Don,

Please keep us posted about your mirror situation.

That's neat about your view of the Orion nebula... about a week ago I saw the
Orion nebula
under pretty good conditions with our 12.5 and it was the first time I saw green
in it,
but I just took a fleeting look.  I was during half-time of the Superbowl!   I
have pretty
good color acuity, and can see red in the Orion nebula naked eye.

I do believe that a scope that size is not meant for planetary except under
optimum
conditions,  something not usual here in New Jersey.  One of my fellow club
members has an
18 inch Obsession, while I marveled at the way the scope picked up planetary
nebulae, I
was dismayed by the fuzzy edges on the planets.  It almost like when you take a
picture
and blow it up, and it loses resolution and begins to go grainy.    I don't know
if it's
your mirror or not and I think you should pursue your side-by-side testing.

Clear skies,

Penny

>
Don D'Egidio wrote:
>
> I believe the word has gotten out on the Discovery Telescope group. I had the
> 17" out last night,
> which was not all to bad, and performed some tests that confirmed the mirror
> was no better than 1/3
> wave. Views of Jupiter were not what I expected from a scope of this size.
They
> would not focus to a
> 'sharp' image. I had the collimation right on and at this size scope
> collimation is a big factor in
> the quality of the images. Once I stopped it down to 7" the images were
> extremely better though
> somewhat fainter. Not unlike my 6" refractor. I'm still in that window of
> opportunity where I can
> still return the mirror for another or have this one refigured. I have tried
to
> arrange some side by
> side comparisons with 2 friends, one with a 17.5" Coulter of worse quality
> mirror and an 18"
> Obsession clone with a better mirror, but the weather just has not been
> cooperative. Will keep
> trying to arrange the side by side and get back to the group when it does
> happen. I do have to say
> that the deep sky views are fantastic. I needed to purchase a Paracorr to
> eliminate the coma at the
> field edges and it has been working great. Several weeks ago I had a view of
> the Orion Nebula that I
> thought I saw a little pinkish tint in the extremities of what I call a bat
> with out stretched
> wings. In fact that night I knocked off about 15 M objects in some casual
observing.
>
> Don
>

Hello,

I am Bob from Murphysboro, Illinois.  I have a 12.5" Discovery Truss
Design and it was one of the first six shipped from Oceanside.  I
have had it a little less that a year and so far I really like it.
It is easy to handle and the views are great.  There are a few items
I would like to alter but will not rush into that.  One item is the
position of the focuser.  I would like to roll it 45 degrees up so
that viewing objects lower down would be easier.  Also I would like
to see a change and the manner that the Truss Tubes are mounted.  I
would see the mounting allow a faster put together time.  I feel like
I am spinning the knobs forever.  I did have to make a mod to the
upper cage so that the truss tubes would allow the cage to bottom out
on the plate.  Therefore allowing a constant setting everytime I
erected it makeing collimation easier.  That is enough for now.

Bob

Penny,

I believe the word has gotten out on the Discovery Telescope group. I had the
17" out last night,
which was not all to bad, and performed some tests that confirmed the mirror was
no better than 1/3
wave. Views of Jupiter were not what I expected from a scope of this size. They
would not focus to a
'sharp' image. I had the collimation right on and at this size scope collimation
is a big factor in
the quality of the images. Once I stopped it down to 7" the images were
extremely better though
somewhat fainter. Not unlike my 6" refractor. I'm still in that window of
opportunity where I can
still return the mirror for another or have this one refigured. I have tried to
arrange some side by
side comparisons with 2 friends, one with a 17.5" Coulter of worse quality
mirror and an 18"
Obsession clone with a better mirror, but the weather just has not been
cooperative. Will keep
trying to arrange the side by side and get back to the group when it does
happen. I do have to say
that the deep sky views are fantastic. I needed to purchase a Paracorr to
eliminate the coma at the
field edges and it has been working great. Several weeks ago I had a view of the
Orion Nebula that I
thought I saw a little pinkish tint in the extremities of what I call a bat with
out stretched
wings. In fact that night I knocked off about 15 M objects in some casual
observing.

Don

----- Original Message -----
From: "Penny Fischer-Otte" <govega@...>
To: <Discovery-Dob-Users@yahoogroups.com>
Sent: Sunday, February 04, 2001 17:58
Subject: RE: [Discovery-Dob-Users] 17.5" TD critique and Discovery's answer


