Orion Optics VX12 1/10pv

[Commanderfish]

37 minutes ago, DRT said:

I just had my first look through the VX12 with the FeatherTouch focuser. 21mm Ethos achieved focus easily. My 8mm Ethos required a barrel extension as more outward focus was required. I have not tried it with the Paracorr yet.

Yeah I have the same problem - the 8mm and 6mm don't reach focus whilst the 21mm does. I'm thinking the solution  will be a focuser with 70mm travel. Moonlight do one, not sure about Feathertouch.

[Paul73]

4 hours ago, Stu said:

I may be wrong but I thought the Paracorr had a weak Barlow in it which is just enough to cover its own length i.e. Leave the same or similar amount of back focus as without it?

Didn't know that.

DRT - Do you really need the Parracor at f5.3? It could be just adding unnecessary weight? With the right non-marring barrel extender, you might get perfect parity with your higher mag eyepiece.

Don't underestimate how much more pleasurable observing becomes when refocusing isn't required. I found that I generally swapped between 21mm Ethos and  a shorter Delos dependent on seeing (17.3 is parfocal anyway). So, just treat the extension as part of the eyepiece.

Paul

[nicoscy]

Stu,

The Paracorr induces a 15% Barlow effect. See here.

[DRT]

6 hours ago, Stu said:

I may be wrong but I thought the Paracorr had a weak Barlow in it which is just enough to cover its own length i.e. Leave the same or similar amount of back focus as without it?

It does, Stu. The Mk II turns my 1200mm fl F4 into an F4.6. I only mentioned it because I didn't try it so haven't confirmed that the result would be the same with each EP

The Paracorr Mk II also has a very long barrel which allows you to use it like a flexible-length extension tube so it might be that I could set it to a length where both the 8mm and 21mm Ethos would reach focus without the 8mm needing the barrel extender.

[DRT]

1 hour ago, Paul73 said:

Didn't know that.

DRT - Do you really need the Parracor at f5.3? It could be just adding unnecessary weight? With the right non-marring barrel extender, you might get perfect parity with your higher mag eyepiece.

Don't underestimate how much more pleasurable observing becomes when refocusing isn't required. I found that I generally swapped between 21mm Ethos and  a shorter Delos dependent on seeing (17.3 is parfocal anyway). So, just treat the extension as part of the eyepiece.

Paul

It's an F4, Paul, not the F5.3. The Paracorr really does make a difference at that speed.

[nicoscy]

Does indeed. We have the same scope and with the Nagler 31, I'd rather pay the penalty of 0.25 degrees FOV to get a super clean image!

[Pig]

Are there a functional restrictions why these focusers are not produced with ample travel ? IE Could the draw tube obstruct the light path when fully closed.

[nicoscy]

You got it! Hence the use of an extension tube, to stop the actual drawtube from cutting the light path.

[Commanderfish]

To the extent that I add risers, they will contain a longer focus tube away from the light path by the same number of mm as the risers are high, correct?  Hmm... my E21 comes to focus with around 20mm of out focus, my E8 and 6 focus at around 70mm.  The paracorr  makes effectively no difference to the focal point. So maybe what I need is a focuser with 50mm travel and 20mm ish of risers from the Moonlite fitting kit for Newtonians?

[John]

2 hours ago, Pig said:

Are there a functional restrictions why these focusers are not produced with ample travel ? IE Could the draw tube obstruct the light path when fully closed.

I think thats exactly it Shaun. A long drawtube would project into the light path when imaging. Extension tubes at least are flexible. With the 50mm extension tube I found that using Baader GO's (which need more inwards travel than most EP's) caused a few mm of the drawtube to intrude into the light path even. 35mm seemed to accomodate everything, even the 6 and 8mm Ethos in 2" mode.

Skywatcher do a low profile focuser with a built in extension tube I think. It's probably not in the same league as Moonlite or Feathertough products though.

[Commanderfish]

Just to confirm that the M4 45mm adjusting screws fit the secondary on my VX16 perfectly  

So much safer than the original Philips head screws!

[Moonshane]

I cannot recall by how much but a paracorr definitely brings the focus point in. If I had a gun at my head I'd guess at 18mm.

[Commanderfish]

I've got my Paracorr Type 1 now, I'll test what it does to the focus point next clear night.

[DRT]

11 minutes ago, Commanderfish said:

I've got my Paracorr Type 1 now, I'll test what it does to the focus point next clear night.

I'll do the same with my Type II when I get an opportunity.

Presumably the amount by which the Paracorr shortens the light path will be in some way proportionate to the focal ratio of the scope?

[FenlandPaul]

On ‎17‎/‎08‎/‎2016 at 16:26, DRT said:

The Mark's Knobs are the M4 45mm size.

A big thanks for this Derek - just what I was after!!