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Anyone have the 150mm IOPTRON mak?

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#26 bobhen

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Posted 08 October 2011 - 08:11 AM


To some extent. Will a 4-inch best or even come close to equaling an 8? Unlikely unless the 8 has a shaving mirror for a primary.


Try an experiment.

Cut a “D” shaped aperture mask for your 8 inch SCT. The back of the “D” should be deep enough to cover the central obstruction. You will now have an unobstructed “D” shaped clear aperture.

Take the mask off - point the scope at the moon. Look at low contrast areas where the lunar grays are close – look at the bright rim walls and peaks where the light is strong.

Put the mask on and revisit the same areas. Remember that the mask has eliminated over half of your aperture. Try this in various seeing conditions.

Report back.

Bob

#27 barasits

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Posted 08 October 2011 - 04:35 PM

How to take all the fun out of astronomy: start handing out homework assignments. :p

My Quantum 4 shows less detail on Jupiter than my 8 inch SCT. Aperture wins. But both are obstructed, and the question is whether obstruction cancels out the resolution advantage of aperture, so I propose another experiment: send me your premium refractor and I'll be happy to compare it with the views provided by my 8 inch SCT. Given the rarity of good seeing at my location, this experiment may take a very long time.

Geoff

#28 rmollise

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Posted 08 October 2011 - 06:32 PM

Try an experiment.

Cut a “D” shaped aperture mask for your 8 inch SCT.


I don't have to report back. I've done this many times. The result is always the same. The 8 blows the doors off the 4. Except...in times of bad seeing, the off-axis aperture mask will deliver an _aesthetically more pleasing_ image. You will, however, always see more details at full aperture--or than you would see with a small refractor--since the seeing almost always steadies out at least briefly.

Sorry...can't fool that cruel old dame, Ma Nature. :lol:

#29 bobhen

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Posted 09 October 2011 - 11:47 AM

Sorry...can't fool that cruel old dame, Ma Nature. :lol:


How do you account for the following? Some of these reviewers have extensive (decades of) experience.

From Ed Tng’s review of a Meade 7” Mak.

“The results were very close. In times of good seeing, the Mak slightly
edged out the FS 102 Takahashi. However, during times of average or slightly un-steady seeing, the refractor won out, and in fact the FS102 gave the more consistently excellent images.”

From Jay Reynolds Freeman’s review of a C14 against a AP 7” Apo Refractor – right here on CN The Apo has half the aperture of the C14.

“With respect to lower-contrast detail, I do not think the C-14 was doing as well as the AP 180. I don't think I had as good a view of the big garland through the C-14, and I had much more difficulty seeing some fine, east/west streakiness in cap of Jupiter's northern hemisphere, say, north of Jovian latitude 50N. Also, prominent color contrasts and intensity variations, seen in comparing large-scale features, such as the equatorial belts and the adjacent zones, did not appear to me to be as pronounced in the C-14 as in the refractor.”

From Rodger Vine’s review (here on CN) between a C8 and a TMB (LZOS) 4” F8 Apo refractor

“(On Mars) The C8 still delivers a big, bright orange ball that just hints at the details the APO shows clearly.
My wife agrees – round one to the APO in these conditions.

(On the Moon) In the C8 the image is much brighter, but there’s less detail. I keep swapping back and forth over a period of several hours to check, but it’s true. A white smudge in the C8 resolves down to a tiny crater in the APO. I see details in Gassendi – rilles, slumping, craterlets, that are just a smear in the C8. From the domes of Mons Rumker to the hills and embayments around Gassendi and the edges of lava flows on the mare near Aristarchus, the APO shows more detail.”

From Mr. Yoshida (from Japan) a seasoned amateur astronomer. “The criterion is how these scopes perform on planet viewing. I think the order is roughly within our expectation.”
Note the much smaller refractors ahead of the C11.

(96 points) ASTRO-PHYSICS 160EDF
(96 points) Zeiss APQ150
(96 points) Takahashi TOA-150
(95 points) TMB 152mm/F8-CNC-LW
(95 points) Takahashi_-250
(93 points) ASTRO-PHYSICS 155EDFS
(90 points) INTES-MICRO ALTER A-608
(90 points) ZEN250
(88 points) C-11”

From Ralph Aguirre’s review between a C8, Tak TSA 102, and a MK67

“For tonight, with steadier seeing conditions, the smaller, but very potent Takahashi TSA-102, was clearly showing more resolution by pulling out surface details (on Jupiter), that the larger mirrors couldn't even see.”

Bob

#30 rmollise

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Posted 09 October 2011 - 12:54 PM

How do you account for the following? Some of these reviewers have extensive (decades of) experience.


They pretty much echoes what I said in my last post. To wit: "In times of poor seeing, a small telescope can present an _aesthetically more pleasing_ image." That does not mean it will deliver more detail.

I'm not obligated to account for anything, btw. If you want to believe that a telescope can best one with a 400% advantage in aperture, that is your right. Just as it is MY right to say that my experience is, "Tain't so." My experience over nearly half a century of observing is "Aperture Always Wins." ;)

#31 BillP

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Posted 06 June 2012 - 03:03 PM

In above average seeing, he felt the Tak TSA 102 delivered the most details and could be pushed to (and take advantage of) higher power over the other two when seeing allowed.


I have no doubt that this was the case for him. Question is why? I have had many an evening where my 4" APO cleanly bested larger SCTs, MAKs, and Newts for planetary observing when all have passive cooling for acclimation. From an operational standpoint I've found this to be the routine case. IMO the driving reasons are: 1) Atmospheric Seeing, and 2) Thermal Acclimation Attributes of each Scope Design.