> Don,
>
> Sounds like you did extensive testing of your mirror,   and it also sounds
like you had
> some work to do before you were able to use your scope :(.   The only thing I
remember
> initially that we had problems with was the fact that the scope came without
the wingnuts
> to screw the bearings on.   We simply had to go to the hardware store and get
four, but
> needless to say, we could not just take the scope out and assemble it and
observe right
> away!   Well good thing our first night was a cloudy night! hehe...
>
>  We called Discovery and they shipped out the nuts.    I do think they are
lacking
> somewhat in their quality control with the packing and final stages. 
Something they need
> to work on.
>
> Thanks for the recommendation again about the Discovery-telescopes  yahoo
groupt too.
> That also looks like a nice group.  I joined today.  Please also let them know
about this
> group too :-).
>
> Best regards,
>
> Penny
>
>  answer
> >
> >
> > Penny,
> >
> > As I said in our private email, here is a copy of my email to Discovery
about
> > the recently received
> > 17.5" TD and their reply to me. Also, I would like everyone to know that
there
> > is another Yahoogroup
> > about Discovery telescopes located at
> > http://groups.yahoo.com/group/Discovery-telescopes where they
> > discuss all scopes made by Discovery but most of the messages are about the
dobs.
> >
> > Here goes with my email to Discovery:
> >
> > From: djd52@b...
> > Date: Saturday, December 09, 2000 22:34
> > To: Telescopes4you@a...
> > Subject: Partial critique of 17.5" truss tube dob
> >
> > Ron,
> >
> > As I mentioned on the phone there were some alignment issues with the 17.5"
> > truss tube dob I
> > received on Nov. 28 that needed to be corrected before the scope could be
used.
> > I will start with
> > the corrections I had to make to bring the scope to the point where it could
be
> > collimated, then I
> > will describe what I liked about the scope.
> >
> > First I have to say that the scope was well packaged. When I unpacked the
upper
> > tube assembly (UTA)
> > the secondary holder's nut was loose. My first initial impression was that
> > something did not look
> > right. What it turned out to be was the board the focuser is bolted to was
> > installed at an angle to
> > make the focuser point to the right with the UTA upside down on a table. By
> > measurement the focuser
> > board was off by 5º to the right and was clearly evident, just looking at
it,
> > it was installed
> > incorrectly and should have been caught by quality control. That angle made
the
> > focuser point about
> > 1" to the right from the correct diametrical point using the center of the
> > focuser as reference. Add
> > to that the spider was off center to the left by about 1/2". Those two
> > conditions combined made only
> > 1/2 of the secondary visible when looking down the focuser drawtube.
> >
> > To remedy those conditions I first needed to shim the left side of the
focuser
> > by 1/4", and did so
> > temporarily, but will need a more permanent solution. I had to modify one of
my
> > allen wrenches
> > by cutting the short leg of the wrench to 7/16" so that it would fit under
the
> > fine focus mechanism
> > of the JMI DX1 focuser. Once the centering of focuser was accomplished, the
> > spider was easier to
> > center by loosening the screw on one side and tightening the screw on the
other
> > side. The secondary
> > was now centered under the focuser and that finished the corrections to the
UTA.
> >
> > The construction of the rest of the scope appears to be very well done. The
> > joints were straight and
> > well fitting and the finish is good. The motions in azimuth and altitude
were
> > smooth and predicable.
> > Use at night was easy to track the stars. I also like the quality of the
light
> > shroud and the carry
> > bags for the wingnuts and truss poles. I'm still waiting for the wheeled
> > handles and since they were
> > ordered in July should not have been in a backorder status. There is also a
> > balance problem that I
> > need to address. I had to temporarily add 10 lbs. of weight to the mirror
box
> > to get the scope to
> > balance with my 2" eyepieces. I will probably add a sliding weight system.
> >
> > Now some analysis of the mirror.
> >
> > As you know I stated many times that one of our club members, with many
years
> > of mirror making
> > experience, was going to perform tests of the optical quality of the mirror.
I
> > delivered the mirror
> > to him on Nov. 29 and we performed an initial Foucault test looking for the
> > smoothness of the
> > mirror's figure. I was pleased with the initial test as it showed no zones
and
> > appeared to have a
> > smooth figure. Several days later, after the mirror had acclimated to the
> > surroundings, my friend
> > performed the actual Foucault test and sent me the results in an email. I
will
> > add the actual data I
> > received later in this message. The final outcome is a 1/2.61 wave mirror. I
> > was disappointed at
> > such a low number. I would have preferred 1/4 wave or better, but my friend
> > suggested to wait for
> > the actual star test before reaching a bad conclusion. We had first light on
> > Dec. 4 and the ease of
> > focusing indicated that the truss poles were of the correct length, but
because
> > of poor seeing
> > conditions could not really assess the quality of the mirror with the star
test.
> >
> > At this point I can give a recommendation as to the mechanical quality of
the
> > telescope, except for
> > the problem with the focuser board which I hope will not happen to other
scopes
> > being produced
> > in the future, but I will have to withhold any recommendations as to the
> > optical quality until
> > further star tests are performed under better seeing conditions. Once that
is
> > done I will send and
> > addition critique.
> >
> > Here is the optical data I received.
> >
> > First, some technical stuff.
> >
> > R = 174.625 inches
> > D = 17.51 inches, yes, 17.51. The blank is actually 17.6 inches
> > Focal ratio = 4.986
> > Mirror thickness at edge = 2.1 inches
> >
> > Mask outside radii
> > zone 1 = 2.64
> > zone 2 = 4.57
> > zone 3 = 5.90
> > zone 4 = 6.98
> > zone 5 = 7.92
> > zone 6 = 8.76
> >
> > Readings
> > zone 1 = 0.0735
> > zone 2 = 0.168
> > zone 3 = 0.256
> > zone 4 = 0.357
> > zone 5 = 0.443
> > zone 6 = 0.5025
> >
> > The mirror surface is smooth, the correction is smooth and there are no
> > apparent zones. There is a
> > slight TDE. ADMIR says 1/2.61 wave. I'd say the next step is to assemble the
> > scope and star test it.
> >
> > Again, thanks for the opportunity to test the mirror.
> >
> > --------------------------------------------------------------------
> >
> > From: Telescopes4you@a...
> > Date: Monday, December 11, 2000 13:47
> > To: djd52@b...
> > Subject: 17TD critique
> >
> > Hello Don,
> >
> > Thank you for your feedback.
> >
> > The reason we use a master reference (certified 1/10th wave) optical surface
is
> > to eliminate the
> > subjectivity of the zonal test. Ask 3 different opticians to do zonal
testing
> > on the same mirror and
> > you'll get 3 different conclusions. Using the double pass laser test with
our
> > master reference flat
> > produces superior mirrors that consistently surpass the defraction limited
> > threshold (if your mirror
> > doesn't produce a superior star test for you, it'll be a first). I'm looking
> > into the UTA issues now
> > and I'll contact you.
> >
> > Dark skies,
> >
> > Ron
> >
> > ---------------------------------------------------------------------
> >
> > Sorry for the long post.
> >
> > Don
> >
> >
> >
> >
> >
> >
> >
> > To unsubscribe from this group, send an email to:
> > Discovery-Dob-Users-unsubscribe@yahoogroups.com
> >
> >
> >
> >
>
>
>
> To unsubscribe from this group, send an email to:
> Discovery-Dob-Users-unsubscribe@yahoogroups.com
>
>
>

