[M]: Re: The ETX article in S&T
| Subject: | [M]: Re: The ETX article in S&T |
| From: | Donald Tabbutt |
| Date: | Wed Jan 01 07:56:54 1997 |
> From: RA <ralpha@softcom.net>
> To: mapug@shore.net
> Subject: [M]: The ETX article in S&T
> Date: Wednesday, January 01, 1997 2:12 AM
>
> Looks like the ETX is a pretty ideal small telescope but will it
> outperform a C5+ for planetary performance?
> Reason I ask is that I am hearing allot of positive hype on the Mak
> design and people are telling me it will out perform a 8" and 10" F10
> Schmidt for planetary use.
> Ive talked with a few people who own both C5 and ETX and they all say
> the C5+ is the hands down winner everytime in every catagory, including
> planetary usage. Isnt this comparison valid: ETX vs C5+ / Meade 7" mak vs
> Meade 10" F10?
>
> Ralph
Hello Ralph,
I have an ETX that I bought mainly for travel. However, I think it may make
a nice guide scope for my 8" f/10 LX200 and I have ordered the Losmandy
stuff to mount it. In the meantime, I used its tripod block to piggyback it
on the LX200 last Sunday night for an A-B comparison. The short conclusion:
there is no comparison; the ETX is a little scope and the 8" SCT is a
comparatively big scope. The most striking and immediate difference is
brightness. One plus to the ETX, though, is when focused on Capella it
forms a perfect Airy disk with a single small diffraction ring...something
Ive never seen in the SCT, although it appears to focus as well...but no
diffraction ring.
Saturn was jumping around in the LX200 like I had lost "vertical hold", but
was O.K. in the ETX...I guess proving small scopes handle bad seeing better
than big scopes. On Christmas night I used the ETX by itself on Saturn and
could see banding at 187X with just a hint of Cassinis division as a
contrast change in the rings. But I couldnt see Tethys or Dione...just too
dim. I see them regularly in the SCT. In short, I couldnt do an A-B on
Saturn because of the seeing Sunday, but have had much better views in the
SCT in the past. I even imaged the ammonia cloud storms on Saturn with a
CCD camera last October through the SCT, and got images nearly as good as
those published by Donald Parker in S&Ts December issue. Until I read that
issue, I thought the storms were some sort of image processing artifact.
With averted vision Christmas night, I think I saw those storms through the
ETX. They appear visually as ragged edges on the south side of the south
equatorial band.
On the deep space side there is really no comparison. One caveat...there is
a lot of light pollution here, and I will have to do another comparison at
a dark site. I put a .63 reducer on the SCT to even up the magnifications
(about 48X) using the standard 26mm Plossl on both scopes. I looked at NGC
1857, a small cluster in Auriga mentioned recently on s.a.a. (they were
having trouble seeing it through a Ranger), and saw it clearly and brightly
in the SCT, but barely in the ETX. The same goes for other small clusters.
They are there, but dim compared to the SCT. I used an O III filter on both
scopes for M76 and NGC 7662 and saw them in the SCT (without the reducer)
but not at all in the ETX. M31 was fine in both scopes, but M33 did not
show up in the ETX (light pollution, Im sure). Later, as M42 cleared the
trees, it was nicely visible in both scopes, but again much brighter and
more finely detailed in the 8". I couldnt see NGC 2024 in either scope. I
didnt try splitting any doubles.
By now, the Moon was rising, and after it cleared the trees I used all
kinds of powers to look at it...up to 300X on the SCT and 187X on the ETX.
Bad seeing caused me to back off, but Id call it a draw on the Moon. Both
scopes were clear, tack sharp, and very contrasty, with the same small
details equally visible. Again, the SCT was brighter, but at lower powers I
have to use an ND filter with it. The ETX was fine without a filter.
In summary, aperture wins. The ETX meets my needs as a traveling companion
and will probably make a good guide scope. The optics, in my experience,
are superb, but it will not outperform a larger aperture scope with decent
optics. The ETX mount is a different story Ill save for another post if
anyone is interested.
I hope this helps answer some of your questions.
Happy New Year!
Don Tabbutt
