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Old 01-06-2018, 03:03 PM
morls (Stephen)
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ED100 vs C8 for planetary (visual only)

Hi,

I posted a while back as I was considering an ED100 for (primarily) planetary observation. I have a vixen super polaris mount.

I visited optics central in Mitcham yesterday, just out of interest to get a look at a few scopes. A staff member, upon hearing of my plans, suggested a C8 might be a better choice. The thought had crossed my mind, but up until now I haven't looked any further into it.

At the moment I have the following assumption about the strengths and shortcomings of each:

1. Aperture rules.
  • C8 - 8 inch, but some compromise in image due to obstruction
  • ED100 - 4 inch, but no obstruction so more contrast

2. Cost - I would need to save for quite a while to get either. ED100 c.$1250, C8 c.$1500.

3. Magnification - C8 can go higher.

4. Cooling - ED100 a lot better in this regard

5. Versatility - although I want to concentrate on planetary for a good while, I'm also interested in deep sky objects. Not to the point that I want a 12" dob - that will probably come later on if I get the faint fuzzy bug.

So, this is the starting point of my limited knowledge of both scopes. I'd be very interested to hear what more experienced members suggest.

At the moment I'm thinking C8 wins easily...

Cheers

Stephen
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  #2  
Old 01-06-2018, 03:12 PM
Imme (Jon)
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I'd suggest ED100 would be a lot less 'fussy' in regards to collimation.
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Old 01-06-2018, 03:40 PM
morls (Stephen)
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Good point Jon. I'm not put off by the need to collimate - I quite like playing around with gear and getting things set up. When I had an 8" dob I really enjoyed the catseye collimation gear, and there's a certain satisfaction in getting it spot on..
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  #4  
Old 01-06-2018, 03:40 PM
casstony
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The C8 easily does better on deep sky due to extra light gathering. If the C8 is cooled and collimated it will outperform on planetary too.

Consider buying a used C8 for much less than new prices and if you're not happy with it you won't lose much at resale.
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Old 01-06-2018, 04:05 PM
Wavytone
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Even an average C8 will easily outdo the refractor on all scores except widest field, if that really matters to you.

100ED vs a C5 is a closer call and even there I'd say the C5 wins if its a good one.
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  #6  
Old 01-06-2018, 04:07 PM
brian nordstrom (As avatar)
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I have a very good 127mm refractor and C9.25 , similar in sizes to a 100mm frak and 200mm CAT and find while my refractor shows things with a little more ' Snap ' than the C9.25 in the beginning , but the C9.25 when fully cooled shows a lot more detail on the moon and planets .

Yes on an average night the 127mm shows a nicer image but I am afraid that even tho the SCT is not as sharp you do see more and thats what planetary observing is all about , eeking out detials .

Another plus for the SCT is that when I have finished looking at the planets ( we are very spoilt at the moment , but sadly it's not always like this ) deep sky is a whole lot more interesting , you can't beat physics as the 127mm is 50,677 sq mm and the C9.25 is a whopping 173,433 sq mm ,

I am lucky to have both and you have to make a choice and if it was me I would get the C8 as its mounted already , I assume the ED100 is not ? you dont say .

Brian.

ps . as you say a refractor is basically ready at a moments notice but the SCT needs cool down time , yes that's true and needs considering before going out , that's why my 127 gets plenty of air .

Last edited by brian nordstrom; 01-06-2018 at 04:44 PM.
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Old 01-06-2018, 04:13 PM
morls (Stephen)
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Thanks everyone, these are all really helpful comments.
regarding your question Brian, I'm just considering both as OTA, I have a mount already
Stephen
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  #8  
Old 01-06-2018, 04:43 PM
brian nordstrom (As avatar)
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Cool Stephen , may I ask , what mount ? .
Thanks .

Brian.
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  #9  
Old 01-06-2018, 05:01 PM
morls (Stephen)
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A vixen super polaris I picked through the classifieds here...
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Old 01-06-2018, 05:05 PM
Hoges (John)
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hmmm....my mileage seems to have varied from the norm. I had a 10" SCT (Meade) well collimated and housed outside in my observatory. Somewhere around the same time I had a friends 4" Genesis refractor on loan. Most nights, the Genesis gave a sharper, snappier and more pleasing image than the SCT. Yes, the SCT did resolve clusters a lot better and showed a bit more detail in nebulae, but not as much as we thought it would. I was never over awed about the images in the SCT whereas nearly everytime I look through my ED100, I am very pleased with the sharpness and contrast. Maybe it's a combination of my astigmatism and prescription glasses but I've just always kept coming back to a refractor.

