13 replies to this topic

[antman73]

Hey all

was hoping for some advice about this scope that I am thinking about picking up.

It's a Megrez 80 SD f/6 and the owner advises that it was a 2001 purchase. The guy reckons it was a gift that he never used.

I can't inspect the scope in person for another week, and even then I doubt the owner would let me 'borrow' it for a star test. Besides which I have never done a star test on a refractor.

I've scoured the net and CN and there are some conflicting opinions and advice.

To the best of what I've been able to figure out:

it's a triplet with an OK-4 element

it might have been stopped - see pictures attached

 

In another thread someone advised that earlier models were stopped down to 77.5mm due to issues with CA. And I've also seen reports that there were issues with collimation and pinched optics with early versions. I've asked the owner to take some measurements of the objective for me but he is definitely not an astronomer and getting a straight answer has proved problematic. Can anyone tell from the photos:

1. If this has been stopped.

2. If being stopped is an issue beyond simply having a smaller effective aperture and respective f/ratio.

3. If this is an 'earlier' model before WO apparently fixed some lens cell and tube design issues.

4. Were there indeed any lens cell and tube design issues?

4. Would I better off getting a 2nd hand late model Skywatcher ED80 doublet for a similar price?

 

With either the Megrez or the Skywatcher, I thought these would be a good wide field grab and go option to complement to my 8" dob. Either way I probably will look to put it on an AZGTi or similar for tracking for when the grandkids come along to viewing sessions.

 

Thanks in advance for any help or advice.

 

Thanks 

 

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[antman73]

Further to the above, and for what it's worth, TMB confirmed that this was his design:

https://www.cloudyni...y/#entry1025627

[Jon Isaacs]

Hi:

 

I don't think this is the OK-4 triplet.  I am quite sure this is the achromat that William Optics first sold.  If it were the triplet, it would be written on the lens cell. 

 

I think it is this scope:

 

https://astromart.co...mm-fl-with-case

 

This is the OK-4 version, the price is out of hand but they go for over $1000.  

 

https://astromart.co...80-f6-99-strehl

 

Jon

[Zhengyi]

I own a Megrez 80SD. It is my first "real" telescope, bought in 2003.

If you are looking to complement your dob, I think it would be a great companion, especially for wide field and grab and go.

But, do expect to see blue halo around bright objects such as the Moon and some bright stars. My other complain is that its focuser is not very strong. It will slip if you use a heavy eyepice.

[Jon Isaacs]

I own a Megrez 80SD. It is my first "real" telescope, bought in 2003.

If you are looking to complement your dob, I think it would be a great companion, especially for wide field and grab and go.

But, do expect to see blue halo around bright objects such as the Moon and some bright stars. My other complain is that its focuser is not very strong. It will slip if you use a heavy eyepice.

 

 

Today, one can buy an ED scope like the AT-70ED ($329) or the AT-80ED ($429) that will have much better color correction and a nice two speed rack and pinion focuser. 

 

I have had my WO 80mm F/7 Megrez II FD since about 2005.  It has the FPL-53 objective, it has excellent color correction but like yours, the focuser was flaky and I ended up replacing it with a steel track style focuser from an AT-106LE. 

 

Jon

[antman73]

Thanks Jon and thanks Zhengyi.

It's not the OK-4 triplet? That's disappointing.

If I get the Megrez I would have to get a 90° diagonal, and probably look to sort out an option for a finder and rings and dovetail maybe do something with the focuser. Seems like I would be better off going with a second hand Skywatcher ED80, or buying an AT80ED from a foreign supplier and shipping it to the land of Aus.

Thanks for the quick reply and thanks for your advice.

[Jon Isaacs]

Thanks Jon and thanks Zhengyi.

It's not the OK-4 triplet? That's disappointing.

If I get the Megrez I would have to get a 90° diagonal, and probably look to sort out an option for a finder and rings and dovetail maybe do something with the focuser. Seems like I would be better off going with a second hand Skywatcher ED80, or buying an AT80ED from a foreign supplier and shipping it to the land of Aus.

Thanks for the quick reply and thanks for your advice.

 

The focuser can be adjusted so it works reasonably well.  But if you want an all-around 80 mm with good color correction, something like the AT80ED or the Skywatcher would be a better choice.. 

 

And let me say Hello and to Cloudy Nights. 

 

Jon

[antman73]

Thanks Jon. Very much appreciated.

[SteveG]

Hey all

was hoping for some advice about this scope that I am thinking about picking up.

It's a Megrez 80 SD f/6 and the owner advises that it was a 2001 purchase. The guy reckons it was a gift that he never used.

I can't inspect the scope in person for another week, and even then I doubt the owner would let me 'borrow' it for a star test. Besides which I have never done a star test on a refractor.

I've scoured the net and CN and there are some conflicting opinions and advice.

