DSLR Focusing help

[cubes]

Hi.

I've got what appears to be a common problem - the DSLR won't focus when on the telescope due to a lack of inward travel.

From what I've read here there's 2 solutions to this? (that don't involve a new telescope!)

low-profile focuser

or

move the mirror up the tube.

the focuser looks relatively easy to change, but how hard is moving the mirror, and are there any instructions?

It's a Skywatcher explorer 200p.

Thanks

[GrantEb]

Hi

I have done this to a SW130, without cutting the tube. I don't have any pictures, but if you post pics of yours, with the mirror removed from the tube, I may be able to help.

Cheers

[Glider]

The design of the mirror frame on a 200P doesn't allow you to move the whole lot up the tube without cutting a ring off the tube.

If you are just lacking millimetres of travel you could try adjusting the mirror right out on its collimation screws to see if this gives you enough movement up the tube before doing anything radical.

Also, search on my posts for an adaptor I made to suite my R&P and a Canon 1000D.

Also search on Steppenwolf(?) to see how he manages it.

[Bizibilder]

What are you using to attach the DSLR to the scope? I attach my Canon 1000D to the 200P with no trouble at all using a t-ring and adaptor to the 2" diameter of the standard focusser. If you have the standard 200P the 2" to 1 1/4" adaptor unscrews into two bits, the 2" bit can then be screwed into the camera adaptor (t-mount).

[GrantEb]

Is it a blue tube 200P? If so it should be similar to the 30? I might be wrong.

I will attempt some drawings to illustrate

[Glider]

My comment is only based on the observation that the mirror mount on my blue tube 200P has a lip that goes over the end of the tube which would therefore mean cutting the tube to shorten it.

Bizibilder, yes you are right, I forgot that stage in my process of connecting a 1000D to the focuser. However, vignetting soon took me to designing the 2" adaptor.

[GrantEb]

Ok, I am really useless at drawing, so please excuse.

Basically, you remove the rear cell. Remove the mirror from the cell. Move the spacers from the old mirror side to the new mirror side, drill 3 new holes in the rear cell, just next to the old ones, and just large enough for the screws. With the new holes, attach the mirror to the cell, with spacers in between. Then screw in the collimating screws in the original threads in the rear cell.

Does this make sense?

[Glider]

Ahhhhh, nice, I completely misunderstood what you were saying.

I was thinking the whole assy at the bottom of the tube was all moving up the tube.

How much movement is there, 10-20mm?

The 3 new holes in the cell are clearance, are the three holes in the plate that the mirror is sitting on threaded?

[GrantEb]

As far as I can remember, they are threaded. When I did this to my SW130, I only had to take 3mm off the focuser, to achieve prime focus with a 1000d.

And this way, there isn't much needed to return it to original condition.

You could also move it further up the tube, with thicker spacers, but any longer, and the mirror might start flopping around, depending on your collimation needs.

[cubes]

Thanks. I'll have to give it some thought I guess.

I'll try putting the t-ring on the 2" adapter with the 1.25" bit unscrewed and see what I get!

[SkyExplorer]

I got focus using my Canon 450d on my Explorer 200p (black and white version) without any issues. I just unscrewed the 1.25" nose piece adaptor as Bizibilder said and attached the camera that way.

[cubes]

Haven't had a chance to give it a go yet - typically it's been cloudy on all the nights I've been free