tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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Luigi - that is very interesting, I like that graph...
Tim
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isramirez
Carpal Tunnel
Reged: 11/04/05
Posts: 1647
Loc: Mexico City
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Quote:
... diffraction spikes cause by thin vanes, and the moderate coma in a Newt don't much bother me, but that's an entirely personal preference...
 I fully agree with you!
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Santel MK9 & MK6
IntesMicro 715 1/8ptv (Killer of TEC140 & Taka 5in APOs planetary-urban-legends)
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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Quote:
The smallish diffraction spikes cause by thin vanes, and the moderate coma in a Newt don't much bother me, but that's an entirely personal preference and I realize they do bother others. I guess I just accept them as a characteristic of the design rather than a flaw. Probably part of that is having seen so many astro photos over the years with diffraction spikes, from the 200" Palomar to Hubble.
I am OK with diffraction spikes, they just have not grown on me for planets... maybe with more experience, I will grow to ignore them, but for planets I like that crisp, clean disc with no spikes...
... and why when I look for a Newt (or build one) I will try to employ some best known methods with curved vanes and razor thin to boot.
Now that we are on the subject of contrast, poorly defined spiders (too thick especially) also will be more than just a cosmetic spike - it too will affect contrast if too thick past a certain limit - much like CO past a certain limit robs contrast - same optical principle as the CO - it is something in the light path blocking the scopes ability to perform in the low - mid spatial frequencies...
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Posts: 15373
Loc: Petaluma, CA
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I generally don't notice diffraction spikes in my Dobs or my Newt on planets. Diffracton spikes seem to be more noticeable on bright point sources like stars rather than bright extended objects like planets.
I've come up with another option here - Parks 8" f/6 Newtonian OTA ($899) with Parallax Instruments Rotating Rings ($450). For less than the cost of a 6" MN (the least expensive scope on my consideration list), I can have an 8" f/6 Newtonian OTA with fiberglass OTA, 22% CO, very nice rotating rings and an optical design I am very familiar with and know suits my observing locale which tends to be quite dew prone.
Valid?
- Jim
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“I observe vicariously, through myself. When I purchase a new telescope, it's value increases. At star parties, attendees line up to observe me. My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things. At historic observatories I am allowed to touch the equipment. My legend precedes me the way the Big Bang precedes everything else.”
- The Most Interesting Astronomer in the Universe
Edited by jrbarnett (10/07/07 05:59 PM)
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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This could be a choice that hits the sweet spot. Looking at their website, the only thing that raises a question in my mind is the lack of data / description of the mirror. All it says is:
"Parks LEGENDARY fine annealed diffraction limited Pyrex mirrors and the highest quality mechanical and optical components throughout."
If its legendary, what is the wave front, reflectivity, etc? Must be a legend to someone, so why not state who makes it, etc?
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Posts: 15373
Loc: Petaluma, CA
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Parks makes its own optics and has been doing so since 1954. The are based in Southern California. Parks also used to manufacture equatorial mounts for Cave. Actually the "better" deal looks to be the 8" f/6 "Superior" set up that includes a traditional Cave-style equatorial pier mount for $2899 as it includes the rotating rings, but portability issues and the 10-14 month wait kind of put that one out of the cards.
True they don't give wavefront data and such, but then again, neither did Zambuto until somewhat recently. There was a multi-scope review in one of the astro-mags in the last several years where the Parks Newtonian (a 6" if memory serves) had the best optics in the bunch. I think the others were mass-produced Asian optics. The mirrors are aluminized and silicon monoxide overcoated. I'd figure 88-89% reflectivity.
I suppose I could make due with some less costly non-rotating rings; that's what I have on my vintage Meade 6" f/8, but I think the rotating rings would be nice.
And yet the seated viewing offered by the M715D still beckons...What to do, what to do...
Regards,
Jim
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“I observe vicariously, through myself. When I purchase a new telescope, it's value increases. At star parties, attendees line up to observe me. My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things. At historic observatories I am allowed to touch the equipment. My legend precedes me the way the Big Bang precedes everything else.”
- The Most Interesting Astronomer in the Universe
Edited by jrbarnett (10/07/07 10:39 PM)
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isramirez
Carpal Tunnel
Reged: 11/04/05
Posts: 1647
Loc: Mexico City
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Jim,
You know you want that 715D  just order that beautiful maksutov and... be happy 
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Santel MK9 & MK6
IntesMicro 715 1/8ptv (Killer of TEC140 & Taka 5in APOs planetary-urban-legends)
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Posts: 15373
Loc: Petaluma, CA
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You are a bad man, Israel. But I respect that.
Thanks,
Jim 
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“I observe vicariously, through myself. When I purchase a new telescope, it's value increases. At star parties, attendees line up to observe me. My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things. At historic observatories I am allowed to touch the equipment. My legend precedes me the way the Big Bang precedes everything else.”