Rodger,

I checked out your webpage, wow, you have some nice scopes!   Amazingly enough,.
Fred,
another member here, also has a 10 inch Discovery and 20 inch Obsession!  I
wonder if this
is a common thing,  I thought Fred was the only one around!

I also noticed that you went to the BlackWater Falls Starparty.  Where are you? 
I went
camping to WVA several times and we really loved it but it's been awhile.  But
talk about
DARK... you can't even see your hand before your face after dark at some of the
state
campgrounds...

We really like star parties and plan to buy the ultimate accessory for our
scope... a
minivan.  That should give us enough room to be able to head out to some good
ones this
spring/summer.

Also, lastly,  I wanted to say,  if we make a table of members, we should also
add
astronomy personal pages.  I have one too.  This is the page of my site that has
info
about my Orion Dob.  Just a bit I set up for my astro club several years ago.

Best!

Penny

>
> Hi all,
>
>   I have a 10" f5.6 DHQ Dob (or at least they call them DHQ now).
> I've had it for about 2 years. I had to do some "diddling" with it
> when I got it, but not much. I've added a fan. I'm not too
> technically inclined (flaky?). I think my mirror is "ok". I was happy
> enough with it to order a 6" DHQ to use to teach Astronomy to cub
> scouts.
>
>   My astronomy page web site URL is:
>
> http://members.home.net/rabradman/astronomypage1.html
>
>   Pics of the "discovery" are on the "my three scopes page"
>
> / rodger blake
> Huntington, WV
>
>
>

That's a great idea Rodger.   Are you up to the task of doing it?  If not, I
will be happy
to.

What do you say group? Want to let us all know what kind of scopes you have?

Also, if anyone has any other files they want to upload to the database, feel
free.  There
is uploading capabilities open for all members.  We uploaded an ongoing "best
of" list
that Edward has been working on for months already.   Feel free to add your
tables, files,
programs, whatever you may want to augument this little group :-).

Penny

> From: rabradman@... [mailto:rabradman@...]
>
> Hi,
>
>  owner moderator - do you think it would be good to have a table in
> the database section listing name and e-mail and size of discovery
> scope(s) owned?
>
> / rb
>
>
>
>
>
> To unsubscribe from this group, send an email to:
> Discovery-Dob-Users-unsubscribe@yahoogroups.com
>
>
>
>

Rodger,

Thanks for your recommendations!    I ordred the 32mm from Orion and we should
be getting
it the forthcoming week.  I really used their Sirius 26mm Plossl to death on my
8 inch
Orion...  but with my 12.5 inch scope,  I find that I like the 15mm Televue I
bought
several years ago as a "second" at the NEAF.    So I am curious as to how I will
like the
32.

What do you think of your 2X barlow? Do you think it makes the field too dark? 
I like the
extra mag, but I think you lose something with some much glass sometimes.  But
it beats
buying too many eyepieces!

Penny

> From: rabradman@... [mailto:rabradman@...]
>
> Penny,
>
>   I have a $129 2" 32mm Konig from U Optics that I uas as a low power
> EP. Much "bang for buck here", Like all Konigs it's soft around the
> edges. For other EP I like the 10.5mm Pentax, a 18mm Meade superwide
> with and without a 2x barlow, 26mm plossl, and a 7mm nagler. I have a
> 10" f 5.6 DHQ Dob.
>
> / Rodger Blake
>
>

Don,

Sounds like you did extensive testing of your mirror,   and it also sounds like
you had
some work to do before you were able to use your scope :(.   The only thing I
remember
initially that we had problems with was the fact that the scope came without the
wingnuts
to screw the bearings on.   We simply had to go to the hardware store and get
four, but
needless to say, we could not just take the scope out and assemble it and
observe right
away!   Well good thing our first night was a cloudy night! hehe...

  We called Discovery and they shipped out the nuts.    I do think they are
lacking
somewhat in their quality control with the packing and final stages.  Something
they need
to work on.

Thanks for the recommendation again about the Discovery-telescopes  yahoo groupt
too.
That also looks like a nice group.  I joined today.  Please also let them know
about this
group too :-).

