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Equipment Discussions >> Refractors

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Jim7728
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Re: Stellarvue "Planet Killer" Limited new [Re: t.r.]
      #5669704 - 02/08/13 08:13 PM

Frugal man's "Planet Killer"

http://www.astronomics.com/bosma-beta-4-f10-refractor-ota_p20070.aspx



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DaveJ
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Re: Stellarvue "Planet Killer" Limited new [Re: David E]
      #5669781 - 02/08/13 09:13 PM

Quote:

Here is a quote from Vic's post on the Yahoo Stellarvue Group:

"So this month, for at least a limited time, I will produce another Stellarvue achromatic refractor, with performance on the level people expect from us. These will not be mere import telescopes which are untested and inconsistent. These telescopes will be triple tested by us, just like any other Stellarvue telescope. Only the best optics can survive our testing regiment."




Hmmm. "testing regiment" Vic must have an entire army of testers.


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stevew
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Re: Stellarvue "Planet Killer" Limited new [Re: Jon Isaacs]
      #5669851 - 02/08/13 10:02 PM

Quote:


In my mind, a "planet killer" requires more than 4 inches of aperture.
Jon




That's the first thing I thought of as well.
I think "planet killer" starts around 10 inches.

I love refractors, and own several, as they provide crisp contrasty images,
but even in mediocre seeing aperture equals resolution.


Steve


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Paco_Grande
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Re: Stellarvue "Planet Killer" Limited new [Re: stevew]
      #5669891 - 02/08/13 10:22 PM

The attraction of "Planet Killer" resonates like Teenage Mutant Ninja Turtles with me. It's a marketing term for children.



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ngc2289
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Re: Stellarvue "Planet Killer" Limited new [Re: KWB]
      #5670056 - 02/09/13 01:59 AM

Quote:

Quote:


I guess it is marketing and shipping constraints that bias manufacturers against long tubes.



I'm guessing it is also user friendliness that factors into the marketing decisions that affect what telescope design gets priority as to hitting the production lines. An F/15 or worse,an F/20 tube is extremely long and requires a really substantial mount that for a user such as myself wouldn't even entertain to owning due to my situation of not being able to permanently mount that setup in some sort of observatory. I have to take each and every telescope setup I own outdoors everytime it gets used,then reverse the proceedure when it's time to call it a night. That's my bias against this design because it requires far less effort to choose a completely different one like a 10 inch dobsonian that is far easier for me to get into action, with more horsepower under the hood in terms of resolution capability. My opinion is there many other backyard observers in the same boat,and that isn't lost on the scope manufacturers. I love 4 inch refractors that are a lot more grab and go capable and believe that desire is more widespread in this hobby.

In the right circumstances for the right individual, a long tubed acro can be a wonderful tool.


You hit the nail right on the head!!

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Da Bear
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Re: Stellarvue "Planet Killer" Limited new [Re: ngc2289]
      #5675021 - 02/11/13 11:59 PM

Just ordered one of Vic's 'Planet Killer's" --should ship in 7 -10 days. I've always wanted a long tube Fraunhofer achro with good coatings. I was looking for something fun, affordable and different from the usual f/7 suspects. While this is primarily a visual scope, I'm thinking that this achro with a Mallincam and a Baader fiilter should be a ton of fun for producing images for a lunar video.

I am blessed to own a "real' planet killer -- an 8" f/8 Cave reflector that I resto modded and mount on a G-11 --- that just rocks my world...Many nights I get a clean, tack sharp 400x with out any issues. For me a "Planet Killer" is a scope so good, that sky conditions are the only limiting factor.

Da Bear


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moynihan
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Re: Stellarvue "Planet Killer" Limited new [Re: Da Bear]
      #5675327 - 02/12/13 06:50 AM

Have the Astro-Telescope version. Same rings, different focuser, no removable section, different logo and focuser. Hope SV kept the dew shield mine and other versions have. A rare production refractor dewshield. 10" long, actually functional in moist air.

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Eddgie
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Re: Stellarvue "Planet Killer" Limited new [Re: DaveJ]
      #5675438 - 02/12/13 09:24 AM

Quote:

Hmmm. "testing regiment" Vic must have an entire army of testers.





First, I would be quite suprised if Stellarvue sold a telescope every day, so it would not be a surprise at all that they could test every telescope they sold by three people.

Second, they don't say how they test their telescopes, but using an artificual star and a clear lens cover with with a central obstruction, you can do a very comprhensive star test in less than 5 minutes that will tell you about the alignment, spherical abberations, or the presence of zones or turned edges, and the smoothness of the optics. If you know what you are doing, it is a pretty quick and easy thing to do.

And since like most manufacturers today, they don't really specify a very objective quality level of their scopes like PTV or Sthreh (Strehl is so much better), they only have to look for meaningful errors (and that is not a bad thing at all if they really do test every telescope to be sure that there are no meaningful errors).

Most of these small specialty companies simply don't sell that big a volume of telescopes, and they may make as much or more profit from the accessories and things they sell (field flattners, mounts, OEM products like eyepeices, etc) as they make from the telescopes they sell (and I am sure this is common in the industry).

I am sure that the quality will be good. Stellarvue has a well deserved reputation of selling good quality equipment.

But I am sure that they can be confident in this because the manufacturers they are using these days (yes, the ones in China) are proving that they can produce very high quality in serial production even with SCTs, with recent vintage SCTs routinely shipping with excellent optical quality.

But it never hurts to check, and even if it is a star test to just confirm that there are no major issues with the scope, Stellarvue is to be congratulated for their quality control efforts.


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ngc2289
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Re: Stellarvue "Planet Killer" Limited new [Re: Eddgie]
      #5675624 - 02/12/13 11:15 AM

Quote:

Quote:

Hmmm. "testing regiment" Vic must have an entire army of testers.





First, I would be quite suprised if Stellarvue sold a telescope every day, so it would not be a surprise at all that they could test every telescope they sold by three people.

Second, they don't say how they test their telescopes, but using an artificual star and a clear lens cover with with a central obstruction, you can do a very comprhensive star test in less than 5 minutes that will tell you about the alignment, spherical abberations, or the presence of zones or turned edges, and the smoothness of the optics. If you know what you are doing, it is a pretty quick and easy thing to do.

And since like most manufacturers today, they don't really specify a very objective quality level of their scopes like PTV or Sthreh (Strehl is so much better), they only have to look for meaningful errors (and that is not a bad thing at all if they really do test every telescope to be sure that there are no meaningful errors).

Most of these small specialty companies simply don't sell that big a volume of telescopes, and they may make as much or more profit from the accessories and things they sell (field flattners, mounts, OEM products like eyepeices, etc) as they make from the telescopes they sell (and I am sure this is common in the industry).

I am sure that the quality will be good. Stellarvue has a well deserved reputation of selling good quality equipment.

But I am sure that they can be confident in this because the manufacturers they are using these days (yes, the ones in China) are proving that they can produce very high quality in serial production even with SCTs, with recent vintage SCTs routinely shipping with excellent optical quality.

But it never hurts to check, and even if it is a star test to just confirm that there are no major issues with the scope, Stellarvue is to be congratulated for their quality control efforts.


Achro's strehl of .9 or better, APO's .95 or better.

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Eddgie
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Re: Stellarvue "Planet Killer" Limited new [Re: ngc2289]
      #5675633 - 02/12/13 11:22 AM

Is this their "Published" and guarenteed optical guality?

Do they use an interferometer to test every sample they receive before it gets shipped?

Or is this the requirement that they simply specifiy to their vendor?

I don't at all doubt that they could provide scopes of .95 strhel or better, but I doubt that they test every sample personally on an interferometer themselves, and that is the primary remark I was addressing.

I have not seen them publish this as a guaranteed standard though, and if they do, my hat is off to them. I wish all manufacturers would do so.

And again, I don't doubt the quality, only that they personally run every sample through an interferometer.

Their manufacturer might, but the post implied that Stellarvue does it themselves. I could see them just doing a quick star test to ensure that everything is OK though.


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ngc2289
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Re: Stellarvue "Planet Killer" Limited new [Re: Eddgie]
      #5675674 - 02/12/13 11:49 AM

SV has their own test equipment, and they do test every lens they receive. If the lens dose not test to their spec.'s it gets sent back. Yes the spec.'s are what the vendor is required to provide.

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peleuba
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Re: Stellarvue "Planet Killer" Limited new [Re: ngc2289]
      #5675719 - 02/12/13 12:13 PM

Quote:

Achro's strehl of .9 or better, APO's .95 or better.




Why only 0.90 for achromatic objectives? Its generally easier to figure achromats as the glass is not as fragile and the curves are usually not as steep. In addition the blanks used are readily found in the highest internal quality.

Seems to me that in the wavelegnth the lens was nulled in the quality should be higer then .90


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ngc2289
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Re: Stellarvue "Planet Killer" Limited new [Re: peleuba]
      #5675748 - 02/12/13 12:28 PM

I would have to guess. But, here are my guesses. 1) Price point. The achro., and ED are sold at a lower price point. 2) Any improvement in detail you would get from a higher strehl would be negated by the chromatic aberration. But those are just my guesses.

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Eddgie
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Re: Stellarvue "Planet Killer" Limited new [Re: ngc2289]
      #5675787 - 02/12/13 12:48 PM

Yes, perhaps it is the polychormatic strehl.

A 4" achromat would have to be about f/16 to have a polychromatic strehl of .95 I think.

Many people feel that polychomatic Sthrel doesn't matter because the scopes are optimized for green, but energy is energy, and if you put some percentage outside of the Airy disk diameter, it still lowers contrast.

Suiter addresses the subject in his book on star testing and comes to the same conclusion.

But anyway, if Stellarvue tests every lens on an interferometer and has will not ship anything below .95/.90, I am happy to hear that. I wish more companies did.


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ngc2289
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Re: Stellarvue "Planet Killer" Limited new [Re: Eddgie]
      #5675802 - 02/12/13 12:56 PM

Vic had to delay production on the 90mm APO one time. Because all the lenses his vendor sent failed to pass the quality check. So the lenses were sent back to the vendor.

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t.r.
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Re: Stellarvue "Planet Killer" Limited new [Re: Eddgie]
      #5675812 - 02/12/13 01:02 PM Attachment (21 downloads)

Quote:

A 4" achromat would have to be about f/16 to have a polychromatic strehl of .95 I think




It would need more than that (F/24) according to this...


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Thomas Karpf
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Re: Stellarvue "Planet Killer" Limited new [Re: Eddgie]
      #5676039 - 02/12/13 03:10 PM

Quote:


And again, I don't doubt the quality, only that they personally run every sample through an interferometer.





Stellarvue does zygo AND star testing of every scope. They're a bit pricier than other 'similar' scopes because that testing takes time, and time costs money.

http://www.optcorp.com/category.aspx?uid=1-600-765


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mikebb
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Re: Stellarvue "Planet Killer" Limited new [Re: Thomas Karpf]
      #5676388 - 02/12/13 06:17 PM

Has any one considered the Lunt 102ed f/7 for $729 over the SV102 "Planet Killer". Since most comments indicate an ED scope will have better color correction, etc. Just musing after reading this thread.

Edited by mikebb (02/12/13 07:08 PM)


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Jon Isaacs
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Re: Stellarvue "Planet Killer" Limited new [Re: mikebb]
      #5677071 - 02/13/13 06:29 AM Attachment (22 downloads)

Quote:

Has any one considered the Lunt 102ed f/7 for $729 over the SV102 "Planet Killer". Since most comments indicate an ED scope will have better color correction, etc. Just musing after reading this thread.




THere are several scopes one might consider, the Lunt is one. The various versions of the Synta/Skywatcher/Vixen/Celestron/Orion ED-100. At F/9 with the FPL-53 doublet, these are pretty darn good.

But to my mind, none of these really qualify as "Planet Killers", an 8 inch F/6 Dob at $380 shipped to the doorstep is much more capable.

Jon

(When I think of a "Planet Killer", this is what I think of:)

Edited by Jon Isaacs (02/13/13 06:34 AM)


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Jon Isaacs
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Re: Stellarvue "Planet Killer" Limited new [Re: Thomas Karpf]
      #5677072 - 02/13/13 06:32 AM

Quote:

Quote:


And again, I don't doubt the quality, only that they personally run every sample through an interferometer.





Stellarvue does zygo AND star testing of every scope. They're a bit pricier than other 'similar' scopes because that testing takes time, and time costs money.

http://www.optcorp.com/category.aspx?uid=1-600-765




Do you get the results of the Zygo with the scope? It is my undertanding that a Zygo Interferometer is useful when figuring the lens but it is also my understanding that these lenses are figured elsewhere, coated elsewhere prior to testing.

Jon


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