- The Most Interesting Astronomer in the Universe
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Posts: 15373
Loc: Petaluma, CA
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The waiting game begins. I pulled the trigger on the M715D. I am buying from Mark at Teton Telescopes in Rigby Idaho. He's a patient fellow and extremely responsive. Israel Ramirez's nice corrector plate shot and Phil Barker's CN review clinched it for me.
Next stop: Mars.
Regards and thanks to each and every one of you for your feedback and guidance.
- Jim
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“I observe vicariously, through myself. When I purchase a new telescope, it's value increases. At star parties, attendees line up to observe me. My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things. At historic observatories I am allowed to touch the equipment. My legend precedes me the way the Big Bang precedes everything else.”
- The Most Interesting Astronomer in the Universe
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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COngrats Jim!!
You do realize you bought my scope, I almost pulled the trigger on that very one Mark had about 4 times... as recently as two days ago, I had discussed perhaps getting it from him! Well, I guess money talks, BS walks! (At least now that you feel guilty, you will let me borrow it for a couple of months )
And you are right, Mark is great to deal with. The astro biz needs more like him... having a guy with such a passion for observing himself, and the experience combined with being a good guy means we the customer get better service in the end... I enjoyed talking with him, the conversations always went to other parts of astronomy as he loves to talk about it...
Tim
PS - You are a busy guy... noticed an ad for a Meade too...
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isramirez
Carpal Tunnel
Reged: 11/04/05
Posts: 1647
Loc: Mexico City
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Congratulations Jim 
That pic is not mine but from a guy with a IM815 scope i've posted it in other threads regarding IntesMicro Mak-Cass scopes too
Tim,
Sounds interesting... I believe i need to chat with Mark from Teton Telescopes, i really need an electronic focuser for my Russian Maks but i don't know which model is the proper for these scopes  ... and by the way, i wonder which diagonal mirror he suggests as a real upgrade from the standard IM diagonl
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Santel MK9 & MK6
IntesMicro 715 1/8ptv (Killer of TEC140 & Taka 5in APOs planetary-urban-legends)
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion
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Luigi
Postmaster
Reged: 07/03/07
Posts: 5317
Loc: MA
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Wow! Great scope. Congrats. It's really nice that it has a fan installed. Fans make a world (a universe?) of difference in CATs.
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17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Posts: 15373
Loc: Petaluma, CA
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Thanks guys. I am looking forward to first lighting the scope as early as this coming Saturday. I am also looking at a diagonal upgrade. I am leaning toward the WO 2" dielectric as it comes with a free SCT thread coupling as well as a conventional nosepiece for a reasonable price.
Regards,
Jim
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“I observe vicariously, through myself. When I purchase a new telescope, it's value increases. At star parties, attendees line up to observe me. My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things. At historic observatories I am allowed to touch the equipment. My legend precedes me the way the Big Bang precedes everything else.”
- The Most Interesting Astronomer in the Universe
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maknewtnut
Member
Reged: 10/08/06
Posts: 1333
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Technical Innovations RoboFocus
MaxBrite or EverBrite with a visual back. If you're going to spend some extra bucks for an a/mkt diagonal, skip over the all to easy to find dielectrics and get the primo stuff.
Tell 'em I sent ya'
Mark
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maknewtnut
Member
Reged: 10/08/06
Posts: 1333
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Made my post to Israel before I saw Jim's, so at least let me add some parity. I use the WO SCT myself right now, but I already had one.
Mark
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Luigi
Postmaster
Reged: 07/03/07
Posts: 5317
Loc: MA
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Before you spring for a diagonal, compare the views through the scope with and without your current diag. This'll demonstrate what your losing with your current diag, and the most you could possibly gain from a diag upgrade.
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17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
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isramirez
Carpal Tunnel
Reged: 11/04/05
Posts: 1647
Loc: Mexico City
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Thank you so much Mark going to check the details of those options
--------------------
Santel MK9 & MK6
IntesMicro 715 1/8ptv (Killer of TEC140 & Taka 5in APOs planetary-urban-legends)
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion
|
isramirez
Carpal Tunnel
Reged: 11/04/05
Posts: 1647
Loc: Mexico City
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Quote:
Before you spring for a diagonal, compare the views through the scope with and without your current diag. This'll demonstrate what your losing with your current diag, and the most you could possibly gain from a diag upgrade.
Luigi,
That's true  actually i did something similar for astrophoto and found my pics were clearly improved but i want the new diagonal for visual... i'm going to do some tests before purchase anything 
Thanks by the advice!
--------------------
Santel MK9 & MK6
IntesMicro 715 1/8ptv (Killer of TEC140 & Taka 5in APOs planetary-urban-legends)
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion
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