257 replies to this topic

[clamchip]

Criterion is one of my favorite telescope makers, and have said if a Dynamax ever comes up

for sale in my neighborhood I'm going to make a serious effort to buy it, even though I own a

marvelous Celestron 8.

Thanks to all the research on these SCT models recently here in the classic forum I know a

lot more about these Criterion SCT's, and I almost, almost, took the Criterion CAT off my list

of telescopes I'd like to own.

A B&L Criterion 4000 came up for sale on Craig's list, and a team of wild stallions couldn't keep

me from going to at least look at it! 

I brought some of my favorite eyepieces for some high and low power testing. Mainly I wanted

to make sure I could focus the telescope sharply up into high power to see if I had something

I could work with, and not a really sour corrector.

It turned out the scope was too dirty and way out of collimation, so no testing was  possible.

The power cord was missing, and we were in the middle of a grocery store parking lot anyway

so no testing the drive.

But you know, none of that really mattered because I wasn't going to leave without that telescope!

I have some pictures, and I'll add more as progress continues on the telescope.

This is the first time I've cracked into one of these Criterion SCT's and I'm finding it fascinating.

First photos are as the scope was found, and the reason the collimation was way out. 

The corrector has a lot of wiggle room, and a hard knock can send the corrector off center, like

this one.

It came with 3 B&L eyepieces and this reticle, which looks like it might be for measuring size.

Missing are the finder, and all the Dec fine-adjust, tangent arm, and lock, hardware.

Robert

 

 

 

[clamchip]

I'm cleaning things up so I can have a look through the telescope.

The front and rear cells unscrew from the aluminum tube. Look at

 this rear cell assembly, this is a very nice high quality, well designed

unit. A rubber O ring keeps the mirror holder from falling off the baffle

tube. The mirror is retained on the mirror holder with a nut and a

cork pad.

 

 

[clamchip]

Corrector and secondary. The secondary holder is all metal. There is no plastic used

in this telescope. 

This is a 4 inch f/12, and the secondary obstruction is 34%.

Look at the tiny secondary mirror.

The corrector on this telescope has no AR coating.

 

Edited by actionhac, 06 May 2017 - 01:30 PM.

[Terra Nova]

It amazes me that the Criterion/B&L SCTs can be so nicely made with regard to the mechanics and yet be such stinkers optically.

[clamchip]

I know, it makes me cry to see all this quality and to know its probably not going

to be so hot to observe with.

I'm just hoping it might be acceptable.

I'll get it cleaned up so I can observe through it and do some optical testing, and

then we will do some bench testing to look more seriously at the problem with

this particular telescope.

 

Robert

Edited by actionhac, 06 May 2017 - 01:47 PM.

[jallbery]

I have two 4000s, so thanks for giving this one a home so I don't have to 

[Joe1950]

The mirrors look good in your photos, Robert.

[photiost]

I have a couple of these and they both work well @ low powers ... actually one performs much better than the other.

 

So there are some really good ones out there.

 

Used one of mine as a second big finder on my C8... the setup looked very cool

 

You may have struck a good sample.

 

Edit: here is an image of my better one.

Edited by photiost, 06 May 2017 - 02:02 PM.

[Cajundaddy]

My brother had a B&L 4000 and after careful collimation it was a decent travel scope.  Not bad but not great.  A better diagonal and 1 1/4 EPs helped a lot and this is the scope I took to the top of Haleakala Maui for one of the best nights of observing ever.  Sometimes "decent" is good enough when the skies cooperate.

Edited by Cajundaddy, 06 May 2017 - 02:10 PM.

[clamchip]

I found assembling the front cell a little challenging, and I can see this task

introducing errors into the system if its not done correctly.

The problem lies in the fact that there is so much room, and you have split

rubber gaskets on both sides of the corrector that want to pouch out while

you are trying to thread down the retaining ring, and you are trying to keep

the corrector centered.

My scope came with a prism star diagonal with a built-in visual back. Its a

high quality unit, but I will probably look for a straight-through plain visual back

to give myself a little more flexibility. The B&L SCT's have their own rear port

thread so Celesrton, Meade, and others won't fit.

Leaving the mount for a later date, the telescope is ready to go out into the

great outdoors for collimation and observation. 

And as we speak it just clouded over and I lost my sun. That a good sign!

Robert

 

[Bomber Bob]

The mirrors look good in your photos, Robert.

THAT's what gets your hopes up.  The mirrors in my DX8 are pristine -- as pretty as the Tinsley's after they came back from Majestic with a new coating.  But put them behind that non-circular corrector...  Sadness.

[clamchip]

Yes the mirror coatings are perfect, and I didn't even need to touch them.

The corrector needed cleaning both sides, and the whole outside of the 

telescope, and the prism, but the mirrors miraculously are perfect.

I have the collimation reasonably close with the sun reflection from

insulators and bumpers, I'll need a star to finish.

Unfortunately I must collimate with the prism star diagonal in the optical

path because its part of the visual back.

In and out diffraction patterns look very much the same with the boiling

bull's eye, I really need to do all this with a star, but I'm glad its close now

because those tiny collimation screws will be a bear in the dark.

