233 replies to this topic

[clamchip]

I love Ed Ting here he reviewed the popular 90mm MCT's:

https://www.scoperev...0mmComparo.html

 

Robert

[oldmanastro]

I’ve never had an ETX. I could never get by all the plastic, especially their huge and clunky version of the fork mount. I can certainly empathize with your disdain and understand how poor it might be in use. However, it is nothing but a cheap imitation of the Questar fork mount, and cheap imitations are seldom as pleasing as what the originals they are imitating. I’m sure there is no doubt as much plastic inside it as there is outside of it and that there is lots of slop and backlash in the movements. However, I am a very satisfied Questar owner and the mount is a beautiful and most functional piece of precision engineering. I find it extremely easy and intuitive to use, smooth and stable in its motions, and quite precise in its tracking. I don’t believe the two are equivocal in any way.

I have both telescopes. The ETX90 has excellent optics but the Questar optics are extra-excellent. I did a comparison of the ETX-Questar optics and reported it on the Questar forum. The Questar had a definite edge over the ETX90. On the mount, there's no question about it. The Questar mount is a pleasure to use. It's precision made parts provide smooth easy movements, the tracking is excellent, there's no slop whatsoever in any axis. You can experience the quality when the instrument is in use. The ETX90 mount has slop, the tracking is less than fair and sometimes the RA motor will just take the image out of the FOV. One has to play with the control to bring it back. 

 

My ETX90 is one of my favorite telescopes and my usual grab and go but it has some realities that go with it and the fork mount is one of them. Meade offered a Questar-like telescope with nice optics at a price that was almost 10 times less than the Questar. They saved the $ on the mount.

[Bonco2]

Thanks Clamchip for posting Ed Ting's thorough comparison. I was impressed with how the new C90 held up and its price point. His review of the ETX was fair and accurate. The ETX strength is its optics and if bought used the price point is good too. While everything he said about the mount is true I've learned to overcome some of its issues and no longer have  problems using the electric slomo controls. I have an electric control for the focuser and like it but it took some time to get used to it. Also  my ETX doesn't have an image shift issue. For me the finder is its weakest feature but I've learned to actually use the almost useless thing. I have a  886 Meade Tripod with flip plate which works perfectly both alt/az and equitorial. I think we all concede that the Questar is in a class all in its own for design, craftsmanship, and eloquence. The price delta reflects that.

 Bill

[oldmanastro]

 Also  my ETX doesn't have an image shift issue. For me the finder is its weakest feature but I've learned to actually use the almost useless thing. 

 Bill

I have never observed image shift in my ETX for 20 years and a lot of use and transport. Like you I have learned to use that miniature finder as best I can. It's not so bad once you get used to it. I took this lunar image with the ETX90EC last January using a smart phone.

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Edited by oldmanastro, 30 May 2021 - 11:22 AM.

[Bonco2]

Guido,

Nice photo example.

Thanks for posting,

Bill

[Benach]

Hmm, dunno if this is appropiate, but still. This topic got me contemplating a bit.

 

A Meade ETX 90 is the first telescope I bought. I was quite satisfied with the optics, not at all with the mechanics just like many others. Now it happens to be that I am a optomechanical engineer. So why not redesign the entire scope around the same optics? I am quite impressed by its portable size and capabilities. However, I know that the entire operation will be more expensive than a Meade ETX, but having access to metal working machines, it should not be as expensive as a real Questar. So, I made a brainstorm: If I were an optomechanical engineer and I have the optics of a 90/1250 MCT, and I want to change to the ETX90 design so that it is a 2021 design without the flaws of the original Meade ETX series. Feel free to add more ideas:

 

• Carbon tube (slight weight reduction)
• Dewheater build in
• Dew shield build in
• Stainless steel axes
• Fork mount made of aluminium which is capable of slewing between the legs of the fork (mine bumped to the base quite often)
• Goto which is compatible with Skysafari
• 40mm Right Angle viewfinder with illluminated crosshair and 2 screw adjustment
• Wormgears better dimensioned
• Preloaded worms
• Clutches on both axes
• Encoders on both axes
• Built in LiFePO4 battery
• Motofocus
• Good primary mirror focusser without image shift
• Piggyback adapter on the tube
• Slewspeed max. about 3degr/s

Anything else?

[GreyDay]

Hmm, dunno if this is appropiate, but still. This topic got me contemplating a bit.

