Very often I find
myself stumbling on an interesting fact, or coming up with a practical
suggestion. I am amazed how much I have yet to learn in the wonderful world
of amateur astronomy! I'd like to share these random"thoughts" on a continuing
basis, as they pop in my head, right here!
10/4/03
I am a bit discouraged
today by an experiment I performed two nights ago. I had fairly dark skies,
limiting mag. 5.3 or so, the Milky Way clearly visible. I could make out
M31 easily naked eye, and I pointed the scope up to M31, the Andromeda
galaxy. Using 14.5" aperture I practiced mentally tracing the dim exterior
portion of hte galaxy against the darker sky. I then put on the 5.5" aperture
mask.
You guessed it.........
The 5.5", even with fairly dark suburban skies (not rural, but close) made
M31 look better with it standing out just as well as at 14.5" full aperture.
This isn't to say that 14.5" won't do MUCH better on higher surface brightness,
or rather, more "compact" targets. Of course, using a light pollution filter,
the larger aperture will work best too. However, on large, spread out galaxies
the larger aperture really didn't help at very low power due to the bright
background sky - an unfortunate limitation.
5/21/03 Binoviewer
"Wars"
I hate to gossip, but
while I wasn't paying attention, there has been another binoviewer manufacturer
that has been born out of the spirit of the BINOVIEWING
ARTICLE on this web site and reviews on CLOUDY
NIGHTS.COM. Denkmeier
is
currently producing the most versatile array of binoviewers both from the
standpoint of quality and the solutions to focus problems normally encountered
with those units. Alas, too bad that Siebert Optics and Denkmeier are in
competition, as they at one point at least started to work together. In
any case, check out the latest Denkmeier II, the first binoviewer to make
a definite statement about its optical quality.
3/26/03 Two amateurs
go professional... and WOW! What results!
Alright, I'm being forced out of hibernation. A new job at WHDH-TV
(Ch. 7, NBC) in Boston has eaten up my free observing time. However, after
years of being in contact with two amateurs who started up businesses (Harry
of Siebert Optics, and Larry from Universal Astronomics) I have now discovered
that both have perfected their craft and need special mention. Harry, has
developed a binoviewer that competes with the Televue unit, and better
yet, he has a superior 1.35x adapter that can be used with the Televue
unit itself. Larry, has perfected an alt-az mount, after I had searched
for years for the best unit. Check it out!
08/26/02 It's so simple
yet....
Testing out a new Astrophysics 92mm scope,
I was convinced that the contrast between the moon and sky should be greater
than what I was observing at the eyepiece a couple of weeks back. Taking
out the star diagonal did the trick, yet again, after remembering what
a huge difference that made the previous summer testing another scope.
Even if you think your star diagonal is clean, additional scatter will
make for less contrast than viewing straight through your scope. In fact,
the star diagonals also may exhibit small optical aberrations, even the
best ones.. so your best bet, if you really want to take it to the limit,
is to go diagonal-less!
11/8/01 Different scopes
and different eyepieces
I won't even begin to describe the optical
reasons (field curvature, etc) but I am more convinced than ever that different
eyepieces do indeed "act" differently on different scopes and designs.
Most folks know this, but I didn't when I first began the eyepiece reviews
back in 1994. This morning for instance, I tried a 24mm Takahashi LE on
a Sky 90 with an Extender Q. Perfect, sharp to the edge. Not so with a
26mm Meade Super Plossl. Try the same two eyepieces without the Extender
Q? The LE is still better, but not perfect. Try it again, this time on
a fast Newtonian (also around f/5.6) Teleport 7? The 26mm SP is sharper
towards the edge than the more expensive 24mm Tak LE. Overall the eye relief
is better on the Tak which makes the difference for me, but the differences
between how they behave between the fast refractor and fast reflector are
interesting.
11/2/01 Teary eyes?
Pick an eyepiece with good relief.
There are a number of high power eyepieces
with larger eye relief now. The Televue radians, the Takahashi LE (marginally)
, the Ludes Czech 5.5mm, and others are now going for the greater relief.
This helps out if you observe in the AM with 'teary eyes' which fog up
the eyepiece within 1 or 2 seconds! With this in mind, I have another suggestion.