Best regards,

Penny

  answer
>
>
> Penny,
>
> As I said in our private email, here is a copy of my email to Discovery about
> the recently received
> 17.5" TD and their reply to me. Also, I would like everyone to know that there
> is another Yahoogroup
> about Discovery telescopes located at
> http://groups.yahoo.com/group/Discovery-telescopes where they
> discuss all scopes made by Discovery but most of the messages are about the
dobs.
>
> Here goes with my email to Discovery:
>
> From: djd52@b...
> Date: Saturday, December 09, 2000 22:34
> To: Telescopes4you@a...
> Subject: Partial critique of 17.5" truss tube dob
>
> Ron,
>
> As I mentioned on the phone there were some alignment issues with the 17.5"
> truss tube dob I
> received on Nov. 28 that needed to be corrected before the scope could be
used.
> I will start with
> the corrections I had to make to bring the scope to the point where it could
be
> collimated, then I
> will describe what I liked about the scope.
>
> First I have to say that the scope was well packaged. When I unpacked the
upper
> tube assembly (UTA)
> the secondary holder's nut was loose. My first initial impression was that
> something did not look
> right. What it turned out to be was the board the focuser is bolted to was
> installed at an angle to
> make the focuser point to the right with the UTA upside down on a table. By
> measurement the focuser
> board was off by 5º to the right and was clearly evident, just looking at it,
> it was installed
> incorrectly and should have been caught by quality control. That angle made
the
> focuser point about
> 1" to the right from the correct diametrical point using the center of the
> focuser as reference. Add
> to that the spider was off center to the left by about 1/2". Those two
> conditions combined made only
> 1/2 of the secondary visible when looking down the focuser drawtube.
>
> To remedy those conditions I first needed to shim the left side of the focuser
> by 1/4", and did so
> temporarily, but will need a more permanent solution. I had to modify one of
my
> allen wrenches
> by cutting the short leg of the wrench to 7/16" so that it would fit under the
> fine focus mechanism
> of the JMI DX1 focuser. Once the centering of focuser was accomplished, the
> spider was easier to
> center by loosening the screw on one side and tightening the screw on the
other
> side. The secondary
> was now centered under the focuser and that finished the corrections to the
UTA.
>
> The construction of the rest of the scope appears to be very well done. The
> joints were straight and
> well fitting and the finish is good. The motions in azimuth and altitude were
> smooth and predicable.
> Use at night was easy to track the stars. I also like the quality of the light
> shroud and the carry
> bags for the wingnuts and truss poles. I'm still waiting for the wheeled
> handles and since they were
> ordered in July should not have been in a backorder status. There is also a
> balance problem that I
> need to address. I had to temporarily add 10 lbs. of weight to the mirror box
> to get the scope to
> balance with my 2" eyepieces. I will probably add a sliding weight system.
>
> Now some analysis of the mirror.
>
> As you know I stated many times that one of our club members, with many years
> of mirror making
> experience, was going to perform tests of the optical quality of the mirror. I
> delivered the mirror
> to him on Nov. 29 and we performed an initial Foucault test looking for the
> smoothness of the
> mirror's figure. I was pleased with the initial test as it showed no zones and
> appeared to have a
> smooth figure. Several days later, after the mirror had acclimated to the
> surroundings, my friend
> performed the actual Foucault test and sent me the results in an email. I will
> add the actual data I
> received later in this message. The final outcome is a 1/2.61 wave mirror. I
> was disappointed at
> such a low number. I would have preferred 1/4 wave or better, but my friend
> suggested to wait for
> the actual star test before reaching a bad conclusion. We had first light on
> Dec. 4 and the ease of
> focusing indicated that the truss poles were of the correct length, but
because
> of poor seeing
> conditions could not really assess the quality of the mirror with the star
test.
>
> At this point I can give a recommendation as to the mechanical quality of the
> telescope, except for
> the problem with the focuser board which I hope will not happen to other
scopes
> being produced
> in the future, but I will have to withhold any recommendations as to the
> optical quality until
> further star tests are performed under better seeing conditions. Once that is
> done I will send and
> addition critique.
>
> Here is the optical data I received.
>
> First, some technical stuff.
>
> R = 174.625 inches
> D = 17.51 inches, yes, 17.51. The blank is actually 17.6 inches
> Focal ratio = 4.986
> Mirror thickness at edge = 2.1 inches
>
> Mask outside radii
> zone 1 = 2.64
> zone 2 = 4.57
> zone 3 = 5.90
> zone 4 = 6.98
> zone 5 = 7.92
> zone 6 = 8.76
>
> Readings
> zone 1 = 0.0735
> zone 2 = 0.168
> zone 3 = 0.256
> zone 4 = 0.357
> zone 5 = 0.443
> zone 6 = 0.5025
>
> The mirror surface is smooth, the correction is smooth and there are no
> apparent zones. There is a
> slight TDE. ADMIR says 1/2.61 wave. I'd say the next step is to assemble the
> scope and star test it.
>
> Again, thanks for the opportunity to test the mirror.
>
> --------------------------------------------------------------------
>
> From: Telescopes4you@a...
> Date: Monday, December 11, 2000 13:47
> To: djd52@b...
> Subject: 17TD critique
>
> Hello Don,
>
> Thank you for your feedback.
>
> The reason we use a master reference (certified 1/10th wave) optical surface
is
> to eliminate the
> subjectivity of the zonal test. Ask 3 different opticians to do zonal testing
> on the same mirror and
> you'll get 3 different conclusions. Using the double pass laser test with our
> master reference flat
> produces superior mirrors that consistently surpass the defraction limited
> threshold (if your mirror
> doesn't produce a superior star test for you, it'll be a first). I'm looking
> into the UTA issues now
> and I'll contact you.
>
> Dark skies,
>
> Ron
>
> ---------------------------------------------------------------------
>
> Sorry for the long post.
>
> Don
>
>
>
>
>
>
>
> To unsubscribe from this group, send an email to:
> Discovery-Dob-Users-unsubscribe@yahoogroups.com
>
>
>
>

I thought I would pipe in here on the subject of eyepieces and the best one to
use. In
none technical terms the best is based on the application. It one has a high
surface
brightness object then one can use higher power eyepieces. If on wants to view a
large
diffused object low power. In fact, seeing conditions often dictate how low one
can go.

