Jump to content


Photo

"Planet Killer"

  • Please log in to reply
62 replies to this topic

#1 Pete-LH

Pete-LH

    Messenger

  • *****
  • Posts: 414
  • Joined: 25 Mar 2009
  • Loc: Wilmington, DE

Posted 27 June 2013 - 03:07 PM

Not crazy about this term but I see they have a $499 version of the SV 4" f11 with a single speed crayford and a $699 version still with the dual speed R&P. Are there any updated reviews on this refractor? I am tempted but already have four in the 90 to 102mm range.

#2 Binojunky

Binojunky

    Mercury-Atlas

  • *****
  • Posts: 2741
  • Joined: 25 Dec 2010

Posted 27 June 2013 - 03:57 PM

Not crazy about this term but I see they have a $499 version of the SV 4" f11 with a single speed crayford and a $699 version still with the dual speed R&P. Are there any updated reviews on this refractor? I am tempted but already have four in the 90 to 102mm range.


I know the feeling, been looking at that myself, also the single speed ED 80,DA.

#3 johnnyha

johnnyha

    Fly Me to the Moon

  • *****
  • Posts: 6500
  • Joined: 12 Nov 2006
  • Loc: Sherman Oaks, CA

Posted 27 June 2013 - 04:04 PM

For the price you could kill planets lots better with a 10"-12" dob... ;) I say this only because you already have four 4" class refractors and f11 isn't going to significantly change the planet destruction.

#4 KerryR

KerryR

    Gemini

  • *****
  • Posts: 3068
  • Joined: 05 Dec 2007
  • Loc: SW Michigan

Posted 27 June 2013 - 04:10 PM

Personally, I consider 4" a little small for dedicated planetary observation.

On the other hand, seeing is far more likely to play nicely with a 4" than it is, say, an 8 or 10", which makes the 4"ers pretty ideal scopes for "average" conditions.

Sounds to me like you're already pretty well covered at that aperture, unless you feel the others have comparatively inferior optics.

#5 BillP

BillP

    Voyager 1

  • *****
  • Posts: 11343
  • Joined: 26 Nov 2006
  • Loc: Vienna, VA

Posted 27 June 2013 - 04:16 PM

One of the Celestron 6" f/8 Achromats likely a better choice as when you stop it down to 4" it is actually slightly better at f/11.9, and then when you open it to full aperture it of course is much better for DSO.

#6 belgrade

belgrade

    Ranger 4

  • -----
  • Posts: 311
  • Joined: 05 Oct 2007
  • Loc: Frisco, TX

Posted 27 June 2013 - 04:24 PM

Anyone knows what's difference between the SV's version for $499 and AT's version for $599 by Hands On Optics? It seems to me the AT's version is the same as the one by SV for $699? And btw, I can't believe that the price of AT's version keeps going up and up... I mean, we're still talking an achro here, either by SV or AT. Or they are really worth that much?! Please advise, I never used either. Thx.

#7 AstroSteve

AstroSteve

    Viking 1

  • *****
  • Posts: 815
  • Joined: 17 Aug 2004
  • Loc: Kissimmee, Florida

Posted 27 June 2013 - 04:49 PM

"Planter Killer" I thought that was the Death Star in the Star Wars movies. Haha!

#8 Astrojensen

Astrojensen

    Fly Me to the Moon

  • *****
  • Posts: 5075
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 27 June 2013 - 04:54 PM

One of the Celestron 6" f/8 Achromats likely a better choice as when you stop it down to 4" it is actually slightly better at f/11.9, and then when you open it to full aperture it of course is much better for DSO.


Not a bad suggestion. I use a 6" f/8 Sky-Watcher myself, which has a dustcap with a smaller aperture stop in the middle with its own cap. It has 4.5" free aperture and an f/ratio of 10.7, when used with the dust cap stop. Planetary performance is quite darn good and false color is very well controlled. Deep-sky is very impressive for a 6", when used at full aperture. Especially at low magnifications with modern 82° eyepieces.

But it is a big and heavy scope. An EQ-6 or similar mount, preferably larger, is almost mandatory. I've tried it on a Vixen GP and can't recommend it. It's fine on an EQ-6 with Baader tripod.

If a 4" refractor is needed, because a lightweight and quick setup is required, then a 6" f/8 achro is definitely not the way to go. Just sayin'.


