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Canon T3 For 8" Dob?

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#1 Udderly Abducted

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Posted 09 January 2014 - 04:19 PM

Hi guys, I have the opportunity to buy a Canon T3 from a friend. I will be using it in my 8" dob. I know this isn't the ideal setup, but would it be good for the brighter planets and the Pleiades? Also, would it allow me to get some decent DSO pics with an EQ platform? I'm not real familiar with photography, but thankfully she can help me with the camera. Thanks!

#2 Jeff2011

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Posted 09 January 2014 - 09:53 PM

I have been down that road. All of the pictures on this link were taken either with my XT8 on my equatorial platform or my DSLR with lens on my platform.

Link

The first issue is that you won't be able to acheive "prime" focus with a DSLR. That is not without modifying your scope. In my case, I solved the problem by replacing the collimation bolts with longer ones which moved the primary mirror up.

Dobs are optimized for visual observing and have smaller secondary mirrors than imaging newts. Moving the primary mirror up will cause some of the light to be lost by overflowing the small secondary. I have minimized this in my case.

The other thing that drove me nuts is the difficulty in framing my target. Not easy to do with a manual push to Dob. Patience and persistance is required for this.

Long duration astrophotography will require guiding and while some top end equatorial platforms support this, they will cost you as much as a good equatorial mount like an Orion Atlas.

I still occasionally do planetary imaging with my Dob on my equatorial platform but do my DSO imaging only with my AVX mount. I have even mounted my XT8 OTA on the AVX with some decent results. However, if you want to go this route the Atlas is much better suited for this.

Have fun with it, but if you plan to get serious, your best bet is to start with a German Equatorial Mount and a short focal length refractor.

#3 Joe Eiers

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Posted 09 January 2014 - 10:04 PM

There are lots of things you can do on an EQ platform with the planets for sure, but for deep sky it's really a challenge unless you have really good EQ gear and some fancy de-rotation at the focuser. I used to have an 18" on a platform and tried to gear up for deep sky. It got REAL expensive and complex FAST. Astrophotography is already killer hard (to do right, something I'm not near achieving) on a German EQ that everything is made for.
But as I say, for Jupiter and Saturn for example, you could get some killer shots.
My 1.5 cents.
Joe

#4 Udderly Abducted

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Posted 10 January 2014 - 02:25 PM

Thanks for the info!

If I use prime focus, what would my magnification be?

I also read that a barlow can help me achieve focus. So how would that change the magnification?

Also, would I be able to achieve focus with the Baader Hyperion fixed focal lengths or zoom?

I'm not planning to get real serious with this because I don't have the time or money. I just want some semi-decent pics.

#5 Jeff2011

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Posted 10 January 2014 - 02:36 PM

Thanks for the info!

If I use prime focus, what would my magnification be?

I also read that a barlow can help me achieve focus. So how would that change the magnification?

Also, would I be able to achieve focus with the Baader Hyperion fixed focal lengths or zoom?

I'm not planning to get real serious with this because I don't have the time or money. I just want some semi-decent pics.



Magnification does not really apply, it is called image scale that is in Arc Seconds per pixel. Here is a good calculator:
http://celestialwond...eScaleCalc.html


Edit: To calculate effects of the barlow, multiply your scope focal length by the barlow magnification factor. Example 2400mm for 2x barlow assuming your scope's focal length is 1200mm.

Yes you can get focus with Hyperion Eyepieces without modifying your scope. I used one and have a special adapter that joins the Hyperion EP to the T-Ring.

Link to Hyperion and T3i

#6 Udderly Abducted

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Posted 10 January 2014 - 02:56 PM

Thanks for the fast reply! Yes, my scope is 1200mm.

How does your XT8 handle the weight of your camera and the Hyperion? Does it need a bracket? Or is it sturdy enough just attached to the eyepiece?

I don't really know how to read Arc Seconds or figure out the image scale. I'm thinking I might be better off with a Baader zoom. Would that be a bad choice?

