Musings on a Lyra 102mm f11 achro

[A McEwan]

Hi all.

I wasn't sure where to put this post. It's not quite a review, not quite a DIY article, not quite an open question.

A few weeks ago I bought a pre-constructed PST stage 2 mod based on a Lyra 102mm f11 achromat. I'd read about these scopes being used as the basis for projects like these with excellent results, and had looked into the price involved in finding all the parts and doing it myself. At the time the cost was too prohibitive, so when a pre-made example came on the market at several hundred pounds less than the parts alone, including a home-made (excellent) MDF storage case, and using a full aperture 112mm Baader D-ERF, well - I had to jump on it.

I got it, I tried it, I liked it. Then I dismantled it and had a look around inside.

An advantage of this setup is that the scope can be returned to normal White-light mode simply by removing the ERF and PST etalong/focuser/blocking filter assembly, and reinserting the chopped off section, returning the OTA to standard. Or by using an extension tube in the focuser.

Well it was in examining the scope "stripped down" that I found a few things that would need tweaking. The objective was dirty. Very dirty. Dirty enough that it resisted my Baader Optical Wonder AND isopropyl alcohol. I removed the cell with objective and shipped it off to Orion Optics for cleaning. They've done this for me in the past and have done excellent work on cleaning objectives.

The original focuser, which in PST mode holds the etalon/focuser/blocking filter assembly, was suffering. The drawtube was not set square-on to the body, the motion was rough, it slipped, and collimation was well off. I got in touch with Glen at Lyra Optic, who sells these OTA's. Although I did not buy directly from him, he still said he'd have a look at the focuser and see what state it was in and if anything could be done. I shipped it off to him and got an email from him confirming my findings, and saying that one of the bearings had been "destroyed" at some point and it needed replacing, and some setting up.

I got the focuser back a couple of days ago and it's like a different beast! The drawtube is set square on, the motion is smooth and "firm", and the bearing has obviously been replaced. (The original bearing looked like someone had driven over it or hit it with a very heavy hammer!) - Thanks to Glen for doing a great job on the focuser!

Once test-inserted into the OTA it began to occur to me that this would actually be a very nice scope. The paint needed some cleaning, which I did, and the interior was not flocked, but rather just had a coat of standard black paint. Comparing the paint with the black velour that FLO supply, the difference was very obvious. So I spent this morning flocking the dew-shield, OTA from front to the first baffle, and from the last baffle to the rear of the tube. I then flocked the interior of the adapter section that allows the tube to be returned to "normal" mode, and the extension section itself. Also touched up a few points in the tube where the paint had flaked off the baffles and the screws holding the crayford runner plate to the drawtube.

Now, EVERYTHING is pitch black in there! I also flat blacked the interior of the PST etalon 2" nosepiece as that was semi shiny too. Don't know if it will make a difference or not...

Then assembled everything (except objective, still to arrive), cleaned OTA to remove some sticky mucky bits, polished up and stood back.

WOW! It's a proper telescope! Only now did it really sink in that I have a very nice 102mm f11 achro for normal night sky observing! And it's a cracker! I'll take some pics when the objective arrives and is reinstalled.

The only other thing I want to do is modify the tuning etalon in PST mode by adding a Skywatcher Autofocus motor to it...

Before that though I'm looking forward to trying the scope out under stars more distant than our local one!

Ant

[John]

Sounds great Ant - thanks for the interesting post

I think these 102mm F/11's are an excellent addition to the ranks of 4" achromats. They seem to be optically very good, a tad better even perhaps than the rightly much praised TAL 100's. Their focal ratio strikes a nice balance between good control of CA while remaining relatively easy to mount steadily. Even their purchase price is not that high, in my view, either.

Plus they really look good too

No wonder Glen jumped at these when they became available !

[foundaplanet]

Excellent telescope, not had mine out enough yet but I am very happy with it.

The mod is a great idea, I bet the solar views are stunning.

[A McEwan]

The PST mod was sufficiently good to show details, particularly detached proms and faint filaproms, that a 60mm Lunt set up beside it could simply not show. I own a Lunt 60 PT as well, and will be keeping it as the two scopes complement each other very well in what they show. Very happy owner.

Ant

[Merlin66]

Antony,

I'm glad to hear it's all finally coming together......

I have the TS102 version set up for both white light (Baader Herschel wedge) and as a 102mm PST mod. It's a good scope which performs very well - enjoy!

[A McEwan]

Thanks Ken. Yes, if definately needed some tweaking but the basic ingredients were all there and very good quality they are too.

My Coronado BF is being replaced due to having gloop intruding into the filter area, so in the meantime will be using my Lunt BF1200 with this setup. That is, when the Sun comes out again and I get a chance to use it!

But it's thanks to the "tweaking" and dissassembling and actually exploring the hardware that led me to realise what a fine potential the 102mm f11 has for all sorts of viewing.

Ant

[A McEwan]

The objective in cell arrived back yesterday, looking pristinely clean! Very pleased once again with the lens cleaning service offered by Orion Optics. Reinserted the cell and awaited a chance to try it out...

And that chance was tonight! Nice clear sky and very good seeing. Collimation is now spot-on and the experience of using the scope with a properly functioning focuser and a clean objective is quite joyful!

Excellent views of Jupiter and the Moon, with great levels of sharpness and contrast. At 234x on the lunar terminator, the CA was becoming a tad distracting, though detail itself was still plentifully sharp and enjoyable to observe. Jupiter was more forgiving, and the addition of a #82a light blue filter did a great job to sharpen up disc detail and reduce the CA fringe around the disc. Even without the filter the view was very good and I could easily have carried on observing without the filter if need be.

