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View Full Version : Re: pre-purchase ccd questions


Chris L Peterson
July 28th 03, 09:15 PM
On Mon, 28 Jul 2003 19:42:58 GMT, (Mike M. Miskulin)
wrote:

>1) I currently do not have an equitorial mount - can any imaging
>be done using the standard azimuthal mount? I am trying to keep
>initial costs down a bit, and if I can get by for a year without
>sinking more $ into a wedge. I'm guessing I would be ok on
>exposures under 3-4 mins?

You can use an altaz mount. However, the combination of field rotation and drive
errors on two axes means that a more realistic exposure time will be around 30
seconds. But you can produce very nice results by stacking 30 second exposures.


>2) Are there other companies besides SBIG and Starlight in the
>personal use market?

Apogee. Finger Lakes.


>3) Would I regret getting a 'one shot' color cam vs using filters,
>ie, MX7-c vs MX716?

I don't know about you. I would. One shot color isn't very good for DSOs. If
you're serious about color imaging, you're going to need to do it through
filters, so you might as well start that way from the beginning. I'd plan on a
camera with a monochrome sensor and a filter wheel, whomever I bought from. But
hold off on the filter wheel until you get the basics of monochrome imaging
under control.


>4) Any oddities or other considerations when using with an older
>LX200 10" f6.3 scope?

Your performance will depend on lots of details of the individual scope. There
is a lot of variation between LX200s. Mine can track for 3-4 minutes unguided,
and has no mirror slop to cause imaging problems. Other people need to use an
AO7 to get reasonable performance. This is something you are only going to find
out once you begin. You may need to adjust the worm tensioners, and you'll want
to invest the effort in getting a good PEC map stored. Depending on how old the
scope is, you may also need to replace the plastic declination bearings with
metal.

You might consider one of the less expensive SBIG models with self guiding,
which will eliminate some of your potential scope problems and allow you to add
an AO7 later if necessary. As I said, don't worry about color for now- there's
plenty to learn first. Consider a motorized focuser, which will allow you to
spend much more time imaging. Otherwise, you may find that focusing takes a lot
of your time. I'd recommend the RoboFocus.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson
July 29th 03, 05:51 AM
On Tue, 29 Jul 2003 04:26:44 GMT, (Mike M. Miskulin)
wrote:

>How does the MX716 hold up to the SBIGs?

For the price, very nicely I would think. I don't particularly like interline
sensors for astrocameras, and in particular I don't like Sony (because they
leave too much stuff unspecified) or EXView sensors (because they have pixel
decay problems.) But the camera is half the price of the ST7, which is in many
respects similar. However, the ST7 gives you a built in guider, and IMO a better
sensor. You can get guiding with the MX716 for only another $240, although it
will cost you half your sensitivity.

For someone just getting involved in this, with a primary interest in aesthetic
imaging, it is hard to beat the MX716 in term of bang for the buck (pound?)

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

David Nakamoto
July 29th 03, 05:50 PM
Hi Mike !

"Mike M. Miskulin" > wrote in message
...
> hey now,
>
> please be gentle - I've a few questions before sinking $ into
> ccd imaging.
>
> 1) I currently do not have an equitorial mount - can any imaging
> be done using the standard azimuthal mount? I am trying to keep
> initial costs down a bit, and if I can get by for a year without
> sinking more $ into a wedge. I'm guessing I would be ok on
> exposures under 3-4 mins?

If this scope is not computer driven so as to track objects in the sky, then
you cannot do deep sky objects. I'm assuming you know that the reason
for an equatorial mount is to track objects, and you need to track objects
in order to take the long exposures necessary to image DSOs.

If it can track, then the exposures are much shorter; more like 10 to 20
seconds, depending on the focal length of the scope. You can try stacking,
and I found this will get the brighter deep sky objects, but it does mean
more work in the processing end of things.



> 2) Are there other companies besides SBIG and Starlight in the
> personal use market?

Yes, but they're the leaders right now because they have the best products.
I favor Starlight Xpress ue to initial very favorable results, and
continuing good
results from their equipment.


> 3) Would I regret getting a 'one shot' color cam vs using filters,
> ie, MX7-c vs MX716?

