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VMC200L problem focusing short fl eps

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#1 tiberio

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Posted 03 August 2005 - 03:01 PM

Hi,

I have a Vixen VMC200L (http://www.vixenamer..._or_Cat=VMC200L and a Orion ED80),and I can't focus a 12mm (meade astrometric) nor a 7.5 mm EP (orion highlight) on it (works fine on the ED80). I think I would need the focuser to move 5-10mm inward to get the EPs into focus. I have an Antares diagonal and a celestron (don't know which model).

I also tried using a barlow (celestron ultima) and it did not help. Should I buy a new diagonal? Which one? I guess I could saw off a 1/2" of the diagonal, but I would like to know if there is a less drastic solution!

Regards,

Tiberio

#2 Guest_**DONOTDELETE**_*

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Posted 03 August 2005 - 03:13 PM

I cant help you directly with your problem, but I can help ya rule out one possible culprit.

1. What was your target at 162x (12mm ep)? Maybe it was too much power on THAT target for those particular conditions.

Gary

#3 tiberio

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Posted 03 August 2005 - 03:53 PM

Hi Gary,

It was jupiter. I think it would focus if I had a few more mm of intravel (it was almost there! ).

regards,

Tiberio

#4 tiberio

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Posted 03 August 2005 - 03:54 PM

BTW, I am using a 2" visual back and a 1.25" adapter ring. I wonder if a 1.25" & diagonal would solve the problem?

Regards,

Tiberio

#5 Guest_**DONOTDELETE**_*

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Posted 03 August 2005 - 04:07 PM

I am just not qualified to answer that question...all i can say is Jupiter can be a pretty tough object at times, so before getting into the mechanics that I am not qualified to answer..try targeting the Moon and see if it can focus or not. If it can focus there, then the problem is not a mechanical one :)

Gary

#6 BZFrank

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Posted 03 August 2005 - 04:08 PM

I also have a VC200L (beside other scopes) and yes, the focus is short, for the Televue 24-8 zoom ocular I have only ~1mm left - also on a 2" diagonal (Intes Micro) with a 1.25" adaptor. My 40mm Antares Erfle is less critical. Since I use the VC200L almost exclusively as photo machine it was not a matter of great concern for me.

I'd try it with a 1.25" diagonal and a short 2"->1.25" adaptor...

CS

Frank

#7 Jason Freeland

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Posted 03 August 2005 - 04:31 PM

What specific visual back are you using? I've had trouble using non Vixen adapters. I have had good luck with my William Optics 2" diagonal.

#8 stevie

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Posted 03 August 2005 - 11:30 PM

a 1.25" might do the trick
i have the sam problem with my ED80/tmb barlow if i use the 2" diagonal
a low profile 2"/1.25" adapter with the 1.25 diagonal would help even more

#9 tiberio

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Posted 04 August 2005 - 02:02 AM

Hi Jason,

I can't tell which visual back I am using, it has no markings at all. I will try a 1.25" diagonal (all my eps are 1.25" anyway)and see how it goes.

Regards,

Tiberio

#10 tiberio

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Posted 18 August 2005 - 08:41 AM

I tried the 1.25" diagonal and now I can focus the 7.5mm and the 12mm.

However, I also got a BV1 and I can't focus it unless I put the 1.6x siebert corrector in front of the diagonal. I think I will need a new corrector too....

Regards,


Tiberio

#11 Harry Pulley

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Posted 18 August 2005 - 09:14 AM

I have an old VC200L, the one that came with a black 50mm extension tube. It used to be that all eyepieces focused fine straight through with the tube, or with a diagonal you used no tube.

Now the new VC200DLG and VMC200's come with that flip-mirror contraption instead, right? Are you using that contraption along with the diagonal? Is there a way to attach the 60mm->1.25" adapter without the flip-mirror in the middle?

It seems like the old system was much simpler. I can even focus most eyepieces straight through with the f/6.4 focal reducer in place, though there is only 86mm of back focus in that configuration.