To the best of what I've been able to figure out:

it's a triplet with an OK-4 element

it might have been stopped - see pictures attached

 

In another thread someone advised that earlier models were stopped down to 77.5mm due to issues with CA. And I've also seen reports that there were issues with collimation and pinched optics with early versions. I've asked the owner to take some measurements of the objective for me but he is definitely not an astronomer and getting a straight answer has proved problematic. Can anyone tell from the photos:

1. If this has been stopped.

2. If being stopped is an issue beyond simply having a smaller effective aperture and respective f/ratio.

3. If this is an 'earlier' model before WO apparently fixed some lens cell and tube design issues.

4. Were there indeed any lens cell and tube design issues?

4. Would I better off getting a 2nd hand late model Skywatcher ED80 doublet for a similar price?

 

With either the Megrez or the Skywatcher, I thought these would be a good wide field grab and go option to complement to my 8" dob. Either way I probably will look to put it on an AZGTi or similar for tracking for when the grandkids come along to viewing sessions.

 

Thanks in advance for any help or advice.

 

Thanks 

I believe the SD designates doublet, and like John said it's likely the achro. At 480 mm, there will be a good amount of field curvature. The early models had very poor focusers.

 

#4 (2), Yes, absolutely better off.

[ris242]

Interesting you brought up Megrez, and a triplet just sold in the classifieds.

Did you buy it?

[antman73]

Thanks for your reply Steve. Seems to be the consensus from those in the know - a 2nd hand late model Skywatcher 80ED is better for the price (around AUD600-700), and the AT80ED has now been pointed out to me as an option by a couple of experienced astronomers.

I just thought I might have found some fancy Russian glass hiding on page 17 of a non-astronomy classified. This fairy tale was not meant to be.

 

Hey Ris - nah, didn't buy. I withdrew interest. It's still for sale on an Aussie classifieds.

[Jon Isaacs]

Interesting you brought up Megrez, and a triplet just sold in the classifieds.

Did you buy it?

 

That was not the 80 mm F/6 Lomo OK-4 triplet , that was an 80 mm F/7 Megrez ll triplet which was based on something like FPL-51.

 

Jon

[Princess Leah]

Hey all

was hoping for some advice about this scope that I am thinking about picking up.

It's a Megrez 80 SD f/6 and the owner advises that it was a 2001 purchase. The guy reckons it was a gift that he never used.

I can't inspect the scope in person for another week, and even then I doubt the owner would let me 'borrow' it for a star test. Besides which I have never done a star test on a refractor.

I've scoured the net and CN and there are some conflicting opinions and advice.

To the best of what I've been able to figure out:

it's a triplet with an OK-4 element

it might have been stopped - see pictures attached

 

In another thread someone advised that earlier models were stopped down to 77.5mm due to issues with CA. And I've also seen reports that there were issues with collimation and pinched optics with early versions. I've asked the owner to take some measurements of the objective for me but he is definitely not an astronomer and getting a straight answer has proved problematic. Can anyone tell from the photos:

1. If this has been stopped.

2. If being stopped is an issue beyond simply having a smaller effective aperture and respective f/ratio.

3. If this is an 'earlier' model before WO apparently fixed some lens cell and tube design issues.

4. Were there indeed any lens cell and tube design issues?

4. Would I better off getting a 2nd hand late model Skywatcher ED80 doublet for a similar price?

 

With either the Megrez or the Skywatcher, I thought these would be a good wide field grab and go option to complement to my 8" dob. Either way I probably will look to put it on an AZGTi or similar for tracking for when the grandkids come along to viewing sessions.

 

Thanks in advance for any help or advice.

 

Thanks 

Hi

Do you still have this scope?

I seem to have a similar scope.

Had to fix the pinched optics you mentioned.

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[maniack]

Thanks for your reply Steve. Seems to be the consensus from those in the know - a 2nd hand late model Skywatcher 80ED is better for the price (around AUD600-700), and the AT80ED has now been pointed out to me as an option by a couple of experienced astronomers.

I just thought I might have found some fancy Russian glass hiding on page 17 of a non-astronomy classified. This fairy tale was not meant to be.

 

Hey Ris - nah, didn't buy. I withdrew interest. It's still for sale on an Aussie classifieds.

There are other brands that sell similar KUO-made 80mm f/7 FPL51 scopes, including Svbony and TS-Optics. I'd shop around and see what you can get in Australia.

 

As a wide-field complement to a larger scope a short achromat might do fine too. Of course you might be tempted to use such a scope for high magnification as well, where EDs and apos are helpful. But for a low-cost wide-field achromat it's hard to beat the Svbony SV48p 90mm. The low-cost Svbony 2" dielectric diagonal is also pretty good, and it's possible with an adapter to mate the diagonal body to a TSFLAT2 visual flattener.