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Skyliner 300p prime focus problems


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Hi i have a skyliner 300p and understand that the primary mirror is to far from the secondary mirror to be able to use for prime focus imaging.

Just wondered if anybody has found a way of overcoming this problem?

Thanks Dean

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I've no idea if this will work but you could use the collimation screws to move the mirror up the tube a little. It may not be enough and it may cause other problems but it could be worth a go.

James

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I did that with my 8" F5 scope - had issues getting a dSLR to focus.

I needeed about 2 or 3 mm of in focus, using the collimation screws I only had about 5mm of "up" movement available - it makes collimation harder IMO.

It'll be better to get a low profile focuser?

Ant

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I did that with my 8" F5 scope - had issues getting a dSLR to focus.

I needeed about 2 or 3 mm of in focus, using the collimation screws I only had about 5mm of "up" movement available - it makes collimation harder IMO.

It'll be better to get a low profile focuser?

Ant

Thanks James/Ant

A low profile focuser was suggested to me at SGL4 but just wondered how much extra in focus i would get if i used the low profile crayford focuser below?

Skywatcher

Thanks Dean

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Hi Dean

I think that's a good deal on that focuser and it will probably give you the appropriate amount of extra focus travel. Give Steve at FLO a ring - he'll probably be able to help you out.

Good luck getting it sorted.

Andrew

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Themos is right, a 2" barlow (just the lens part) could be scewed into the 2" adapter. This effectivly brings the focus point out.

The only draw back with that is that it increases the focal length (decreases the field of View) - but a DSLR has a large FOV so this may not be an issue - as long as the exposures can be kept quick.

I think your best bet would be to estimate the amount of in focus you need - then see how much in focus you'll gain with the low profile focuser.

You may find that the only alternative you have is Themos' barlow idea.

Cheers

Ant

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I think I can get my DSLR (450D EOS Canon) to focus when I use an old 1.25" TeleVue 2.5x Barlow (not Powermate) but I should check and report back. That's with the original 300P focuser.

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