ED 80 vs ED 100

[JamieDay]

I think I have finally decided to buy a nice refractor for imaging. It will mainly be DSO imaging but I will want to use my neximage on planets every now and then as well. There are two candidates for my next purchase a new skywatcher evostar 80 ed or a used, but good condition evostar 100 ed. I realise the 80 has a wider field of view but would it be ok for imaging planets as will or is it's focal length too short? The ED100 is slightly more expensive. Thanks

[shaunster]

The ED100 is pretty slow for DSO imaging at f9.. I would choose the ED80 if DSO imaging is the main aim

[JamieDay]

Yeah I thought that would be a problem. I just don't want to have to buy a new scope when I get an itch for planetary imaging

I was hoping the ED 100 might do both.

[shaunster]

I was hoping the ED 100 might do both.

It can do... and the focal reducer makes it slightly faster but its not an ideal DSO imaging scope IMO!

[martin_h]

I use both the ED80 and the 100 for imaging - with reducer attached, and the 100 tho not ideal gives me good results, tho it may take a bit longer to get those results.

[russ]

There is the option of the Ikharus 102ED from Ian King. It's priced between the ED80 and ED100, and the price includes a field flattener and 3" Crayford. And it's a faster F7 focal ratio.

There is a snag, as you would expect with such a keen price. The grade of glass is lower than either Skywatcher scope. But in practice that may not amount to too much difference. Perhaps a bit of CA in the images that could be processed out anyway.

Here's a link for you:

http://www.iankingimaging.com/show_products.php?category=171

[JamieDay]

the focal reducer makes it slightly faster

I was looking at that but the 15% decrease in focal length seems a little pointless, especially for £150.

[JamieDay]

There is the option of the Ikharus 102ED from Ian King.

Thanks for the link. It might be a little bit out of my budget as getting the evostar ED100 is only possible because it is secondhand. It is a nice scope though...

[shaunster]

I was looking at that but the 15% decrease in focal length seems a little pointless, especially for £150.

Not really!... in reality this can make a lot of difference, also if your using your DSLR you will likley need a flattener anyway whichever scope you choose

[JamieDay]

Concerning planetary work with the ED80 if I use my neximage and a 2x barlow, I will be looking at 240x mag, which is the limit of this scope. Will this be pushing it too much, or is there some tolerance there. I know that the rule of thumb is generally 50 x aperature in inches which would be 150x, so where do they get 240x from? I'm assuming the quality of the lenses allow this increase?

[russ]

Forget the 50x rule, it doesn't apply to planetary imaging, that's a visual thing. I've seen some incredible images taken with the ED80 that you wouldn't have thought possible. You'll need more than a 2x barlow though, the image scale will be tiny. This where the F9 focal ratio of the ED100 will be more beneficial. But to be honest you would probably get better results from the Explorer 150PL for planetary imaging. And save a load of cash.

I used to use an ED100 as a dual purpose imaging scope. Combined it with a Celestron F6.3 reducer for deepsky, that brought the focal ratio down to F5.67. While for planetary imaging i used it with a TV Powermate 5x. Had some reasonable results on Mars in 2005.

[michael.h.f.wilkinson]

For planetary imaging use your 10" newt with barlow (4x) and it will completely kick the backsides of both the 80 and 100 ED scopes. For planetary photography, the central obstruction is not an issue: most of the best pictures are shot with Schmidt-Cassegrains. I have both an 80mm triplet and a C8, and the C8 is much better on planets.

[JamieDay]

For planetary imaging use your 10" newt with barlow (4x)

Unfortunately I'm looking at offloading the newt to raise the funds for the refractor. The newt can't focus with my dslr with a t adapter. I will also use it very little for imaging as I will have to wait for nights when it's clear, no wind, and I'm not at work.

So I thought the refractor would be a better option.

