16" Lightbridge woes.

[epk]

Some very useful stuff there, Steve, and the distancing Cheshire method to reduce parallax intrigues me. I'll PM you with my email address, and I'll work on the mirror clamp loosening and screw-down over the next few days.

I was actually pricing re-coating by Orion Optics today.Do-able but expensive, but having the mirror checked by them as well would put my mind at rest.

Calibos...no, I certainly didn't think you were running down the Hotech.

It does become a compromise between perfection and price, as I said, and people sometimes have too many other priorities for their money. It's necessary to find out what's around and particularly to get evaluations from experienced users.

[calibos]

Hi Mick,

Just dug out my old email from Howie and the pricing still seems to be the same today. Below is the spec I got:

2-1 1/4" 650nm holographic $185

2" Blug $65

Shipping: Express mail $35 or Priority mail $24

Taking the priority mail option that works out at GBP170. Howie IIRC was prepared to send it via USPS which as you may know interface with the respective national postal carriers. Royal Mail in the UK and 'An Post' here in Ireland. The ironic thing is, is that the national postal services are paradoxically the least likely carriers to charge Customs Duty and VAT. I understand this is the same in the UK as here in Ireland. Funny isn't it that the State owned/ex state owned carriers are the least likely to impose the taxes of the state! Anyway, Howie 'accidentally' also marked the invoice value down. How lucky was that In other words I was not charged Irish Customs and VAT on my order.

You can compare that pricing with your Baader and Hotech and make your decision.

Basically my reason for getting the best in the Howie Glatter was that with my Orion XT12i I had made every effort in all my mods to make the scope as easy and as quick as possible to setup and to have it delivering its best views as soon as possible. It was all about spontaneity. With the patchy weather we get in the UK and Ireland, one has to take advantage of all the viewing opportunities we can. I wanted everything to be quick and easy so that I would be less like to see a clear patch on the Sat images but decide, "Meh, too much trouble to set up, its only an hours worth of a clear patch"

This is where my collimation problems came in. I had a Cheshire/Sight-tube combo tool but it was a hassle to use at night with the torch and having to go backwards and forwards numerous times while doing the primary. If I did the collimation inside with the cheshire before going out, I'd invariably end up banging the scope on the way out the door and down the step and knock the collimation back out. Now I wouldn't knock it out much at all but I am a bit **** about very accurate collimation which is important at the F4.9 of my Orion and even more important on our F4.5 LB16's.

So then I bought an Orion Lasermate Deluxe laser collimator so I could collimate at night outside without all that torch malarkey. This collimator has a 45º target face that is visible from the back of the scope. No more going backwards and forwards! I thought I was sorted! Then I learned all about laser barrel/focuser slop (Which I discovered I had in spades) lasers being out of collimation themselves (Which mine was) and the inherent innaccuracy of a straight laser in collimating the primary In Fast Newts.

I then learned about the Barlowed Laser technique for collimating the primary. With my 2x barlow inserted between the laser and focuser with a white target fixed to the front of the barlow, I could now collimate the primary to a high degree of accuracy without worrying about focuser slop or mis collimated lasers. Back to going backwards and forwards again though to look up the drawtube to see the barlow target from the front of my solid tube. However the barlowed technique does not help with secondary alignment would still be affected by slop and laser miscollimation.

Then I heard about the Glatter. The precision machined barrel in combo with my new moonlite focuser would resolve most of the slop issue. The Glatter having the reputation of always arriving in collimation and never going out of collimation short of being dropped on concrete from 6 foot high would resolve my laser miscollimation worries. Thus I could now be confident in accurate secondary alignment. I went for the 2"/1.25" combo version to keep my options open. I went with the red laser 650nm version because the extra expense of the brighter 635nm version did not seem to be needed. The 650nm version is plenty bright even during the day. The Green laser version at 350 dollars definately didn't seem worth it as cool as a green laser collimator might be! and who collimates in direct sunlight anyway!! I got the Holographic attachment as it can replace the function of a site tube for checking secondary centering in the field without the hassle of torches. I got the Blug, which is a 45º face target with a small barlow lense that inserts on the inside end of the drawtube. Now with my solid tube this did not solve the backwards and forwards from the primary issue but it did mean that I could angle the Blug forwards and just quickly pop my head around the open end of the tube to check the donut shadow whereas before with my Orion laser with homemade target on a conventional barlow which was hidden up the drawtube, I would have to basically put my head inside the end of the scope to see the barlow target. In the end I rigged up a vanity mirror on a stalk which allowed me to see the Blug target face from the back of the scope! So even on my solid tube scope, the Blug was an advantage, but the real reason I went for the Blug was that I knew in the future I would probably end up owning a truss. Now with my LB16 truss its just ridicukous how quickly I can get perfect collimation. With a Truss, one angles the Blug towards the back of the scope and one can see the target from the back. The other part that comes with all glatters is an attachment called the 1mm apeture stop. Used for secondary alignment, what it does is make the laser project a tiny bright dot instead of a much larger oblong laser dot like most laser collimators. As you may have experienced, once a standard laser dot hits part of the primary donut it flares bright which obscures whether you have the dot properly centered in the donut. With the 1mm apeture stop it basically stops this flaring and one can see exactly when one has the secondary perfectly centered within the donut.

