ED100 vs C8 for planetary (visual only)

[morls]

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

[Imme]

I'd suggest ED100 would be a lot less 'fussy' in regards to collimation.

[morls]

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..

[casstony]

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.

[Wavytone]

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.

[brian nordstrom]

:question: 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 :eyepop: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 :question: , 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 .

[morls]

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

[brian nordstrom]

:thumbsup: Cool Stephen , may I ask , what mount ? .
Thanks .

Brian.

[morls]

A vixen super polaris I picked through the classifieds here...:D

[Hoges]

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.

[brian nordstrom]

:thumbsup: 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.

[brian nordstrom]

:thumbsup: 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

[morls]

Yes, this is what I hear from others too...



I don't know...the model I'm thinking of is the Celestron with StarBright XLT coatings:
https://www.opticscentral.com.au/celestron-8-xlt-optical-tube-assembly-ota-cge-mount.html?___SID=U



That's a very generous offer, thanks. I'll see how things go.

Cheers

Stephen

[morls]

Cool. Just so I can get an idea of the Vixen's capacity, how much does your iStar weigh?

[Atmos]

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!

[brian nordstrom]

:shrug: 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.

[brian nordstrom]

:thumbsup: 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.

[brian nordstrom]

Stephen , here is a C8 on a Super Polaris mount , they work well together .

Brian.

[morls]

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.




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 :P

[Tropo-Bob]

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.

[morls]

It seems, from people's comments, that there aren't too many negatives where a 4" refractor is concerned...as long as the quality is OK.

Bob, do you think the 8" SCT would be used more if it was the only scope you had, and was on the mount permanently? Or to put it another way, is the weight of mount + OTA too great to carry at once, say from a garage to the viewing site 30m away?

[morls]

This might deserve another thread, but what about an 8" ritchey-chretien?

https://optcorp.com/collections/ritchey-chretien-telescopes/products/tpo-8-carbon-fiber-f-8-ritchey-cretien-reflecting-ota-telescope

OTA weighs around 8.5kg, so maybe too heavy...

[Tropo-Bob]

If I only had one scope, however humble, it still would be used a lot!

Actually, part of the attraction of the 4" is that I can pick it up and dodge trees etc.

Still, in some wonderful world where the physical ergonomics of using either scope was equal, for the brighter objects (say anything over Mag 8), I would rather the 4". These have become my preferred objects to view and I love the crispness of refractors.

However, if U go down the path of observing galaxies, U will want a larger scope. The last time I looked at the splendid galaxy NGC 253 under a dark sky with the 8", I was blown away. However, till then, I was thinking that I chose the wrong scope for the evening. After that, I wished I had brought 2 scopes!

That said, if U have an 8" scope for observing them, U will probably soon will be dreaming of a 12" Dob.

[Tropo-Bob]

My understanding is that they are a much better imaging scope, than a visual scope.

[Atmos]

If you want one scope for everything and one that you can leave out for extended periods then the 8” would probably be the better fit, especially if you’re comparing it against an 8” Dob.

An 8” when cooled will out perform a 4” on everything. I’ve got a 10” and a 4” but my 4” is used a lot more because the skies don’t usually support the effort of setting up the 10”. Most of what I look at is the moon, planets and open clusters, all of which a 4” does really well at. When it comes o Omega Centauri or other globular clusters, the 10” leaves the 4” for dead. Galaxies? Neither are worthwhile from my backyard hehe

[MortonH]

I have a 1990's C8 and recently bought a used ED100. I set them up side by side and the C8 blew away the ED100 completely. Yes, the refractor is a bit sharper and has a bit more contrast but the C8 has twice the aperture and four times the light-gathering ability. I traded up the ED100 to an ED120 and it's a lot closer to the C8 in performance but the C8 still wins.

Cooldown is usually only an issue if you take the C8 from a heated home outside into the cold or from an air conditioned room outside into a warm night.

