Upgrade? ED80 to 8" Newtonian

[luka]

Hi

Would an 8" f/5 Newtonian be much of an upgrade from ED80 for astrophotography?

I know that it is trickier to set up but there is a significant gain in aperture (and almost double magnification) which would help with planetary imaging and visual as well (ED80 is not the best for either).

Also I know that HEQ5 is probably the minimum for 8" Newtonian but how would EQ5 cope with the weight? I just spent all this time/money customising my EQ5 with custom motor drive with GOTO, guiding etc. and would not like to upgrade to HEQ5 at this stage. What about for visual/planetary only?
I can see people putting even 10" on EQ5... I thought that would be crazy.

Thanks
Luka

[janoskiss (Steve H)]

Let me share my inexperience. ...

I'd invest in a focal reducer / field flattener for the ED80 (if you haven't yet) and stick with it for a while longer, i.e., at least a year: new targets come into view as the seasons pass, many well within reach of an ED80. It's easier to sharpen your skills on a small refractor than an 8" Newtonian.

But if you're keen on planets then you definitely need more aperture...

[thegableguy (Chris)]

Thanks for asking the question because I'm in the exact same camp. Have had an ED80 for less than two months and am already contemplating the next upgrade.

Thanks also to Steve for the recommendation to just slow the hell down.

Dunno about you but I'm far better off sticking with what I have and mastering at least the basics before rampaging off down the bigger aperture / longer focal length avenues. Walk before running.

You might be vastly more advanced than me - in which case I await with keen interest to hear what your next OTA is, because given another $2k to spend I honestly have absolutely no idea which way I'd go between Newt, Mak or RC.

[thegableguy (Chris)]

Also - would have thought focal length was vastly more important for planets than aperture. They're plenty bright enough, they're just reeeeally small.

[janoskiss (Steve H)]

Originally Posted by thegableguy

Also - would have thought focal length was vastly more important for planets than aperture. They're plenty bright enough, they're just reeeeally small.

You need aperture to resolve detail because of the wave nature of light (web search "diffraction limit" for more info). For visual 6-8" is pretty good. For imaging approx 8" is a minimum and up to about 16" will yield more detail. At ~16" and above atmospheric blurring and other hassles with a large mirror win out.

Re getting more focal length: that's why God gave us the Barlow.

[silv (Annette)]

I used to use an 8" newt on an EQ5 for imaging.
It's too heavy. It didn't work for longer than 13 secs.

EQ5 can carry 10 kg for visual. Half that load is recommended for astrophotography.

My 8" did weigh 8kg I think, it's a long time ago. Carbon would still be ~7.3kg - too heavy for an EQ5.

Understandable that you want to keep your trustworthy mount.
Some 6" newts weigh under 5kg, and more newts at 4" = 130mm.

Add the weight of the finder, your camera and this and that... 6" could work

But it definitely would work with an HEQ5.

Or you can get one of those cool cameras that produce such detailed images with only 1 sec exposure !!! (x2000) - then you can get away with bad tracking of an 8" on an EQ5

(Discussion of this new ZWO camera here: http://www.iceinspace.com.au/forum/s...d.php?t=144427 )

[luka]

Thanks to everybody for replies.

Chris, as Steve suggested, definitely stick with your ED80 for at least a year. I would say that your next step should be guiding, it will improve things significantly. You already have a good mount and ED80 is a great scope. Upgrading later will be easier than for me (with EQ5).

And I have been following the new ZWO camera thread... I bought my ED80 and EQ5 in 2007 and after a few years of happy imaging I had to take a break for few years only to "resume" about 6 months ago. It felt like waking after being 20 years in a coma. Everything has changed and things have advanced so much.
Perhaps I should take another break and in few more years I will be able to hand-hold my ED80 and get Hubble-like images

[Atmos (Colin)]

If you get some narrowband filters you can take images in the Hubble Palette
The other benefit to narrowband is that you also no longer have to worry about the non complete optical correctness of a doublet

[luka]

Ah, the narrowband. The holy grail of imaging. Unfortunately even the cheapest solution costs over $3K once you add filters + wheel.

I am working on a cold finger for my "new" 450D and I am sure I will try debayering it at some stage.

[janoskiss (Steve H)]

You don't need to spend anywhere near that. You can get one or two narrowband filters for a few $100 and combine the data with your RGB captures. You only need a filter wheel if you need to rapidly change between filters; like when you're doing planetary imaging, and then RGB is all you need (narrowband won't do anything for planets).

Unlike planets, DSOs don't change their "face" so there is no rush to change filters. You could even do RGB one night, H-alpha the next. A mono or at least IR-filter modded camera for narrowband stuff would be helpful but not essential.

Also, instead of a specialised filter like e.g. H-alpha or O-III, you might start out with a general purpose nebula filter, something like the DGM NPB, which will increase detail and contrast on most nebulae. You can use filter captures as e.g. luminance data (or whatever your preference).

[luka]

Thanks for your reply Steve. That is very, very, very interesting. My 1200D is already IR modded and a cold finger on my 450D is in the works. Your comments stress again that a mono DSLR should be my next step. Not having mono means 1/4 efficiency for H-alpha due to Bayer matrix. Debayering the sensors is not the easiest task though... Glen went through few sensors until he managed to debayer one.

I was actually reading more today and figured out that I cannot even use a wheel with ED80 + flattener + DSLR. The DSLR have large flange-to-sensor distance and with a flattener there is is simply not enough space/focus to fit the filter wheel
Unless I find a way to insert the wheel before the flattener...

[Atmos (Colin)]

You can get clip on filters for the Canon (Astronomik), means manual change of filters but it does allow the best of both worlds I believe.

[luka]

Colin, thank you. I didn't think of that as that spot is used up by the light pollution filter. But with narrowband filter I don't need the light pollution filter.

And you opened my eyes, I also could screw a 2" filter into the flattener. That spot is currently taken by the IR/UV cut filter :-)

Again thank you guys.

edit:
I suppose the whole exercise will eventually end up with me buying a CCD at some stage, like Glen did. The point now is buying filters etc that can be used in the future.