I love the physical format of the SCT/MAK - easy to mount and doesn't suffer from vibration as much as a longer scope. Maybe SCT's have got a lot better than they where when I bought my Meade around '97.

I've had my ED100 probably longer than any other scope I've owned and am really pleased with it but if I was in your position looking for a good planetary scope that could handle some deep sky stuff and stay small and portable, I'd also consider a 150/180 Mak. I recently got a 127 Skymak and it's not far off the ED100 in contrast and sharpness and gives a reasonable size field with a 2" diagonal and 27 Panoptic.

Mind you, C8, ED100, 150/180 Mak - all pretty darn good scopes that would provide years of viewing pleasure and all easy transportable. Can't go too far wrong either way. Since you're going to be saving for a while, see if you can get to Heathcote (ASV dark sky site), Vicsouth or Snake Valley - you're bound to be able to look through a few examples of each. If you want to take a trip up to Ballarat, you're welcome to come up and have a look through my ED100's (they're bino's but you can always close one eye) or 127 Mak.

Cheers - John.
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  #11  
Old 01-06-2018, 05:15 PM
brian nordstrom (As avatar)
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Sweet , it will carry both with ease , I have one under my 102mm f10 Saxon so here is a photo to give you an idea of how an ED100 will look .
It also carries my iStar 127mm f8 refractor ok , if balanced just right and like you I am a visual guy only .

Brian.
Quote:
Originally Posted by morls View Post
A vixen super polaris I picked through the classifieds here...
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  #12  
Old 01-06-2018, 05:22 PM
brian nordstrom (As avatar)
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Well said John .
Some real food for thought coming out here , good to see as the old saying goes , ' Not one single telescope does it all '.

Brian
Quote:
Originally Posted by Hoges View Post
hmmm....my mileage seems to have varied from the norm. I had a 10" SCT (Meade) well collimated and housed outside in my observatory. Somewhere around the same time I had a friends 4" Genesis refractor on loan. Most nights, the Genesis gave a sharper, snappier and more pleasing image than the SCT. Yes, the SCT did resolve clusters a lot better and showed a bit more detail in nebulae, but not as much as we thought it would. I was never over awed about the images in the SCT whereas nearly everytime I look through my ED100, I am very pleased with the sharpness and contrast. Maybe it's a combination of my astigmatism and prescription glasses but I've just always kept coming back to a refractor.

I love the physical format of the SCT/MAK - easy to mount and doesn't suffer from vibration as much as a longer scope. Maybe SCT's have got a lot better than they where when I bought my Meade around '97.

I've had my ED100 probably longer than any other scope I've owned and am really pleased with it but if I was in your position looking for a good planetary scope that could handle some deep sky stuff and stay small and portable, I'd also consider a 150/180 Mak. I recently got a 127 Skymak and it's not far off the ED100 in contrast and sharpness and gives a reasonable size field with a 2" diagonal and 27 Panoptic.

Mind you, C8, ED100, 150/180 Mak - all pretty darn good scopes that would provide years of viewing pleasure and all easy transportable. Can't go too far wrong either way. Since you're going to be saving for a while, see if you can get to Heathcote (ASV dark sky site), Vicsouth or Snake Valley - you're bound to be able to look through a few examples of each. If you want to take a trip up to Ballarat, you're welcome to come up and have a look through my ED100's (they're bino's but you can always close one eye) or 127 Mak.

Cheers - John.
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  #13  
Old 01-06-2018, 05:41 PM
morls (Stephen)
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Quote:
Originally Posted by Hoges View Post
...nearly everytime I look through my ED100, I am very pleased with the sharpness and contrast.
Yes, this is what I hear from others too...

Quote:
Originally Posted by Hoges View Post
Maybe SCT's have got a lot better than they where when I bought my Meade around '97.
I don't know...the model I'm thinking of is the Celestron with StarBright XLT coatings:
https://www.opticscentral.com.au/cel....html?___SID=U

Quote:
Originally Posted by Hoges View Post
Since you're going to be saving for a while, see if you can get to Heathcote (ASV dark sky site), Vicsouth or Snake Valley - you're bound to be able to look through a few examples of each. If you want to take a trip up to Ballarat, you're welcome to come up and have a look through my ED100's (they're bino's but you can always close one eye) or 127 Mak.
That's a very generous offer, thanks. I'll see how things go.