Clear skies!
Thomas, Denmark

#9 Pete-LH

Pete-LH

    Messenger

  • *****
  • Posts: 414
  • Joined: 25 Mar 2009
  • Loc: Wilmington, DE

Posted 27 June 2013 - 04:59 PM

Actually, I try not to reveal my insanity ... But I also use a C9.25, C-8, 5" f/12 Superplanetary, 100mm f/13 Carton, 102mm Tak FS-102, 90mm FL90S, 90mm 90M f/11(also Vixen).

I guess in looking for sanity, my plan is to someday just have a 4" refractor and the C-8 which will be easy to set up in my olde age.

As I said I don't like the term "Planet Killer". On good seeing nights I may use the C9.25 or SP, and on nights when the seeing is not so good and I don't have much time to sit and ponder the wonders of the universe at leasure I set up a small scope and get some quick quality time in. And usually I waste too much time deciding which one to set up. And double stars and star clusters are typically my target although planets and DSO's are on the card as well.

Still I feel the refractor force.

#10 Pete-LH

Pete-LH

    Messenger

  • *****
  • Posts: 414
  • Joined: 25 Mar 2009
  • Loc: Wilmington, DE

Posted 27 June 2013 - 05:04 PM

[Regarding the difference]

Probably should not have started another thread but the SV has a better focuser I believe, one or two speed now, the ability to shorten the tube for binoviewers and the "StellarVue" brand. I'm not sure $200 is warranted in going from 1 to 2 speed but I do prefer an R&P focuser.

There is a thread in April that describes all this.

#11 BigC

BigC

    Gemini

  • *****
  • Posts: 3112
  • Joined: 29 Sep 2010
  • Loc: SE Indiana

Posted 27 June 2013 - 05:19 PM

I suggest you consider a 120 f8.3 for your "olde age".

Keep the goto 8" SCT of course.

#12 Don Taylor

Don Taylor

    Viking 1

  • -----
  • Posts: 583
  • Joined: 12 Jul 2009
  • Loc: South Kansas

Posted 27 June 2013 - 09:55 PM

From what I can see on SV's website the $699 scope uses the Stellarview 2 speed r&p focuser which is a bit different than the long-perng r&p used on the hands on optics version, which is the version I have.

Originally the HOO version and the original Stellarview versions used the Kunming 2 speed Crayford, as some other versions of this scope still appear to. The original version of the HOO scope was $499 before the focuser was upgraded.

If its of any value, the long-perng rack and pinion works very well although I have not been able to compare to the 2.5" Stellarview focuser. There has also been some variation in the length of dew shield between the various versions available.

The scope is excellent btw.

#13 Mark Harry

Mark Harry

    Vendor

  • *****
  • Vendors
  • Posts: 6142
  • Joined: 05 Sep 2005
  • Loc: Northeast USA

Posted 28 June 2013 - 04:33 AM

Had the exact same idea with my 'in the works' 8" achro.(!)
Working on the crown lens now. Masked down, it'll be a 5" F/12.5~. A bit more ap than a 4; should make things interesting on planets, yet still has 8" of glass for DSOs.

#14 Niklo

Niklo

    Viking 1

  • -----
  • Posts: 564
  • Joined: 29 Mar 2013
  • Loc: Bavaria

Posted 28 June 2013 - 06:17 AM

Hello Pete,
so you already have a 100mm f/13 Carton and a 102 Tak FS-102 so you have two very good 4" refractors.
The 4" f/11 really looks interesting and seems to be a good refractor but I expect that both the Tak and the Cartoon or at least the Tak is better.
So you needn't buy it but I can understand you. It's nice to compare telescopes, play with different ones and if it looks nice ;).... I feel that I tend to collect telescopes for that reason too. ;)
Cheers,
Roland

#15 stanislas-jean

stanislas-jean

    Surveyor 1

  • -----
  • Posts: 1991
  • Joined: 22 Oct 2008

Posted 28 June 2013 - 06:29 AM

Personally I had now the RS100 Tal, last model, and the 120ED SW in hands, owned the vixen 100F10.
Lastly on saturn the 120ED and the tal 100 exhibited fine results but with actually no significant different results about the accessible features.
I have to compare this also on venus where the 100RS shows already fine banding structure on the atmosphere.
I donot agree with forumers here about the fact that 100mm aperture is confidential or too small.
This is with these kind of apertures that visual observers may train their vision with acurate optics in order to go deeper and deeper on a planet image.
I donot know what is this "planet killer" 100F11 but surely not outperforming what I tested already.
Stanislas-Jean

