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CG5 question


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Hi,

What sort of exposure times would I be looking at on a CG5, with motors (not the goto version)?

Obviously I'm not expecting much, but do you think (if properly aligned) that I could expect 2-3 mins? Or is the tracking simply not that good.

Obviously no guide port on the converted model.

It may come down to price, and as this CG5 comes with a C100EDR on top ... it's very tempting!

Cheers, Jeff

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The answer depends entirely on your focal length. With a 50mm camera lens you might expect 10 minutes. With a 2 metre FL SCT it would be more like 10 seconds!

The ED100, unfortunately, has a slow f ratio and a rather demanding 900mm focal length so you would be pretty limited, around 2 mins at most for a guess and a lot of scrappers. Added to that, at F9 two minutes will not get you very deep at all.

I confirmed the spec on Celestron's website and came across a new bit of astro marketing nonesense. It is an 'apo style' refractor. Frightened of litigation, I guess, so put in the word 'style.' By all accounts the colour correction is good on this one though, alas partly because it is so slow.

Olly

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Hi Jeff - I started with one of these "kits" and had it "upgraded" with an EQ5 Sysncan. My polar alignment wasn't great (although I also had a polarscope fitted) but when tracking I could sometimes get as high as 120s, but normally 60s was about max.

As Olly said, for DSO's f9 is really too slow... but the 100ED was actually pretty good for the money (very similar to the SW100ED).

At the time I was looking to buy my first "proper" mount/scope, I was advised to look at an HEQ5/SW80ED combination. I ignored this advice as at the price, that CG5/100ED package was very attractive. However, although nothing against either the mount or the scope, I soon regretted it for what I wanted to do and I ended up selling it on within 6 months.

I did have fun with it though... :)

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I'm sure it is a nice setup for visual planetary observing in a compact format. But they don't go for high prices second hand and are discounted as in the link simply because they don't appeal to the imagers, I'm sure. I think they can use the 0.8 reducer which would help but it is still slow. Almost invariably, non-imaging refractors fetch low prices.

In truth you will want to autoguide very early on in your imaging. TBH it is a fact of imaging life that isn't going to change very soon.

Olly

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