Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

smaller refractor for planets, doubles, moon, etc?

  • Please log in to reply
70 replies to this topic

#51 Chris Johnson

Chris Johnson

    Ranger 4

  • *****
  • Posts: 310
  • Joined: 08 Sep 2004
  • Loc: Stockholm, NJ

Posted 04 August 2020 - 07:51 AM

I have mounted my AT102ED on the SE mount but, you can only use it up to a max of 60deg in elevation. It s not any more stable than the 8” SCT. My 80mm William Optics does very well on that mount and I can move it forward to clear the mount at higher elevations. When using the 8” SCT I mount the SE on a CPC heavy duty tripod.



#52 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 04 August 2020 - 08:21 AM

I have mounted my AT102ED on the SE mount but, you can only use it up to a max of 60deg in elevation. It s not any more stable than the 8” SCT. My 80mm William Optics does very well on that mount and I can move it forward to clear the mount at higher elevations. When using the 8” SCT I mount the SE on a CPC heavy duty tripod.

Thanks.  So with the 6SE/8SE mount, is the problem of shakiness more due to the tripod rather than the mount itself?  I have a Meade 8" that I was planning on putting on the 6SE mount, but it's not stable enough, IMO.  Does the CPC tripod fix this?  Then again, that decreases portability even further.



#53 sw196060

sw196060

    Mariner 2

  • -----
  • Posts: 219
  • Joined: 16 Apr 2020

Posted 04 August 2020 - 08:27 AM

TV-85?



#54 dweller25

dweller25

    Vanguard

  • -----
  • Posts: 2,050
  • Joined: 30 Aug 2007
  • Loc: Lancashire, UK

Posted 04 August 2020 - 09:39 AM

How about this refractor......

 

https://www.firstlig...-refractor.html

 

But you may need a different mount.


  • Galicapernistein and mikeDnight like this

#55 Chris Johnson

Chris Johnson

    Ranger 4

  • *****
  • Posts: 310
  • Joined: 08 Sep 2004
  • Loc: Stockholm, NJ

Posted 04 August 2020 - 09:56 AM

I am not sure that the original tripod is the complete problem. The SE mount has 3 rubber pads on the bottom the extend beyond the base approximately 1/8”. I think that this adds to the vibration problem. Thus, I still experience some vibration when mounted on the CPC tripod with the 8” tube.

 

 The 80mm refractor works well on the original SE setup with acceptable vibrations.



#56 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 04 August 2020 - 10:05 AM

I am not sure that the original tripod is the complete problem. The SE mount has 3 rubber pads on the bottom the extend beyond the base approximately 1/8”. I think that this adds to the vibration problem. Thus, I still experience some vibration when mounted on the CPC tripod with the 8” tube.

 

 The 80mm refractor works well on the original SE setup with acceptable vibrations.

Thanks.  I don't think I'm going to keep the 8".  On the SE mount, it's still light enough to carry easily, but I think it's just too much scope for the mount.  So, that means a bigger, beefier mount, which is more than I want to deal with right now.  The 6" on the SE mount is so darned convenient.

 

As for refractors, I wonder if there will be a meaningful difference if I go with an 80mm or 90mm apo, vs just staying with the 6" SCT.  The only thing I can really complain about with my 6 is the contrast doesn't always seem so great.  However, I'm not sure if that's the scope's fault, or more due to the terrible light pollution.  The sky around here is always some shade of gray, so the contrast is not good even when looking with the naked eye, lol.



#57 Chris Johnson

Chris Johnson

    Ranger 4

  • *****
  • Posts: 310
  • Joined: 08 Sep 2004
  • Loc: Stockholm, NJ

Posted 04 August 2020 - 10:29 AM

Have you tried to use the mount with the 8” scope? If you are basing your decision on the current views of Jupiter and Saturn From a location in the northern hemisphere that is a mistake. The planets only reach an altitude of 28deg. No scope or mount is going to do well at that latitude. You are better off spending your money on a vacation to Cape Town or other location south of the equator with the 6SE. The planets are high in the sky south of the equator.