Wider field eyepieces have more "play", if you will, in that they will
allow you to hold back from the eyepiece a bit, losing a small amount of
the outer fov, but not the on-axis portion of the view. For instance, I
was thinking about trading for a 12mm nagler this morning, considered the
fairly tight relief, but then remembered that should I start fogging the
eyepiece, I can pull back, retain a good 50 degree fov, and have decent
relief enough to end the fog, so to speak.
7/26/01 How LARGE a
scope for your skies?
There is a lot of misunderstanding regarding
using larger aperture in light polluted skies. Even a 30" in downtown Manhatten
will be able to be utilized to better resolve globular clusters and to
see small, high surface brightness planetary nebulas. However, it is true
that larger scopes have limited performance, and in fact may make things
look even worse at medium and especially low powers in the city or brighter
suburbs. As a rule of thumb this is my experience..
City Skies.. 60mm to 8" aperture is best
Bright Suburban skies (LM 4.5) 8-12" is
about the tops
Typical suburban skies 10-14.5" tops
Darker suburban skies 14.5-18" tops
Anything approaching dark skies, greater
than 18"
Note that optimal planetary performance is achieved starting around 10 or 11", with rarely anything over 14" needed... you don't really need more than that, since skies are rarely steady enough to give you the extra boost, so keep that in mind (in other words, if you are a planet/lunar observer, consider larger than 8" even if you live in the city, since light pollution doesn't affect most solar system work, but don't go crazy, as you don't really need to go much over 11 or 12")
7/24/01 Ooops, Celestron
goofs
Unbelievable as this may sound, Celestron
initially sent all their new NEXSTAR GPS scopes (11" premium model) in
poorly packed cartons. Many reports of damaged scopes initially came in.
Thankfully, Celestron will be packaging them differently here on out.
7/16/01 Yahoogroups...
and Nextstar GPS.
A bit of history for you. When I first
got back into nighttime astronomy in 1994, I immediately joined and posted
to the "newsgroup" on USENET, "sci.astro.amateur". I was very impressed.
However, I was even more impressed with "Astromart", run by Robert Fields,
and especially his Meade support group (mail list) for lx200 users. I took
over that very list about 2 years later for a year+ stint, then handed
it off to John Hopper (johnlx200@aol.com). However, I was very impressed
with the amount of help the LX200 user could get on that group. Since then
I have run many mail lists, and was involved with the Ultima 2000 mail
list, also run by Mr. Fields. It was, (the Celestron Ultima2000 group)
however, not very well attended. I am happy to announce that with the introduction
of "yahoogroups" a larger compendium of mail-lists, the NEXTSTAR, and NEXTSTAR
GPS (supporting Celestron scopes) groups are doing great. The NEXTSTAR
group has over 1700 members, and the NEXTSTARGPS is already solving
the first problem that has been detected in the scope that has just first
arrived at users homes within the past week. Personally? I am running the
Starlight Xpress group for that line of CCD cameras, and I help manage
the Astrophysics Mount mail list: AP-GTO. Come and join us.
6/19/01 GREAT Martian
Tip
Not only does red filtering bring out
the darker features better, but it "beats the seeing" somewhat.. with the
red wavelengths less affected by the turbulence in the atmosphere!
(7/13 UPDATE: Got a nice email today from an observer who couldn't
figure out why Mars was featureless. In the past two weeks, Mars has been
gobbled up by what is apparently the largest global duststorm in the past
quarter century. You won't see much! See you next apparition. (If you observed
Mars earlier this season, take another look! What a change!))
6/19/01 REMEMBER.. chuck those cheapie diagonals. Some 1.25" diagonals like Meade and Celestron aren't up to the task. Get a really good one like from Lumicon, Televue, etc.
5/15/01 Binocular "Revolution"
There is almost nothing more satisfying
than panning dark skies with binoculars, and I have some good news... very
good binoculars have become easier and easier to get at low cost over the
past decade. Import dealers such as Telescope Warehouse (702 897-8481)
have brought over Russian binoculars for years, that were mechanically
inferior, and had questionable coatings, but were simply great for the
money. 20x60s, 12x45s, etc, all different sizes. Now the Chinese are producing
some big aperture binoculars with all the goodies, from excellent coatings
to BAK 4 prisms. These include some 15x70s, 12x60s, 20x60s and more, and
are running 75-150.00. Mechanically they are much better as well,
although not perfect.