Ultimately, the Glatter gave me the spontaneity back. With the out of collimation Orion and me being **** about collimation, all the spontaneity I had gained with my other mods was lost by feeling I always needed to check and adjust the lasers collimation itself before each session. Collimating the laser on a V block I found harder than everyone described and very fiddley, and even when I got it close, it would be out of whack again 2 or 3 uses later. With the Glatter I could 100% trust it. There was no more, "well I should go out and take advantage of that clear patch...Nah, it'll take me 20 minutes to check and adjust the Orion laser collimation"

So there you have it, the reasons I paid the premium for the Glatter. Basically piece of mind and taking the frustration out of the collimation game.

All that said however!!

I am selling the Orion XT12i, now that I have my LB16 and am making progress with my mods. I wanted to provide the new owner with an accurate means of collimation at night...but without giving them my beloved Glatter.

I eventually hit on a brainwave that resolved all issues I had previously had with it. Now it turns out that I was re-inventing the wheel as I discovered that others had hit on this idea before but I was still chuffed that I had thought of this independently myself.

First issue was slop between the Orion and the LB16 GSO 2 speed I transferred from my LB16 to the Orion as I was obviously putting my Moonlite on the LB16 instead. I had some spare teflon tape from another mod that wrapped around the Orion barrel and took out the slop. Second issue was laser mis-collimation. I realised that instead of messing about with V-blocks, I could collimate the scope accurately with a cheshire, then insert the Orion, making sure I inserted it in the focuser orientated the same way each time (ie. aligned the O for Orion on the sticker with a drawtube screw. Now I knew the scope is collimated perfectly after the cheshire but that the miscollimated laser is shining its dot outside the donut. Instead of centering the dot in the donut with the secondary screws (remember, I know its already perfect), instead one centers the laser dot by adjusting the laser itself collimation screws. After rotating the laser in the drawtube, all dot wander eliminated with the laser dot staying perfectly centered in the donut. Next issue was still having to go backwards and forwards to check primary collimation. Remember that although the Orion has a 45º face for viewing from the back, that this is without a barlow and we know that using a laser for primary collimation without a barlow for the barlowed technique especially on a fast newt is a definate innacurate NoNo. Was I back to the situation of having to go up front 20 times and stick my head inside the tube to see my DIY barlow target on the end of the barlow up the drawtube??

The answer was no!. I had remembered a recent thread where someone had realised that although the donut shadow reflected on the 45º face of the Orion would be much larger and much more diffuse because the return beam and shadow had to pass back through the barlow lense (unlike the blug), that because the Orion Lasermate deluxe had a white Bullseye marked target face unlike the plain metal 45º target face of other similar collimators, this meant that one could still easily see the big diffuse donut shadow on the white face and acccurately center it within the outer rings of the bullseye target!! Meaning one could now use the Orion Lasermate deluxe in combination with the barlow method, while still utilising the 45º target face and thus being able to collimate the primary from the back of the scope in seconds instead of all that back to front malarkey and "damn it, turned the collimation bolt the wrong way again..."

So basically I now had an Orion collimator that the new owner could use to get as much accuracy as my Glatter!

Heres a few pics to illustrate using the Orion from the back with the barlow method:

(photo quality isn't the best. Despite donut shadow being much larger and more diffuse than the small dark black shadow of the Blug or barlowed methods where the shadow/beam does not have to pass back through the barlow. In reality the Orions (2pass barlow) shadow is more distinct than the photo's would indicate. To re-iterate, its the Orions Bullseye rings that help to accutarely center this large diffuse shadow. Much harder to do on a non bullseyed target face)

[jarbi]

Jarbi had an astigmatic secondary on his 16" LB. I asked him what led to suspect he had an astigmatic secondary in this thread.

I just saw this thread, and I would like confirm that a new and perfect secondary solved all my optical complains on the LB ( not a Meade secondary, don't ask me how much was it .. ). To split the double-double is out of question, I use the 8mm Ethos on global clusters and I have stunning views on Saturn as well !

epk, just let me know if I can help you further to nail down the problem.

Two more remarks:

1. My primary is not held by the 3 clamps at all, only protected by them from falling out ( the clamps are 1mm above the mirror ). This makes it 100% tension-free.

2. I have discovered a hidden reason for getting out of collimation when moving the scope: the aluminium brackets holding the ends of the truss tubes were not tightly fixed on the tube !! After tightening all small screws on the edge of the upper and lower cage, I have nearly perfect collimation after every dissassembling /reassembling.

cheers,

Janos

[epk]

Jarbi, the idea of a faulty secondary is scary.

I check all the screws regularly in case of loosening, but the primary mirror will be getting loosened this weekend to see how that goes.

This thread has been very useful in widening my options, so thanks folks.