Technically, the best "match" eyepiece for a scope is based on what is called
the exit
pupil. The light coming out of the eyepiece should be about what the observers
ability to
dialate to the largest size. The average maximum seems to be about 7mm. So the
eyepiece
which will match this will grant good resolution of faint objects. So if one
owns a f/4.5
scope and uses a 32mm eyepice this would be very near the optimal eyepiece for
the faint
fuzzies (7.11), assuming one is in a very dark sight. If there is any light
pollution  it
may be better to aim for a 5 ratio.

Edward

> --- In Discovery-Dob-Users@y..., glitterstarz@y... wrote:
> > We just ordered a 32 mm and I think it will be the best eyepiece we
> > have yet. (2 inch of course). From what I heard, this is a good
> size
> > low power for the Big Dob range. What are some other
> recommendations?
> >
> >
> > Penny
>
> Penny,
>
>   I have a $129 2" 32mm Konig from U Optics that I uas as a low power
> EP. Much "bang for buck here", Like all Konigs it's soft around the
> edges. For other EP I like the 10.5mm Pentax, a 18mm Meade superwide
> with and without a 2x barlow, 26mm plossl, and a 7mm nagler. I have a
> 10" f 5.6 DHQ Dob.
>
> / Rodger Blake
>

Hi all,

   I have a 10" f5.6 DHQ Dob (or at least they call them DHQ now).
I've had it for about 2 years. I had to do some "diddling" with it
when I got it, but not much. I've added a fan. I'm not too
technically inclined (flaky?). I think my mirror is "ok". I was happy
enough with it to order a 6" DHQ to use to teach Astronomy to cub
scouts.

   My astronomy page web site URL is:

http://members.home.net/rabradman/astronomypage1.html

   Pics of the "discovery" are on the "my three scopes page"

/ rodger blake
Huntington, WV

Hi,

  owner moderator - do you think it would be good to have a table in
the database section listing name and e-mail and size of discovery
scope(s) owned?

/ rb

--- In Discovery-Dob-Users@y..., glitterstarz@y... wrote:
> We just ordered a 32 mm and I think it will be the best eyepiece we
> have yet. (2 inch of course). From what I heard, this is a good
size
> low power for the Big Dob range. What are some other
recommendations?
>
>
> Penny

Penny,

   I have a $129 2" 32mm Konig from U Optics that I uas as a low power
EP. Much "bang for buck here", Like all Konigs it's soft around the
edges. For other EP I like the 10.5mm Pentax, a 18mm Meade superwide
with and without a 2x barlow, 26mm plossl, and a 7mm nagler. I have a
10" f 5.6 DHQ Dob.

/ Rodger Blake

Penny,

As I said in our private email, here is a copy of my email to Discovery about
the recently received
17.5" TD and their reply to me. Also, I would like everyone to know that there
is another Yahoogroup
about Discovery telescopes located at
http://groups.yahoo.com/group/Discovery-telescopes where they
discuss all scopes made by Discovery but most of the messages are about the
dobs.

Here goes with my email to Discovery:

From: djd52@b...
Date: Saturday, December 09, 2000 22:34
To: Telescopes4you@a...
Subject: Partial critique of 17.5" truss tube dob

Ron,

As I mentioned on the phone there were some alignment issues with the 17.5"
truss tube dob I
received on Nov. 28 that needed to be corrected before the scope could be used.
I will start with
the corrections I had to make to bring the scope to the point where it could be
collimated, then I
will describe what I liked about the scope.

First I have to say that the scope was well packaged. When I unpacked the upper
tube assembly (UTA)
the secondary holder's nut was loose. My first initial impression was that
something did not look
right. What it turned out to be was the board the focuser is bolted to was
installed at an angle to
make the focuser point to the right with the UTA upside down on a table. By
measurement the focuser
board was off by 5º to the right and was clearly evident, just looking at it, it
was installed
incorrectly and should have been caught by quality control. That angle made the
focuser point about
1" to the right from the correct diametrical point using the center of the
focuser as reference. Add
to that the spider was off center to the left by about 1/2". Those two
conditions combined made only
1/2 of the secondary visible when looking down the focuser drawtube.

To remedy those conditions I first needed to shim the left side of the focuser
by 1/4", and did so
temporarily, but will need a more permanent solution. I had to modify one of my
allen wrenches
by cutting the short leg of the wrench to 7/16" so that it would fit under the
fine focus mechanism
of the JMI DX1 focuser. Once the centering of focuser was accomplished, the
spider was easier to
center by loosening the screw on one side and tightening the screw on the other
side. The secondary
was now centered under the focuser and that finished the corrections to the UTA.

