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Dedicated planetary imaging scope suggestions

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#1 jtaylor996

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Posted 06 November 2012 - 10:16 PM

I sold my C11 a couple of years back, and I really miss doing the planetary imaging with it. I've been away from astro for those years, so I'm not sure what the hot planetary scopes are at this point.

I'm thinking of getting a scoped dedicated to this task that would be using a DBK camera, and sitting on my atlas EQ mount.

I was thinking a 12"+ reflector. But what else is out there (mak newts, go bact to SCT, etc)? Budget is ~$1500 ish on this.

What native focal ratios to look for?

Thanks!

#2 PiotrM

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Posted 07 November 2012 - 01:52 AM

I has to be big so a SCT, or a Newtonian if you have the space and mount for a such big Newtonian. C11, C14 and alike.

#3 flava

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Posted 07 November 2012 - 04:03 AM

If I had to chose a dedicated planetary scope, I'd go either with a long focal Newtonian (F9 Dobson probably) or a Cassegrain (no corrector plate) with a long focal like F15 maybe even F20.
In both cases the optical tube does not use refraction so you can get all light focused on the same plane (in the center of the field of course).
The Dobson would be IMO way cheaper.
SCT's are fine, this is what I have, but I think that optical tubes like those described above, if the optics ar good, would be better at the same diameter.
For the diameter, I used to have a 6" now I have a 10", I think that something like 14" is goos if you have good seeing. If you got bad seeing most of the time, stay with a smaller scope.

#4 Eddgie

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Posted 07 November 2012 - 09:21 AM

I am seeing more and more planetary imageing being done by Newtonians.

The focal lenght is not really an issue. You are going to have to barlow even with very long focal lenghts. I use a C14 and still have to barlow up for planets, so as long as you can get a barlow with enough magnification, then it doesn't matter what the focal length is.

I use about 7800mm and still don't quite fill the frame of my webcam chip baeed camera.

The big issue with the Newtonian is of course the problem of keeping it from vibrating. If you have breezy nights (set up in the open a lot), this can be an issue with a big Newtonian on an Atlas.

If you are a patient guy, you can also buy a 12" Dob and ship the mirrors off to be re-finished by a good optical shop. There is nothing like getting a high quality mirror in a big Newtonian. These scopes can be amazing planetary performers.

The Newtonian can also be easier to cool or you can use boundry layer fans.

Or, just go with a C11. I think your results could be better with a 12" Newt with refinished optics, but it is a lot of scope for an Atlas mount to hold steady.

#5 jtaylor996

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Posted 07 November 2012 - 04:52 PM

For vibration, does this really matter with the current stacking methods? If I'm taking 60 frames/sec, and the frequency of the vibrations is >1/60s (likely), then the stacked images will still be fine, right?

I could go C11 again, but I also did other imaging with it, and I just never got over the blobby stars... which is why I'm leaning towards a newt here.

However, with a newt, it becomes, how much focal length can the mount handle, which I just don't know. The longer the focal length, the smaller the secondary, and the better the contrast... and this is without regards to getting the proper image scale with barlows, etc (which I have 3x and 4x sieberts for planetary imaging already).

A straight cass would be super $$$, probably more than an RC scope, due to the surface figures used, and the fact that nobody uses them. I think even more gregorian scopes get made now than classical cassegranians.

Are Mak-newts no good for this stuff?

#6 Eddgie

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Posted 07 November 2012 - 06:24 PM

First, many fairly fast Newtonians have secondary mirrors that are smaller than 25%, so if the quality is decent, they can provide excellent contrast.

Second, you can always put a smaller secondary mirror in. For planetary imaging, you only need 100% illumination at the center of the field. If you put in a smaller secondary mirror, you may loose illumination at the edge of a wide field eyepice, but you may still have 100% illumination at the center of the field, and of course you will get improved contrast.

Once again, focal lenght in itself is not important. You can use various barlow lenses to get the image scale you need.

Even a decent 10" Newt with a 20% secondary mirror should o offer better contrast than a C11. And for a modest cost, you can have someone make the mirror almost perfect.

Or, you can buy something like a Discovery 10" f/6 and it will come with a very good mirror right out of the box.

But vibration is vibration.