5/9/01 Takahashi Camera
Angle Adjuster
Did you know that some Takahashi scopes
come with camera angle adjusters standard, others it is an add-on,
and that it makes life so much easier! Basically, it is just a piece at
the end of the tube (towards the eyepiece end) that allows you to
fully rotate, 360 degrees, your camera, your diagonal/eyepiece, or anything
else fluidly, at any time, on a whim. This comes in handy for framing film
or ccd shots perfectly (such as aligning galaxies long-ways across), but
also is convenient for visual. Soooo, when the refractor is on an equatorial
mount, as you spin the scope around to different parts of the sky, it becomes
extremely easy to spin the diagonal around simultaneously, to avoid it
pointing sideways or even downwards as it normally would. The normal way
around this would be to loosen the screws of the diagonal, and flip it
over, but the camera angle adjuster makes this much easier to do.
5/9/01 - See 4/24 Mars comments below.. updated.
5/7/01 NEAF 2001 and
Televue announcements:
I have discontinued my "rumors/hot news"
page as I was having trouble keeping it going and fresh, but here is one
for you: There is a great astronomy gathering yearly in the northern suburbs
of NYC (NEAF) where among other things, Televue (whose offices are nearby)
announces new products. This year the announcements included news
that there will be a new 3-6mm "Nagler" zoom eyepiece, and a new slightly
shorter, and improved version of the Televue 101mm.
5/4/01 Use your finder
as a TELRAD!
I mistakenly left the cover on my finder
this morning.. but I had the illuminated cross hairs on, shining red. Using
two eyes I centered Vega in the finder, and thus in the eyepiece. Moments
later, I was shocked when I realized the cover wasn't even taken off the
finder.... the finder works just like a very precise Telrad or 1x pointer..
when the crosshairs are lit, but the cover left on. (as long as you use
TWO eyes.. the other eye will see the star and mentally project it under
the crosshairs that you are seeing with the OTHER eye!
5/3/01 Refractor vs.
Reflector : Planets
Just a reminder to those new to these
pages, that there is a basic misunderstanding about refractors vs. reflectors
when it comes to planetary and lunar performance. Conventional wisdom runs
anywhere from "aperture rules" (in favor of reflectors due to the greater
resolving power) to "refractors are for planets" (citing the lack
of central obstruction and better contrast). Actually, when it comes to
solar system objects, larger scopes such 8"+ reflectors, if of good quality,
will POTENTIALLY deliver higher resolution on planets. However, smaller-than-8"
refractors offer more consistency for a variety of reasons. Firstly, if
skies aren't all that steady, the planets will not shake around as much
and look clearer for longer periods of time. Also, in this situation, refractors
can "beat the seeing conditions" more handily, less affected by turbulence
due to the lack of central obstruction (**has to do with how the light
is distributed in terms of airy disk and diffraction rings in-focus - see
note below). Lastly, with any kind of thermal problem (such as cool down
or tube currents), the refractors deal with only 1 light path to the eyepiece,
reflectors have 2, (in and bouncing back up). The same holds true with
SCTs and other compound designs. Overall then, given a narrow set of circumstances
and the larger aperture will show far more detail, but refractors offer
more consistency. That is what you should be considering. If you live down
south where seeing conditions are often good and temperatures usually warm,
the larger scope is your best bet.
**Note: To help illustrate the difference between these two kinds of scopes, take a peak at the double-double side by side in a 5" reflector or SCT and a 4" refractor as an example. Both will resolve the double-double cleanly most of the time. However, on a steady night you will notice that the reflector will show more of the first diffraction ring, making the split look a little "dirtier" rather than just four stars staring back at you. The airy disks will be visible but will each be surrounded by a diffraction ring in the reflector/sct while that will hardly be noticeable in a fine refractor. This has a direct bearing on both contrast and sensitivity to seeing conditions (turbulence) One way to get around some of this for reflectors is to have an off-axis mask made, which tends to sharpen planetary views much of the time, but limits the potential due to restricted aperture.
5/2/01 Reboot the computer,
stupid!
