Using 2" filter with 1.25" eyepieces in SW 200p

[TwoPi]

Hi all, this is my first post so please go easy on me! Been speaking to Martin @ FLO and he suggested I post here to see if anyone else can come up with a creative solution to my question.

I bought a Skywatcher 200P FlexTube GOTO at the beginning of the year and have had some great views over the last few months. I've added a couple of 1.25" eyepieces (a Williams Optics 6mm and just recently a Baader Hyperion 24mm) and have just bought a 2" moon filter too.

I thought I was being clever by buying a 2" filter - this way I could leave the filter in place when changing eyepieces. However, I now realise that the standard 2" to 1.25" adaptor Skywatcher supply with my telescope does not have a 2" filter thread. Definitely a lesson for me there!

I've searched previous posts and see that a few others have asked a similar question and that one solution suggested has been to replace the adaptor with something like the Antares 1.25" to 2" eyepiece adaptor with filter thread. However, if I understand how this would work correctly then this will attach to my Skywatcher's 2" eyepiece holder and I'm worried that the resulting setup might 1) result in focus issues as the distance between the eyepiece and secondary mirror will have changed or 2) provide the possibility of an eyepiece hitting my brand new moon filter and damaging it.

To complicate matters further, I might get a barlow lens in the future and believe that this could also add to my focusing woes, judging by other posts on here?

Has anyone got any experience of whether this adaptor might do the trick with my scope or can you think of another approach that might be better?

Thanks for any suggestions or help you can provide,

Gav.

PS: One last thought. I am vaguely considering upgrading the focuser altogether and have my eye on the Moonlite CR2, which has a 2" filter thread built in to its 1.25" adaptor and I believe will solve my problem. However, not sure I'm ready to take the plunge just yet and so wanted to see if there's a ~£20 option rather than the ~£270 option!

[crashtestdummy]

I'm sure there are other 2"-1.25" adaptors with screw fitting for a 2" filter.I have a moonlite with the adaptor you speak of and you can buy them seperately.

[John]

As above but ...... the Skywatcher focusers have a unique approach to 1.25" and 2" adapters which makes using another adapter (with a 2" filter thread) quite difficult.

Upgrading the focuser to one which uses more conventional adapters might be a good plan !

[RikM]

I use an Orion self-centring 1.25" adaptor with a 2" filter thread. This fits in my 2" SkyWatcher extension / adaptor but the one I have is a short 35mm extension. Sometime you get a 47mm long one and these seem to have focus issues when used with self-centring adaptors. If you have a shorter extension though, I can highly recommend the self-centring adaptors.

[Andrew*]

I've got one idea which is not particularly elegant, but I think will solve your issues. Buy an adaptor with 2" filter thread. Your points 1) and 2) are correct if you get a standard one, so get this in addition: http://www.firstlightoptics.com/baader-planetarium/baader-hyperion-finetuning-ring.html

This will put the filter far enough away from the eyepiece so there's no chance of it hitting your moon filter. It will also allow you to pull the 2" adaptor further out of the focuser and securing it there to get focus. As I said, not elegant, but it will delay the need to purchase a replacement focuser.

Why Skywatcher can't just stick to the standard 2" straight on the focuser I'll never know....

Andrew

[TwoPi]

Thanks for the replies guys, really useful. I've just measured my SW 2" eyepiece holder and of course it's the 47mm one Rik, so suspect I'm in for some frustration.

Andrew, with regard to the Baader FTR, I'm a bit confused. Presumably the setup would be my existing SW 2" eyepiece holder, the filter screwed into the FTR, the FTR screwed into the 2" to 1.25" adaptor with 2" filter thread and finally the 1.25" eyepiece?

If I'm right then I see how this helps in terms ensuring there's enough space between my filter and eyepiece, but (and I could well be wrong here), I thought the issue with focus was that it was unlikely that my eyepiece would be close enough to the secondary to achieve focus, not that it would be not far enough away?

Apologies if I've got the wrong end of the stick here!

Thanks again for all your help,

Gav.

[Andrew*]

Thanks for the replies guys, really useful. I've just measured my SW 2" eyepiece holder and of course it's the 47mm one Rik, so suspect I'm in for some frustration.