When you are imageing at 7000mm, it is like using 500x. Even the tiniest little vibtation will make the image bounce completly off of the frame!!!!


And this is what makes the C11 a contender. It will without a doubt be more stable on the Atlas.

But performance wise, expect a good quality 10" f/6 Newt to provide an image that is as good or perhaps even better if the mirrors are excellent and you minimize he obstruction

#7 PiotrM

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Posted 07 November 2012 - 06:24 PM

For planetary I use a big SCT, and for DS imaging - small APO. Seems to be the best solution. Anything big or a SCT for DS imaging is quite hard or much more problematic than a small scope.

#8 edsplace

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Posted 09 November 2012 - 10:49 PM

Dob Dobson with tracking. I have been at this since the Phillips ToUcam pro and before Registax V1. Nothing trumps apputure in good seeing. I am using a16" dob and an 11" sct.

#9 tim53

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Posted 10 November 2012 - 12:53 PM

If all I had was $1500 and I wanted to do planetary imaging, I'd sell the Atlas mount and look for a classic Cave, Optical Craftsmen, Meade, Trecker, Star-Liner, Edmund, Criterion, or any one of a half dozen other makers I'm forgetting at the moment: 10" or 12.5" f/5-f/8 Newtonian on a GEM.

If you go with a dob, you're going to want a tracking platform or altaz tracking for imaging, raising the cost of the dob option to that of a classic Newt on a GEM anyway.

SCTs are obviously good planetary scopes as well, but they're closed tubes and large COs aren't really compensated for by their ease of setup in the larger sizes (your mileage may vary of course, that's largely just my opinion after owning several - e.g., my 10" f/6 Newtonian is easier to set up and use than my Nexstar 9.25GPS on a wedge, by a large margin).

Alternatively, if you can build your own 12.5" OTA around a set of optics, you might be able to mount something like a truss tube on that Atlas.

-Tim.

#10 old_frankland

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Posted 10 November 2012 - 03:45 PM

Are Mak-newts no good for this stuff?


The Mak-Newts are excellent for lunar and planetary, but most working class folks cannot afford one with an aperture larger than 8".....they also tend to be heavy for their aperture, and slow cooling.

#11 BKBrown

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Posted 11 November 2012 - 09:29 AM

If you are going to put it on an Atlas I would be looking for another C11. A 10" to 12" f/5 Newt will be a huge PITA if you have to set it up and take it down all the time. Balancing is a tricky proposition, amongst other things, and I think you would spend much of your time fighting your kit...instead of imaging. Just my :penny: :penny: worth, but the image below is from a C11 and a DBK21AU618.

Attached Files



#12 Rankinstudio

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Posted 11 November 2012 - 10:25 AM

I have an Atlas and am shooting planetary shots with a 10" F4.7 OTA from Orion. The Atlas handles it fine even in a slight breeze. Usually if it is breezy the seeing is trash anyway ;).

The atlas can handle the weight. You will want the wide losmandy style adapter for the dovetail and the wider dovetails from ADM or some other place. They really improve the stability of the Atlas. I have mine self hyptertuned and with a good drift alignment 7 minute pin point exposures are no problem with that scope... 40lb OTA.

The only drawback with newts is with a faster focal length the collimation has to be much more accurate. There is way less room for error and the slightest offsets can drop image quality. I can collimate in about 10 minutes, not a big deal.

I've attached my best image of Jupiter to date with my 10" scope on the Atlas. Taken with a Mono Flea3.

S.fire here at CN has a 14" newt on an Atlas. You'll have to translate the site in google, but I am going to use a set of optics for a 12.5" mirror to build a similar setup to his. He produces some of the best images that appear on this site.

http://sfire.astrocl...upgrading-tis-m

Good luck!

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#13 jtaylor996

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Posted 12 November 2012 - 11:01 PM

I did plenty of imaging with my C11 on a Cassady TGAD/ADM SBS setup with my 102/800 refractor, before I sold the C11. I'm familiar with the weight handling ability of the mount, as I had like 90# of weight on it (not counting counterweights).

I'm starting to wish I had another C11 around. Right now, my budget seems to have gone away. Seems like I'll have to shelve my plans for a later date. Thanks for the suggestions, everybody!






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