Posts Made By: Vahe Sahakian

If planets are one reason for considering the 5" IM Mak I would reconsider a 5" MN which has a smaller co. and is much better on planets.
6" would be the smallest Mak that I would consider for planets.

Vahe

ApoMax is a primarily a visual refractor, at f/12 any of the glasses that you have listed will produce a decent performer. In the early nineties AP used FPL52 for their smaller F/8 and larger F/9 triplets with very good color correction. As a planetary refractor 130mm aperture is the main issue with this scope, to me the minimum aperture for capturing serious planetary detail starts at 6”, I do not see spending that kind of $$ on a planetary scope with aperture limitation.

Vahe

Largely depends on your location, a 6” MC is small enough to function without cooling fan if your observing location experiences temperature drops in the range of 20 to 25º F during day and night. In high and dry locations where temp variations can reach 40º F you will need some form of active cooling to keep up with the ambient during rapid temperature drops that begins right after the sunset.

Vahe

For what you have to pay for the kit you can purchase a mint condition Russian Mak.
I constructed a 6" Gregory Mak some years ago, for a DIY's assembling the mechanical parts with all the precision required to do justice to this scope really is not worth the effort, particularly now that you can purchase a fully assembled system for the price.

Vahe

I have one of the earliest G11’s, it has Celestron on it, the most important maintenance for this mount is de-greasing the clutch discs. The clutch design is the weak point of this mount and when it gets greasy it loses what little grip that it has. The grease will somehow find its way to the plastic clutches and when that happens you must clean up the assembly.
With my mount I generally clean the clutches twice a year, it really makes a huge difference in the holding power of the mount particularly if you are using a longish refractor with heavy accessories hanging on its tail.

Vahe

Several cents worth of opinion from a TEC6 owner.

First, the TEC6 with a 29.6% co is a general purpose MC, the new IM615 is optimized for high power use, in Maksutov Cassegrains you can not have it both ways, you need to decide what you want based on your priorities and go for it.

In Gulf Coast area the cooldown has not been a problem with my TEC6, but with larger TEC Maks, yes, cooldown is an issue.

For lunar/planetary work a Mewlon180 is preferable to TEC6, aperture wins. As for a 4” apo recommended by others, my opinion on that is that for planets 4” aperture is too small for capturing serious detail, TEC6 roughly equals to a 5” apo on planets, the 180Mewlon should come closer to a 5.5” apo.

With smaller than 250 Mewlons watch for considerable image shift, make sure that you can live with that problem. TEC6 has zero image shift.

Vahe

Do not sell, make a binocular scope with the pair. Can not think of the name but someone has and offers the eyepiece end prism assembly to make this work as a binocular setup.

Vahe

Another and much less understood source of light scatter in sealed tube catadioptrics are the internal thermal issues. I have noticed this phenomenon in my various Maksutovs, when these Maks are not thermally stabilized I can see considerable sky glow or brightening around the bright planets, when the system is in thermal equilibrium most of that glow goes away.
I initially attributed this effect to the fact that aluminized surfaces do in fact scatter light, but I have learned that this light scattering is much overstated.

Vahe

"Maybe someone with ties to the "industry" can answer a question for me. Why are there no SCT's designed for high resolution/high contrast observing? The cost of a 10 inch MAK or Refractor is well beyond the financial abilities of the people I associate with yet I find this size of telescope to be excellent when you balance the size of the scope against high power image brightness, detail, and average seeing conditions. A 10" cooled high definition SCT produced by Celestron or Meade should be affordable to all who desire a medium cost, large, high power instrument."

There exists a high end 10” F/15 SCT with smallish co., can not think of the name but it is produced in central Europe, it costs at least as much as a 10” high end Maksutov.
Takahashi also produced a high end SCT, 9” F/12 with 27% co. I believe that they produced 100 units before the production stopped, these do show up on Astromart from time to time for about +/-$5K.

Celestron and Meade are not set up to produce high end SCT’s, their production methodology is geared towards mass production and they do a reasonably good job at that. Re-figuring the mirror to a 1/8 wave will not turn a commercial SCT to a high end instrument, for that the entire design process needs to be re-examined resulting in a new instrument, from ground up.

Vahe

Dave Sewell said:
remember the 2 part SCT review or their evaluation of 10 inch mirrors? Those reviews also included a lot of impressive testing data too. How's everybody else feel about this? ...

The two part SCT review along with the 10” mirrors review was the last time that S&T ventured into serious optical evaluation, from what I hear makers of these products were not at all amused with the published results and probably made it clear that they definitely expected support from S&T in return for their full page color ads.

As for the Orion 6” Dob review, in all fairness to S&T, a brutally honest evaluation of a scope like this is asking too much, the entire package to include the mount, the ota, focuser, finder scope and two eyepieces, all for $250 is clearly an el cheapo package intended for very low end beginners. An interferometry on the optics would cost more than the entire scope package and what is it going to tell you?

I am in fact amazed at S&T ability to fill several pages of commentary along with pictures on this scope. This scope is for folks who want a scope but know nothing about scopes and the review is pretty helpful much like product reviews in Consumer Report magazine.

Vahe