I just about proved my "thought" from
4/24 regarding Mars untrue this morning, as very steady skies reached Massachusetts
under a broad high pressure ridge. I predicted this and took out with delight
my brand new MX7c ccd camera to get some shots. Being familiar with this
line of ccd cameras and having previous experience with planetary
photography I knew there was a good chance I might get my best Martian
shot ever, with Syrtis Major on the meridian. But noooooooooooo, thinking
the camera was broken, it didn't occur to me that the saturated images
came just because my computer needed rebooting! I didn't think of that
until already in the car on my way to work after missing the golden opportunity.
4/24/01: The Mars Apparition-
A bust? But.. fight RED with RED!
I was in Florida recently,
and even there, Mars is barely up in the sky even at it's highest point
around 5am. This apparition coming up may be close, but it is terribly
situated for anyone over 35 degrees in north latitude. It will take miraculous
seeing conditions to see Mars clearly even in the finest scopes up north,
don't get frustrated this time round if you can't get a crisp view. My
own photographs have been borderline useable at best, but I did manage
to artificially stabilize the sky and add contrast with a RED filter. Red
light is less susceptible to poor seeing conditions, and brings out the
martian features the best.
4/9/01: So What about the C5?
The more I think about
it, the more it seems to me that the best low-cost alternative to an airline
portable refractor is simply a C5 OTA from Celestron. These have been coming
out with great optics again for the past 6, or 7 years, and can be outfitted
with an adapter that allows use as a spotting scope on a tripod. Very high
quality planetary views, and with the standard reducer, some decent wide
field views. Enough aperture to split M13. I am going to test this scope
against my 90mm refractors shortly. While the NEXTSTAR is too bulky for
easy airline carryon the tube is not, and I cannot see why this wouldn't
be a great alternative to a 3-4" refractor.
2/22/00: More comments on star testing
I posted on the "newsgroups":
In response to someone who was saying
star testing is not very accurate:
Your comments are well taken but miss
the most essential part of star testing:
finding the myriad of scopes that have
fairly substantial flaws. Even the highest quality scopes are riddled with
bad apples. I have returned no fewer than 8 high end scopes due to :
1. astigmastism
2. pinched optics
3. collimation
4. unknown weird error (don't ask)
5. spherical aberration that was all
too obvious
6. course optics
In one case I should not have really returned the scope, and the manufacturer was being kind to me by refiguring the scope even further. I was just being picky. In all other cases, the returns and re-do , or reissue was well founded.
In one case, (the rough optics) the refigured mirror became legendary.
You make excellent points, but take the situation two days ago here at channel 7, boston. A Bostonian emailed me and said he suspected something was wrong with his new TV85. I said bring it down. I did an indoor star test and voila! Obvious miscollimation, easy fix at televue, they will do it for free with a smile.
I am NO EXPERT at this and it makes me even more formidable, as if I see an error, then it's pretty obvious. Too many scopes, mostly by innocent shipping problems, develop these kinds of errors which show up right away in star tests, and all of us on SAA should become verse in doing them.
I wholly agree with you that more care should be given to it though, just as you state.
Todd Gross
ps. take another important example. Many scopes develop flaws in the star test when it gets very cold. High end scopes. I have therefore been able to take "with a grain of salt" the fact that these very scopes (4") are doing worse than my 3" scope of another brand when it falls under 20 degrees. I would have just thought the 3" scope was better if I didn't have the star test to show me what was going on.
Todd
2/2/01: Rushing to judgement
Following up on the comment below, evaluating
a scope and then publicly posting one's findings should be done with care.
I myself have violated that basic rule. Recent criticism on the net regarding
one particular manufacturer was in my opinion, too much, too fast. There
are usually problems (such as collimation) with many scopes, including
refractors which can be corrected especially when you buy from the right
dealer. Atmospheric conditions, poor collimation due to shipping, certain
eyepieces, certain outdoor ambient temperatures, mismatched magnifications
when testing, differing diagonals, are all culprits that can make a perfectly
good scope look bad, and has indeed fooled me on occasion. I know it is
important and desirable to get an initial evaluation of a new product out
quickly, but it is equally important that one move slowly and carefully
while doing it, without rushing to judgement about a scope, or a company
that produces it.