My suspicions that this was a nice "normal" telescope for regular observing were completely confirmed! It's nice that it is in effect a "do-it-all" scope. I coul take this one scope away for a weekend, use it with the PST mod kit installed for H-alpha observing, then switch that out and add the Herschel Wedge for white light solar, then when night falls reattach the choppd tube section and a regular diagonal for excellent night-time views.

Oh and it looks very cool on my HEQ-5... LOL

Ant

[Merlin66]

Ant,

I only use the "reduced" OTA for the PST mod...the Baader Wedge just sits in the normal focuser and works well.....

[A McEwan]

I haven't actually tried the wedge in this scope yet, Ken. I know in my 6" f8 I had in-focus issues and needed to get a low profile adapter for the focuser to allow enough in-travel. It's good to hear that it should work normally in this scope though.

Ant

[allcart]

That sounds like the scope I was after. Glad you like it and know enough to get it all put right. It sounds like it was worth it.

[ibraidwo]

Well it was in examining the scope "stripped down" that I found a few things that would need tweaking. The objective was dirty. Very dirty. Dirty enough that it resisted my Baader Optical Wonder AND isopropyl alcohol. I removed the cell with objective and shipped it off to Orion Optics for cleaning.

Hi Ant,

Can I ask how easy it was to remove the cell? My objective is fairly 'dirty' and probably needs a really good clean.

Also, my focuser is fairly squeaky when rotating it around (i.e. where it fits onto the tube, not the focusing knob itself) - any thoughts on what might cause this?

Thanks,

ian

[Merlin66]

Ian,

I haven't had to remove the objective, so I'll leave others to comment.

Re the focuser rotation....make sure the nylon thrust washer is still in place on the OTA shoulder. The three grub screws are nylon tipped running on an anodised finish...a small (VERY small) wipe with candle wax or boot polish on the tapered section will "smooth" the motion.

HTH

[A McEwan]

The cell is screwed into place.

First unscrew the dew shield by gripping the black part and unscrewing the white shield. This exposes the cell, which also unscrews.

The optic and coatings will be revealed in all their glory once they've been properly cleaned. In my case it really was night and day. It cost me £75 including return postage. A bit pricey but I can't fault the work and appreciate it every time I look through it.

Ant

[argonaut]

Hi Ant,

Can I ask how easy it was to remove the cell? My objective is fairly 'dirty' and probably needs a really good clean.

Also, my focuser is fairly squeaky when rotating it around (i.e. where it fits onto the tube, not the focusing knob itself) - any thoughts on what might cause this?

Thanks,

ian

I agree with what Ant and Merlin66 say about the little problems your having with the OTA. The rotatable focuser uses 3 equi-spaced nylon tipped screws for placement. Just remove the rotating part and check that the nylon tips are still in place. I did have one OTA where the nylon tip had come off causing the screw to marl the inner ring which it rotates on which can cause roughness in the rotating part.

Just a couple of more points then I'll shut up. The threads on the cell and dew shield are quite fine and you need to treat them with care. I use Baader Wonder Fluid when necessary after blowing off all the grit and any other course but small particles.

If I can be of any more help please don't hesitate to get in touch.

Kind Regards,

Glen,

Lyra Optic.

[ibraidwo]

Thanks for the responses everyone - just need to find some time to investigate both ends further...

[A McEwan]

I've just come in from the first real night-time observing session with this scope in ages, and certainly the first one from a truly dark sky site.

I set it up on the AZ-4 mount with 13" extension column and a Telrad finder to find my way.

Glorious sky. Good seeing and transparency.

I'll cut to the chase. I jusde optics by how they reveal the Veil Nebula. Tonight I had my best view of it ever in a medium sized scope. With a 2" OIII filter and 42mm Superview the detail within the nebula strands was evident, in both eastern and western sections. The central portion was also seen, and even without the filter in place the nebula was still seen, though not as obviously (obviously )

M81 and M82 in the same field with a 17 Nagler T4 both showed obvious detail.

The Double Double was split cleanly at 122x (no false colour evident).

M31 and companions very nicely framed in low power view.

Every objects observed showed well with very high contrast and pinpoint stars. M13 resolved surprisingly well and was a beautiful sight (more so than M15, as expected).

In short I'm very impressed with this scope as a "general" observing scope, and on the alt-az AZ4 it is such a simple to use system. Very rewarding!

Ant

[Naemeth]

I've just come in from the first real night-time observing session with this scope in ages, and certainly the first one from a truly dark sky site.

I set it up on the AZ-4 mount with 13" extension column and a Telrad finder to find my way.

Glorious sky. Good seeing and transparency.

I'll cut to the chase. I jusde optics by how they reveal the Veil Nebula. Tonight I had my best view of it ever in a medium sized scope. With a 2" OIII filter and 42mm Superview the detail within the nebula strands was evident, in both eastern and western sections. The central portion was also seen, and even without the filter in place the nebula was still seen, though not as obviously (obviously )

M81 and M82 in the same field with a 17 Nagler T4 both showed obvious detail.

The Double Double was split cleanly at 122x (no false colour evident).

M31 and companions very nicely framed in low power view.

Every objects observed showed well with very high contrast and pinpoint stars. M13 resolved surprisingly well and was a beautiful sight (more so than M15, as expected).

In short I'm very impressed with this scope as a "general" observing scope, and on the alt-az AZ4 it is such a simple to use system. Very rewarding!

Ant

At F/11, the Lyra is quite long isn't it? Does this pose any problems for the AZ-4 (is it modified?) or is it very smooth?

[A McEwan]

It is very smooth. I adjust the tension so that there is a little Dob-like "stiction". Changing eyepieces with big weight differences requires rebalancing, which takes a few seconds.

I use a 13" extension on the mount which helps with eyepiece position.

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