#58 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 04 August 2020 - 10:34 AM

Have you tried to use the mount with the 8” scope? If you are basing your decision on the current views of Jupiter and Saturn From a location in the northern hemisphere that is a mistake. The planets only reach an altitude of 28deg. No scope or mount is going to do well at that latitude. You are better off spending your money on a vacation to Cape Town or other location south of the equator with the 6SE. The planets are high in the sky south of the equator.

Yep, I tried the 8" yesterday, and immediately put my 6" back on afterwards.  The 6 is very stable, but the 8 wobbled like crazy whenever I touched the focusing knob.  Doable?  Yes.  Enjoyable?  Not really.

 

If I do get an APO, the AT92 sounds like it'd be right up my alley.  However, it seems they aren't in stock anywhere.



#59 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 04 August 2020 - 01:37 PM

What do you guys think of the AT80EDT vs the AT92?  Is there going to be a big difference for visual observing? 



#60 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 16,901
  • Joined: 24 Jun 2009

Posted 04 August 2020 - 02:52 PM

What do you guys think of the AT80EDT vs the AT92?  Is there going to be a big difference for visual observing? 

The difference between 80mm and 92mm is significant.  I haven't used my 81mm since the 92mm showed up, to be honest.  And the 81mm is an excellent little scope.

 

The AT92 is a special case in that it is f/5.5.  We have people here who like observing with very fast scopes.  I think Jon uses an NP 101 (Televue) which is f/5.4.  And he uses it at very low powers.  

 

Be advised that an f/5.5 scope with a high quality wide field 30 or 40mm eyepiece will scrounge out your eyeball for the slightest trace of organic (in your eyeball) astigmatism.  There is also, in the AT, significant field curvature at very low powers.  

 

The point being that you may end up using it with a 30mm wide field ocular instead of a 40mm wide field ocular and as a result you will not be using the full field of view for which you have in paid.  If that's the case you might be better off with a refractor in the f/6 range for visual.  There is an AT field flattener for about $150 but that seems to be used mostly for photography.

 

I personally, having looked through a few of the f/5 ish scopes at their lowest powers, and having owned an f/6.4 and an f/6.5, and f/8.1, and currently owning an f/6.3 and an f/6.9, would say flat out that I would want nothing to do with an f/5-ish telescope for my personal use.  I am not severely astigmatic but it is enough of an issue that I know when to stop with the whole wide field business.    And that is quite aside from field curvature, where you if you focus at the edge you're out of focus at the center, and vice versa.

 

So no I wouldn't go for an f/5.5 and in fact when I ordered my CFF 92mm I had the option of specifying it either f/6.0 or f/6.9 and I am SOOOO glad that I chose f/6.9.  The vast majority of CFF's 92 mm orders (about 19) went for f/6.0 only two went for f/6.9.  The others I think were imagers.

 

If you hang around these groups you will find (setting aside the achromat guys and their specific needs) some people who speak glowingly of their f/8 and f/9 refractors and wouldn't have it any other way.  I don't think I'm ready for f/9 but I can say that having pursued the short focal ratio side of refractor viewing for quite a while it gradually dawned on my thick head that I wasn't interested in going any more in that direction.

 

One other thing, with an f/5.5 92mm you're going to need very short focal length oculars (say, 4 mm and under) to get effective magnifications for planets.  There are some good options at these focal lengths today but you'll have to spend a bit more to avoid the teensy weensy peephole oculars that are sold to the unwary.  I find them practically unusable (excepting a few of the high priced unusual ones, like the Pentax XO 2.5).  

 

On this score opinions vary as some wise people well say if I want to look at Jupiter I'll put out a bigger scope.  Meantime I'm not looking at Jupiter and I don't have astigmatism and I want widest field possible.  If that's you, f/5.5 is a reasonable choice.

 

Greg N


Edited by gnowellsct, 04 August 2020 - 02:55 PM.


#61 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 04 August 2020 - 03:43 PM

Just to throw these into the mix....

Price seems very good on this one,but not sure about performance?

https://optcorp.com/...r-telescope-ota

 

Then there is this carbon fiber model

https://optcorp.com/...-telescope-9534



#62 213Cobra

213Cobra

    Viking 1

  • -----
  • Posts: 524
  • Joined: 24 Aug 2018
  • Loc: Los Angeles, California, USA

Posted 04 August 2020 - 04:32 PM

The AT92 field curvature can be corrected with an aftermarket flattener for visual, namely the TSFlat2. It's inexpensive, so FC should not be an inhibitor to choosing this option. Further, with a fast scope, you want great optics, which the AT92 has. With its superb triplet objective as foundation, you can use all the advantages of f/5.5 wide fields while leveraging extenders, Powermates or Barlows to get excellent, high magnification views at higher effective f ratios.

 

f/5.5 isn't so fast for visual. My largest scope is f/3.3 with a corrected flat field. Perceived liabilities of modern fast refractors and reflectors are very easily overcome without compromising visual performance.

 

Phil



#63 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 16,901
  • Joined: 24 Jun 2009

Posted 04 August 2020 - 08:39 PM

Just to throw these into the mix....
Price seems very good on this one,but not sure about performance?
https://optcorp.com/...r-telescope-ota

Then there is this carbon fiber model
https://optcorp.com/...-telescope-9534


AT92 is better than either imo.
  • Jon Isaacs likes this

#64 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 05 August 2020 - 06:36 AM

Another one I'm leaning towards is the Skywatcher 100ED.  Since this would mostly be for visual, I think a doublet would be OK.  Also, this one has a longer FL, so wouldn't need as many smaller EPs.  My mains right now are a Hyperion 8-24 (including barlow) and Meade 5.5 UWA.

 

As far as tripods/mounts go, are there some decent, lightweight Goto models that are good for 8-10 lb scopes?  Again, since I'm thinking of mostly visual, and AltAz would probably work.

 

One reason I'm more inclined to get at least a 100mm is I'm not sure I'd be happy with any smaller aperture.  Coming from an 6" SCT, 80mm seems awfully small.


  • mikeDnight likes this

#65 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 16,901
  • Joined: 24 Jun 2009

Posted 05 August 2020 - 07:10 AM

Another one I'm leaning towards is the Skywatcher 100ED.


One reason I'm more inclined to get at least a 100mm is I'm not sure I'd be happy with any smaller aperture. Coming from an 6" SCT, 80mm seems awfully small.

If you wish to think strategically you get the 80mm with more mount than you think you'll need, like a G11. Then when you get tired of 80mm you can get a c8 or 9.25. And put the 80mm up top.

You can have an inexpensive alt az mount to use the 80mm by itself. And finally when opportunity knocks you can get a 5 inch apo to use when in the mood, as an alternative to the c8/80mm.

At that point you will have two mounts and three telescopes. Think of it as a 5 year plan. In the second five year plan you upgrade to 100% Pentax or Delos and get a C14 or 14 inch dob.

You will have 4 telescopes two mounts premium oculars and finally arrived at a reasonable kit.

Edited by gnowellsct, 05 August 2020 - 07:11 AM.


#66 Galicapernistein

Galicapernistein

    Viking 1

  • *****
  • Posts: 605
  • Joined: 24 Sep 2007

Posted 05 August 2020 - 07:24 AM

Another one I'm leaning towards is the Skywatcher 100ED.  Since this would mostly be for visual, I think a doublet would be OK.  Also, this one has a longer FL, so wouldn't need as many smaller EPs.  My mains right now are a Hyperion 8-24 (including barlow) and Meade 5.5 UWA.

 

As far as tripods/mounts go, are there some decent, lightweight Goto models that are good for 8-10 lb scopes?  Again, since I'm thinking of mostly visual, and AltAz would probably work.

 

One reason I'm more inclined to get at least a 100mm is I'm not sure I'd be happy with any smaller aperture.  Coming from an 6" SCT, 80mm seems awfully small.

The Skywatcher 100ED would be a good choice. At F9, you wouldn’t have to spend a fortune on wide field eyepieces. So you could get high power views and wide fields in one scope. I agree that an 80mm might not give you the bright images you’re used to. 