#16 Niklo

Niklo

    Viking 1

  • -----
  • Posts: 564
  • Joined: 29 Mar 2013
  • Loc: Bavaria

Posted 28 June 2013 - 07:40 AM

Hi Stanislas-Jean,
the Tal 100 RS is a nice and interesting 4" refractor, too. I was curious and started a thread. Comparing Tal 100 RS with TS 102 f/11.
It seems that have similar performance and it seems that the f/11 is a little bit better (probably a little bit less chromatic aberration) but the Tal 100 has a smaller focal length that helps to get an larger angle of view. So both have their advantages.
After short time I was told that the ED refractors are much better although I haven't asked for that comparison ;)
The name "planet killer" is a little bit weird but OK. ;)
Clear sky,
Roland

Personally I had now the RS100 Tal, last model, and the 120ED SW in hands, owned the vixen 100F10.
Lastly on saturn the 120ED and the tal 100 exhibited fine results but with actually no significant different results about the accessible features.
I have to compare this also on venus where the 100RS shows already fine banding structure on the atmosphere.
I donot agree with forumers here about the fact that 100mm aperture is confidential or too small.
This is with these kind of apertures that visual observers may train their vision with acurate optics in order to go deeper and deeper on a planet image.
I donot know what is this "planet killer" 100F11 but surely not outperforming what I tested already.
Stanislas-Jean



#17 stanislas-jean

stanislas-jean

    Surveyor 1

  • -----
  • Posts: 1991
  • Joined: 22 Oct 2008

Posted 28 June 2013 - 08:17 AM

From my comparisons with the said scopes, the ED brings in fact nothing more consistent about the acquisition of data, but with a more pleasant view only.
The 100RS has already a confidential CA level that can be annealed by the use of the MV Lumicon filter (that cut the violet halo under 410-415nm).
Now the ED (chineese) should do better that is not effectively and there are reasons for that are subtil.
It would be interresting to see the Arcturus star for example at high power in each case and to study their diffraction patterns.
The Tal involves a pattern very clean (circular airy disk with say max 2 rings appearing and some other so faint despicted on a light violet halo, discret), the ED involves a strange pattern consisting in an airy disk circular surounded by a first ring not strongly lighted and others, a dozen of distinct rings having a light degradation in intensity low. The rocnchi pattern has black lines straight (grid of 10 lp/mm) with no appearing curvatures that mean faint readable spherical aberration 1st order, but the other orders? The ED at 300x shows a coloured halo around Arcturus.
This is the fifth ED that I had in hands with similar effect (100mm, 110 and 120mm). Consequence is that small contrasts of fine details are washed.
The achromats (100mm and 150mm) didn't exhibit this effect, but low contrasted fine details were present visually.
This is my observations about sothat when the quality is actually here at a high level a 100mm even achromat gives excellent results and enough for making acurate and useful results at the level of an almost perfect aperture.
At present with the experience of ED scopes, they disapointed me a lot.
If somebody expect a 100mm achromat he can go to the vixen 100mm achromat that is without surprise about the quality level which is extra-fine.
Stanislas-Jean

#18 GOLGO13

GOLGO13

    Gemini

  • *****
  • Posts: 3031
  • Joined: 05 Nov 2005
  • Loc: St. Louis area

Posted 28 June 2013 - 11:49 AM

Certainly this is a marketing ploy more than anything. It's not much longer than the Celestron 102mm F9.8 scopes. Now, those do very well on planets (had one back in the day), but I can't say they are planet killers. Quite frankly I'd say you would need at least one more inch in aperture to get into a more serious planetary killing scenario. A few more inches would really help there.

