Help required collimating my Tasco 16T

[MrZuiko]

Hi all I really need your help to collimate my Tasco 16T,it's of the "bird jones" design Ithought I had acheived collimation last night but when I star tested it the stars had tails!

Can anyone please describe in detail what I should do and what it should look like in the eyepiece etc I've got a collimation cap and a cheshire tool with an adapter so I can use it on this scope.

I have read that it's required to take out the corrector that's infront of the flat is this correct.

I've looked online for help but I'm confused as to what I'm looking at etc plus the flat to my mind cannot be adjusted for tilt as it only has a single screw in the middle of the flat holder and a tiny grub screw above it.

I know that the 3 screws on the mirror cell are to adjust the postion with the longer screws are for locking down the adjustment screws.

Can anyone describe in detailed steps as to what I should do.

 

Many thanks Ash.

[EssexMigrant]

Hi there

I see nobody has answered you yet, and I’m afraid I can’t help either, perhaps it’s because it’s such an uncommon scope.  It looks beautifully made. Have you found this link yet?

https://www.cloudynights.com/topic/224896-a-very-rare-tasco-find-i-got-the-16t/

 

[EssexMigrant]

Also found this. Have a look at the drawing in one of the included pics. In some ways this is similar to the Tasso Starguide 114 which I collimated a week or two back.  But with that there’s a central locking screw and three adjusting screws. Also there’s a correcting lens in the eyepiece tube. 

https://www.ebay.ph/itm/Mizar-CX150-Astronomical-Catadioptric-Telescope-D-153-mm-Fl-1310mm-/173661361395

 

[Peter Drew]

I think it is likely that the secondary/corrector assembly is preset at the factory and no user adjustment is provided. We have a donated Bresser version and this has the conventional Newtonian type secondary adjusting screws. Because of the design, you can't really use the usual collimating aids, I've found the best option is to use an artificial star and adjust the primary mirror cell screws until the defocused "star" image is both round and evenly illuminated at the periphery. I wouldn't recommend removing the corrector lens, replacing it accurately is likely to be a lottery.   ?

[inFINNity Deck]

Hi Ash,

Perhaps a bit late and you may already have found out yourself, but today I collimated a Mizar 153mm f/8.5 Catadiaptric with a similar design as yours. You already found out how the main mirror is done, for those who are unknown with it: indeed the thinner screws hold the mirror in place, so loosening them all the way separates the mirror-cell from the tube. This is handy as it allows to mark the centre of the mirror, which is required to properly collimate the secondary prism/lens assembly.

The 153mm Mizar has two of those rings with a knurled knob stacked on top of each other as shown in you picture. These rings are wedges and thus tilt the whole prism/lens assembly when they are rotated. In order to collimate you will have to slightly loosen the Philips-head screw (the 153mm Mizar has a 13mm capped hex-nut). I can recommend using a laser collimator, although it may not fit if your telescope has a 1" eyepiece holder. I encountered that same problem and decided for the moment to firmly press the laser collimator against the eyepiece holder and fixate it using painter's tape. Moving the laser dot to the centre of the mirror is done in two ways: by rotating the whole secondary prism/lens holder along the telescope's optical axis and by turning around that ring with the knurled knob. Turning the former is simply done by grabbing that secondary with you hand through the spider. You will see the laser dot making a curve along the centre. When you found its closest approach, use the ring with knob to get that closest approach even closer to the centre. After a few iterations you will have the laser dot dead centred. After that you need to tighten the Philips-head screw again. Make sure to hold the prism/lens barrel when doing so, as otherwise your secondary adjustment will be off again.

Adjusting the primary mirror is easy as long as you keep it pressed against the tube during the process. Putting a think piece of foam behind the mirror-cell with a straps to the front, may help in this process.

Hope this helps...

Nicolàs