a pretty effective set-up, not too big, not too much focal length, sturdy mount.

Apart from the optical train questions which will solve themselves when you get all your toys together, what are you going to guide with?

You are far too high up the focal length scale to use an EQ6 unguided. There are good shoestring options to do this and keep the prices down. But factor this in now or your rig will only be good for shots of the moon.

PS when you are putting it together for the first time test it looking at terrestrial objects this will save you a lot of frustration in the dark.

Tamtarn
26-06-2008, 07:55 PM
Thanks also for your input Dennis and Ric.

It seems like there are two versions of setting up the imaging train.

We have now ordered all the required items to set up either way so we will be able to try both set ups.

Tamtarn
26-06-2008, 08:20 PM
Monte we presently guide with a Skywatcher 70 x 500 ota, our guide camera is a DSI Pro and we use a GPUSB Adapter and PHD.

We are looking forward to the challenge ahead of the extra focal length.