I used one for several years, the MX5-C. Definitely the easiest way to get
color. No need for additional equipment such as filter wheels and making
sure everything is right before each if the three exposures. No need to
take
three exposures. No need to refocus for the individual filters. etc.

For a beginner, this is the way I would go.

Mike M. Miskulin
July 30th 03, 05:11 PM
While pondering the Universe, (Stefan Lilge) wrote
>:

>Mike,

>I have seen some people who have changed from the one shot colour
>cameras to mono cameras, but not vice versa. As you will be limited to
>short exposure times without the wedge (and even with the wedge if you
>don't also buy an autoguider or the STAR2000 thingy)

Another poster seemed to imply that I would have reduced sensitivity
using guiding on the MX vs the SBIG 7, but being new to this I might
have misunderstood(?). The price of the MX though is certainly more
managable.

>I would very much
>recommend a mono camera because of it's much higher sensitivity.
>If you are interested in some MX716 pictures taken through an 8" LX200
>you could take a look at my website at www.ccd-astronomy.de

Those look great to me! In your captions you state 8" at f/6.3,
is that the normal for your scope or are you using a focal reducer?
I've read that f/3ish would be ideal for this size ccd, but my
scope is native 6.3. Using a reducer would give me 4 or 2. Do you
feel its needed to a) use one and b) which choice woould be better?

>My pictures are not as good as those by some other people, but that's
>mainly the fault of my city skies, not of the MX716. Apart from some

I've moved my setup to my vacation condo in Vermont, its quite dark
up there. Otherwise I would be in the nyc suburbs, nearly as bad
as it gets.

Question for those in the states who have bought this - have any
of you bought directly from the UK and skipped the VAT? It seems
to me that would save about $250 which could be used for other
items.

Thnaks for all your help.

Mike

Chris L Peterson
July 30th 03, 05:29 PM
On Wed, 30 Jul 2003 16:11:23 GMT, (Mike M. Miskulin)
wrote:

>Another poster seemed to imply that I would have reduced sensitivity
>using guiding on the MX vs the SBIG 7, but being new to this I might
>have misunderstood(?). The price of the MX though is certainly more
>managable.

If you use the MX for self guiding, half the pixels get used for that function
and half for imaging. This means that only half the photons received contribute
to the image. In contrast, SBIG uses a separate sensor for guiding, so the main
imaging sensor gets all the light. With the MX, you guide on a star in your
imaging field; with SBIG you guide on a star in an adjacent field.

If you aren't using self guiding, you can expect the sensitivity to be about the
same as the SBIG cameras.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Roger Hamlett
July 30th 03, 05:33 PM
"Mike M. Miskulin" > wrote in message
...
> While pondering the Universe, (Stefan Lilge) wrote
> >:
>
> >Mike,
>
> >I have seen some people who have changed from the one shot colour
> >cameras to mono cameras, but not vice versa. As you will be limited to
> >short exposure times without the wedge (and even with the wedge if you
> >don't also buy an autoguider or the STAR2000 thingy)
>
> Another poster seemed to imply that I would have reduced sensitivity
> using guiding on the MX vs the SBIG 7, but being new to this I might
> have misunderstood(?). The price of the MX though is certainly more
> managable.
The sensitivity loss, is because half the light gathering area of the CCD,
is being used to guide. Conversely though, the advantages of these cameras,
is that you can guide on any object in the FOV, and they have lower noise
levels than the SBIG cameras (can allow you to operate without dark frames).
The guiding however also results in some more thermal noise being generated
by the readout operations (this increases the more frequently you do guide
corrections).
The SBIG system, has a seperate guide CCD, so there is no loss from the main
CCD, and no added 'guide noise' on the main CCD. The 'downside', is it can
be very hard to find a suitable object to guide on (the guide CCD, is quite
small, and a fixed distance from the main chip). Hence it is common when
imaging with the SBIG cameras, to use a tool like SkyMap, and generate an
overlay, with the sizes and locations for both the main, and guide CCD, for
your own scope, to allow planning to find a suitable guide object. This
approach is therefore perhaps better for 'planned' imaging, than 'casual'
imaging.
I have one Starlight camera, and one SBIG camera. The Starlight, is very
good, provided you are aware of the disadvantages, and much quicker/easier
to use for 'quick' imaging. I use mine on my smaller scope, as a 'mobile'
instrument (where the lower weight is a really big advantage). The MX716, is
a truly 'great' little camera.

