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IEQ45, 10" Astrograph, Capable of DSO?


timtrice
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I have the IEQ45 iOptron mount currently using a Nexstar 6 on but looking to upgrade to a 10" Astrograph. The mount is spec'd to hold up to 45lbs visual payload. My Nexstar is 11. My camera equipment is nearly 2lb so photographically it handles 13lbs well. The Astrograph is 25.5lbs so now I'm looking at a 28lb setup.

iOptron customer service says typically half the visual payload is the barrier for photography but then said my 28lbs should work well.

Does anyone agree/disagree?

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Totally disagree. I think the iOptron claims are way out. I've used two iEQ45s and two EQ sixes. The EQs could easily handle our TEC140 for imaging. The iOptrons couldn't handle it for visual, let alone imaging. Now the big thing that seems to make the iOptron struggle is is tube length, where the spring loaded drive motors are easily pushed out of mesh by the moment of a long OTA. A 10 inch Newt isn't long but it is a wind sail and will test the elasticity of the spring loaded drive in the slightest wind. I'm not a hater of the iEQ45 by any means. It has its virtues. However, I consider it a mount for OTAs which will not offer much resistance to where it want s to point them. Weight is a very naive and innacurate way to estimate that resistance.

To be brutally honest, the EQ6 was sitting there waiting to be de-throned and the iOptron didn't do it. It did some of it, and if you have a nice small refractor or even maybe a light, long FL imaging reflector then it might deliver. I say 'might' because it is nearly always 'might' at long focal lengths!! I've seen AP900s go AWOL so what hope the rest of us?

Olly

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So perhaps going to the 8" would be better? It is 8lbs lighter. I've already purchased the mount and from what I had read (not from iOptron but several other places) I thought I might have room to grow up to a 10-inch when ready (now). The 8" is 200mm shorter as well.

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So perhaps going to the 8" would be better? It is 8lbs lighter. I've already purchased the mount and from what I had read (not from iOptron but several other places) I thought I might have room to grow up to a 10-inch when ready (now). The 8" is 200mm shorter as well.

It would be a safer bet, certainly. A refractor would be safer still. I never tried an 8 inch Newt on the 45.

Olly

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It is worth remembering that aperture on it's own is almost irrelevant in deep sky imaging. The factors you should be considering are the focal length you want to image at, since this sets the field on your chip, and the focal ratio. Faster focal ratio is to be preferred, (up to the mechanical limit of the OTA), as this gives you more data for a given exposure time. Aperture is therefore a by-product of the focal length & ratio you choose.

e.g. I image at 50mm f/4, 300mm f/5.6, 750mm f/5 and 1,200mm f/4.7

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It is worth remembering that aperture on it's own is almost irrelevant in deep sky imaging. The factors you should be considering are the focal length you want to image at, since this sets the field on your chip, and the focal ratio. Faster focal ratio is to be preferred, (up to the mechanical limit of the OTA), as this gives you more data for a given exposure time. Aperture is therefore a by-product of the focal length & ratio you choose.

e.g. I image at 50mm f/4, 300mm f/5.6, 750mm f/5 and 1,200mm f/4.7

I agree, though the spring loaded drives of the 45 are a special case in that they have relatively low resistance to nudges or moments. So the mount can handle longish focal lengths when it's on form provided they are in a compact, short telescope. The 45 doesn't like long OTAs one bit. I'd not expect it to be good in the wind with a physically large scope, either.

Olly

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I agree, though the spring loaded drives of the 45 are a special case in that they have relatively low resistance to nudges or moments. So the mount can handle longish focal lengths when it's on form provided they are in a compact, short telescope. The 45 doesn't like long OTAs one bit. I'd not expect it to be good in the wind with a physically large scope, either.

Olly

So to image at about a metre of focal length on the iEQ45, the OP would better off with his existing Nexstar 6 and an f/6.3 reducer than an 8 or 10" Newt at f/4. What is to be gained by changing the OTA? Okay f/6.3 to f/4 will more than double the data gathered but certainly there would be little change in field of view and a lot more hassle with the mount.

What's the solution? An f/3.3 reducer <shudder>! or a change to a shorter FL wider field of view with refractor. I know that's what I would do, but it depends on the FL / field of view the OP wants.

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I'd like to see if anyone pulled it off to image with a large OTA on the iEQ45. There may well be good results out there.

As for me, I tried 1.6m and 1m and the mount transformed itself to a rather accurate metronome...