The construction of the rest of the scope appears to be very well done. The
joints were straight and
well fitting and the finish is good. The motions in azimuth and altitude were
smooth and predicable.
Use at night was easy to track the stars. I also like the quality of the light
shroud and the carry
bags for the wingnuts and truss poles. I'm still waiting for the wheeled handles
and since they were
ordered in July should not have been in a backorder status. There is also a
balance problem that I
need to address. I had to temporarily add 10 lbs. of weight to the mirror box to
get the scope to
balance with my 2" eyepieces. I will probably add a sliding weight system.

Now some analysis of the mirror.

As you know I stated many times that one of our club members, with many years of
mirror making
experience, was going to perform tests of the optical quality of the mirror. I
delivered the mirror
to him on Nov. 29 and we performed an initial Foucault test looking for the
smoothness of the
mirror's figure. I was pleased with the initial test as it showed no zones and
appeared to have a
smooth figure. Several days later, after the mirror had acclimated to the
surroundings, my friend
performed the actual Foucault test and sent me the results in an email. I will
add the actual data I
received later in this message. The final outcome is a 1/2.61 wave mirror. I was
disappointed at
such a low number. I would have preferred 1/4 wave or better, but my friend
suggested to wait for
the actual star test before reaching a bad conclusion. We had first light on
Dec. 4 and the ease of
focusing indicated that the truss poles were of the correct length, but because
of poor seeing
conditions could not really assess the quality of the mirror with the star test.

At this point I can give a recommendation as to the mechanical quality of the
telescope, except for
the problem with the focuser board which I hope will not happen to other scopes
being produced
in the future, but I will have to withhold any recommendations as to the optical
quality until
further star tests are performed under better seeing conditions. Once that is
done I will send and
addition critique.

Here is the optical data I received.

First, some technical stuff.

R = 174.625 inches
D = 17.51 inches, yes, 17.51. The blank is actually 17.6 inches
Focal ratio = 4.986
Mirror thickness at edge = 2.1 inches

Mask outside radii
zone 1 = 2.64
zone 2 = 4.57
zone 3 = 5.90
zone 4 = 6.98
zone 5 = 7.92
zone 6 = 8.76

Readings
zone 1 = 0.0735
zone 2 = 0.168
zone 3 = 0.256
zone 4 = 0.357
zone 5 = 0.443
zone 6 = 0.5025

The mirror surface is smooth, the correction is smooth and there are no apparent
zones. There is a
slight TDE. ADMIR says 1/2.61 wave. I'd say the next step is to assemble the
scope and star test it.

Again, thanks for the opportunity to test the mirror.

--------------------------------------------------------------------

From: Telescopes4you@a...
Date: Monday, December 11, 2000 13:47
To: djd52@b...
Subject: 17TD critique

Hello Don,

Thank you for your feedback.

The reason we use a master reference (certified 1/10th wave) optical surface is
to eliminate the
subjectivity of the zonal test. Ask 3 different opticians to do zonal testing on
the same mirror and
you'll get 3 different conclusions. Using the double pass laser test with our
master reference flat
produces superior mirrors that consistently surpass the defraction limited
threshold (if your mirror
doesn't produce a superior star test for you, it'll be a first). I'm looking
into the UTA issues now
and I'll contact you.

Dark skies,

Ron

---------------------------------------------------------------------

Sorry for the long post.

Don

>
> Edward,
> If you liked S Cephei, be sure to check out R Leporis too.  It is
> high in the southern evening sky right now, and it is definitely one
> of my favorite telescopic stars.  With an average magnitude of about
> 8, it is a little brighter than S Cephei, but otherwise very similar
> in color and periodicity.  (I haven't looked at it this winter, so
> I'm not sure what it's exact magnitude is right now.)  A good
> description of it can be found on pages 1093-1099 of Burnham's
> Celestial Handbook.  Maybe your e-mail regarding S Cephei will
> inspire me to go out and search for it again.  It is the
> quintesential "crimson star" and (in a good telescope) easily ranks
> as one of the most beautiful stars in the sky.
> Rich

Yes Rich I am going to look for R Leporis too. The problem with these stars is
you never
know if when you look for them if they will be at minimum. By the way, Gamma
Leporis is a
great, widely separated, colorful double nearby.

Edward

> If anyone has ordered and recieved one of the 10" PDHQ scopes could
> you lets us know what you think of the optical quality.
>
> Thanks,
> Mike

How cool! They now make a Premium 10"! That should cover the market with Orion
who uses
the standard mirror for their 10" model!

Edward

Great. Thanks for the word. Let me know when you get yours.

> Edward,
> I have heard mixed reviews regarding the tech 2000 system. I just
> bought a 10" PDHQ and had it shipped to Lenord Stage in texas. Lenord
> is building me a Goto mount from scratch. I belive his intend is to
> have a retro kit avaiible in the near future. You can check out his
> web page at www.gototelscopes.com.
>
> He is in the final stages of my project and it sounds like it is going
> to turn out great.
>
> Mike
>

Hi Mike,

Our friend Fred,  also a member of this group, purchased a 10-inch Discovery
Telescope
about a year and a half ago.

We were simply awed and amazed at the clarity of the images the first time we
tried out
the scope during a club meeting.

The next time we had the opportunity was at a star party for a school that Fred
was nice
enough to come to to lend a hand with us.

It became clear that the first time we had viewed through his DHQ was not an
anomoly as
the images was just as pin-sharp and bright.  There was absolutely no blurring
and the
stars at the edge of the F.O.V. were just as sharp as the central stars.  This
was after
he had transported the scope about an hour, mind you, to get to the star party!

It was these sharp images that stuck in our minds when we started looking for
more
aperture for another Dob purchase, to augument my 8-inch Orion.