1/05/01: Never trust your glasses
I have to admit, my glasses help me a
lot now that my astigmatism has worsened, but I was recently evaluating
a scope and was thrown off for several days before I suspected, yup, my
glasses as the culprit. In testing the Sky 90 from Takahashi, I found that
the dispersion of color on either limb of bright stars and planets was
aggravated by my glasses. Since this wasn't as obvious in other scopes,
at first, I attributed it to the scope itself. After I realized what was
happening, I got confirmation from OTHER observers that this was the case
with them as well when viewing through this scope. I'm sure it's not limited
to the Sky 90, and is more a function of the single-glass of my high index
glasses which are a fairly new style for me. (These are my thinnest glasses
yet). However, it drives home the point once again, that your glasses my
be part of the optical system, and should not be ignored from the equation.
11/20/00: USING the Moon as a gauge
(for seeing conditions)
In 1999, Sky and Telescope magazine kindly
published an article of mine about light pollution, seeing conditions and
choosing your object(s) to view based on both factors. One MAJOR point
that I made that was left on the editing room floor is just how important
the Moon is in judging seeing conditions (how stable the atmosphere is.)
A quick glance at the moon at high or medium power will instantly tell
you what KIND of seeing conditions you are dealing with. For instance,
the other night, in med.-larger aperture, 14.5", Jupiter did not look very
crisp, but many small features were discernible. While I suspected "fast
seeing".. that is very quickly moving air aloft which works rapidly to
defocus the image slightly, I couldn't be sure until I turned to the moon.
Indeed, I was able to see very crisp, contrasty crator shadows, but they
were being interrupted by quick defocus/focus. "Slow seeing", or larger
waves of in and out of focus images can also be clearly seen when looking
at the moon. Once you are certain of just how good, and what kind of seeing
conditions you are dealing with, you can make a much more intelligent determination
of how well you are doing on the planets or high power deep sky observing.
Are the stars less than pinpoint because seeing is poor, or is it your
optics? Having trouble seeing the Cassini division on Saturn in front of
the planet? What kind of seeing conditions are fouling you up? The moon,
if available, can tell you just how much the atmosphere itself is working
against your clear window to the stars. Check it out first (but use your
other eye so you don't ruin your dark adaptation!)
OCT. 30, 2000 USE HIGH POWER to
TEST OPTICS
I can't tell you how many times somebody
emails me how great their optics have performed on the planets, and continue
to tell me they used somewhere around 200X magnification (I am referring
to VISUALLY). Excuse me? To truly test how well you are resolving the planets,
especially with aperture of 6" or more, please use something closer to
300X or preferably above, otherwise you won't be able to discern the small
features.
Here, do this. Take MY 10/26/00 JOVIAN IMAGE and bring it over to PAINTSHOP, PHOTOSHOP or any other image processing tool. Reduce it in size to 30%, and save the original. Now compare the two. Look at the subtle, but obvious small white oval well into the North Polar Region ON THE MERIDIAN in the larger image. Notice how it no longer is visible at all in the smaller image. These images correspond to roughly 800-900X for the larger image in how it would appear in your eyepiece (visually), and 250-300X in the smaller image. You see why image scale is important? The features that can be made out visually, at the eyepiece, are limited if your magnification is not quite high enough. Once you get above 350-400X, you are pretty much in great shape in discerning some of the smallest features, such as the Encke Gap on Saturn , given steady skies, and great optics. (You can see this again by watching that oval and resizing my image to 40%, 50%, etc.. 50% would be equivalent to roughly 450X)
In terms of ccd imaging, this is also a
good reason to "boost" your image scale as large as is feasible, given
an aperture that is over let's say 4". (4" and less the image scale won't
help that much due to the Dawes limit, as resolution is greatly hindered
by your aperture, get over 6" and this is not an issue, just other limiting
factors such as light gathering, tracking, etc.)
OCT. 30, 2000 JUPITER LOOKS
LIKE MY FLOOR
I've known for quite some time now that
the bands of Jupiter actually appear, in color, much like the red oak floor
throughout my house. That is the color I discerned when I first observed
the two main belts through the 16" several years ago. However, this weekend
I proved it to myself. After tweaking THIS
IMAGE I found the perfect color balance, comparing to older
images and images from the great Jupiter imagers such as Maurizio DiScullo
and Damian Peach. Then I took the image, printed it out, and layed it right
on top of my red oak, polished floors. Perfect match!
FOR MORE RANDOM THOUGHTS OF THE WEEK... CHECK THE ARCHIVE
.
.