One for the Quark/optics boffins?

[Floater]

Well, two questions, actually.

Using a Quark Chromo in my TV76 (f/l 480mm), if I want to view a full solar disc in the EP (32mm plossl) I have to put a focal reducer on the nose of the Quark. This works. However, if I screw the focal reducer onto the EP it doesn't 'reduce'. There seems to be no difference in the view with or without the reducer on the EP. I don't understand how that can be. Can anyone explain, please? I'll work hard at understanding!

Second - and probably more important - is it safe to have the focal reducer before the Quark in the focal train? I always use a UV/IR filter before the diagonal and on a couple of occasions I've tested after several minutes of use to see if the reducer is heating up. It doesn't appear to be. Holding my hand over the diagonal things get a bit too hot, of course. But the light is being focused onto my hand there. With the focal reducer being so much closer to the diagonal perhaps it's cooler 'down' there?

Any advice, opinions, experiences very welcome.

 

[Pig]

1) Its the change in the focal length I guess Gordon the glass of the reducer is in a different position from the objective thus when in the eyepiece (magnification increase) the disc becomes larger.

2) I don't think its dangerous Gordon but its best to check with Daystar (good luck on that one ), heat transfer would be pretty fast and you have tried it with no effect. I wont comment on the filters because you already have them in the correct position

[DRT]

This might be nonsense but here goes...

The Quark has a 4x barlow built in so your 480mm fl scope effectively becomes 1920 f/l. The reducer at the nose of the Quark (assuming it's a 0.85x) makes the f/l 1632mm.

A 32mm plossl with a reducer on the Quark will therefore give x51 mag.

The 32mm plossl on its own gives x60 mag.

A reducer on the plossl will make it 27.2mm, so you would get x70 mag.

Shoot me if that's wrong

...and I don't think it is a problem so long as the reducer is behind the ERF.

[Floater]

Thanks for the quick replies, guys, and your reassurance, Shaun. But I've had enough grief dealing with Daystar before and I'm unlikely to go down that route. ??

Derek, I can follow the maths and get my head round what's happening. Thanks. Very helpful.

However, the reducer is in front of the ERF ... that's why I'm wondering about safety. But, as I wrote, I can't detect any heat build up.

[DRT]

Sorry, when I said ERF I meant the UV/IR filter you have on the nose of the diagonal. So long as everything is behind that you are ok

[Floater]

Good stuff. Thanks for the help.