 

If I were an optomechanical engineer and I have the optics of a 90/1250 MCT, and I want to change to the ETX90 design so that it is a 2021 design without the flaws of the original Meade ETX series. Feel free to add more ideas:

 

• Dew shield build in
• Stainless steel axes
• Fork mount made of aluminium which is capable of slewing between the legs of the fork (mine bumped to the base quite often)
• 40mm Right Angle viewfinder with illluminated crosshair and 2 screw adjustment
• Wormgears better dimensioned
• Preloaded worms
• Clutches on both axes
• Good primary mirror focusser without image shift
• Slewspeed max. about 3degr/s

Anything else?

Rip out the plastic back end flip mirror setup and replace it with a machined aluminium VB, something like the B&L4000,

Dedicated hardcase for travel.

Dual speed focuser

 

That's about it for me

[ALman]

Hello, my comments were mostly in jest. I had the privilege of using a friends questar for a few nights in Australia. It actually wasn't too bad. And yes quality wise the motions were excellent.
I will however say that at some elevations with a fixed diagonal in the EQ configuration was not fun. And I'm not sure that is a think you can fix on a similar fork mount. That said it was very pretty. And I see the appeal to a well made scope.
I will say, I think the Meade has similarly excellent optics. I can see why they are so frequently de-forked.

Edited by ALman, 31 May 2021 - 05:19 AM.

[Benach]

Greyday: Thanks for thinking along with me. Trust me, the plastic back will certainly go out.

 

Not sure yet about the flipmirror concept but if it stays in, it will be more rigid and besides, parfocal with the cameraport. I have a funky idea with it that has to be worked out.

 

The dedicated hard case is added to the personal list.

 

I am still looking for a nice way to combine the dual speed focusser with a motorfocus. I vaguely remember Starlight had a solution for that

[LukaszLu]

Hi, let me revive this thread to ask about an example I came across recently. It does not contain holes for the screws that attach the tube to the fork. Is this a model that was mounted differently or sold as OTA, without fork mount? How do you estimate the age of this example? There is a UHTC sticker on the tube, so at least 2002?

 

 

 

 

Edited by LukaszLu, 20 November 2023 - 01:09 PM.

[oldmanastro]

I may be mistaken but it seems to be from the earlier 2000s when the UHTC coatings were being offered. You may have something unique. I have never seen them offered as an OTA. You will find the optics to be excellent.

Edited by oldmanastro, 20 November 2023 - 10:54 PM.

[LukaszLu]

I am very curious about this item. It's on the way to me from Germany :-)

[deSitter]

Hi, let me revive this thread to ask about an example I came across recently. It does not contain holes for the screws that attach the tube to the fork. Is this a model that was mounted differently or sold as OTA, without fork mount? How do you estimate the age of this example? There is a UHTC sticker on the tube, so at least 2002?

 

 

 

 

There was an ETX spotter version.

 

-drl

[LukaszLu]

Bull's-eye! :-)
https://www.opticspl...de-etx90ss.html
http://www.discovery...ext_90-125.html

[ericb760]

May I suggest that you consider a Wegat back plate for your new ETX-90? Since it was never on a fork mount but still has the flip mirror apparatus if it was mine I would definitely consider this upgrade. In fact, I have plans to de-fork my ETX-125 and add one of these.

[LukaszLu]

Thank you very much. I'm not sure what condition this telescope is in - neither in terms of optics nor mechanics. If it turns out to be a keeper, I will consider various forms of upgrade, perhaps also the issue of the finder etc.

[deSitter]

Thank you very much. I'm not sure what condition this telescope is in - neither in terms of optics nor mechanics. If it turns out to be a keeper, I will consider various forms of upgrade, perhaps also the issue of the finder etc.

If you remove the visual back you will see that there are 3 collimation screws. This may convince you to "improve" the scope, but - leave it alone. They are set in the factory with fancy equipment and cannot be improved with tinkering. On mine the collimation screws have thread lock visible.

 

Not sure what that expensive visual back it designed to do, but you don't need it. The thread on the stock item is non-standard but you can get an adapter to convert it to a standard T-thread. I do this and then install a 1.25" visual back.

 

-drl

[clamchip]

Whatever it is I like it, not having the unsightly bosses for the fork tines and the scratches

typicaly found around the area from unforking.

UHTC coatings are a big plus.

I think you will be very surprised, the ETX series are pretty impressive.

I did buy a wegat adapter for a ETX125 and it is very nice but I missed the stock control

box with it's flip mirror so I  put it back on.

I still have my ETX90. I sold my 125 and an even bigger mistake I sold my Meade 7" Mak.

I'm starting to think the Maksutov is what I'm destine to end up with, I like the Mak very

much.

