169 replies to this topic

[Jeff B]

About 2 months ago I took delivery of what may well be the last LZOS 254MM F9 objective lens assembly to be imported in to the US.  I had a TEC250VT F9 on order with Yuri for perhaps an early summer delivery, but dang it, Markus has a LZOS 254 F9 objective in stock along with a compatible straight through tube assembly.   After a series of communications with Markus, I bit the bullet and made the order for the APM/LZOS assembly.  I let my order with Yuri stand as I wanted it as a back up in case for some reason things did not work out to my liking with the LZOS objective.   However, "things" have worked out very well with the LZOS objective and I recently cancelled my order with Yuri.  I must say, Yuri was great to work with, professional and very understanding.  

 

The 350 pound APM "coffin" arrived about three weeks after I placed the order. Working with Markus was a pleasure.  He was professional and kept me informed at every step of the order and shipment process, including pictures too.  The individual parts were all professionally boxed/crated and separately wrapped inside the main coffin (yes, assembly was required but being an ATMer I really enjoyed it).  The objective came in its own stout LZOS wood case which was itself crated and then secured in yet another box and finally carefully positioned in the coffin.  Uncrating of the parts and assembling them were straight forward (though my lower back takes exception to that statement). 

 

The ~12" O.D. tube assembly is nicely done and rather light weight for its size.  It has a very nice powder coat finish, simple but robust countercell for the objective and an excellent, fixed dew shield with endcap.  The tail end has a slick sliding weight assembly.  The backplate has three removable knobs that are very useful handles and an excellent adapter to take the FT focuser.  The focuser adapter has three sets of push/pull screws to easily align the focuser with the center of the lens.  The alignment plate is also threaded to take an AP 2.7" focuser but had a FT adapter (this came in handy later). 

 

The objective cell is very robust with a thick flange on the back which holds the attachment/collimation screw sets.  The objective and cell weighs in at about 55 pounds(!)

 

Included accessories were a 2", 80mm long extension tube, a couple of very nice preinstalled Synta style finder brackets and some drop dead beautiful, robust, mounting rings. 

 

The total OTA weight sans rings and sliding weight system is around 95 pounds. 

 

Attached are some pictures.  Note the comparison with the scope it replaces, the TEC 200ED.  The 200ED looks (and IS) small in comparison!

 

More later.

 

Jeff

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Edited by Jeff B, 01 April 2022 - 11:57 AM.

[Villa_il_Gioiello]

So you’re saying there’s a TEC250VT waiting for someone to grab? 
 

Wow! I can’t believe how little the TEC200 looks. 

[Etendue645]

Thats massive! Congratulations! You will have to post a picture with it mounted. What mount will you use?

[Andrey Kobelev]

Jeff,

 

please, tell us more about the mount, flattener/reducer you will be using and other details!!

 

Best,

Andrey

[Jeff B]

Wow, thanks for the interest and here are some more details and pictures.

 

First, the objective lens "money shot" with its nice case.

 

Jeff

 

 

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[Jeff B]

Here is the aft finder scope and counterpoise weight assembly.  It consists of two nice Parallax rings, large finder rings, a big but "finder" (my old TV Oracle 3 is back in service!), a conventional 50mm finder and a sliding adjustable weight assembly counterpoise to the finders.  This adds much needed weight to the back of the tube to balance out the weight of the objective and dew shield.  I dismantled the really nice stock APM weight system as the pictured system has more capacity and adjustability but I have the capacity to reinstall the APM system if desired.  The entire assembly as pictured with the main rings and dovetail plate mounted on my Mathis MI-500, ready to observer weighs around 110 - 115 pounds and is nicely balanced.

 

My only real carp with the OTA as supplied is that it did not have the stated 220mm of back focus, which I interpreted as meaning from the top of the 3.5" FT focuser fully retracted inwards.   It had ~150mm of back focus, making it bino-unfriendly.  In fact I could not reach focus with my Denk II at the low power switch position or the Baader MK V with the 1.25X GPC even with the Baader BBHS silver T2 diagonal.  Fortunately I swapped out the stock 3.5" Feather Touch for an excellent FT 3035 focuser I had residing on my old AP178 F9 Blue Tube OTA and with the Baader BBHS, diagonal, all is well and bino friendly.  This is where I really appreciated the focuser collimation feature on the aft plate.

 

My only other quibble is that the powder coat finish on the OTA is too good.  It is very smooooth, a little too smooth really as I had to really, really tighten down the main rings to keep the assembly from very slowly sliding backwards when the scope is pointed  within about 10 degrees of vertical.  The simple solution was to put about 6" long strips of painters blue tape on the tube directly  "upstream" of both main rings.  The tape has incredible shear strength so no more sliding (one of these days when I get my final configuration settled upon...if ever...I'll put the tape under the rings).  

 

Speaking of pointed straight up, when so pointed, the eyepiece height is a very comfortable 39" +/- up off of the floor.  I will be making a slightly elevated roll about base for my adjustable observatory chair fr when the scope is pointed more southerly (in fact, the scope is very easy to use straight through for lower elevations).