You can get either a C8 or ED100 for around $600-$800 used and get your money back if you sell so I recommend this rather than buying new.

[skysurfer]

Nice topic.
I have a similar scope (ED110), which is my travel scope for dark sites in South Africa or Australia. At home I use it rarely, but my tabletop 80mm I use more often and sometimes my 40cm Dobson. The latter is really nice for deepskies but the light pollution here spoils a lot. Moreover, clear skies are rather rare, as on many cloudless nights the air is too hazy or in summer nights are extremely short due to the high latitude (52º).

[morls]

That sounds like the way to go.

[morls]

Hi,

I thought I'd post an update, as I've reached a decision in this particular quest.

I've spent the last few weeks thinking of the various suggestions and advice I've been given, and had pretty much decided on a C8, despite the compromises of this type of scope.

After the post by John (Hoges) suggesting mak-cass as an option, I did some more research, and found some very interesting reviews of the skywatcher 180mm. In particular, the observation that this scope offers very good contrast got me thinking. The long focal length (f17) is also interesting in terms of magnification possibilities when observing moon and planets. There are a couple of reviews which helped convince me:
http://www.astro-baby.com/reviews/Skymax%20180/Skymax%20180%20Review.htm
https://stargazerslounge.com/topic/216208-skywatcher-180-mak-or-celestron-c8-sct/

These both described the cooling period as being 30-60 min, completely ok by me. Also noted that it can offer APO-esque contrast, and is good for a range of objects other than planets.

So, today I put down a deposit on a Skywatcher 180mm Mak ($1699 as optics central offer price matching...). Comes with Finderscope, 2-inch Dielectric Star diagonal, 2-inch visual back, 2 inch 28mm eyepiece and dovetail Mounting. The OTA weighs 7.8kg, so the super polaris should be ok. :prey:
https://www.opticscentral.com.au/skywatcher-black-diamond-180-2700-maksutov-cassegrain-telescope-ota-only-2545.html?___SID=U

It'll take a couple of months to arrive, as there doesn't seem to be a great demand for them. I'm paying off the lay-by over 3 months.

I'm glad to have reached a decision, and to have made this step. I think it'll be a great scope, and will be a ripper for lunar and planetary. If I get into DSO's I reckon a 10 or 12" dob will keep me happy.

So, thanks everyone for your input. I know this won't be the last scope I buy, but it's a significant investment for me, and it's been really helpful to hear from everyone.

Cheers

Stephen

[Hoges]

Nice one, Stephen. I've read only good things about the 180mm and would be keen to look through one myself. Cheers - J.

[raymo]

You won't regret it, terrific scope, pin sharp; its a pity they don't make a
larger one, maybe one day. Tell us how you go with it.
raymo

[Atmos]

I’ve never looked through one but the reviews of these are consistently very good :thumbsup:

[Wavytone]

Hi Stephen, congratulations - I had one which was excellent optically and mechanically, and they’re excellent if you need a portable scope. Only reason I sold mine was to upgrade to my current big mak.

I also had a 130mm f/7 triplet APO side by side for a while with the SW 180mm Mak, and the Mak won every time.

Forget refractors. For small apertures they're OK, but ultimately aperture rules especially if the optics are good.

[cometcatcher]

You'll love the 180mm Mak! I had the best ever view of Saturn through one.

[morls]

Thanks for all the comments.

I was actually intending to buy the 127 or 150mm - I'm not the most patient person around, and I was thinking I could pay it off in a month or so. Then I realised that this would be a mistake - I knew I'd definitely wish I'd got the 180mm, and probably sooner rather than later! That was the last piece of the puzzle, and so I put the deposit down straight away.

It's going to take longer to pay off, but the wait will definitely be worth it.

[morls]

Getting the 180 Mak Friday, first light will include the Mars opposition :party:

[Nikolas]

weather in Melb won't be kind for this unfortunately

[morls]

:prey::prey::prey: