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Old 14-07-2015, 10:57 PM
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Atmos (Colin)
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Looking for some telescope advice

Hello everyone,

In recent times I have bought myself a new (old) EQ6 Pro from a member here, bought a new (old) CCD from a member here. Now I feel like I need to upgrade a telescope!

I have been doing near solely visual astronomy for a decade or so now and I have more recently caught the AP bug. Definitely NEVER going to give up on VP but I do want to begin to focus more on AP.

To help fund this I am planning on selling some more telescopes. SW 100ED will most likely go, as with the 16" Meade Lightbridge (as fantastic as it has been at my dark site, just don't get used often enough) and then there is the el'cheapo SW 10" F/4.7 Newt (blue). I guess it even really depends on what telescope I choose to go with in the future depends on whether I keep the trusty and faithful LX200 GPS 10" ACF. It's half decent for AP but it does suffer from more field curvature than I would like and i don't think it is correctable within an already "corrected" SCT.

As for my actual budget, not 100% sure! Gotta wait and see what the taxman is going to be giving back

Really though, I am unsure what path I want to go down. Refractor, reflector? Currently have a ST2000XM with 7.4 micron pixels but I am thinking about moving to something with an 8300 in the future, its a sensor that's all the rage!

A part of me wants to spend that bit extra and get a Skywatcher Esprit 150ED Triplet. $7,000 as is and it's probably starting to encroach on the 20kg limit after accessories. I have Hence, for a refractor I am probably stuck at the 120-130 range. With the shorter focal lengths I guess I can drizzle more resolution out when doing photometric studies.

On the other hand I could get a carbon fibre RC-8 F/8 and get it all upgraded for ~$4,500. Of course, then there is the thermal tube currents to contend with that do not appear with a refractor as much. Plus there is the 50% central obstruction and the spider veins messing up with my nice pristine airy disk and giving those nasty diffraction spikes (don't mind them at times but prefer not to have them if I can help it, I mean, they can be added later ).

Not really sure how well the Celestron's Aplantic-Cass compares to the Meade ACF SCT, so my hype coming from both of them, never know who to believe. I do like the idea of the Fastar/Hyperstar, seen some great images come out of them but I am just waiting for the "BUT". Almost seems a little too good to be true. "Works great for deep at F/10-11... But wait! You can also do F/2!"

There is a good chance I'll probably just end up keeping my eyes on the second hand market and see what pops up. Just hoping to get some ideas on a direction to head towards from people that have practical experience. Technically I am an astrophysicist so I should really just go with an RC simply because that is what the "big boys" use

I am open to suggestions
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  #2  
Old 14-07-2015, 11:24 PM
raymo
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A great choice would be the 190mm Mak/Newt. Great images, room for
the weight of accessories, and cheaper than your mentioned scopes.
raymo
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Old 14-07-2015, 11:40 PM
DJT (David)
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It's probably driven by what you want to image? Your ST2000 is pretty good for photometry?

Cool down on the RC8 is pretty fast by the way and I haven't seen much in the way of issues with thermal currents. Surprisingly, focus holds very well, as does collimation when you stop tinkering with it.
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Old 14-07-2015, 11:55 PM
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Shiraz (Ray)
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Quote:
Originally Posted by raymo View Post
a great choice would be the 190mm mak/newt. Great images, room for
the weight of accessories, and cheaper than your mentioned scopes.
Raymo
+1 - may need to keep a close eye on weight though.
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Old 15-07-2015, 12:24 AM
glend (Glen)
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Quote:
Originally Posted by raymo View Post
A great choice would be the 190mm Mak/Newt. Great images, room for
the weight of accessories, and cheaper than your mentioned scopes.
raymo
Well I am biased because I have one, but I do agree its a great scope. Weight hasn't been much of an issue, it's still lighter than my 10" imaging newt. Sits on a NEQ6 nicely.
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Old 15-07-2015, 08:56 AM
loc46south (Geoffrey)
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Hi - My two cents worth - if the SW100ED you have is the old GOLD Pro model hang on to it and use that one for a starter - it is the second telescope I bought, even though it is slow at f9 it is still a very good imaging scope for the price with good optics and a nice flat field.

Attached is a pic of NGC2070 taken with a ST4000XCM to give some idea - picture is unprocessed apart from a stretch.

Cheers
Geof Wingham
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Old 15-07-2015, 10:07 AM
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rmuhlack (Richard)
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What image scale do you want, as that will dictate focal length. As per Ray's thread from a few weeks ago, sensitivity is related to pixel size (fixed now for you at 7.4 um) and f-ratio. So then, considering those factors (image scale and f-ratio) together with the load limits of your mount, will help narrow down the choices.

ps for imaging, i'd caution against loading an EQ6 all the way up to the 20kg limit. My own current deep-sky setup (modified VC200L with ST10XE, filterwheel, robofocus and extra guidescope) would be about 14kg, and I reckon that is about as much as i'd want to go.
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Old 15-07-2015, 10:29 AM
glend (Glen)
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Quote:
Originally Posted by rmuhlack View Post

......ps for imaging, i'd caution against loading an EQ6 all the way up to the 20kg limit. My own current deep-sky setup (modified VC200L with ST10XE, filterwheel, robofocus and extra guidescope) would be about 14kg, and I reckon that is about as much as i'd want to go.
Agree absolutely, I try to keep the weight of all the imaging gear on the NEQ6 to 15kg, and that's on my pier. My 10" imaging newt just gets within the limit and the MN190 is a little lighter.
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Old 15-07-2015, 10:33 AM
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Speaking of the Vixen VCL200 that is an amazing scope. I have often been surprised at the quality of images from those. I would get that over a MN190. I don't recall ever seeing quality images from one of those but then they may not be used for imaging too much. How small is the central obstruction? Imaging really needs it to be large not small.