Cheers

Stephen
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  #14  
Old 01-06-2018, 06:15 PM
morls (Stephen)
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Quote:
Originally Posted by brian nordstrom View Post
It also carries my iStar 127mm f8 refractor ok , if balanced just right and like you I am a visual guy only.
Cool. Just so I can get an idea of the Vixen's capacity, how much does your iStar weigh?
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Old 01-06-2018, 06:32 PM
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Atmos (Colin)
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One big consideration is your observing style. Do you typically have short viewing sessions or longer? Do you do all your observing from your house or do you plan on heading out to a dark site?

The C8 will take a lot longer than the 100ED to cool down so if you’re like me and have a lot of shorter viewing sessions (especially during the warmer months) then a 4” may be better.
If you don’t have to go to bed early and can just leave it sitting outside to cool down for a few hours and do your observing later in the evening, a C8 could be better.

If you don’t plan on heading to a dark site then the extra aperture will help resolve some globular clusters but not much more than that.

Open star clusters and quick planetary/Luna views are where the 4” excels as aperture doesn’t help much with open clusters. A lot of them are quite large too!
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Old 01-06-2018, 06:35 PM
brian nordstrom (As avatar)
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10kg.s or so without accessories , its a beast .
Its OTA is 140mm in diameter and 1100mm long , this shot is of it on my CI700 mount , the same size mount as a Losmandy G11 , its BIG ! and the roof in my shed there is 2000mm high and there is about 50mm clearance .
Hope this helps .

Brian.
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Originally Posted by morls View Post
Cool. Just so I can get an idea of the Vixen's capacity, how much does your iStar weigh?
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Old 01-06-2018, 06:44 PM
brian nordstrom (As avatar)
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Yes another thing to think about Colin , I think you have a typo in this reply ? .. ' where the 4" excels ' ,, should read ,, ' where the 8" excels ' .

Brian.
Quote:
Originally Posted by Atmos View Post
One big consideration is your observing style. Do you typically have short viewing sessions or longer? Do you do all your observing from your house or do you plan on heading out to a dark site?

The C8 will take a lot longer than the 100ED to cool down so if you’re like me and have a lot of shorter viewing sessions (especially during the warmer months) then a 4” may be better.
If you don’t have to go to bed early and can just leave it sitting outside to cool down for a few hours and do your observing later in the evening, a C8 could be better.

If you don’t plan on heading to a dark site then the extra aperture will help resolve some globular clusters but not much more than that.

Open star clusters and quick planetary/Luna views are where the 4” excels as aperture doesn’t help much with open clusters. A lot of them are quite large too!
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Old 01-06-2018, 06:55 PM
brian nordstrom (As avatar)
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Stephen , here is a C8 on a Super Polaris mount , they work well together .

Brian.
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  #19  
Old 01-06-2018, 07:13 PM
morls (Stephen)
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Quote:
Originally Posted by Atmos View Post
One big consideration is your observing style. Do you typically have short viewing sessions or longer? Do you do all your observing from your house or do you plan on heading out to a dark site?
Good point. I'll generally be in the back yard at Blackburn. I have a good view of the meridian, and the light pollution is much less than I had in Randwick, 5km from Sydney CBD. I had the 8" dob there, and really enjoyed it.

I hope to get to dark skies a couple of times a year at least.


Quote:
Originally Posted by Atmos View Post
The C8 will take a lot longer than the 100ED to cool down
I'll be able to leave it outside permanently, in the garage. Are we talking 3 hours to cool down?

It looks good on the Vixen, Brian. So does an ED100
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Old 01-06-2018, 07:20 PM
Tropo-Bob (Bob)
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For visual viewing, IMO 4" is the Goldilocks size: Its not too big, its not too small. In an ideal world, every stargazer will have a quality 4" refactor.

Its strange in a way, because larger scopes may cost more, but are often used less (except perhaps the first month.)

I use my smaller refactors (80 to 100mm) most days, even pushing my luck on unsuitable nights, especially with the 81mm. In contrast, my 8" SCT is used only a handful of nights each year.
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