Best Wishes

> >I would very much
> >recommend a mono camera because of it's much higher sensitivity.
> >If you are interested in some MX716 pictures taken through an 8" LX200
> >you could take a look at my website at www.ccd-astronomy.de
>
> Those look great to me! In your captions you state 8" at f/6.3,
> is that the normal for your scope or are you using a focal reducer?
> I've read that f/3ish would be ideal for this size ccd, but my
> scope is native 6.3. Using a reducer would give me 4 or 2. Do you
> feel its needed to a) use one and b) which choice woould be better?
>
> >My pictures are not as good as those by some other people, but that's
> >mainly the fault of my city skies, not of the MX716. Apart from some
>
> I've moved my setup to my vacation condo in Vermont, its quite dark
> up there. Otherwise I would be in the nyc suburbs, nearly as bad
> as it gets.
>
> Question for those in the states who have bought this - have any
> of you bought directly from the UK and skipped the VAT? It seems
> to me that would save about $250 which could be used for other
> items.
>
> Thnaks for all your help.
>
> Mike
>
>
>

Stefan Lilge
July 31st 03, 08:56 AM
Mike,

> Another poster seemed to imply that I would have reduced sensitivity
> using guiding on the MX vs the SBIG 7, but being new to this I might
> have misunderstood(?). The price of the MX though is certainly more
> managable.

This question was already answered by others. Of course you could use a
separate autoguider (as I do) to avoid the halved sensitivity when
selfguiding with the STAR2000 box, which often will still be cheaper than
buying a ST7. Even quite a lot of people that use SBIG cameras use a
separate autoguider because the integrated guidechip doesn't always see good
guidestars when imaging through narrow filters.

>
> >I would very much
> >recommend a mono camera because of it's much higher sensitivity.
> >If you are interested in some MX716 pictures taken through an 8" LX200
> >you could take a look at my website at www.ccd-astronomy.de
>
> Those look great to me! In your captions you state 8" at f/6.3,
> is that the normal for your scope or are you using a focal reducer?
> I've read that f/3ish would be ideal for this size ccd, but my
> scope is native 6.3. Using a reducer would give me 4 or 2. Do you
> feel its needed to a) use one and b) which choice woould be better?
>

My scope is also a native f/6.3. I do own f/6.3 and f/3.3 reducers (which
bring the scope to f/4 and f/1.9) to accomodate the field of view to larger
objects. The f/3.3 reducer doesn't have sharp stars at the edge of the field
with the "fast" f/6.3 scopes, still it is nice to have such a wide field. I
would still recommend the f/6.3 reducer though, which should give a nice
scale at your 10 incher. If you are just starting imaging it will save you a
lot of frustration to use the reducer as it makes guiding much less
forgiving and allows for shorter exposure times (the added light sensitivity
of f/4 against f/6.3 is very obvious).

Stefan

Mike M. Miskulin
July 31st 03, 02:42 PM
While pondering the Universe, (Stefan Lilge) wrote
>:


>My scope is also a native f/6.3. I do own f/6.3 and f/3.3 reducers
>(which bring the scope to f/4 and f/1.9) to accomodate the field of view
>to larger objects. The f/3.3 reducer doesn't have sharp stars at the
>edge of the field with the "fast" f/6.3 scopes, still it is nice to have
>such a wide field. I would still recommend the f/6.3 reducer though,
>which should give a nice scale at your 10 incher. If you are just
>starting imaging it will save you a lot of frustration to use the
>reducer as it makes guiding much less forgiving and allows for shorter
>exposure times (the added light sensitivity of f/4 against f/6.3 is very
>obvious).
>
>Stefan


Thanks for that follow up Stefan, and thanks to everybody else. You've
cleared up a number of points for me, and I hope to get on board with
a system soon.

THanks again.

mike