I would have probably purchased the 10 inch myself,  but my husband wanted more
aperture.

From what I have seen of the optics,  I highly recommend that size.

Best regards,

Penny




>
> If anyone has ordered and recieved one of the 10" PDHQ scopes could
> you lets us know what you think of the optical quality.
>
> Thanks,
> Mike
>

Edward,
If you liked S Cephei, be sure to check out R Leporis too.  It is
high in the southern evening sky right now, and it is definitely one
of my favorite telescopic stars.  With an average magnitude of about
8, it is a little brighter than S Cephei, but otherwise very similar
in color and periodicity.  (I haven't looked at it this winter, so
I'm not sure what it's exact magnitude is right now.)  A good
description of it can be found on pages 1093-1099 of Burnham's
Celestial Handbook.  Maybe your e-mail regarding S Cephei will
inspire me to go out and search for it again.  It is the
quintesential "crimson star" and (in a good telescope) easily ranks
as one of the most beautiful stars in the sky.
Rich

--- In Discovery-Dob-Users@y..., "Edward Otte" <exogyra@m...> wrote:
> Ok so I finally got out and checked out what is billed as one of
the reddest
> stars. Sure it was not a faint fuzzy galaxy involved in galactic
> cannabilism, or a real tight double spilt, but was "stoplight" red
as Penny
> put it. Who says little color can be found in stars! By the way I
also
> observed Mu Cephei which is also a red star but naked eye visible.
It is not
> as red as S Cephei (S is a N class, and Mu is a M class.) I would
call the
> color of Mu copper orange. Also it should be noted that S Cephei is
a
> "Carbon" star and is a Long-Period Variable. It seems to be fairly
up near
> its brightest (7.4) presently.
>
> Edward

If anyone has ordered and recieved one of the 10" PDHQ scopes could
you lets us know what you think of the optical quality.

Thanks,
Mike

Edward,
I have heard mixed reviews regarding the tech 2000 system. I just
bought a 10" PDHQ and had it shipped to Lenord Stage in texas. Lenord
is building me a Goto mount from scratch. I belive his intend is to
have a retro kit avaiible in the near future. You can check out his
web page at www.gototelscopes.com.

He is in the final stages of my project and it sounds like it is going
to turn out great.

Mike

Hello all,
I just stumbled on this e-group by accident while signing up for Steve Tuma's
Deepsky 2000
e-group.  I have heard quite a few good testimonials about Discovery Dob scopes
(especially the premium Dobs and truss Dobs), and decided to take a chance and
order their
15" truss Dob last week (just in time to beat the Feb. 1 price increase, of
course).
Apparently this e-group was only begun yesterday, so I feel almost like a
charter member!
Hopefully, I will be happy with my new Discovery - and I think that I will be
because, as
I said, most of the feedback that I have read has been very favorable.  Except,
of course,
from some of the "Dob-snobs" in the BigDob e-group who wouldn't think of looking
through,
let alone buying anything less than an Obsession or a Starmaster scope.  I can't
wait
until I get my hands on my new scope so that I can give it a thorough star test,
and then
we shall see whether they are right or wrong.  (After all a Toyota certainly
isn't a
Mercedes, is it? But just because it costs a lot less and doesn't have all the
luxury
features doesn't mean that a Toyota is a piece of junk either, does it?) Anyway,
greetings
to all, and I look forward to a great scope and a very informative e-group.
Rich Dodson

Hello Rich,

Glad to have you "on-board" so to speak.  As far as I know the Premium mirrors
are among
the best in the industry.  They are 1/10 wave accuracy and 94% reflective. That
beats the
rest of the industry's 1/8 wave accuracy and 88%  reflectivity! In fact,
Discovery makes
the "standard" 1/8 and 88% for almost all American telescope companies. This
includes
Orion! In any case, Truss seems to be the way to go for portability. You should
be able to
resolve about a mag better than a 12.5" scope with the 15". Let us know how it
goes.

Edward

Penny,
Thanks for the welcome!  The phone rep at Discovery said the scope
might be ready in as little as two months (i.e, late March or early
April).  Hopefully, he's right, but I suspect (and won't be too
disappointed) that it might take a little longer.
Regards,
Rich

--- In Discovery-Dob-Users@y..., "Edward Otte" <exogyra@m...> wrote:
> Rich,
>
> Congratulations and welcome to our little (but growing!) group. And
congratulations on
> your new purchase!
>
> Like many people you probably ordered your Discovery sight-unseen
and with some
> trepidation. After all, it is a relatively new company.  Like many
people though, you have
> seemed to have done your research.   You obviously checked out
other companies before you
> ordered.
>
> I have looked in Starmasters,  I have spent time gazing through
Obsessions.  No, you
> cannot buy a Mercedes with a Toyota price tag, but who is the
smarter one?   There is a
> limit to what I can spend on a scope, just like there is a limit to
what I can spend on a
> car.  So...let the BigDob people snub the more modest Discoverys.
I say they present the
> most "bang for the buck".
>
> So... any word on how long til you get it? :-)
>
> Clear skies,
>
> Penny
>
>
> Rich wrote:
>
> Hello all,
> I just stumbled on this e-group by accident while signing up for
Steve Tuma's Deepsky 2000
> e-group.  I have heard quite a few good testimonials about
Discovery Dob scopes
> (especially the premium Dobs and truss Dobs), and decided to take a
chance and order their
> 15" truss Dob last week (just in time to beat the Feb. 1 price
increase, of course).
> Apparently this e-group was only begun yesterday, so I feel almost
like a charter member!
> Hopefully, I will be happy with my new Discovery - and I think that
I will be because, as
> I said, most of the feedback that I have read has been very
favorable.  Except, of course,
> from some of the "Dob-snobs" in the BigDob e-group who wouldn't
think of looking through,
> let alone buying anything less than an Obsession or a Starmaster
scope.  I can't wait
> until I get my hands on my new scope so that I can give it a
thorough star test, and then
> we shall see whether they are right or wrong.  (After all a Toyota
certainly isn't a
> Mercedes, is it? But just because it costs a lot less and doesn't
have all the luxury
> features doesn't mean that a Toyota is a piece of junk either, does
it?) Anyway, greetings
> to all, and I look forward to a great scope and a very informative
e-group.
> Rich Dodson