I have also had a number of evenings where an APO much larger than my 4" did not show any more details on planetary as well. To me this is just further evidence that we really do live in a seeing-limited universe here on Earth. I always find it curious how professional observatories fight and strive to ever get to have consistent sub 1 arcsec seeing, yet most user reports find that they can see more details routinely when compared to 1 arcsec scopes (i.e., 114mm objective). I think what is more likely, is that people have a few fractions of a second views here and there when seeing is truely sub 1 arcsec and of course we all remember the best of the views for the evening and not the average. For myself, I would estimate from my observing location that maybe 20% or less of the evenings I observe have seeing steadier to show more details than what my 4" can reliable achieve. So they do happen, but a lot less frequently than we are led to believe IMO.

On the second point of equillibrium, I think this is probably the biggest reason that smaller APOs beat larger other designs...especailly for passively cooled scopes. I've had 3 or 4 passively cooled SCTs and it took them forever and once there they could never keep up with the changing temps. This being the case once we got to operating planetary mag the 4" APO would more often show a better picture with more and clearer details than the larger ones could. Sure there would be microseconds where the larger scopes would see more, but it was an in and out affair and frankly probably 10% of the eyepiece time was with the more details and the rest of the time was waiting. With the more thermally stable 4" APO however, it is generally opposite with way more that 80% of the observing image stable and shapr with only occassional jitters.

Bottom line, there are so very many who report the same thing, that smaller refractors show more details than larger other designs, that it is really impossible to say it does not happen often because we see that it does for numerous observers. The question is not that it does not, but why it does fall out this way. So the physics of resolution are not really at issue at all and these smaller scopes are not performing magic optically, they are just engineered for the enviornments they are in better, so therefore perform better over a given time period on average. As always, the best option it to have a smaller refractor teamed with a larger mirrored instrument so that way you get the best of both worlds. Oh yes, this is only for planetary observing...turn to DSO and the larger will always see more.

#32 saemark30

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Posted 06 June 2012 - 03:58 PM

I have found that a good 6" Newtonian like RV-6 will beat an Intes MK67 when observing Jupiter.
The Newt has 25% obstruction or less, which really does make a difference.
I agree with BillP, we are mostly seeing limited or thermally limited. Put a fan near the mirror and see if that improves matters.
An unobstructed 4" telescope does show more constrast than a 6" MCT. Take the formula 6" - 2"=4". That's with 33% obstruction.

#33 seeindoubles

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Posted 04 December 2012 - 01:39 AM

I purchased one of the iOptron 150 Maks last July. When it arrived it was double boxed. The first being a heavy cardboard overpack carton. Inside was the factory carton with iOptron logo tape over all the box flap joints. Original factory pack seals.

When I opened my new OTA I immediately had the following observations:

First, I heard a clunk. Upon investigation I found that all the collimation screws were backed off allowing the primary mirror to flop around during shipment. It was still loosely anchored to the rear cell but only by a few threads. S&T never reported anything like this in their fairly glowing review.

Second, the finder mount is not of the common and more stable and higher quality Vixen type vee mount. Instead it was a fairly imprecise "tray" type mount where the finder base can slide through instead of in to a point where it gets tighter and more stable. One 6mm clamp screw secures the base. When tightened it seems to lock up stable enough but compared to a Vixen type base it seems sloppy.

Third, The finder provided seems fairy high quality. It is a bright and clear 50MM straigh-through unit. However the means of holding and centering the finder OTA in the provided rings leaves much to be desired. The finder had two cheesy pieces of clear cellophane film or tape to go between the 6, 6mm holding/adjusting screws. The cellophane film is easily dislodged allowing the screws to directly impact the nice pebbled finish paint on the finder. This whole arrangement seems very second-rate to what they could have easily done. I tapped out the 6mm screw holes to 8/32 thread and used six Nylon thumbscrews. This allows perfect alignment of the finder without the worry of marring the paint finish on the finder tube assy.

Fourth, the dovetail rail bolted to the substantial OTA is not exactly a Vixen pattern rail. It is black anodized and has a thicker bottom section that can be marred by installation in a CG5 or EQ5 type mount. I used a Skywatcher EQ5G with the scope. While the mount is well matched to the scope, the mounting of the vee block is much less secure feeling than if the OTA had an actual Vixen dovetail. It forces you to over-tighten in order to be sure the OTA is secure in the mount. Doing so marrs the nice black anodized dovetail.

Fifth, there was no operational manual, certainly nothing that would help guide a novice in making normal adjustments. Collimation for example.

It was fairly quick to collimate the optics of the iOptron Mak using a Cheshire eyepiece. Once done the images were very good to excellent once the OTA cooled down. Nice clean airy disks on stars and beautiful lunar and planetary detail on Saturn were the reward for some fine adjustments on my rough alignment of the optics. Double stars like Epsilon Lyrae (The Double-Double) and Porrima were split pretty easily when the air was stabilized. I was also able to obtain a few test shots of Saturn via my Canon DSLR running Backyard EOS.

The dual speed focuser supplied with the OTA is very nice. It also really does help keep control of image shift and function is very smooth.

The quick detachable dew-shade is a nice touch, although the weight when added can affect scope balance on your German equatorial mount. I plan to modify my dew shade by carefully locating three holes on the scope end of the dew shade and tapping to 8/32 and installing some nylon clamp screws. This should make the dew shade a much better fit.

#34 ohioalfa64

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Posted 04 December 2012 - 08:36 PM

I take possession of mine on Thursday.






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