 

Robert

[deSitter]

Whatever it is I like it, not having the unsightly bosses for the fork tines and the scratches

typicaly found around the area from unforking.

UHTC coatings are a big plus.

I think you will be very surprised, the ETX series are pretty impressive.

I did buy a wegat adapter for a ETX125 and it is very nice but I missed the stock control

box with it's flip mirror so I  put it back on.

I still have my ETX90. I sold my 125 and an even bigger mistake I sold my Meade 7" Mak.

I'm starting to think the Maksutov is what I'm destine to end up with, I like the Mak very

much.

 

Robert

You can use the flip mirror in a manner similar to a Questar. I put in a 0.965" diagonal and 40mm eyepiece and it makes a good finder. You adjust the path length until it matches the main eyepiece.

 

-drl

[clamchip]

Here's mine doing what you are discribing, it works great, flip from finder to main.

And here is a way to convert to standard SCT visual back.

Robert

 

[deSitter]

Here's mine doing what you are discribing, it works great, flip from finder to main.

And here is a way to convert to standard SCT visual back.

Robert

 

post-50896-0-68431200-1622039613.jpg

post-50896-0-62226100-1622040157.jpg

post-50896-0-26044300-1622040197.jpg

Nice I throw in a diagonal for a 4th reflection and so a RACI view! I need to get off my headquarters and tweak the flip mirror so that it matches the back port's optical axis.

 

-drl

[LukaszLu]

It has arrived. I'm not sure if I can avoid collimation because it gives the impression of an instrument with a rich history. The mirror has a round chip near the sleeve, which may indicate that it was once removed...

 

I was a bit disappointed by the seller, because although I understand the risk of buying remotely, I think it should be expected that the buyer is mentioned about defects visible to the naked eye, and unfortunately the seller did not want to warn me about the damage to the mirror... On the other hand, the telescope probably cost little, and such a defect probably has no noticeable effect on the image. Apart from that, the telescope appears to be in decent condition. The mirror moves smoothly and does not swing from side to side. Well, there remains a certain disgust.

 

Is it safe to unscrew the meniscus housing and clean it from the inside?

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[deSitter]

It has arrived. I'm not sure if I can avoid collimation because it gives the impression of an instrument with a rich history. The mirror has a round chip near the sleeve, which may indicate that it was once removed...

 

I was a bit disappointed by the seller, because although I understand the risk of buying remotely, I think it should be expected that the buyer is mentioned about defects visible to the naked eye, and unfortunately the seller did not want to warn me about the damage to the mirror... On the other hand, the telescope probably cost little, and such a defect probably has no noticeable effect on the image. Apart from that, the telescope appears to be in decent condition. The mirror moves smoothly and does not swing from side to side. Well, there remains a certain disgust.

 

Is it safe to unscrew the meniscus housing and clean it from the inside?

Bummer. Yes it will go right back where it belongs, just don't take the meniscus out of the cell without recording the correct orientation somehow.

 

While it is off, be sure to push on the baffle glued around the center spot and verify it didn't wander around. I have to check mine every couple of months. It's a bug of this scope that the forward baffle can detach from its glue ring.

 

-drl

[deSitter]

It has arrived. I'm not sure if I can avoid collimation because it gives the impression of an instrument with a rich history. The mirror has a round chip near the sleeve, which may indicate that it was once removed...

 

I was a bit disappointed by the seller, because although I understand the risk of buying remotely, I think it should be expected that the buyer is mentioned about defects visible to the naked eye, and unfortunately the seller did not want to warn me about the damage to the mirror... On the other hand, the telescope probably cost little, and such a defect probably has no noticeable effect on the image. Apart from that, the telescope appears to be in decent condition. The mirror moves smoothly and does not swing from side to side. Well, there remains a certain disgust.

 

Is it safe to unscrew the meniscus housing and clean it from the inside?

As for that crack - I'm guessing that happened when one of the collimation screws was overzealously tightened.

 

Ah me. The evil spirit behind Bob's Knobs. So many casualties. Maksutovs are collimated in the factory and should never require it again until the mirrors come out for recoating.

 

BTW if the collimation is checked with the top port, it may seem out of collimation because the flip mirror is not exactly at 45 degrees. The mechanism is rather crude. Collimation MUST be checked at the back port.

 

-drl

[clamchip]

My latest project has a chip just like yours and I have not found it to affect anything.

I think chips around the mirror perferation could be from rough handling in transit.

A hefty blow and the mass of the mirror does not want to stop and gets

chipped by the mirror carrier or baffle tube.

Robert

 

Edited by clamchip, 21 November 2023 - 05:02 PM.