Rich,

Congratulations and welcome to our little (but growing!) group. And
congratulations on
your new purchase!

Like many people you probably ordered your Discovery sight-unseen and with some
trepidation. After all, it is a relatively new company.  Like many people
though, you have
seemed to have done your research.   You obviously checked out other companies
before you
ordered.

I have looked in Starmasters,  I have spent time gazing through Obsessions.  No,
you
cannot buy a Mercedes with a Toyota price tag, but who is the smarter one?  
There is a
limit to what I can spend on a scope, just like there is a limit to what I can
spend on a
car.  So...let the BigDob people snub the more modest Discoverys.  I say they
present the
most "bang for the buck".

So... any word on how long til you get it? :-)

Clear skies,

Penny


Rich wrote:

Hello all,
I just stumbled on this e-group by accident while signing up for Steve Tuma's
Deepsky 2000
e-group.  I have heard quite a few good testimonials about Discovery Dob scopes
(especially the premium Dobs and truss Dobs), and decided to take a chance and
order their
15" truss Dob last week (just in time to beat the Feb. 1 price increase, of
course).
Apparently this e-group was only begun yesterday, so I feel almost like a
charter member!
Hopefully, I will be happy with my new Discovery - and I think that I will be
because, as
I said, most of the feedback that I have read has been very favorable.  Except,
of course,
from some of the "Dob-snobs" in the BigDob e-group who wouldn't think of looking
through,
let alone buying anything less than an Obsession or a Starmaster scope.  I can't
wait
until I get my hands on my new scope so that I can give it a thorough star test,
and then
we shall see whether they are right or wrong.  (After all a Toyota certainly
isn't a
Mercedes, is it? But just because it costs a lot less and doesn't have all the
luxury
features doesn't mean that a Toyota is a piece of junk either, does it?) Anyway,
greetings
to all, and I look forward to a great scope and a very informative e-group.
Rich Dodson

Penny Fischer-Otte
40.297N  -74.359W 
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Manager, Space Forum
http://www.forumsamerica.com/space
Monmouth Mobile Observer's Group
Monmouth County, New Jersey
http://www.monmouth.com/~govega/mmogindex.htm
Penny Fischer's Astronomy Page
http://www.monmouth.com/~govega
*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~

We just ordered a 32 mm and I think it will be the best eyepiece we
have yet. (2 inch of course). From what I heard, this is a good size
low power for the Big Dob range. What are some other recommendations?


Penny

Hi Edward,


Thanks for the intro message.

Like all new products, Discovery has a few glitches in it's design.  All in
all though we are very happy with it and would recommend it. I am curious
though as to what other users have to say about their Discovery scopes.   I
am wondering if some of the problems we have encountered with it are:

* Size-related
* Unique to our scope

Despite some of the problems,  I do agree with Edward that for the money the
optics are phenomenal.

Now... if only Discovery comes out with it's own line of eyepieces ;-).


Penny


On Friday, February 02, 2001 7:26 AM, Edward Otte
[SMTP:exogyra@...] wrote:
> Well here goes! Start a new group and start posting!
>
> Penny and I have owned our 12.5" for about a half a year now. When we
> started looking for a sizable "upgrade" to her 8" Orion we were obviously
> lookinh for the best buy. We were obviously familiar with the Orion line
of
> scopes as well as the Meade line. (Meade is the best selling scope maker.)
> Penny was very much negative to the Meade Croporation experientially for
she
> did not feel the optics were very good. We were looking for a Dobsonian,
> larger than a 10", so the market range was rather limited to Meade,
> Discovery, and Coulter. As I started to look into the optics of each I
> became more and more aware of Discovery's edge. (I also found out that
> Coulter's optics are no long made by them but a subcontracting Japanese
> company which does not make the mirrors to the same precision as was
> previously done.) I have always been a big proponent of American made
> products, and am aware that on-site manufacturing of anything allows for
> better Quality Contro, both of which were satisfied by Discovery. Looking
> further I found that Discovery's optics are actually sold to almost every
> other medium to large scope company! The limitation being however that
> Discovery sells a "standard" mirror, not the Premium mirror which goes
into
> their telescopes, to everyone else. The difference I feel is very big. For
> example, Orion telescopes, which have Discovery mirrors now, 88%
reflective,
> and have 1/8 wave accuracy. Discovery Premium scopes have 94% and 1/10
wave
> accuracy. The choice got to be very easy at that point. The cost was also
> very good, only $1100 for the 12.5".
>
> Edward Otte << File: ATT00000.htm >>