 

I'll be posting more info soon.

 

Jeff

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[salico]

Wow, looks impressive! Good to read, that there are also people, who make good experience with APM/ Mr Ludes...

[Tyson M]

Whoa you outdid yourself here Jeff!

Impressive! And I agree, Markus is great to work with. Especially when I ordered my APM AZMAXLOAD to fit on my losmandy tripod.

[slavicek]

So you’re saying there’s a TEC250VT waiting for someone to grab? 
 

That was my first thought too.... 

[CHASLX200]

A easy 1000x scope in my seeing.

[Kent10]

Come on, Jeff.  Get the Tec too and make a comparison.  That would be amazing!  Can't wait to hear your reports.  Congrats!

[Jeff B]

Come on, Jeff.  Get the Tec too and make a comparison.  That would be amazing!  Can't wait to hear your reports.  Congrats!

Honestly Kent, I was actually considering that....

[weis14]

Wow Jeff, what a fantastic scope! Congrats!

[vahe]

Jeff B I do not know where are you located but for a 10" you will need a decent seeing, how is your average seeing?

.

Vahe

[stuart keenor]

Looking good Jeff !! It looks amazing I must thank you also for all the help and advice you gave me before my 9” purchase . Can’t wait to here a observational experience
Regards stu

[Jeff B]

Jeff B I do not know where are you located but for a 10" you will need a decent seeing, how is your average seeing?

.

Vahe

Vahe, you are sooo right and my average seeing is just that, average. 

 

Around here in SW Ohio, the best seeing typically occurs in the spring, fall and on hot muggy days in the summer.   For evening viewing we may only get 5 to 10 total days when the seeing lets me use the full aperture for extended periods of observing time (and anything over a span of 10 seconds is an outright gift).  However, seeing is typically much better in the early morning.

 

And this is the main reason why I've made a series of aperture stops that fit nicely and easily in the dew shield.  I made 9.5", 9.0" and 8" stops but I'll probably make a 7" stop as well. With the stops, I can better match the aperture to the prevailing seeing.  Also, if the objective is in a cooling (or warming) mode (more on thermal performance later), the stops mask the outer edge of the lens, improving its performance across the reduced aperture.  I'll have more to show about the stops when I post the DPAC images.

 

Jeff

[Jeff B]

Looking good Jeff !! It looks amazing I must thank you also for all the help and advice you gave me before my 9” purchase . Can’t wait to here a observational experience
Regards stu

Thanks Stu.  We are big LZOS brothers.  And tell us more of what you are seeing too.  

 

Jeff

[Jeff B]

So how about some test stuff?

 

Let's start with the LZOS supplied documentation.

 

The interferometric documentation (contour and analysis report) in green light shows:

 

PTV :  .150 wave

 

RMS:  .032 wave

 

Strehl: .961

 

I can't read Russian so I'm not sure what the STRH number means (low versus high?).

 

So it has a mild-ish center zone and a mild-ish turned up edge that covers about 20% of the circumference and extends about to the 90% to 95% zone.  The Strehl is excellent. 

 

I've included older but similar contour/PSF plots for LZOS 130F9 and 152 F8 objectives for comparison as well, which give similar stories.

 

Jeff

 

 

 

 

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[Wildetelescope]

About all I can say is wow. How the heck do you move that thing around when not on the mount.

Jmd

[Yu Gu]

That tiny TEC200ED looks cute!

Waiting on DPAC tests...

[Jeff B]

About all I can say is wow. How the heck do you move that thing around when not on the mount.

Jmd

I don't.  The contractor I had working the observatory is mentoring two strapping young lads who attend the local Career Center trade school.  He told me to "Work them like dogs!"  So I did and they did all the transporting and lifting for me.  I'm having them back soon to look through what they helped create.  They thought it was pretty cool.

 

Jeff

[Jeff B]

That tiny TEC200ED looks cute!

Waiting on DPAC tests...

Speaking of which.

 

First at full aperture.  Hover your cursor over the shot to see the labels.

 

Jeff

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Edited by Jeff B, 02 April 2022 - 04:19 PM.

[Yu Gu]

Excellent lens!

[Jeff B]

The objective is slightly under corrected spherically in green with best correction seeming just to the "left" of green.  You can readily spot the usual bit of spherochromatism to be seen in the blue and red with the lines bending in opposite directions.  

 

You can also see the mild center zone.

 

But color correction is excellent, the spherochromatism well controlled and finish is nicely smooth (guessing ~1/30 wave or less on average) for such a very large air spaced triplet.  

 

Theses results seem to validate the supplied LZOS documentation.

 

But where is that regional mild turned edge?  I should be able to readily see it in DPAC, just like the mild center zone

 

So I went looking for it by simply rotating the Ronchi screen until.... it appeared...as you can see in this shot.

 

Jeff

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[Suavi]

Congratulations Jeff. Thank you for sharing your impressions with the new beautiful beast of a telescope and I wish you many crystal clear and steady nights.