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Subject: [M]: LX200/Pictor 216xt and parfocal eyepiece
From: Graham Warrellow
Reply To: mapug@shore.net
Date: Thu Feb 26 02:37:28 1998

Hi Steve,
Glad you found the info useful. Thought I should change the subject
line a little as we seem to have moved the discussion on from cables :)

In message , Steve Isaacs <ToolsSmith@foothills.eznet.com> writes
>The parafocus eyepiece is new to me. I didn't notice mention of such a
>device when I was researching scopes and trying to decide what to purchase.
> Thanks for mentioning this I'll check it out.

The parfocal eyepiece is simply an eyepiece from your collection which
is modified by the addition of a locking collar (supplied with Pictor)
placed around the barrel of the eyepiece. When you first find focus
with your CCD you replace it with the eyepiece/collar combination and
lock it at the position in the drawtube which gives you best visual
focus. I did this originally in daylight on a distant object (I had to
use a cardboard mask over the front of the LX200 to reduce the effective
aperture) and refined it later using the moon. You will find that once
done this will take you very close to CCD focus in the future. If you
are using a flip mirror you just "flip and image" :)

When you receive your 216xt you will find info on how to produce a
parfocal eyepiece in the manual. If you can't wait go to the Meade site
and check out the on-line Pictor manuals under the Technical
archive/information section :) In fact, I found there was more info on
the Meade site than in the manual supplied to me, particularly on the
topic of using the 216xt as an autoguider. Check it out.
>
>Actually, I'm purchasing the 216XT to use as an autoguider (using an
>off-axis adapter) for 35mm stuff and a future CCD (Starlight Express
>Color). I would have gone with the 208 but I got a good price on the 216.
>The 216 gives me the added advantage of being able to learn CCD stuff and
>at the same time capture some pretty good images while I'm waiting to
>accumulate the funds necessary to purchase the Starlight Express.

This is exactly what I have done. I am currently in the process of
sorting out using my 216xt to autoguide a Starlight Xpress SXL8. I have
to say that at the moment I still prefer my 216xt for lunar and
planetary work despite the smaller chip.

You need to be aware that there have been problems with using the 216xt
as an autoguider using the current PictorView software, though it may be
only a short time before Meade have this sorted given their current
approach with the Beta versions. John Hoot's DOS based software does
work fine though and is available for download from the Meade site (once
again under the Technical.. section)
>
>Against the advice of some I decided to purchase the f6.3 10" LX200 and use
>a focal reducer with that. I'm not sure how it will work out but I'm hoping
>that for 35mm work with the deep sky objects I want to bag, the f6.3 will
>be a little more flexible. For CCD I decided to get a the f6.3 reducer to
>produce an effective f4 with this scope. The relatively small area of the
>CCD should help avoid problems due to distortions at the edge of view
>introduced by the focal reducer.
>
I believe that the f6.3 focal reducers were specifically designed for
the f10 'scope. No reason why you couldn't use it on the native f6.3
but it would be interesting to know something about the image quality.
Anyone done this? As you say, for CCD work, your comment about the
relatively small imaging area may help reduce aberrations.

>In the future I might purchase a tele-extender to go back to f10 for the
>planetary stuff if I should get the urge to bag a planet or two. Maybe a
>barlow is a better approach or the same thing -- I don't know right now.

I think lunar imaging is a great way to start on the CCD trail given the
large object (even I could place it on the chip :)) and very short
exposures required. I believe that this is one area where the Pictor
cameras score over the SBIG cameras, i.e. shorter minimum exposure
times. You might find that you will need to push beyond f10 for lunar
and planetary imaging; I use around f20 to f30, and yes, the consensus
seems to be that the Barlow is the way to go but eyepiece projection
will work also.
>
>> Your life is about to change... :))
>
>Yeah. This is actually the realization of a dream I had when I was a teen
>and carried through the years but didn't resurface until I moved back to a
>rural setting and was reminded on a regular basis how brilliant the Milky
>Way can be in a dark sky.
>
Same for me. After building a 6" reflector at school and later moving
from rural England to the outskirts of London it became impossible to
star-hop in mag 3.5 skies so my practical astronomy sessions declined.
Although the GOTO features of the LX200 are often knocked (luddites!!)
it's reawakened visual astronomy for me. I can actually find the peas
in the pea-soup :)

>I'm not known for being much of a night person. I'm hoping my wife will
>still love me and my boss won't complain too much when I start showing up
>late at work. :-)
>
>Steve
>
In the early days my wife used to say "you love that damn telescope more
than me!" I didn't argue :)
Now she's got used to my sessions into the early hours she just says "at
least I know where you are!"
As for your boss, just say you witnessed a once in a lifetime event,
show them some of the images and they'll be encouraging you to do more.

Bet you're counting the days,
Regards,
Graham