Harry

#12 tiberio

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Posted 04 September 2005 - 11:21 PM

Hi Harry,

Sorry for the late reply, I moved and I am back to my routine just now. I think I have the old system (I bought the VMC200L on astromart) and I don't have the flip mirror. I have an extension tube, but I don't know how long it is.

I could focus the bv1 straight through without diagonal, but it is awkward to look through in that position. I could not focus it with the diagonal. When my scopes arrive, I will try it again and report back.

Regards,

Tiberio

#13 Harry Pulley

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Posted 05 September 2005 - 09:35 AM

To focus with a diagonal you MUST remove the black
extension tube. The tube gives about the same
distance as the diagonal.

Harry

#14 tiberio

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Posted 05 September 2005 - 09:17 PM

Hi Harry,

I don't use extension tube, I think it is for astrophotography. I believe the issue with the BV1 is that I need a new corrector. The one that I have is for refractors and AFAIR it won't focus with or without the diagonal. Without the corrector I can focus if I don't use a diagonal, but it is very awkward to observe.

Regards,

Tiberio

#15 Harry Pulley

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Posted 06 September 2005 - 07:03 AM

Yes, the extension can be used for photography.

Sorry, I was confused about the corrector issue. No, I wouldn't expect a refractor, or SCT for that matter, corrector or reducer to work in that scope as it is specialized. Unfortunately, I don't think Vixen has yet released a reducer and/or corrector lens for the VMC design yet, nor do I know if one is planned.

Just curious: why are you using the 1.6x corrector?

I have the VC200L f/9 and I use the Vixen f/6.4 reducer with it but I don't know if that would work with the VMC (Vixen does not advertise it as being compatible).

Harry

#16 tiberio

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Posted 06 September 2005 - 10:15 AM

Hi Harry,

I think I have the 1.6x Siebert corrector. I will check when my scopes arrive (~2 months :-( ). It works well on the ED80, but the VMC200 is another story...

I don't have the focal reducer, but eventually I hope to have one (I will check with Vixen before buying it, to see if it works). I may also e-mail Mr. Siebert and see if another corrector would work on the VMC.

Regards,

Tiberio

#17 Joe Cipriano

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Posted 06 September 2005 - 03:50 PM

I have the VC200LDG, and I can't reach focus with my Celestron 12.5mm Ortho Reticle and a WO 2" diagonal (or, for that matter, the flip mirror that came with the scope). I need to barlow it to reach focus (Celestron 1.25"). As I also use the scope primarily for photography, it has not been a major issue. Seems that both Vixen Cats have the same problem.
I've got a Tak LE 5mm en route for the upcoming Mars close approach, and I'm hoping to use the Vixen for observing; I'll post any focusing problems if evident.

#18 Harry Pulley

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Posted 06 September 2005 - 03:54 PM

I have the old VC200L, not the DLG version. I can focus a non-reticle Celestron 12mm ortho fine with either 1-1/4" or 2" diagonals but it may be a completely different beast. The old one didn't come with a flip mirror and it makes me wonder if they didn't change the back focus somewhat to accommodate the flip accessory.

For Mars, 5mm is 360x which requires good seeing. I have a 5mm Celestron Ultima but I have yet to use it much on Mars. More commonly I use an 8mm TV Plossl or the aforementioned 12mm Celestron ortho barlowed 2x to 6mm for 300x but even that requires the best morning I've had so far.

Harry

#19 Joe Cipriano

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Posted 06 September 2005 - 07:37 PM

Harry:

I've also got a TV 15mm Plossl & Ultima barlow en route, and a TV 25 Plossl in my case; with the barlow, I'll have 7.5mm (240X) and 12.5 (144x) - just in case the Chicago area LP and seeing are as bad as they are every night... :rolling:

Sorry - not trying to hijack the thread...

#20 tiberio

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Posted 23 November 2005 - 12:55 AM

Hi All,

My stuff arrived last week and I could give a few more tries on this issue. I removed the corrector lenses assembly from the tube it came from and screwed in front of a 1 1/4 diagonal and then I could reach focus on the VMC200L and ED80. However, I'm probably getting 2.5 to 3x out of the 1.6 corrector.

Regards,

Tiberio


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