[Horus]

From personal experience I think the 80 is a good all round scope

[michael.h.f.wilkinson]

Unfortunately I'm looking at offloading the newt to raise the funds for the refractor. The newt can't focus with my dslr with a t adapter. I will also use it very little for imaging as I will have to wait for nights when it's clear, no wind, and I'm not at work.

So I thought the refractor would be a better option.

A DSLR is not the best at planetary photography, use a web-cam instead (and stack hundreds and hundreds of frames). If you want to offload the Newtonian, and just want one scope, the 100 will be better on planets, but not by a huge margin. Just stick in a decent barlow to reach F/20 - F/25 (or even F/30 for Mars and Venus), and away you go. You can always add a little Mak (the skywatcher 127s are great in this respect) if the planetary bug bites.

[JamieDay]

A DSLR is not the best at planetary photography, use a web-cam instead

I got the dslr for deep sky I do have a neximage for planetary work.

[step_hen]

I have an ED80 and an ED100 and had the 150PL that Russ mentioned. I agree with Russ that the 150PL with a barlow (2.5x or more) is good combination on planetary with a webcam like your neximage, and i prefered that setup and got better results with it than either ED scope or the 127 Mak i just sold. TBH, all three of these scopes would be fine for planetary imaging if you barlow up to around F20- F30. The ED100 is a good all round visual scope but is slow for imaging, and really requires the flattener/ reducer which i havent bothered to get. I use a WO FF/R II on the ED80 for imaging and a 5x powermate gets used occasionally for planetary. There is a good reason why most imagers seem to have an ED80 in their collection, its a great scope, especially if you are new as its short focal length is more forgiving of tracking inaccuracies. My advice would be to save a few pennies and get a second hand ED80, and maybe a flattener and powermate with the rest of your budget. Do you plan to guide with the Meade 80mm and Neximage?

Stephen

[step_hen]

Russ how did you find that Focal reducer on the ED100?

I used to use an ED100 as a dual purpose imaging scope. Combined it with a Celestron F6.3 reducer for deepsky, that brought the focal ratio down to F5.67. While for planetary imaging i used it with a TV Powermate 5x. Had some reasonable results on Mars in 2005.

[JamieDay]

Do you plan to guide with the Meade 80mm and Neximage?

I've never used autoguiding before so I might manually guide for a bit first. Yes the Meade will be used for guiding which shouldn't be to bad as it has a focal length of 800 and it's very light.

[step_hen]

Trust me, you'll want to autoguide! you'll have everything you need to get started anyway once you buy a frac to piggyback with the Meade

stephen

[ollypenrice]

As above, forget hand guiding. You are likely to add more errors than you take away. Nighmare.

For DS imaging a fast f ratio is important. Aperture on non point sources has no bearing on exposure time, it goes as the square of the f ratio. So f10 is four times slower than F5.

The ED80 has a killer track record in DS imaging. A scope for DS and planetary does not exist in small apertures so I would hesitate to try to find a compromise between the two. My choice would be the 80.

Olly

ollypenrice's Photos

[JamieDay]

My advice would be to save a few pennies and get a second hand ED80, and maybe a flattener and powermate with the rest of your budget.

Sounds like a good idea to me. Although I havnt been able to find a secondhand ED80 in the past few weeks. I have also been looking at a secondhand Equinox ED100 as well, but it has a focal ratio of F9, it's just temping as its only £450.

[russ]

Russ how did you find that Focal reducer on the ED100?

It worked surprisingly well with the 300D. And was a very cheap option at the time (the only option i think in 2005). I picked up the reducer for £40.

[step_hen]

It worked surprisingly well with the 300D. And was a very cheap option at the time (the only option i think in 2005). I picked up the reducer for £40.

think i'll give that a bash- what was the spacing for the DSLR?

(Sorry for the thread hijack!)

[michael.h.f.wilkinson]

It worked surprisingly well with the 300D. And was a very cheap option at the time (the only option i think in 2005). I picked up the reducer for £40.

Neat idea. Maybe I could give it a bash on the 80mm F/6 (going down to F/4??)