Also, would a Canon T3 be good for videoing planets? Or would a webcam be better?

Sorry for all the questions. I know I will get it all figured out.

#7 Jeff2011

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Posted 10 January 2014 - 03:35 PM

Thanks for the fast reply! Yes, my scope is 1200mm.

How does your XT8 handle the weight of your camera and the Hyperion? Does it need a bracket? Or is it sturdy enough just attached to the eyepiece?

I don't really know how to read Arc Seconds or figure out the image scale. I'm thinking I might be better off with a Baader zoom. Would that be a bad choice?

Also, would a Canon T3 be good for videoing planets? Or would a webcam be better?

Sorry for all the questions. I know I will get it all figured out.


Yes it is quite a bit of weight, but it handled it pretty well with some flexure of the OTA. I am not aware of any bracket you could use. I don't know how the zoom would work, but it would give you different fields of view.

For planetary, I get better results with my webcam style camera (QHY5L-II), but I have seen some good results that others have done with DSLRs. Now that I have Backyard EOS, I think I could do a better job imaging planetary with a DSLR.

Personally I don't think you will be satisfied with going the way you are going. But Hyperions are good eyepieces, so if the imaging part does not work out for you, you will be able to enjoy them for visual observing.

#8 Udderly Abducted

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Posted 10 January 2014 - 04:05 PM

Alright, I think I will just stick to visual and taking pics of the moon with my iPhone held up to the eyepiece. I can get some really nice pics with my ES 68º 24mm, but the shorter focal lengths are a lot tougher.

A couple of last questions. Would I be able to frame the moon with prime focus using a 2x barlow? A 3x barlow would zoom me in even further, correct? If I knew how to tell the FOV, I could figure all this out in Stellarium.

#9 Udderly Abducted

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Posted 10 January 2014 - 04:09 PM

Oh, and I would need to use prime focus without a barlow to frame the Pleiades, correct? Would an eyepiece such as the Baader Hyperion Aspheric 31mm work? I would also need tracking, right? Or could I just stack images?

Sorry for the extra questions. Haha

#10 Jeff2011

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Posted 10 January 2014 - 04:55 PM

"Prime" focus will give you the clearest cleanest image of the whole moon. But you will need to modify your scope to reach focus.

You will not be able to frame the entire moon with a barlow. I think it would be possible with a 31 mm eyepiece using EP projection. With EP projection, the further back the camera is from the eyepiece, the larger the object will be so it is hard to determine the exact size.

Imaging DSO objects well requires tracking and in many cases auto-guiding.

The Pleiades is over 2 degrees in size and not even prime focus on your scope will frame that. If I were to image M45, I would use my 430mm focal length refractor.

If you go back to my Flickr link in my first post, you can look at my images to get a feel for what you will get. If you click on the image, I list how the image was taken, Prime, 13mm Hyperion, 2x Barlow or combination of Hyperion and Barlow. I even have some IPhone pics in there.

#11 Udderly Abducted

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Posted 12 January 2014 - 04:46 PM

Thank you very much for all the help!

#12 KelownaDave

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Posted 14 January 2014 - 08:38 AM

Several years ago I bought a Canon XTi (400d) for AP.
I wanted to use my 14.5" Starmaster for AP but the first issue is there not enough In-focus. You could modify your equipment as others have noted, but I chose to purchase a Denkmier OCS unit which enabled me to avoid wrecking a $5000+ telescope.
Although the OCS resolved the in-focus issue, there is still the complexity of exposure time when you're not tracking. Hence only very short images are possible unless you're into egg shaped stars or star trails. However things such as luna pics come out pretty decent and a first try at M42 also showed potential. Probably would get some decent images of Jupiter and Saturn too.

However I ended up buying an NEQ6 Pro mount (Skywatcher) and a 6" Ritchey-Cretien from Astronomics. I've only been at it a few months, but now I have decent equipment for both imaging and for visual use.






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