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Kunming 152mm observing report from TSP

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#1 Don Taylor

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Posted 28 May 2014 - 12:42 PM

As reported in this CN forum early this year I'd bought one of these wide field 6" refractors from fellow CN'er Joshua B. Kansas winter and subsequently a move back to Texas has prevented more detailed observing and a suitable report until now.

While I've attended OTSP and RMSS several times this is my first TSP. But I've been observing out here many dozens of times with 8, 10, 14, 16, 18, 25, 30, 36, and 82" scopes so have a reasonable idea of conditions.

A club member offered me space in his RV this year and since he was bringing a 22" Dob I elected to bring only the 6" on the Duo-T alt azimuth mount, binoculars, and a small selection of eyepieces.

As has been discussed/debated as nauseum here - fast achromats have a lot of limitations - chiefly lots of CA on bright objects, and not enough aperture to show the faint fuzzies.

All that said - I'm having a wonderful time with the late spring sky here. The scope delivers pin point stars across the field. It's very easy to use, and shows many objects far brighter than I would have expected. While no big Dob, nor the first choice for finding ring galaxies I've really enjoyed the level of detail visible in galaxies and bright nebulae. I can see how this might be a killer Messier Marathon instrument as Jim Barnett suggested.

Probably the only letdown was trying to see the entire Veil nebula at once - the Meade 5000 SWA 40mm yields 22.5x and a 3 degree field in this scope. But the Veil was (of course) displayed around the extreme edge of field. An odd sensation. Use averted vision by staring straight ahead I guess? Anyway, not the scope's fault. A little more aperture would help the O-III filter though.

Views of Omega Centauri were quite breathtaking in every eyepiece used from the 40mm to the ES4.7 but it seems to really like the Meade 5000 SWA 28mm, and 17T4, 13T6, 9T6 Naglers. Fun to compare to the many globs visible - especially to note the differences in size, brightness, and condensation.

Poking around in Sagittarius and Scorpio was amazing - the low magnification lets you jump from cluster to nebula to star cloud to .......and suprisingly nice views of the showpieces. Really what this scope is intended for.

While having a look at the Sombrero I did have a go at the Antennae and yes, the combined nuclear condensation was visible with some detail. Spiral structure quite obvious in M51 and M83. Not bad.

Poking around in the Virgo cluster was good too - and the wide field made following Markarian's Chain child's play with the 28mm and 17T4. I guess I should have tried that with the 40mm and had it all in the FOV at once. Maybe I'll try that tonight.

CA? Only on Jupiter and the bright stars and I didn't come out here to observe them. Loss of contrast compared to an APO? - yes, can't overcome the optical laws. But would the 6+ times cost for a 6" apo be justified? That of course is a personal decision and depends on one's interests and desires. I'll leave that to each of you.

Aperture? - enough to see detail in many many interesting objects from a dark sky. But If you want stunning detail you really need a big Dob.

So - should this be one's only scope? Probably not unless one's interests are sweeping a dark sky and soaking in the grandeur of it all. And having a closer look when detecting something interesting. No - it won't replace my Lightbridge and not the scope for fine planetary detail but a heck of a lot of fun.

It has challenged me to be a more patient observer - less horsepower, wider field, more about the large scale of the sky. I'm glad I brought it to TSP.

And I'm glad I bought it.

#2 Markab

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Posted 28 May 2014 - 12:54 PM

How high up is Omega Centauri from there? Seems like south Texas isn't nearly southern enough to have a good view...I saw it in Costa Rica, but of course, that is around 1,500 miles south of the southern tip of Texas.

And I agree with you, this last winter in Kansas was horrible, although I do remember Texas having a lot of subfreezing afternoons as well.

#3 Don Rudny

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Posted 28 May 2014 - 01:20 PM

How high up is Omega Centauri from there? Seems like south Texas isn't nearly southern enough to have a good view...I saw it in Costa Rica, but of course, that is around 1,500 miles south of the southern tip of Texas.

And I agree with you, this last winter in Kansas was horrible, although I do remember Texas having a lot of subfreezing afternoons as well.


Looks like it's 14 to 15 degrees on altitude in south Texas. It's 22 to 23 degrees here on the Big Island of Hawaii. We're the furthest southern point in the US. We can see the Southern Cross from here.

I have the ES 152 AR f6.5 and like it as well.

#4 Don Taylor

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Posted 28 May 2014 - 01:20 PM

Omega is at -47 and TSP is at +30.6 so it culminates at ~ +12

The local terrain at Prude Ranch is a line of hills to the south so it's about 5 degrees above the local terrain ( a clenched fist's height at arms length).

There was a little atmospheric extinction last night but much more detail seen in Omega than any other glob in the sky last night.

I have previously observed Omega from the McDonald observatory parking lot with an 18" Obsession and of course the views were even better.

A couple of years ago we set up at Cheney Lake SP west of Wichita Ks purely to see Omega Centauri. Terrain is flat with a distant tree line and it was visible above the trees but poor view due to atmospheric conditions. I recall Wichita is about +38 and it was just above the trees.

Last night Omega was more obvious to the naked eye (and visibly larger) than M13 well up in the eastern sky.



#5 Markab

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Posted 28 May 2014 - 01:28 PM

Good report, Don! Thanks! I live in the KC area so at nearly 39N...in actuality it could never be seen here due to atmospheric extinction. Gives me another reason to go back to Costa Rica! :) From there, the Southern Cross was about 30 degrees high or so...beautiful!