/Jesper

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So to image at about a metre of focal length on the iEQ45, the OP would better off with his existing Nexstar 6 and an f/6.3 reducer than an 8 or 10" Newt at f/4. What is to be gained by changing the OTA? Okay f/6.3 to f/4 will more than double the data gathered but certainly there would be little change in field of view and a lot more hassle with the mount.

What's the solution? An f/3.3 reducer <shudder>! or a change to a shorter FL wider field of view with refractor. I know that's what I would do, but it depends on the FL / field of view the OP wants.

I wanted to go bigger knowing my FOV would be reduced mainly so I could grab fainter objects. One of the main reasons I've always wanted to do AP was to potentially hunt for comets/asteroids or at least provide obs on new ones. Speaking of reducing FOV, what would be wrong w/ trying to mosaic DSO's that are beyond my FOV? Is that blasphemy in AP? I wouldn't care. Anyway, The Nexstar I was planning on just keeping for planetary photography and visual use when the bigger one is in op. But....

I'd like to see if anyone pulled it off to image with a large OTA on the iEQ45. There may well be good results out there.

As for me, I tried 1.6m and 1m and the mount transformed itself to a rather accurate metronome...

/Jesper

The IEQ 45 sucks with the 10-inch. No, it doesn't suck. It freaking blows. Visual use? No, that's not even the issue. This thing can't even hold the 10" and I highly doubt it can hold the 8". To say I'm disappointed is beyond an overstatement. I struggled to find a good balance w/ the 11" rod and two 11lb counterweights given. Eventually, I found this website:

http://www.robincasady.com/Astro/WeightCalc.html

So, at best, I need 35 to 70 lbs of counterweight for this scope (70lbs if weights are to be as close to axis as possible).

This is my own fault as I didn't catch the part of the iOptron's web page that said max payload 40lbs WITHOUT weights. My rig was 30lbs itself. One 11lb counterweight was not going to cut it.

Not even close.

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I wanted to go bigger knowing my FOV would be reduced mainly so I could grab fainter objects. One of the main reasons I've always wanted to do AP was to potentially hunt for comets/asteroids or at least provide obs on new ones. Speaking of reducing FOV, what would be wrong w/ trying to mosaic DSO's that are beyond my FOV? Is that blasphemy in AP? I wouldn't care. Anyway, The Nexstar I was planning on just keeping for planetary photography and visual use when the bigger one is in op. But....

Tim, this is kind of my point. You don't necessarily need to get a bigger OTA to reach for 'fainter' objects in AP; that's visual astronomy thinking. To image fainter objects you need longer exposure times or faster optics (or darker skies!). The typical Newtonian astrographs are about f/4 and that's plenty fast, if you are using an f/6.3 reducer with your Nexstar, then an f/4 Newt will be more than twice as fast. If you are not using a reducer, adding one to your Nexstar will get you f/6.3 instead of f/10 and will give you fainter objects for the same exposure time with your existing scope.

So, your mount won't take a big fast Newtonian :( but it will take a small fast Newt or smaller slightly slower APO refractor + longer exposures :) and either of those options will allow you to image 'fainter' objects :D

Mosaics are most definitely not frowned upon in AP. In fact, if pulled off well, they are held in very high esteem indeed :)

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The darker skies is a big reason I wanted to get a faster scope. I have the 6.3 reducer on my Nexstar but I also have Bortle 7 skies so long exposures won't cut it. Which is why I was even considering the 10" to begin with. I know I can do some DSO imaging w/ my Nexstar but I felt I could catch fainter objects with a bigger scope imaging. I looked for the new nova last night and snapped piggy back pics soon as I found it; I enjoyed it. But most nova aren't between 4-6 magnitude. But at the same time there's also that part of me that'd like to see some better detail in Mars, Jupiter and Saturn my Nexstar doesn't quite give me visually I was also hoping to capture for my son who has a lukewarm interest in astro right now. So basically I'm trying to just get the best of all worlds right now.

The low cost of the Astrograph was a huge selling point obviously. That's my budget for a second scope. I don't need the mount (obviously). Just a good second imaging scope I can put on for roughly the same price.

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Mosaics are the most respected of all images because they are quite tricky to do well, but very satisfying. They allow you to show 'object X' in higher resolution than with a shorter FL 'all in one' image.

Rik's right to say that for deep you need fast or long or both. Mere aperture in isolation from F ratio is meaningless.

Olly

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