#19 PJ Anway

PJ Anway

    Double-Star Observer

  • *****
  • Moderators
  • Posts: 2626
  • Joined: 04 Jun 2003
  • Loc: North Coast

Posted 28 June 2013 - 03:06 PM

IMO aperture size is only one factor in planetary observing. There are certainly other factors that can determine choice. For instance, because I live under very dark yet often turbulent skies, a 4" long-focus refractor makes a lot of sense for me for use on planets.
Those factors (in contrast to a large scope)are:
(1) the convenience of setting up a small refractor,
(2) the forgiveness of a long focal length when it comes to less-glass eyepieces,
(3) lower irradiation of the eye enhances contrast,
(4) less turbulent air to deal with.

Of course when it comes to faint "fuzzies" the light-grasp of a larger scope wins.

#20 Pete-LH

Pete-LH

    Messenger

  • *****
  • Posts: 414
  • Joined: 25 Mar 2009
  • Loc: Wilmington, DE

Posted 28 June 2013 - 04:30 PM

Stanislas-Jean,
Totally understand your "the acquisition of data" reference verses more expensive scope designs. There is a good article in a recent Astronomy League "Reflector" on how some young attendees to star parties/outreach gatherings may be scared away by the expense of some equipment. Personally when considering the "the acquisition of data" aspect, I get as almost all visual data with my simple 90mm Vixen 90M (probably can get for less than $300 used) as with any of my other telescopes. I have found that with 80 and 60mm scopes as well. Can't argue though that when conditions are good the views with my C9.25 or 5" refractor are just wonderful.

#21 richardr

richardr

    Vostok 1

  • -----
  • Posts: 161
  • Joined: 07 Nov 2006
  • Loc: Seattle, WA

Posted 28 June 2013 - 05:19 PM

"achromats" are not planet killers IMO. I have had a 4" f11 and it had plenty of color on the planets. The MV-20 filter improved the situation but, did not get rid of the color and degraded the image compared to an apo. I recommend a used 4" ed100 if you want to get a cheap refractor. They cost around $400 to $500. Or an f6 to f8 reflector on an equatorial will work.

Dobs will work but require wide field eyepieces, or you will lose the object at high powers. Good wide fields are expensive and I personally would have a hard time buying eyepieces that cost far more than the telescope. From personal experience, I don't care for the cheap wide fields as they are too much work to see through as well as a source of frustration. YMMV.

#22 Niklo

Niklo

    Viking 1

  • -----
  • Posts: 564
  • Joined: 29 Mar 2013
  • Loc: Bavaria

Posted 29 June 2013 - 01:28 AM

Hi Stanislas-Jean,
I think that a good achromat is a good telescope that can show most details that the aperture can show but I'm surprised by the bad experience with ED refractors. I have no experience with ED refractors but theoretical they should show much less chromatic aberrations than the most achromat refractors and I would expect that a good Skywatcher EVOSTAR ED100 Pro - ED APO 100/900mm should have less chromatic aberrations and and little other aberrations. So it could show more details or at least the same details as an achromat with f/10 (depending on the object and the seeing). The Skywatcher EQUINOX 100/900mm should be even better. Both ED refractors should show less chromatic aberrations and more contrast especially on bright objects like Jupiter or Venus. I think I can live without an ED refractor but I'm curious if the bad experience is normal. If a 4 " f/10 shows details in the cloud structure of Venus then the ED f/9 should show at least the same with at least a little bit more contrast. Maybe Venus needs a filter because Venus is very bright (especially in a 120 ED). Maybe a little gray filter or a pol filter can help to dim Venus a little bit. I expect that it is the same problem with larger newtons?
If the 5" ED is no scrap it should show more details (depending on the object and the seeing) than a 5 " f/10 and less color than a 5 " f/15 and more details than a 4 " achromat with f/10. If it shows strange refraction rings and more colour and less details (even with gray filter) then I would say that it is a bad ED refractor and I would sent it back to the seller.
How is the experience from people who have both a good achromat and a good ED (idally both scopes with the same aperture)?
What can be the reason that the 4 " f/10 show more details on Venus (too bright in the 120 ED)?
Or the example with Arcturus. (Interesting would be the behaviour with lower magnifications. A magnification of 300 is very high.)
Hmmm, maybe normal achromats show blue or violet around bright objects and ED show yellow around bright objects which does look worse?
I'm really curious to hear your experience.
Kind regards,
Roland