#6 Phillip Creed

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Posted 28 May 2014 - 06:01 PM

Love the report, Don. A 6" scope is small-ish in the reflector world, but quite sizable among refractors. And as you point in your report, even a small scope is quite lethal given a dark-enough sky. A fine example of "QRP Astronomy", as Rod Mollise might say.

Clear Skies,
Phil

#7 BillP

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Posted 29 May 2014 - 07:44 AM

About as perfect of an observing report as I have ever read! Excellent job at bringing home the attributes and limitations of this observing tool and the joy you found in its use :waytogo:

#8 Don Taylor

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Posted 29 May 2014 - 10:09 PM

Markab, Don R, Phil, and Bill: Thank you for the kind remarks!

#9 stevew

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Posted 30 May 2014 - 12:05 AM

Great report!
A good RFT under a dark sky is certainly an enjoyable way to spend a night under the stars. I had a 6 inch F-5 Jaegers for many years and always enjoyed the wide filed views.
It's such a shame Kunming 152 is no longer available in North America.

Steve

#10 Lane

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Posted 30 May 2014 - 02:33 AM

Very Nice report and good to see someone else enjoying one of these scopes. I have been taking mine to the dark site the last few months instead of my C11 and I have been very impressed with its performance on just about everything. Really a lot of fun using this scope. I am planning to do some side by side comparisons to my C6 and C8 in the future, but I wish I knew someone close by that has a 6" APO, I would really like to see what the actual difference is beyond the CA issue.

#11 jbalsam

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Posted 30 May 2014 - 08:02 AM

Glad to hear my scope has found a good home. I do regret selling it occasionally...

#12 kmparsons

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Posted 30 May 2014 - 09:52 AM

Thanks, Don, for the great observing report.

I have seen Omega Centauri quite clearly from the latitude of Atlanta (latitude 34 degrees), so it is pretty easy to see well from here in the Houston area (29 degrees). Of course, nothing compares to being able to see it high in a dark sky from a southern hemisphere site.

The issue of aperture vs. glass is one that gets discussed quite a bit here. For those, like me, who are forced to to most of our observing from light polluted sites--like my back yard--a small to medium sized apo is a great thing to have. The glare of the yellow-eyed son-of-a-*BLEEP* of a nearby streetlight washes out pretty much all of my deep sky. But the apo compensates by giving great views of what I can see-the moon, the planets, and the brighter clusters, double stars, and nebulae. Under a dark sky, though, I think aperture really is king. Since a 152mm gathers over twice the light of a 102mm, it really can reveal the richness of the deep sky.

#13 MtnGoat

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Posted 03 June 2014 - 12:53 PM

Thanks for the great report, you do a nice job of capturing your intent, reservations, and appreciation as you figured out exactly what to use it on!

I was a latecomer to the refractor game, having started out with my buddies 6" newt back in the day until I picked up an 8", and then on up from there. A couple years ago I picked up a ST90 on a whim because it was portable, and I installed a new pier next to the reflector/SCT pier.

As time went by in side by side use, I found myself gravitating to the ST90 for a heck of a lot of objects. Yes, the CA was a pain...but on everything else but very bright things, a wonderful field of view...fainter...but the stars are soooo pinpointy! And all the way across the field, too! This is when I realized that i was becoming appreciative of the ol refractor magic...and then of course, I needed more.

So then came the CL deal on a meade DS2102 for fifty bucks. Spectacularly sucky focuser, (magically, the rack is NOT stripped)but 12 more precious mm, and pretty nice views! But then even that wasn't enough, so last fall came the AR6.

This is when I became fairly enthralled with what 6 clean inches of aperture can do, and as you describe perfectly...what it can do, it does in spectacular fashion. The girlfriend says she loves the tack sharp focus compared to the LX200 10". Both have crayfords..but the fact is, we both agree the pinpoints are pinpointier in the AR6, and we both love that!

Lugging out the 10 is now reserved for nights when I feel like going deep, because the rest of the time, the AR6 has taken over the show. I am continually amazed at the just how much it does reveal, even on galaxies where I was certain aperture was 100% king. I now think it's 70% king, because the fact is, to me the AR6 reveals context and a crispness the SCT doesn't, even if the SCT goes deeper and brighter. Same on globs...yup the 10 knocks you out, but the refractor is *crisp*.

So I came to the party late on the refractor deal, but I like this party, and I'm staying! That 6 will do me. For now. Though, I did see Istar has some 8" glass for under 2k, and ........

#14 Jon_Doh

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Posted 04 June 2014 - 08:59 AM

Lugging out the 10 is now reserved for nights when I feel like going deep, because the rest of the time, the AR6 has taken over the show. I am continually amazed at the just how much it does reveal, even on galaxies where I was certain aperture was 100% king. I now think it's 70% king, because the fact is, to me the AR6 reveals context and a crispness the SCT doesn't, even if the SCT goes deeper and brighter. Same on globs...yup the 10 knocks you out, but the refractor is *crisp*.

So I came to the party late on the refractor deal, but I like this party, and I'm staying! That 6 will do me. For now. Though, I did see Istar has some 8" glass for under 2k, and ........


That's been my experience as well comparing a good quality refractor to an SCT that has a much bigger aperture.

#15 Scott in NC

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Posted 04 June 2014 - 09:02 AM

Very nice report, Don! I'm sure Omega Centauri looked fantastic in that scope. :jump:


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