  • ET_PhoneHome likes this

#67 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 05 August 2020 - 07:30 AM

And it's on sale at the moment =)  If it was my only scope, I would spend more, but I don't want to go too crazy just yet.  Around 100mm seems to be a sweet spot for refractors before they start to get really big.  I really like the look of the short tubes, but it sounds like that's just not optimal for visual.  Now for photography? Yeah.  I might pick one of those up someday for that purpose.  For now, I've got my DSLR and a whole kit of lenses to play with.



#68 Hesiod

Hesiod

    Skylab

  • *****
  • Posts: 4,142
  • Joined: 13 Jan 2013

Posted 05 August 2020 - 10:25 AM

Except that a 100mm refractor easily ends up being just as large as your 5" Meade+mount, which you have found to be "huge, heavy and cumbersome".

Take note that one of the reason of the big success of 120ED (and TSA120) is that these are basically as large as their 100mm sibling...

 

I have a very good 100/900 myself and must admit that it is not the most handiest telescope, especially if like so much the SE6: forget that kind of ergonomics and be ready to a 12-20kg telescope (to save weight have to get more expensive mounts).

 

The only "small" goto alt/az I can think of is the minitower, but is still over 12kg; a suitable eq mount will be as heavy as your current Meade mount, or heavier (or much more expensive)



#69 Bill Barlow

Bill Barlow

    Aurora

  • *****
  • Posts: 4,666
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 05 August 2020 - 10:37 AM

If you wanted to use your SE mount with a refractor, an 80mm f/7 might work or the AT 92mm f/5.5 might be able to point to the zenith without hitting the base.  I have a Tak FC76 and an A-P 92 Stowaway and have had them out side by side.  The 92 is a tad brighter on all objects but not a big “wow” factor.

 

Bill


  • ET_PhoneHome likes this

#70 ET_PhoneHome

ET_PhoneHome

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 22 Aug 2017

Posted 05 August 2020 - 10:47 AM

I guess some extra weight is the price to pay.  My Meade scope is 15 lbs, and the tripod is apparently 35 (not sure if that includes the huge counterweight).  OTOH, the Evo 100 is 6.6 lbs, and something like the EQM-35 is 37 lbs total.  The Evo tube also shorter.  All in all, it is still heavy, but I don't think I'll get much better unless I go with a very small refractor and very light, non-tracking mount.  Even with a small, 80mm triplet, I'd still need a pretty beefy mount, so it seems like there's no good way around the weight issue.

 

I didn't mention this before, but aside from my 6" SCT, I also have a 90 Skywatcher Mak, so I suppose that would make a good grab and go package.

 

As far as mounts go, I see there are some that are lighter than the EQM-35, but their max loads are only like 11 or 12 lbs, and I think that'd be cutting it close with a 100mm scope.  Plus, some of them have plastic gears, and are probably not that well made.

 

In the end, it's all about compromise, like most things.  I like to do wildlife photography, but I don't like big, heavy gear.  Unfortunately, wildlife shooting means big,heavy gear (if you want quality).  I was lucky enough to get a 500 PF (phase fresnel) lens from Nikon which is like half the size and weight of a normal 500mm prime.  It's still pretty hefty, but it's the best compromise I could find.



#71 Hesiod

Hesiod

    Skylab

  • *****
  • Posts: 4,142
  • Joined: 13 Jan 2013

Posted 05 August 2020 - 11:06 AM

Figure something in the 5kg range for the 100/900 ready to be used, especially if opt for a 2" diagonal.

I would not like to use it with an eq3, but is nonetheless a doable match thanks to the mounts' tracking.

As far as I remember the eq3.5 is around 10kg, half for the head, half for the legs; the AVX is around 15kg (again, half for the head, half for the legs), so not catastrophically larger but sturdier (and I like much more the software). As I said earlier, the iOptron MiniTower is not that heavier than the eq35, if prefer alt/az

At higher prices may look into the more capable Losmandy GM8 (US pricing is especially good) or Vixen SXD2 (I use this with my 100/900: the head is 7kg, the stock tripod is 5kg, and the mount has a clever design which is pretty light on counterweights, and could balance the 100/900 with the included 1.9kg one or, if have one, an even lighter CW)


  • ET_PhoneHome likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics