Help! H-alpha Solar Observing: Coronado Maxscope 40 or SM40/10?

Hi all,

I've decided to take the plunge into Ha solar observing. The question
now is: "which set-up?"

I've narrowed my options down to two. The PST from Coronado was my
initial choice, especially at its price point. The downside is that
with back orders and the fact that they haven't shipped yet (at least
to my knowledge), it may be 3-5 months before I can get my hands on
one. Also, the bandpass on this unit is optimized for prominences at
the expense of solar surface detail

The remaining choices a Cornado SM40/10, and the Coronado Maxscope
40mm.

I have a 4" f8 (~800mm focal length) refractor. The SM40/10 at first
blush is slightly less expensive than the Maxscope, but with the
addition of an adapter plate to mount it on the objective of the
refractor, the cost works out to be +/- the same. The maxscope is
smaller than my 4" scope, so there is the portability factor.

Does one of these options have any other benefits over the other? Can
the Maxscope be "de-tuned" i.e. is there a mechanism to change the
filter's angle to move the band-pass away from the H-alpha line to
observe fast moving (doppler shifted) events? Anyone know what the
lead-time is on the Maxscope? The SM40/10 is in stock at a couple of
places, but I haven't seen the Maxscope in stock.

Thanks for any input!

- Craig

Craig Levine
Observing Chairman
RASC, Halifax Centre

Craig Levine wrote:
The remaining choices a Cornado SM40/10, and the Coronado Maxscope
40mm.

I have a 4" f8 (~800mm focal length) refractor. The SM40/10 at first
blush is slightly less expensive than the Maxscope, but with the
addition of an adapter plate to mount it on the objective of the
refractor, the cost works out to be +/- the same. The maxscope is
smaller than my 4" scope, so there is the portability factor.

Does one of these options have any other benefits over the other? Can
the Maxscope be "de-tuned" i.e. is there a mechanism to change the
filter's angle to move the band-pass away from the H-alpha line to
observe fast moving (doppler shifted) events? Anyone know what the
lead-time is on the Maxscope? The SM40/10 is in stock at a couple of
places, but I haven't seen the Maxscope in stock.

Thanks for any input!

I have the SM40/10, which I use with my Tele Vue Ranger. I have not
tried the MS40, and I don't know where it might be in stock.

My understanding is that the doublet in the MS40 is optimized for H-alpha
observing. Since longitudinal chromatic aberration is out of play, I
take that to mean that the issue is spherical aberration. Ordinary
refractors are probably corrected for a shorter wavelength than H-alpha,
which sits at 656.3 nm. I'm not sure exactly how much difference this
makes with a 40 mm aperture, where the Airy disc size is already about
3 arcseconds full-width half-maximum (I think that's about right). It
might depend on the effective focal ratio, which is f/12 for the Ranger
stopped down to 40 mm, but is f/20 for your refractor. However, I really
don't know.

As far as I know, the MS40 and the SM40/10 (as currently packaged) both
come with the T-Max tuner, so that Doppler-shifted events can be viewed.

I like my SM40/10 quite a bit. It's the chief use for my Ranger now.
I put it on the photo bracket of my C5+ for tracking. It looks a bit
ungainly but works fine. I do hanker for a bit more aperture, but I'm
certainly happy with the purchase.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

On Sat, 17 Apr 2004 16:12:01 +0000 (UTC), (Brian Tung)
wrote:
I have the SM40/10, which I use with my Tele Vue Ranger. I have not
tried the MS40, and I don't know where it might be in stock.

My understanding is that the doublet in the MS40 is optimized for H-alpha
observing. Since longitudinal chromatic aberration is out of play, I
take that to mean that the issue is spherical aberration. Ordinary
refractors are probably corrected for a shorter wavelength than H-alpha,
which sits at 656.3 nm. I'm not sure exactly how much difference this
makes with a 40 mm aperture, where the Airy disc size is already about
3 arcseconds full-width half-maximum (I think that's about right). It
might depend on the effective focal ratio, which is f/12 for the Ranger
stopped down to 40 mm, but is f/20 for your refractor. However, I really
don't know.

As far as I know, the MS40 and the SM40/10 (as currently packaged) both
come with the T-Max tuner, so that Doppler-shifted events can be viewed.

I like my SM40/10 quite a bit. It's the chief use for my Ranger now.
I put it on the photo bracket of my C5+ for tracking. It looks a bit
ungainly but works fine. I do hanker for a bit more aperture, but I'm
certainly happy with the purchase.


Thanks for the reply Brian, I appreciate it.

My brother took the initiative and ordered a PST for me. I don't know
what the leadtime is for one of these. Some have supposedly shipped to
dealers. They sure are cute looking! I think that I want the ability
to tune the filter, so I think that I may up the order to the MS40.
It's certainly smaller and lighter than my AP 102mm. The APO is less
"Grab and go" and more "lug and go".

Cheers,

- Craig

Craig Levine wrote:
My brother took the initiative and ordered a PST for me. I don't know
what the leadtime is for one of these. Some have supposedly shipped to
dealers. They sure are cute looking! I think that I want the ability
to tune the filter, so I think that I may up the order to the MS40.
It's certainly smaller and lighter than my AP 102mm. The APO is less
"Grab and go" and more "lug and go".

One thing to consider is that the PST is not so much optimized for
prominences as it is pessimized for surface detail. It won't show the
prominences any better, I don't think, than the MS40 will. The surface
detail, incidentally, may be why the PST doesn't come with the T-Max
tuner; it wouldn't do enough good to warrant including it. Still, if
I were on a limited budget, the PST would look like a very attractive
option.

I went with the SM40/10 in part because I think there's a chance that I
will want to use it with other telescopes. If that's a possibility with
you, too, you might consider it.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Brian Tung wrote:
: My brother took the initiative and ordered a PST for me. I don't know
: what the leadtime is for one of these. Some have supposedly shipped to
: dealers. They sure are cute looking! I think that I want the ability
: to tune the filter, so I think that I may up the order to the MS40.
(snip)
: One thing to consider is that the PST is not so much optimized for
: prominences as it is pessimized for surface detail. It won't show the
: prominences any better, I don't think, than the MS40 will. The surface
: detail, incidentally, may be why the PST doesn't come with the T-Max
: tuner; it wouldn't do enough good to warrant including it. Still, if
: I were on a limited budget, the PST would look like a very attractive
: option.

I talked to a woman at the Coronado booth at NEAF about the PST. She said
that on Tuesday (I assume 4/20/04) they are starting production on a "Mark
2" PST

The difference? I think she said it will be able to be tuned when you add
the additional filter.

Richard in Boston, MA, USA

On Mon, 19 Apr 2004 01:51:43 +0000 (UTC), Richard G Amirault
wrote:


: option.

I talked to a woman at the Coronado booth at NEAF about the PST. She said
that on Tuesday (I assume 4/20/04) they are starting production on a "Mark
2" PST

The difference? I think she said it will be able to be tuned when you add
the additional filter.

Richard in Boston, MA, USA

Hi Richard,

I wonder: Are they starting development, or starting production; and
will the older units be able to be retrofitted???

Accckkk!!!!!!!

- Craig

Richard G Amirault wrote (of the PST v2):
The difference? I think she said it will be able to be tuned when you add
the additional filter.

Interesting. Because right now the etalon is internal and untunable,
so that the T-Max on the additional filter would only be good for, they
claim, avoiding reflections.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

On Sun, 18 Apr 2004 19:57:43 +0000 (UTC), (Brian Tung)
wrote:

One thing to consider is that the PST is not so much optimized for
prominences as it is pessimized for surface detail. It won't show the
prominences any better, I don't think, than the MS40 will. The surface
detail, incidentally, may be why the PST doesn't come with the T-Max
tuner; it wouldn't do enough good to warrant including it. Still, if
I were on a limited budget, the PST would look like a very attractive
option.

I went with the SM40/10 in part because I think there's a chance that I
will want to use it with other telescopes. If that's a possibility with
you, too, you might consider it.

Brian Tung

Good points all, Brian. The PST is at a nice pricepoint. I do think
that the SM40/10 may in the long run be a better option, as is the
MS40. I think that (given that I'm renovating two bathrooms, painting
two rooms, installing a new window and putting up new gutters) the PST
is a good "toe in the water". I'll probably pick up another filter to
drop it down to about .06 angsteom as well. Here's a link to an
unretouched prime-focus shot from a PST:
http://www.astronomike.net/photos/p/...adet_15910.jpg.

Sure is pretty!

Cheers,

- Craig

Here's a link to an
unretouched prime-focus shot from a PST:
http://www.astronomike.net/photos/p/...adet_15910.jpg.

Here's a shot taken with a 90 mounted on a 105 Traveler taken by Paul Hyndman:

http://www.astro-nut.com/sun-disk04apr16.jpg