250px with Revelation Astro 2.5x Barlow

[knobby]

As promised...

[knobby]

sorry somehow did 2 of the same image

[richyrich_one]

Found it.

Check out from 5:20 onwards...Am I misunderstanding something here or is he talking rubbish?

[Stephen]

Found it.

Check out from 5:20 onwards...Am I misunderstanding something here or is he talking rubbish?

Rubbish in what regard? That's blatently not a 250px

Some of the smaller scopes have 1.25" only focusers, as each line evolved the focusers changed on them, some custom (needs SW adaptors,) some 2"

[richyrich_one]

The principle of a barlow moving the focal point further out rather than further in.

[knobby]

Rubbish in what regard? That's blatently not a 250px

Some of the smaller scopes have 1.25" only focusers, as each line evolved the focusers changed on them, some custom (needs SW adaptors,) some 2"

I think Richy is referring to the effect a Barlow has on focus position, not the size of the focuser

[Stephen]

I think Richy is referring to the effect a Barlow has on focus position, not the size of the focuser

I will go back and listen again, the bit at 5:20 was talking about barrel size, I missed the above point about focus point :facepalm:

[Stephen]

Right listened again (until I got bored)

He says that adding the Barlow moves the focus point out - that's correct?

[richyrich_one]

Right listened again (until I got bored)

He says that adding the Barlow moves the focus point out - that's correct?

In the real world it would appear to be the opposite, hence this thread.

[knobby]

In the video he says it moves the focus point out ,but we're not sure this is correct ?

I'm going to drag the dob out and try mine ...

See you soon

[Stephen]

I can tell you for a fact that a Barlow moves the focal point AWAY from the OTA

[richyrich_one]

I can tell you for a fact that a Barlow moves the focal point AWAY from the OTA

If this is correct, and I don't presume to be an expert in these mattters by any means, why am I running out of inward focus travel when using the barlow?

[knobby]

I'm back ...

2 Piccys, both focused on Mars , with and without Barlow ...

Judge for yourselves

I'd say that's inwards but it's subjective I guess .

The Barlow moves the focus point out further but when you take into account the length of the Barlow you are actually moving the focuser inwards !

So it's a yes and a no

[Stephen]

If this is correct, and I don't presume to be an expert in these mattters by any means, why am I running out of inward focus travel when using the barlow?

I would suggest it's because your "full in" point is actually "full in" plus the extension provided by the Barlow tube - it would seem (remarkably) that the Barlow tube is too long to allow you to achieve focus?

[richyrich_one]

I would suggest it's because your "full in" point is actually "full in" plus the extension provided by the Barlow tube - it would seem (remarkably) that the Barlow tube is too long to allow you to achieve focus?

I would agree, and Knobby's pics prove it.

[TwinkleTwinkle]

Do I use the Barlow with an eyepiece or is the Barlow / eyepiece ment to be used solo?

Many thanks

[knobby]

Scope - Barlow - eyepiece

[richyrich_one]

You can try this when it arrives...

uploadfromtaptalk1397648628427.jpg

It's arrived, and with the cloud to go with it!

Hopefully I'll get a chance to give it a try over the weekend. I'll let you know the results.

[richyrich_one]

Thanks to everyone who participated in this thread, it's been an interesting education.

[mdstuart]

The tube coming out of the focuser looks long to me from memory when I had a 250px...

Is that the standard one????

Mark

Sent from my BlackBerry 9320 using Tapatalk

[knobby]

The tube coming out of the focuser looks long to me from memory when I had a 250px...

Is that the standard one????

Mark

Sent from my BlackBerry 9320 using Tapatalk

Who's tube Mark ?

[mdstuart]

Yours. The tube coming out from the focuser assembly looks longer than I remember?

Might be worth measuring it and asking another px user to measure their focuser tube.

Mark

Sent from my BlackBerry 9320 using Tapatalk

[TwinkleTwinkle]

Thankyou knobby

[richyrich_one]

Success!

Barlow worked nicely with the low profile adaptor. However...

I found that without the Barlow I couldn't then get focus as there wasn't enough outward travel. Even with the Barlow I had to move the eyepiece out a bit. So looks like I need something in between.

Can you get extension tubes in the order of 25mm say that would fit the low profile?

[richyrich_one]

Just thought I would update, this might prove useful to someone else.

Ok, so all working nicely now, except the weather of course.Just managed to get out and test everything last night before the cloud started coming in.

I got me one of these from astroboot...

It gives only 35mm of extension instead of the 48mm that the stock SW one gives.

Now everything focuses in any combination, even my modded webcam.

What's next...oh yeah some decent eyepieces.

Knobby if you can PM me your address I'll get your adaptor back to you. Thanks again.