As the telescope is right now, it could easily pass as a pretty nice telescope

to the average consumer, a amateur astronomer might have a problem with it.

Very good at 50X, and starting to loose its sharp edge at 100X, but this is

daytime, with a freshly appearing sun heating things up rapidly, and a scope

not quite collimated.

Robert

 

Edited by actionhac, 06 May 2017 - 08:09 PM.

[Augustus]

I will probably look for a straight-through plain visual back

to give myself a little more flexibility. 

I found 6 of those.

[clamchip]

I saw those too and I am so tempted! I'll bet before the nights out I'll

have bought one.

Oh these darn telescopes!

 

Robert

[clamchip]

Well now there's only 5!

I'm going to have a 1000 bucks in this scope before I'm finished!

 

Robert

[Augustus]

Well now there's only 5!

I'm going to have a 1000 bucks in this scope before I'm finished!

 

Robert

It's all my fault......

[clamchip]

I might have a clear night and the B&L 4000 is ready.

I mounted the telescope in rings, I'm lucky to have the right size, and

a dew shield, I'm lucky to have the right size, luck is with me!

Our model is wearing B&L Ray-Ban Aviator's.

 

Edited by actionhac, 07 May 2017 - 01:48 PM.

[jallbery]

Looks great.

 

Before I bought a C5, I used my B&L 4000 spotting scope (I also have an astro model) on a 4/5SE mount.   I simply used the existing tripod block with a short V-style dovetail: one 1/4"/20 machine screw secures the dovetail to the tripod block, and a second with nut securely against the block restricts any movement should the first screw come even the slightest bit loose.  Makes for a very lightweight OTA, and you can relocate the tripod block for side mounting.

 

Of my two 4000s, it is the older resin tube model that has the better optics.  My aluminum tube astro clearly has pinched optics, but even it seems quite a bit better than some of the horror stories you read about here and elsewhere.  One day I'll open it up and see if I can fix it.   If I can't I'll probably swap the resin tube model into the astro mount.   The astro mount is wonderful to use, although the 4000 wedge is a pain to set up.   Fortunately, it doesn't have to be very accurate for star hopping-- anything close gives you pretty decent tracking.

 

The 4000 wedge mounts on a single 1/4"/20 tripod thread, and the scope mounts to the tripod the same.   The 4000 astro is so compact it makes for a great vacation scope.   I have a 1/4"/20 adapter for my bogen tripod so that I can mount the 4000 on the tripod in alt-az for terrestrial use, or add the wedge for astronomy use.

[GreyDay]

But you know, none of that really mattered because I wasn't going to leave without that telescope!

Been there so many times. I know i shouldn't buy the item but sometimes I think that i'm doing the world a favour by buying and repairing them myself. This is how i end up with scopes that cost the same or more than a good one to start with.

 

There's been a B&L 4000 on a uk sale site for a few weeks, £100 just for the OTA and i can't quite bring myself to buying it as i already own a Skymax102. If the fork mount was with it then i may have been tempted

[clamchip]

Nurse Mendy knew exactly what the mysterious reticle that came with this scope is used for.

It a Measuring Reticle Eyepiece.

If you want to know how big? or how far? this will tell you.

The reticle goes along with the B&L 12.7mm eyepiece that also came with this scope.

The MRE allows you to measure the angle subtended by a object viewed through the 

telescope.

If the object's diameter is known, you can determine how far away it is.

If you know the objects distance, you can compute the size.

 

[Augustus]

Nurse Mendy knew exactly what the mysterious reticle that came with this scope is used for.

It a Measuring Reticle Eyepiece.

If you want to know how big? or how far? this will tell you.

The reticle goes along with the B&L 12.7mm eyepiece that also came with this scope.

The MRE allows you to measure the angle subtended by a object viewed through the 

telescope.

If the object's diameter is known, you can determine how far away it is.

If you know the objects distance, you can compute the size.

 

B&L 4000 051.JPG

B&L 4000 009.JPG

So is the reticle a separate component that screws into the eyepiece? 

[clamchip]

Yes it is, you can see it next to the eyepiece in front of nurse Mendy.

It works with that particular 12.7mm size eyepiece for the calculations.

[astro140]

 

You may also have an instruction book.  Although "designed" for the B&L 4000, the booklet explains how to use it with longer focal length scopes.

 

Steve

New Mexico

[clamchip]

Strangely my 4000 is showing evidence of pinched optics.

3 bites out of the outside ring, or more technically, distortion

120deg apart affecting the outer 2 to 3 rings.

I thought it might be over-tightened secondary collimation

screws, but no its not that.

I'm having a difficult time with the prism diagonal in the path

while I'm conducting all this analyzing.

Fortunately I have a straight-through visual back on it's way. 

The reason for the prism with built-in visual back is so the

telescope will fit inside the fork, its just short enough.

 

Robert

Edited by actionhac, 08 May 2017 - 10:10 AM.

[DAVIDG]

 Test the optics via double pass with your flat. A warped poorly figured corrector will show like pinched optics and you know what is wrong vs guessing and wasting time trying other things that won't work.

 

                - Dave