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Old 15-09-2008, 06:53 PM
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Rockinghorse (Simon)
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Choosing a scope for imaging

Hi,
I have a 12" Dob which is GREAT for observing but not much good for imaging DSO's.

I'm thinking that rather than going for a Schmidt-Cassegrain, a more cost effective option (since I already have a largish aperture scope for visual use) might be a refractor on an iOptron mount.

My question is: am I thinking down the right track?
And if so: what apeture would I need to image DSO's (with say a meade DSI)?
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Old 15-09-2008, 07:51 PM
Ian Robinson
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Well , no .... keep the OTA and buy a good solid equatorial and you will be on the way to having a fine imaging instrument.

Even if you might need to make a few mods to the OTA ... depends on how the primary is supported by the mirror cell.
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Old 15-09-2008, 08:17 PM
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rat156
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I agree with Ian. Keep that scope, or perhaps buy a small refractor (ED80 type), but invest in a good mount. A good mount make a huge difference when imaging. Goto can be a real boon when trying to place things on a CCD chip that you can't see.

Be very careful when getting into this imaging thing, it can be very expensive if you're even the tiniest bit obsessive.

Cheers
Stuart
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Old 15-09-2008, 08:52 PM
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This question is one that I think has to be asked... How much money are you willing to spend??

Its all good and well to say keep the 12" and mount it on a good solid GEM, but do you really want to spend $4k - $6k on a gem to start imaging?

A heq5 pro, ed80, guide scope, guide cam and 350D for imaging would set you back about $2500~$3000 (roughly) and you'd be well on your way. to use the 12" for deep sky imaging, you're aiming towards spending AT LEAST $3800 for a Losmandy G11 without Gemini, you'll want some kind of push-to, so add $1k for an argo navis, rings for the 12" come in at HUGE prices, then a guide scope, guide cam and imaging cam.. you're looking at big money...

In the long run, buying a big mount is great, but if you're just getting started, theres really no need to be spending MASSIVE MASSIVE amounts of money... Although that comment coming from me sounds a bit silly...

Oh well.. food for thought I suppose...
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Old 15-09-2008, 09:50 PM
Ian Robinson
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Quote:
Originally Posted by AlexN View Post
This question is one that I think has to be asked... How much money are you willing to spend??

Its all good and well to say keep the 12" and mount it on a good solid GEM, but do you really want to spend $4k - $6k on a gem to start imaging?

A heq5 pro, ed80, guide scope, guide cam and 350D for imaging would set you back about $2500~$3000 (roughly) and you'd be well on your way. to use the 12" for deep sky imaging, you're aiming towards spending AT LEAST $3800 for a Losmandy G11 without Gemini, you'll want some kind of push-to, so add $1k for an argo navis, rings for the 12" come in at HUGE prices, then a guide scope, guide cam and imaging cam.. you're looking at big money...

In the long run, buying a big mount is great, but if you're just getting started, theres really no need to be spending MASSIVE MASSIVE amounts of money... Although that comment coming from me sounds a bit silly...

Oh well.. food for thought I suppose...
The tuberings can be home made if you have the tools.

I couldn't be bothered mucking about making my own tube-rings-clamps so I commissioned Orion Optical to make me a set to suit my new tube - which is PVC storm water pipe construction. Not all that expensive at all to get.

You actually don't need GOTO , but you do need a good solid GEM with good dual axis drives , PEC is handy too , as is a autoguider port, but , you can image OK with either PEC or an autoguider - it's how us oldies did it , by using a guiding eyepiece and manually correcting as required.

Last edited by iceman; 16-09-2008 at 06:50 AM. Reason: Removed parts against TOS
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Old 16-09-2008, 04:53 AM
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montewilson (Monte)
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I don't know if the Ioptron is an equatorial mount, if not, it is no good for imaging.

As noted below you need to decide the price range but if you are not as rich as Bill Gates here is a common, easy to use combo.......

Get a good mount, at least an EQ6 (others will say an EQ5 is OK but you need growing space that a 5 can't give) an ED80 with corrector and your choice of CCD or DSLR. Probably add a small guide scope and webcam guider too.

The mount is non-negiotable. You will give up in disgust if you don't get a good strong mount. The other bits can be taylored to your particular imaging style and object preferences.
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Old 21-09-2008, 12:36 PM
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kosh (Goran)
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I agree with Alex and monte.

Even with an EQ6 pro (something i am looking at) a 12" dob would be really heavy wouldn't it? Then add everything else like a camera guidescope etc and it's also immensely cumbersome.
I know these mounts have a large payload but i sold my 10" GSO dob about a year ago (still regret it) and i know how big that was!
Then of course there are much more expensive mounts out there as mentioned above but if you were in the market for one of those, I would guess you don't really need to worry about saving your pennies and keeping the Dob OTA anyway.
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Old 22-09-2008, 04:18 PM
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..... All i can say that the 12" Meade LX200R that i have access to, starting from the ground, the SS tube legs... SOLID, Base plate and cast tube leg mounting SOLID, Fork arms to hold OTA.... WOBBLETRON. If i get a "slight breeze" and i mean slight in the range of 3 -4km/h which is no more than walking pace, my images i chuck away. null and voiding long exposures. Im with Monte and Alex.... a ccd is SENSITIVE and will pick up a photon if it is there..... so regardless of aperature you can still take excellent photos. Put what ever it is that your going to buy (OTA wise) on a mount that far exceeds the weight capabilitys. If you live in the city.... a goto mount i say is nearly mandatory. I don't know about you guys but there isn't a star around where the Tarantchula neb lays but yet i can see it in my ep easily!... no star hopping The other thing is remember the FOV, this doesn't sound like much but when you have a SCT it reduces your FOV dramatically so go a faster scope F5 F7 ish, and finally Alt Az mounts are crappy for photography you need feild de rotators and a whole lot of other gear, go GEM polar align with drift align and youll be set for hour long exp with no problems...! so
A. Beefy GEM mount
B. Good CCD
C. Reasonable ota + Guide scope.(or get crafty and get a Dual CCD camera (one to take images and the other chip to guide) Kill 2 birds with one stone and not have a problem with alignment.
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Old 22-09-2008, 08:13 PM
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Brendan - Autoguiding doesnt solve all alignment problems... although it will continiously point at the guide star, if your alignment is incorrect, you will still get field rotation over time.

However, everything else you said, I agree with.

A wise man once told me, the finest optics in the world mean for nothing if your mount wont hold it steady.
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