Andrew, with regard to the Baader FTR, I'm a bit confused. Presumably the setup would be my existing SW 2" eyepiece holder, the filter screwed into the FTR, the FTR screwed into the 2" to 1.25" adaptor with 2" filter thread and finally the 1.25" eyepiece?

If I'm right then I see how this helps in terms ensuring there's enough space between my filter and eyepiece, but (and I could well be wrong here), I thought the issue with focus was that it was unlikely that my eyepiece would be close enough to the secondary to achieve focus, not that it would be not far enough away?

Hi Gav,

Yes, you've got it right. I thought the 2" adaptor is actually a 2"-2" extension, but it's not, is it? Are there any alternative, shorter versions of this most inconvenient Skywatcher 2" adaptor?

Another (drastic) alternative would be to shorten the adaptor with a hacksaw and drill and tap M5 thumbscrew threads...

Bummer.

If you decide to go down the new focuser route, put up a "what focuser?" thread as there are lots of good ones out without having to go to a Moonlite (though they are superb) and you'll really want to make sure you get the fitting right first time.....

[TwoPi]

Haha, yes you're right about getting a new focuser - if it doesn't work first time there'll be trouble!

As both you and John say, upgrading to one with more convenient adaptors would be a good starting point! Maybe I can use this as the reason why yet another accessory is required when I have to justify the purchase to our house's finance committee...

[RikM]

You might be interested in this thread http://stargazerslounge.com/topic/192050-self-centering-adapter/page__st__40#entry2010617 there are a couple of links to 35mm 2" extensions. If your eyepiece barrel is too long and there is a risk of contacting the filter, then screw the Baader FTR between the filtyer and the bottom of the adaptor to move the filter further away.

[TwoPi]

Thanks Rik, I've read through the posts and looked at the links. Still seems like there's going to be a fair bit of trial and error involved to end up with a solution. Going to have a think about replacing the focuser and then might return to the adaptor approach for my existing focuser. Cheers again for all the suggestions.

[rwilkey]

Hi Gav, I have the same Orion adaptor that Rik has and it works superbly with my 200P adaptor,no problem with focus, though I was perturbed to read of another post on this forum about someone not achieving focus. However, I love my Orion Self-Centering Adaptor and use it all the time, along with filters. Just to note that 1.25" nosepieces do not usually touch the filter, but as an extra measure I sometimes use the Baader 14mm FTR attached to the Orion adaptor to make sure there is no problem, it fits really well.

[TwoPi]

Thanks Robin. Out of interest, do you have the shorter (35mm) SW 2" eyepiece holder that Rik has, or do you have the 47mm version? I think I saw the thread you mention about someone struggling to achieve focus and wondered if that was with the longer 2" eyepiece holder I have.

Good idea re the Baader FTR - these seem like very useful bits of kit!

[rwilkey]

Hi Gav, mine is the 47mm version, so I guess the focus problems lay with the 35mm? Which goes against Rik's comments?

[TwoPi]

Hmm, confusing business this isn't it! I must admit, I've just for the nuclear option and ordered a new focuser!

[RikM]

Hi Gav, mine is the 47mm version, so I guess the focus problems lay with the 35mm? Which goes against Rik's comments?

I'm quite sure it's the 47mm that doesn't focus on my 250PX with the Orion adaptor, I had to dig it out of my spares box to take the pic of it. I am not now 100% sure if there are focus issues with my 150P and the 47mm extension, but the 35mm plus Orion adaptor definitely works fine on both my scopes. Perhaps the focus position is different between 150P, 200P and 250PX? Or different between particular OTA's in general?

[TwoPi]

Could it be anything to do with focal ratio? I notice that some 200P's are f/6 (like mine) whereas some are f/5 (like Robin's)? Apologies if I'm throwing in a red herring here.

[rwilkey]

Could it be anything to do with focal ratio? I notice that some 200P's are f/6 (like mine) whereas some are f/5 (like Robin's)? Apologies if I'm throwing in a red herring here.

Yes Gav, my 200P is f/5, shorter tube (1000mm I think), perhaps it does make a difference? Bit technical for me haha!