Greg.
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Old 15-07-2015, 11:09 AM
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Atmos (Colin)
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Quote:
Hi - My two cents worth - if the SW100ED you have is the old GOLD Pro model hang on to it and use that one for a starter - it is the second telescope I bought, even though it is slow at f9 it is still a very good imaging scope for the price with good optics and a nice flat field.
I think the only reason I'd get rid of this one is if I upgraded with another refractors. As much as I love my LX200 for visual work, it has nothing on that little ED when it comes to Luna viewing.

Quote:
What image scale do you want, as that will dictate focal length
Thought I'd mentioned that but I guess I didn't, that's what I get for starting a thread moments before going to bed! I am aiming for 1-1.4 arcsec/pix. At that scale it works well when seeing isn't fantastic and leaves some wiggle room for drizzling out some finer details when seeing is good.

Thinking about it this morning id either end up getting a 8300 sensor (5.4 micron) or for a shorter refractor, something along the lines of an Atik 460 (4.54 micron) so there is a bit of overlap in FL but ultimately, 670 - 1150 mm.

At the moment I am not too fussed with the pixel scale I get with the ST2000XM as I am looking at upgrading in the future.
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Old 15-07-2015, 11:25 AM
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The longer the focal length the more precise the fine tuning must be. This can lead to frustration, but can be rewarding with persistence.

I concur about deciding on the image scale you want to achieve. The targets you want to image will dictate this factor. In particular how much detail do you want to show.
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Old 16-07-2015, 07:48 AM
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Atmos (Colin)
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It occurred to me late night as I was trying to fall asleep that I was trying to break the laws of physics in my mind! Yep, didn't even take into consideration the Rayleigh Criterion of telescope aperture.

So, now I have narrowed it all down to a 120-130 triplet refractor. A TV or Tak would be nice, maybe in 20 years haha

Off the top of my head this puts the SW Esprit 120mm, WO 132mm, Sky Rover 115 and 132 (triplet Lanthenum or something).
What would ya'll suggest?
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Old 16-07-2015, 03:26 PM
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Shiraz (Ray)
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you don't really need to consider scope resolution for DSO imaging with most scopes - provided there are no major aberrations. The atmosphere will determine the FWHM, not the scope (ie you will be pretty much seeing-limited with all but the smaller refractors in Australian conditions).
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Old 16-07-2015, 04:43 PM
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As this site has shown very clearly these last 2 years, incredible images can be achieved with smaller aperture high quality optics (which are becoming easier and easier to get) and a smallish CCD like the Sony sensors or the KAF8300.

100mm, 106, 120, 130. All good. Whatever you can afford. Larger sensors is where the cost rises exponentially for a smaller and smaller gain.

KAF8300 coupled with a 120mm scope should nail every bright extended object with years of imaging choices and do very very well.

3nm narrowband filters have also shown that dark skies are not a prerequisite either except for LRGB imaging.

Greg.
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Old 16-07-2015, 09:47 PM
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Atmos (Colin)
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Well right now I have narrowed my search down to either a Sky Rover 115 or 130. From my research both use the FPL-53 glass, have no idea what the Lanthanum glass is, about to do some more digging. It is basically a rebadged United Optics (Kunming) and possibly optically identical to the WO132.

Going to get a QHY9, 50ºC below ambient cooling! KAF8300 and should end up with a pix scale around the 1.5 mark which should work really well.
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Old 17-07-2015, 08:36 PM
kosh
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Hi colin,

I have a QHY9S mono with a 127mm triplet and I'm very happy with it. You will have plenty of fun if you decide to go with the setup you mentioned above.

Goran.
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Old 17-07-2015, 10:40 PM
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Atmos (Colin)
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Hi colin,

I have a QHY9S mono with a 127mm triplet and I'm very happy with it. You will have plenty of fun if you decide to go with the setup you mentioned above.

Goran.
That's good to know! I've placed my order for the 130mm, QHY9M and finderscope, hopefully pick it up in about two weeks :-)
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Old 18-07-2015, 08:19 AM
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rmuhlack (Richard)
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Have you decided what field flattener you will use?
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Old 18-07-2015, 01:39 PM
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Atmos (Colin)
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Have you decided what field flattener you will use?
Sky Rover ED Flattener/Reducer. Has the more typical 0.8x but should fully illuminate my full frame DSLR. Has ~65mm back focus.
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