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Old 21-05-2018, 05:48 PM
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Slawomir (Suavi)
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Window shopping - what’s next?

Dear fellow astrophotographers,

I think it is safe to say that I’m well and truly hooked onto astro-imaging and this will be my main hobby/passion for the years to come.

I currently have a very nice 105mm f/6 that I’m enjoying very much. Having said that, sometimes I wonder if/when/why could I complement it with an instrument of a larger aperture.

I really like the simplicity of a refractor, therefore one possible candidate could be a nice 5” -5.5” refractor that should ride nicely on my Mach1 and would allow to chase smaller DSOs.

On the other hand, I sometimes wonder if a fast f/3 or thereabouts 10” Newtonian would give me even higher resolution in images needed for small targets - I’m thinking of spot sizes in a 4” vs 10”. Yes, I do understand that f/3 is quite extreme, but in theory such instrument would also ride well on Mach1 and give a similar #of arcesconds pet pixel as a 5” refractor.

But there are so many things that may require attention and extra care with such Newtonian...I had a Newtonian in the past but it was f/8 so collimation was easy and didn’t need to be very precise for my purposes at the time.

So in short - would it be worth complementing a 4” with a 5” or the difference in spot sizes (diffraction due to aperture) would be minimal and I should more seriously consider a reflector?

RC is also an option, but it would require a different camera so I’m thinking that a Newtonian would be better for me.

At this stage this is a purely hypothetical upgrade.
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Old 21-05-2018, 06:03 PM
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RickS (Rick)
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Hi Suavi,

I'm impressed with the quality of the data that Jim & Linda Powell are getting from their TEC-160FL at Deep Sky West. I share their data and it compares really well with the stuff I get from much bigger corrected Dall Kirkham scopes at SRO and DSW. I think it's a great compromise between resolution and FOV with a largish sensor (currently a STXL-16200.)

Just sayin'

Cheers,
Rick.
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Old 21-05-2018, 06:35 PM
glend (Glen)
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Have a look at the Skywatcher MN190 f5.3 Mak-Newt, focal length 1000mm.

Easy collimation, holds it for months. It's an astrograph, flat field and no coma thanks to the front corrector. No diffraction spikes, and a small secondary compared to regular newts. Fully baffled tube. Supports camera sensors to APS-C with the original small secondary, and larger formats in the recently released slightly larger secondary model. It resists dew wonderfully, just wrap a heater strap around the front corrector and it stays fog free all night. Great all rounder. Can be used visually, and takes high magnification. Large APO type image at 1/3 the cost.
Focuser is adequate to start with, and Moonlight now has a good adaptor for focuser upgrades.

And 10% off at Andrews this week.
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Old 21-05-2018, 07:03 PM
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LewisM
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FSQ-130. You KNOW you HAVE TO Suavi.
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Old 22-05-2018, 12:03 PM
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billdan (Bill)
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Benklerk has been producing some fabulous images with his 6in RC at 1350mm focal length, only $450 at Bintel. I believe the collimation on the RC6 is a lot more stable and friendly than the bigger units.

I was fantasizing about buying two side by side, and do OSC on one and Lum / NB on the other one.

Cheers
Bill
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Old 22-05-2018, 01:00 PM
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Marke (Mark)
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If you like big refractors have a close look at the Skywatcher Esprit 120 and 150 they are very nice for the money
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Old 22-05-2018, 04:44 PM
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Atmos (Colin)
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It is an interesting conundrum! From reading many many reviews of different telescopes (haven’t used many but I’ve read a lot ) I would strongly advise against going below F/4 unless you’re willing to soend the big bucks. Just look at the mechanical issues that Paul has been having with his GSO F/4. Optically they’re good but mechanically they are made to a price point that doesn’t allow the stiffness and tolerances required.

The next consideration is whether you want a complement or a replacement for your 4”. If you want a complement I’d suggest going down the path of maybe a CFF 10” RC and getting a KAF-16200 as Rick suggests. This would give you a wide field setup of 2”/pixel with the 4” and a DSO setup of 0.5”/pixel with the 10”.

If you’ve only got one mount and going to use one telescope at a time, you may as well get a single camera to make the best use of most systems

If you don’t mind a replacement, getting a 5-5.5” refractor is a good choice. If you wanted different resolutions you could use something like a QHY183M with its 2.4 micron pixels and a KAF-16200/16803 for wider fields
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Old 22-05-2018, 05:23 PM
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Suavi,

I get where you are coming from. I enjoyed my time with refractors but then I started wanting more aperture. The RC is good and has produced some nice images but then I thought about experimenting again.

I have learnt an important lesson regarding fast Newtonians, my previous experiences with Newtonians were an f7 in the 1980's and an f4.5 in the early 2000's, but an f4 and faster are a different kettle of fish. I bought the AG12 in a response to the problems I had worked with in the GSO 12" f4. I'd recommend a very careful selection of an f3 scope. I cannot at this stage make comment about the AG12, but I have seen enough good images from them to see they have a handle on mechanical issues.

I guess ultimately it depends on your budget but they get awfully expensive if you want stable.
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Old 22-05-2018, 05:31 PM
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xelasnave
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F5 reflector on a truss frame is my ideal approach.
I dont know if it works but what fun is it trying to work out what is really best☺..and how you can make it better☺
Alex
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Old 22-05-2018, 05:33 PM
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Slawomir (Suavi)
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Thank you all very much for your advices and for sharing your invaluable experiences.

This is what I really like about our IIS community - a wealth of collective knowledge and experience. I’m in no rush and will continue to ponder, analyse, dream...and keep learning to get the most of what I have.

I really appreciate everyone’s comments
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Old 22-05-2018, 06:22 PM
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I spent months umming and ahhing. Some of my astro friends here in Adelaide I am sure got sick of hearing my ruminations over which scope I should buy. It's all about budget really.
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Old 22-05-2018, 06:27 PM
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Slawomir (Suavi)
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I totally agree with you Paul about the budget being the main deciding factor. Thank you again for your advice.
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Old 22-05-2018, 07:05 PM
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Atmos (Colin)
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Maybe?
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