#23 Niklo

Niklo

    Viking 1

  • -----
  • Posts: 564
  • Joined: 29 Mar 2013
  • Loc: Bavaria

Posted 29 June 2013 - 01:46 AM

Hi Richard,
the question is how much more details a ED shows on planets like Saturn, Mars, Venus or Jupiter. I don't know your filter but I expect that there are filters that can reduce the colour fringe around e.g. Jupiter so it's almost invisible or invisible. The main problem is that an achromat loose a little bit of the possible contrast so a good ED or APO could theoretically show a little bit more details. That's the advantage of APOs and should be the advantage of ED refrators. A little bit dark purple around bright objects doesn't bother me. Loosing details bothers me a little bit but I think that I see the most details for my aperture and that seeing is more limiting so that's OK for me ;)
Kind regards,
Roland

"achromats" are not planet killers IMO. I have had a 4" f11 and it had plenty of color on the planets. The MV-20 filter improved the situation but, did not get rid of the color and degraded the image compared to an apo. I recommend a used 4" ed100 if you want to get a cheap refractor. They cost around $400 to $500. Or an f6 to f8 reflector on an equatorial will work.

Dobs will work but require wide field eyepieces, or you will lose the object at high powers. Good wide fields are expensive and I personally would have a hard time buying eyepieces that cost far more than the telescope. From personal experience, I don't care for the cheap wide fields as they are too much work to see through as well as a source of frustration. YMMV.



#24 stanislas-jean

stanislas-jean

    Surveyor 1

  • -----
  • Posts: 1991
  • Joined: 22 Oct 2008

Posted 29 June 2013 - 09:21 AM

ED seams a magic logo.
The 120ED shows color aberration at 300x on Arcturus with coloring depending on the seeing from blue-greenish to orange at the focus (a strange figure). It exhibits the same level of olororation intensity than the 100RS at 250x equiped with the MV lumicon filter but with a light blueish color.
The 120ED is fading above 250x about sharpness, may be the sign of just average quality.
The 100RS keeps his sharpness at 250x.
I saw 250x on mars and moon feasible with the 100mm mostly.
I had a 150mm F10 achromat that did a lot on planets with almost each time with 300x sometimes 375x (250-300x on saturn) without sharpness fade.
I think if we want a little more contrast we should go to apo, but not chineese, for getting a real gain.
The interest of the 100RS can be its ability to get good views in blue channels (see the wolfgang rohr german website for test results). On sky this is actual and better than the vixen on that point.
But as a conclusion if an actual apo can do better by the contrast (relatively) the data acquired by the 2 kinds remain the same.
A 4" well managed can perform excellent jobs, with color filters to see what happens in each color (see venus applications, mars as well).
Indeed a 6" newtonian can do as well or better but it is preferable to watch confortably seated at the back of the OTA.
What must be researched this is the minimum peak to valley front errors on the optics with the better surfaces or the minimum level of RMS. The CA when confidential is not disturbing the images so much in order to hide most of the data.
Just to select the right doublet, tal, istar, vixen, dgo.
We can select a F15 but I found the 150 F10 OK and enough for observing planets.
About CA, just a conclusion as
if the 120 ED is with the same FH glasses it would involve 1.2 x 10/7,5 = 1.6 more CA
with FPL glass this CA is reduced to 1,6/3= 0.5 say (with FPL glass 3 times less CA than a FH doublet).
When inserting the MV Lumicon (that cut under 410nm) the CA is reduced by 2 around.
This means at final a similar CA level (recall here the Arcturus observations). The ED has therefore no significance but they should give better optical performance by reduced geometrical aberrations (not found here) and better optical levels (the P/V and RMS but poor to average here). Too many expenses for so few advantages if existing actually.
Stanislas-Jean

#25 richardr

richardr

    Vostok 1

  • -----
  • Posts: 161
  • Joined: 07 Nov 2006
  • Loc: Seattle, WA

Posted 29 June 2013 - 09:11 PM

I compared an ed100 with a 4" f11 vixen and found that for planets that the ed100 could take higher magnification and simply showed more. It was like standing behind a screen door at a slight distance and then opening it. You didn't notice the difference until the ed100 showed that there was one. The purple haze in the planet and around it became more apparent. The other reason to go ed or apo is size IMO,as large telescopes(or heavy) require bigger mounts and are a lot of trouble. The ed100 easily rides on a Vixen GP and the Vixen achro was just a bit too long and too heavy for it.
Richard






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics